Every weed does its best to survive, but some are craftier at this than others. If this were an Olympic sport, crabgrass might win the gold. This highly resilient summer annual does well in dry, compacted soil that other plants avoid, and it spreads quickly by tillers. Each plant produces up to 150,000 seeds that germinate the following spring. And the stems spread out low and wide like crab legs or spider legs, too low to hit with a lawn mower.

If you are ready to go to battle against crabgrass in your turfgrass, your best option is using a pre-emergent herbicide. You may have heard this type of crabgrass control called a crabgrass preventer. It can be very effective but only if you apply it in a very narrow window, before the crabgrass wakes up.

This “perfect moment” can be anywhere from February to May, depending on your climate. We’ll show you how to figure out the exact best moment in your own location.

Crabgrass Is Everywhere

Crabgrass is a common weed that grows in all 50 states, thriving in USDA Hardiness Zones 2 through 11. That means that your landscape is not exempt. If you aren’t familiar with crabgrass, its blades look like regular grass but wider. It grows in clumps, forming low, circular mats that look a bit like crab legs.

Where might you see crabgrass? It is often found in turfgrass lawns, particularly compacted or thin turf. Crabgrass loves hot, sunny conditions and grows quickly in full-sun locations.

You might also see it in cracks in your driveway. Crabgrass is not one of those weeds like dandelions, for example, that some people like to grow. It is considered a nuisance weed in every state.

Using Pre-emergent Herbicide on Crabgrass

The best way to get rid of crabgrass is to use pre-emergent lawn herbicides in the springtime. You have to be very careful to hit “the pre-emergent window” to apply the crabgrass preventer. The basic idea is to apply the herbicide before the grass seeds germinate. Some gardeners relate the timing to when the forsythia bushes are blooming. Their bright yellow flowers are among the earliest blossoms to open in spring. You can find Scotts Crabgrass & Grassy Weed Preventer on Amazon or from your local hardware store.

But it’s probably better to be more precise by basing your timing on the temperature of the soil. It’s more work but it’s worth it, since an application at the perfect time will not only prevent crabgrass from emerging but also other common weeds including chickweed.

When to Apply Crabgrass Preventer

This type of herbicide prevents the seeds from the last growing season from germinating. So you need to apply the pre-emergent herbicides before soil temperatures get warm enough for the seeds to germinate. That temperature, taken at 0-2 inches depth (0-5cm), is between 60 and 70 degrees F. Some 80 percent of seed germination takes place when temperatures are consistently between those temperatures.

So how to figure out the best moment? Use a soil thermometer to take readings starting on February 1 - if you live in the south, somewhat later if you live in the north. Keep checking every few days. Apply crabgrass preventer when the soil temperature reaches 55 degrees Fahrenheit for a few consecutive days.

A simple soil thermometer like this one from Urban Worm on Amazon has an easy-to-read color coded dial for fool-proof monitoring. Or you could opt for a 4-in-1 soil moisture meter, thermometer, pH meter, and light meter which is also available from Amazon.

Other Crabgrass Tips

• Mow your lawn a few days before you apply crabgrass preventer. This will help the preventer get down to the surface of the soil.
• Clear all leaves and other debris off of the lawn before you apply the herbicide.
• Avoid any type of soil disturbance, including seeding grass, around the time you are applying the crabgrass preventer.
• You’ll get the best crabgrass control if you split the application. Apply the first half in early spring, then the second half six to eight weeks later.
• Water in the product in the pre-emergent herbicides within 24 hours of application.
• Do everything you can to keep your turfgrass healthy and dense. This will involve adequate irrigation, fertilization, and mowing the grass high.

Crabgrass Prevention Essentials

Japanese barberry has been a favorite landscaping shrub for years, but its dense, humid thickets shelter far more black-legged ticks than native plants do, raising Lyme disease risk around homes—pulling it out cuts down tick numbers and makes yards safer.

Japanese barberry spread across landscapes because it handled tough spots nobody else wanted. Shady corners, dry slopes, deer-prone areas—it took them all without complaint. Those thorny branches and reliable color kept it in nurseries for decades.

The same features that made it popular create prime tick territory, though. Dense growth near the ground traps moisture and blocks wind, giving ticks the cool, humid cover they need. Preventing ticks in the landscape often comes down to breaking up those exact conditions barberry builds so well. Controlling Japanese barberry will help to reduce tick populations in your area and also support native wildlife better than this invasive does.

Why Japanese Barberry Caught On

Gardeners grabbed Japanese barberry (Berberis thunbergii) for problem areas that other plants wouldn’t tolerate. North-facing foundation beds that stayed dark and damp? It thrived. Rocky banks with thin soil? No issue. Property lines needing a natural deterrent? The thorns worked perfectly.

The plant basically asked for nothing once established—drought, shade, salt spray, compacted dirt, it handled the lot. Deer walked right past it, rabbits too. Colorful cultivars like 'Crimson Pygmy' brought red foliage to dull spots without extra work. For anyone planting tough sites on a budget, barberry felt like the easy fix that actually stayed put.

The Tick Connection

Black-legged ticks need humidity and shade to survive dry days. They hide in leaf litter, climb low branches waiting for hosts, and quest in protected spots. Japanese barberry delivers all of that in one dense package.

The shrub's arching branches pile up leaves underneath, building deep litter layers that ticks love. That canopy keeps the ground cooler and more moist than open areas around it. White-footed mice—the main Lyme bacteria carriers—nest safely inside the thorny thickets, infecting more ticks that drop off. On average barberry patches can host several times more ticks than nearby native shrub areas.

Identifying Japanese Barberry

Japanese barberry gets to 3-6 feet (1-2 m) tall, with branches that arch out and pile into those dense, rounded clumps—once you spot one, they jump out everywhere. The leaves are small and spoon-shaped, lining up alternately along the stems instead of opposite like on many shrubs. Right under each leaf sits a single sharp thorn that snags clothes or skin every single time.

Spring brings little clusters of tiny yellow flowers hanging underneath the branches. Then come the bright red berries that stick around through winter—birds grab them and scatter seeds all over. Leaves shift to orange-red in fall before they drop. Once it digs in, it shoves natives aside quickly, building thorny messes along roadsides, fences, and wooded edges.

Removing Japanese Barberry Safely

Removing invasive plants is important for the health of your local ecosystem and, in the case of ticks, human health. Small plants come out easiest after rain—grab low at the base wearing thick gloves and pull straight up. Roots usually release if soil stays loose. Larger shrubs fight back hard, resprouting from any root pieces left behind.

Cut the top growth first to make handling easier, then dig wide around the base to expose the root ball. A Fiskars mattock like this from Amazon or a digging bar helps pry stubborn roots free.

Heavy-duty thorn-proof gloves will save your hands from serious scratches during the job. Bag everything—stems, berries, roots—and dispose off-site. These abrasion- and puncture-resistant work gloves from Amazon will keep you safe during shrub removal.

For big stands, painting cut stumps with concentrated triclopyr like this from Amazon right away stops regrowth better than cutting alone. Please follow all safety instructions on the packaging when using chemical applications.

Native Alternatives to Barberry

Native shrubs step in for the same roles without building those thick, tick-loving hideouts. They handle rough spots, throw in color or berries, and actually help local wildlife instead of giving pests a home. Try some of these barberry substitutes in your yard.

• Inkberry Holly. Inkberry (Ilex glabra) keeps its leaves year-round and hits 3-6 feet (1-2 m) tall, matching barberry size-wise. It takes shade fine, wet or dry soil, and barely needs attention once settled. Deer mostly ignore it.
• Winterberry Holly. Winterberry (Ilex verticillata) loses leaves but loads up with bright red berries that hang on all winter. It deals with soggy spots well and grows to about the same height. Birds go for the fruit without causing the spread problems.
• Northern Bayberry. Northern bayberry (Morella pensylvanica) has those aromatic leaves and waxy gray berries people use for candles. It shrugs off poor soil, salt, and drought, staying 5-8 feet (1.5-2.5 m) tall with a nice natural mound. Reliable native inkberry shrubs get going fast and handle the same jobs without the invasiveness or extra tick worries.

Why Removal Actually Matters

Lyme disease keeps showing up more where Japanese barberry has taken over. A single shrub probably won't move the needle much, but when whole neighborhoods are full of it, people run into ticks way more often. Pulling it out really disrupts that pattern.

Getting rid of barberry won't kill off every tick, but it hits their best hiding spots hard. Pair that with keeping grass short and clearing leaf litter regularly, and the drop in ticks happens quickly. The plant doesn't do anything useful for ecosystems anyway—ditching it boosts biodiversity, lowers tick risk, and makes room for natives that fit right in.

It’s important to think carefully about every plant and shrub you bring into your garden, particularly if you care about local wildlife and regional ecosystems. Many people plant invasive shrubs because they look nice or require little maintenance. The problem is that invasive shrubs can spread outside of your yard and cause harm to your local ecosystem and to native wildlife like butterflies and bees.

Here, we take a closer look at some of the most common invasive bushes that find their way into gardens – and introduce you to unique native shrubs that are non-invasive, equally lovely, and reliable as planting alternatives.

When is a Shrub Invasive?

Before we identify invasive plants you need to think twice about, it helps to understand what we mean when we talk about these types of shrubs. A plant species is considered invasive if it is both non-native to an area and causes harm to that area. Often the harm is related to the native ecosystem – for instance, an invasive species may crowd out native species or make it harder for that native species to sustain or survive. The harm can also be economical or to human health.

One of the major ways that invasive species cause harm is by spreading aggressively. Non-native plants that don’t spread readily and don’t cause harm usually are not listed as invasive to native plant environments.

Why It Is Important To Find Native Alternatives

It’s always best for the environment and your local ecosystem to plant native species. Even if you are after the finest flowering bushes, it’s important to avoid using non-native plants that are listed as invasive. Alternative native species are much better and prevent much of the harm caused by invasives, which:

• Outcompete native plants
• Create monocultures instead of diverse habitats
• Reduce appropriate habitat and resources for wildlife
• Spread outside of yards and harm other areas
• Are difficult to remove and control

Awareness is essential when avoiding invasives, especially if you are keen on gardening with native plant alternatives. There are plenty of knockout native flowers you can grow in your backyards, and the same as true of shrubs and bushes. Check with your local extension office or your state’s government agency that oversees decisions about invasive plants to find out what plants are invasive in your area.

The popularity of several invasive shrubs can make it more difficult to landscape responsibly. These are some examples of bushes you might be tempted to use but should avoid – along with excellent non-invasive bushes that make good native alternatives for your gardens.

1. Burning Bush

Burning bush (Euonymus alatus) has a distinctive bright red fall foliage that makes it popular in gardens. Unfortunately, burning bush is non-native and invasive. It grows readily and aggressively in a variety of conditions, outcompeting many native shrubs. Birds eat the berries and spread burning bush to other areas.

Try this instead: Instead of burning bush, try Fothergilla major or F. gardenia. These two southeast native species of fothergilla have excellent fall color and fragrant spring flowers. They are hardy as far north as zone 5.

You could also try black chokecherry (Aronia melanocarpa), native to most of the eastern US. This has good fall color and hardness up to zone 4.

2. Japanese Barberry

Japanese barberry (Berberis thunbergii) is popular for its low-maintenance needs, compact form and pretty purplish foliage. However, it spreads very aggressively and is now found in many natural areas, crowding out several native species.

Try this instead: Common ninebark (Physocarpus opulifolius) is a good alternative with a similar compact size. Look for cultivars with purple foliage. It is native to most of the central and eastern US and is hardy to zone 3.

3. Autumn Olive

The autumn olive or Elaeagnus umbellata (aka cherry silverberry) is a large shrub that can also be grown as a small tree. It spreads readily when wildlife eat the berries and disperse the seeds. Autumn olive was originally used in landscaping for its ability to thrive in tough conditions and its rapid growth.

Try this instead: One of the best non-invasive shrubs you can try is the highbush cranberry (Viburnum trilobum). This is a good alternative as it grows to a similar size as autumn olive and also has attractive berries. As a bonus, you can use the berries in jams or sauces. It is native across most northern states and is hardy to zone 2.

4. Bush Honeysuckles

Honeysuckles that take a shrub form are invasive. These include Amur honeysuckle (Lonicera maackii), Morrow’s honeysuckle (L. morrowii), Japanese honeysuckle (L. japonica) and Tatarian honeysuckle (L. tatarica). They spread rapidly, form dense thickets, crowd out native plants, and provide birds and other wildlife with fruits that may be edible but which are not very nutritious.

Try this instead: Summersweet clethra (Clethra alnifolia) is a native alternative with similarly fragrant summer flowers that attract pollinators. It is hardy to zone 4 and is native in most of the eastern states. If you’re willing to try a vine in place of a shrub, native vining honeysuckles have similar fragrant flowers.

5. Privet

Several species of privet (Ligustrum amurense, L. obtusifolium, L. vulgare) are invasive but they are prized for their dense growth, especially in hedge planting. Invasive ligustrums are also very easy to grow and tolerate tough conditions, which means they outcompete natives.

Try this instead: For a pretty and practical native hedge shrub, try one of several viburnum varieties. Arrowood (V. dentatum) and maple-leaved viburnum (V. acerfolium) are two examples of native viburnum species that can be pruned into an attractive dense hedge with the right spacing and growing conditions.

Frequently Asked Questions

California is lucky enough to house some 5,000 native plant species, giving it the greatest natural botanical diversity of any state. But it also has 1,500 non-native species that have become established here. More than a few of these are important invasive species of California. Nevada is also a western state with abundant native flora and some invasive non-natives too.

Non-Native Species in California

Invasive has a specific meaning when it comes to plants. It refers to plants that are normally not found in the wild in a particular region but have been introduced and naturalized there. These plants are not just passing through; they can survive and reproduce indefinitely in the new location without any human assistance.

If you cultivate non-native, naturalized plants in your garden and they remain there, they do not pose a problem. The ones that can do significant damage are those that spread away from their initial planting location and spread into wild areas or natural habitat. They are termed invasive because they “invade” and disrupt natural ecosystems.

Economic Damage of California Invasive Species

California invasive plants are a real threat to the state’s economy. Some invasive grasses of California endanger natural forage and reduce the quality of grass consumed by livestock. This can jeopardize animal health, which leads to human health issues as well.

Invasive grasses can also increase fire risks in California. Invasive aquatic weeds can impede access to water sources for livestock, impair the movement and navigation of private and commercial vessels, and block irrigation systems.

Ecological Damage of California Invasive Species

Invasive plants also endanger and damage California’s ecology in natural areas, causing dramatic changes that have a detrimental effect on both natural flora and wildlife. These plants are more adaptable than desired native species, which lets them move into a natural landscape and essentially take it over.

California invasive plants exhaust the region’s natural resources, including light, water, and nutrients. For example, the giant reed (Arundo donax) has infested the Santa Ana River in Southern California and uses 57,000 acre feet more water annually than the native vegetation used. They can also alter the fertility of the soil, promote soil erosion, and colonize mudflats crucial for the survival of shorebirds.

In addition, invasive non-native plants are detrimental to native insects, which are used to feeding on specific native plants. As the native plants are crowded out, the insect population diminishes and birds and reptiles are left without a primary source of nutrition.

The worst offenders are termed landscape transformers, since they cause substantial changes to the invaded habitat. These include saltcedar, (Tamarix ramosissima) and yellow starthistle (Centaurea solstitialis).

Invasive Species in Nevada

Of course, California does not have a monopoly on invasive plants. There are similar invasive species in Nevada that impact the landscape the same way that California invasive species do.

Non-native invasive plants are difficult to control in both California and Nevada. Their harmful impact is far reaching and they can damage the West economically and environmentally. Some of the worst offenders in Nevada include salt cedar, cheatgrass, knapweed, musk thistle, perennial pepperwood, and hoary cress. Many are threats to pastures and rangeland, out-competing native species.

Many non-native species of plants were originally introduced as beautiful ornamentals for residential and commercial landscaping throughout Central gardening states. While many species are well behaved, some escaped into natural areas. Invasive plants in Illinois and other Ohio Valley states have damaged the ecosystem by crowding out native species and reducing biodiversity.

Invasive Trees in the Ohio Valley

Invasive species of trees don't provide the same food and shelter as native species. For instance, wild Bradford pear trees (Pyrus calleryana) don't host caterpillars, which many species of birds use to feed their young. When these trees overtake an area, bird populations can decline. This loss of biodiversity continues as it affects other species up the food chain.

Here are three more trees listed as invasive species in West Virginia and other Ohio Valley states:

• Norway maple (Acer platanoides)
• Tree of heaven (Ailanthus altissima)
• Princess tree (Paulownia tomentosa)

Invasive Shrubs in the Central Garden Region

Invasive shrubs often grow faster and are more competitive than native plants. These create monocultures which block the sunlight for other species. One example is the Autumn Olive (Elaeagnus umbellata). This invasive species can grow 6 feet (2 m) in a year and quickly reach a mature height and width of 15 feet (5 m). Autumn Olives spread by producing an abundance of fruit and are difficult to eradicate once established.

There are a number of shrubs considered highly invasive plants in Tennessee and the Ohio Valley region. Here are a few to avoid:

• Amur honeysuckle (Lonicera maackii)
• Burning bush (Euonymus alatus)
• Chinese privet (Ligustrum sinense)
• Wine raspberry (Rubus phoenicolasius)
• Multiflora rose (Rosa multiflora)

Invasive Flowers in Midwest Gardens

Once planted for their beautiful blooms, some species of ornamental flowers have escaped garden borders and invaded meadows, waterways, and roadsides. As an example, Dame's Rocket (Hesperis matronalis) was introduced in the 1600s and has naturalized across many Midwest states. Easily confused with Garden Phlox (Phlox paniculata), gardeners might mistakenly believe Dame's Rocket is a native species.

In the Midwest, there are several invasive flowering species which have overtaken natural areas and can also be mistaken for native plants:

• Birdsfoot trefoil (Lotus corniculatus)
• Flowering rush (Butomus umbellatus)
• Oxeye daisy (Leucanthemum vulgare)
• Purple loosestrife (Lythrum salicaria)
• Yellow flag iris (Iris pseudacorus)

Vining Invasive Plants in Indiana and Central States

Labeled as invasive in many states, English ivy (Hedera helix) was brought to the U.S. by colonists and is a popular groundcover throughout the Midwest. Unfortunately, this vining plant is difficult to control and has readily naturalized in both open and wooded areas.

Due to the way they grow, it can be particularly difficult to prevent some types of vining plants and groundcovers from spreading into unwanted areas. Here are a few that become problematic in the Ohio Valley region:

• Chinese wisteria (Wisteria sinensis)
• Crown vetch (Coronilla varia)
• Periwinkle (Vinca minor)
• Sweet autumn clematis (Clematis terniflora)
• Wintercreeper (Euonymus fortunei)

Grasses Labeled as Midwest and Ohio Invasive Plants

Ornamental grasses add color, texture, and vertical appeal to landscaped beds, but some species are quite adaptive to the Ohio Valley climate. For example, Chinese maiden grass (Miscanthus sinensis) was introduced in the U.S. in the late 1800s and became one of the most popular types of ornamental grass. Spread by both windblown seeds and underground rhizomes, this species has naturalized in several states.

Other grass species were introduced as turf grass or pasture fodder for livestock, such as tall fescue (Schedonorus arundinaceus). Brought to the U.S. in the early 1800s, this species has spread to many areas outside of pastures and lawns. Like the following invasive species, tall fescue competes with and crowds out native plants.

• Johnson grass (Sorghum halepense)
• Lyme grass (Leymus arenarius)
• Reed canary grass (Phalaris arundinacea)

When choosing plants for home landscaping, gardeners are encouraged to substitute native species for potentially invasive ones. Native plants are better adapted to the local climate and require less care than introduced ornamental species.

An invasive plant is typically described as being non-native and either intentionally or accidentally introduced to an area. But can a native species be invasive? Native invasive species are a hot topic in ecology and climate science. There is an argument to be made that some plants that have become problematic in or near their native ranges.

Native Species vs. Invasive Species

A native species is an indigenous plant that evolved in place and without human intervention. A non-native species is one that was moved to another area either on purpose or unintentionally by human activity.

Not all non-native species are invasive. What marks a plant as invasive are these characteristics:

• Not indigenous to where it currently grows
• Introduced outside of its native range by human activity
• Causes harm to the local ecosystem or economy

For instance, garlic mustard is an invasive species settlers introduced in North America as a food and for its medicinal properties. It is harmful to the native ecosystem because it outcompetes native species and creates vast monocultures in woodland areas.

An example of an invasive plant causing economic harm is the kudzu vine, which has taken over much of the south. It has cost the economy millions of dollars in productivity in several industries. Power and forestry companies, for instance, pay millions to manage infestations of the vine.

Can a Native Plant Be Invasive?

The traits of an invasive plant seem to run counter to the definition of a native species, but there is a case to be made that some native plants that become problematic, maybe even invasive.

Ecological change is the force behind native species moving outside their usual range. The effects of the shift might be bad, good, or mixed, depending on your perspective and how much change it brings to its new habitat.

An example of a native plant moving right now is the black locust. Several states in New England consider it invasive. It is native further south and has been moving north into new territory. Does this make it invasive? What is driving the change?

When a plant moves into a new area like this, it can be a sign of environmental degradation. The plant takes advantage of a decline in other species and moves in. It can also simply be environmental change. The northward migration of black locust trees is likely a sign of climate change.

Migrating Native Species

An example of the latter that comes from the past reaches back to the last ice age. When glaciers retreated from the eastern U.S., ash, oak, and birch trees grew in the freed up space. Then, later, American chestnut arrived and outcompeted many of the earlier species. This obviously had nothing to do with human intervention. Today, these types of environmental changes seem more sinister, as the human role in warming the climate likely plays a role.

When native species move into new areas, they inevitably bring change. Whether that makes them invasive depends on several factors. It remains to be seen just how much black locust will change the existing ecosystem in New England and whether it is bad, good, or just neutral.

Is Eastern Red Cedar Invasive?

Another example is eastern red cedar. Native to the eastern half of North America, it is migrating west. This is concerning for many people as it moves into grasslands and prairies, a completely different ecosystem from forests. The remnant grasslands are what is left of a historically vast ecosystem. Many people worry about losing what remains.

The question of whether native species can be invasive doesn’t have a clear answer. Researchers are working in several areas to determine the potential changes that could occur as plants migrate into new territories and put pressure on other native species.

Invasive weeds in the Pacific Northwest reduce biodiversity resulting in the loss of native plants and animals through competition for resources thereby altering habitats. The Pacific Northwest is a large region encompassing not only invasive plants in Oregon, but also Washington and Idaho. Government agencies wage a war against invasive species in the area, but citizens can help too by recognizing Pacific Northwest invasive plants and reporting them. Read on to learn how to identify invasive species in your area.

About Invasive Plants

If you aren’t familiar with the native species for your area, it isn’t easy to distinguish between the native and non-native plant species. Once you get to know which plants are invasive, it is surprising how many plants don’t belong in the ecosystem for that region.

How do they get there? Invasive plants are brought in by people, sometimes purposefully and sometimes by accident. Invasive plant seeds may hitch a ride on ocean transported cargo or on Fido’s fur after a hike in another state's natural area. Birds bring in non-native seeds, dispersing them as they eliminate their bowels. Even the wind is guilty of dispersing non-native species.

Non-native plants aren't always invasive. Your roses, for example, are likely not native to the area but aren’t considered invasive. They aren’t hardy enough or spread rapidly enough to be considered invasive. Washington, Oregon, or Idaho invasive species are those that take root and propagate easily, wiping out native plants and habitats.

Invasive Plant Criteria

For a plant to be considered invasive it must reproduce and spread seeds easily and rapidly. Invasive plants have few, if any, natural predators and thrive in areas where other plants find it difficult to take hold.

Invasive plants are also notoriously difficult to kill. These plants are difficult to eradicate since they use all their survival skills to live. Often invasive plants survive fire, chemical controls, and even digging or chopping up of the plant, often regrowing from a single root fragment left behind.

Pacific Northwest Invasive Plant Species

In Idaho alone, the state has listed 71 weed species and 4 genera as noxious. Of these 54 species are terrestrial. Cytisus, Genista, Spartium, and Chameacytsus are the four genera listed as noxious by the state.

Leafy spurge, rush skeleton weed, spotted knapweed, Eurasian watermilfoil, Canada thistle, oxeye daisy, toadflax, houndstongue, and orange hawkweed are all noxious weeds that reduce forage for livestock and wildlife rendering them a place on the invasive weed list of Idaho.

Many of these weeds have crossed over into Washington state and are also listed as noxious. Such is the case with many Oregon invasive plants such as butterfly bush, spurge laurel, English holly, English laurel, Himalayan blackberry, English and Irish ivy, garlic mustard, poison hemlock, Italian arum, pokeweed, and lesser Celandine.

Noxious plants listed for Washington state are likely to be found in Idaho and Oregon. To find out if a plant is listed as invasive in your state, contact your local extension office or Noxious Weed Control for your county. The Pacific Northwest Invasive Plant Council also has a comprehensive listing of non-indigenous plants affecting the region. Report sightings of invasive weeds to your state’s invasive species council.

An invasive species is a non-native plant (or animal) that causes economic damage or harm to the local ecosystem and native species. Invasive plant control methods require a lot of manpower and can be expensive. Everyone can do their part to slow or stop the spread of these damaging plants. 

How Do Invasive Species Spread? 

Most invasive species spread into new areas accidentally, but many were intentionally brought from other countries. Some species spread from one area to another and are considered invasive in the new location. 

Both invasive plants and animals come into new areas in the ballast water on ships, in firewood and shipping pallets, and in the form of plants for sale in nurseries. Many invasive plants are considered problems because, once in the environment, they spread rapidly, crowding out native species. 

For example, in Michigan wetlands, purple loosestrife is a problematic invasive plant. It spreads rapidly by producing and dispersing a lot of seeds and through roots that easily separate to grow new plants. A native wetlands species, cardinal flower has a hard time competing because it has smaller seeds and a shorter life cycle. 

Preventing Invasive Species Spread

Killing invasive plants is a big job. As in human health, prevention is the best medicine. Home gardeners can do several things to help stop the spread and avoid the need for extensive invasive plant removal later: 

• Know your plants. Knowledge is power. Find out what plants are invasive and native in your area. Your local extension office can give you that information. When you buy new plants from nurseries, only choose native species or non-invasive non-natives. 
• Clean your gear. If you go hiking, clean off your shoes before leaving the area. They spread seeds. Fishing gear can also carry hitchhiking aquatic plants, so wipe it down before you leave the lake. Even your car and tires can bring invasive species to new areas.
• Plant natives in disturbed areas. Any area of your property that is disturbed by tree removal or construction is a prime target for invasives. Re-populate those areas quickly with native species to help them take root. 
• Act fast. If you do find invasives in your garden or on your property, remove them quickly. They spread rapidly and become very difficult to eliminate later. Removal methods vary depending on the species—pulling, suffocation, mowing, chemical control—so talk to your extension office about the best way to get rid of them. 
• Volunteer. In many states, the department responsible for natural resources looks for volunteers to help control invasive species on public lands. Join a volunteer team to remove plants and slow their spread. 

According to the Invasive Plant Atlas of the United States, invasive plants are those that “have been introduced by humans, either purposely or by accident, and have become serious environmental pests.” How to spot invasive plants? Unfortunately, there is no simple way of identifying invasive plants, and no common feature that makes them easy to spot, but the following information should help.

How to Tell if a Species is Invasive

Keep in mind that invasive plants aren’t always ugly. In fact, many were transported because of their beauty, or because they were effective, fast-growing groundcovers. Invasive species identification is further complicated because many plants are invasive in certain areas but perfectly well-behaved in others.

For example, English ivy is beloved in many parts of the U.S., but these fast-growing vines have created serious problems in the Pacific Northwest and eastern coastal states, where attempts at control have cost taxpayers millions of dollars.

Resources for Identifying Invasive Plants

The best way to recognize common invasive species is to do your homework. If you aren’t sure about identifying invasive species, take a picture and ask experts at your local cooperative extension office to help you identify the plant.

You can also find experts at places such as Soil and Water Conservation, or Departments of Wildlife, Forestry, or Agriculture. Most counties have weed control offices, especially in agricultural areas.

The Internet provides an abundance of information on specific invasive species identification. You can also search for resources in your particular area. Here are a few of the most reliable sources:

• Invasive Plant Atlas of the United States
• U.S. Department of Agriculture
• Center for Invasive Species and Ecosystem Health
• U.S. Forest Service
• EU Commission: Environment (in Europe)

Most Common Invasive Species to Watch For

The following listed plants are invasive pests in many areas of the United States:

• Purple loosestrife (Lythrum salicaria)
• Japanese spirea (Spiraea japonica)
• English ivy (Hedera helix)
• Japanese honeysuckle (Lonicera japonica)
• Kudzu (Pueraria montana var. lobata)
• Chinese wisteria (Wisteria sinensis)
• Japanese barberry (Berberis thunbergii)
• Winter creeper (Euonymus fortunei)
• Chinese privet (Ligustrum sinense)
• Tansy (Tanacetum vulgare)
• Japanese knotweed (Fallopia japonica)
• Norway maple (Acer platanoides)

Is butterfly bush an invasive species? The answer is an unqualified yes, but some gardeners either are not aware of this or else plant it anyway for its ornamental attributes. Read on for more information about controlling invasive butterfly bushes as well as information about non-invasive butterfly bushes.

Is Butterfly Bush an Invasive Species?

There are pros and cons to growing butterfly bushes in the landscape.

• The pros: butterflies love the long panicles of bright flowers on the butterfly bush and the shrubs are very easy to grow.
• The cons: butterfly bush readily escapes cultivation and invades natural areas, crowding out native plants; what’s more, butterfly bush control is time-consuming and perhaps impossible in some cases.

An invasive species is usually an exotic plant introduced from another country as an ornamental. Invasive plants spread quickly in nature, invading wild regions and taking over growing space from native plants. Usually, these are easy-maintenance plants that spread rapidly by generous seed production, suckering, or cuttings that root readily. The butterfly bush is such a plant, introduced from Asia for its beautiful flowers. Do butterfly bushes spread? Yes, they do. The wild species Buddleia davidii spreads rapidly, invading riverbanks, reforested areas, and open fields. It forms thick, shrubby thickets that preclude the development of other native species such as willow. Butterfly bush is considered invasive in many states, as well as England and New Zealand. Some states, like Oregon, have even banned sales of the plant.

Controlling Invasive Butterfly Bushes

Butterfly bush control is very difficult. Although some gardeners argue that the shrub should be planted for the butterflies, anyone who has seen clogged rivers and overgrown fields of Buddleia realizes that controlling invasive butterfly bushes must be a top priority. Scientists and conservationists say that one potential way to begin controlling invasive butterfly bushes in your garden is to deadhead the flowers, one by one, before they release seeds. However, since these shrubs produce many, many blooms, this might prove a full-time job for a gardener. Growers are coming to our rescue, however. They have developed sterile butterfly bushes that are currently available in commerce. Even the state of Oregon has amended its ban to allow the sterile, non-invasive species to be sold. Look for the trademarked series Buddleia Lo & Behold and Buddleia Flutterby Grande.

If you’re an environmentally conscious gardener, you’ve no doubt come across confusing terms such as “invasive species,” “introduced species,” “exotic plants,” and “noxious weeds,” among others. Learning the meanings of these unfamiliar concepts will guide you in your planning and planting, and help you create an environment that is not only beautiful, but beneficial for the environment inside and outside your garden. So what is the difference between introduced, invasive, noxious, and nuisance plants? Keep reading to learn more.

What Does Invasive Species Mean?

So what does “invasive species” mean, and why are invasive plants bad? The United States Department of Agriculture (USDA) defines invasive species as “a species that is non-native or alien to the ecosystem – the introduction of the species causes or is likely to cause harm to human health, or to the economy or environment.” The term “invasive species” refers not only to plants, but to living beings such as animals, birds, insects, fungus, or bacteria. Invasive species are bad because they displace native species and alter entire ecosystems. The damage created by invasive species is mounting, and attempts of control have cost many millions of dollars. Kudzu, an invasive plant that has taken over the American South, is a good example. Similarly, English ivy is an attractive, but invasive, plant that causes incredible environmental damage in the Pacific Northwest.

What are Introduced Species?

The term “introduced species” is similar to “invasive species,” although not all introduced species become invasive or harmful – some may even be beneficial. Confusing enough? The difference, however, is that introduced species occur as a result of human activity, which may be accidental or on purpose. There are many ways species are introduced into the environment, but one of the most common is by ship. For example, insects or small animals are tucked into shipping pallets, rodents stow away in ship’s cellars and various forms of aquatic life are picked up in ballast water, which is then dumped in a new environment. Even cruise passengers or other unsuspecting world travelers can transport small organisms on their clothing or shoes. Many species were innocently introduced to America by settlers who brought favorite plants from their homeland. Some species were introduced for monetary purposes, such as the nutria – a South American species valued for its fur, or various types of fish introduced into fisheries.

Exotic vs. Invasive Species

So now that you have a basic understanding of invasive and introduced species, the next thing to consider is exotic vs. invasive species. What is an exotic species, and what’s the difference? “Exotic” is a tricky term because it is often used interchangeably with “invasive.” The USDA defines an exotic plant as “not native to the continent on which is now found.” For example, plants that are native to Europe are exotic in North America, and plants native to North America are exotic in Japan. Exotic plants may or may not be invasive, although some may become invasive in the future. Of course, chickens, tomatoes, honeybees, and wheat are all introduced, exotic species, but it’s difficult to imagine any of them as “invasive,” although they are technically “exotic”!

Nuisance Plant Info

The USDA defines noxious weed plants as “those that can directly or indirectly cause problems for agriculture, natural resources, wildlife, recreation, navigation, public health or the environment.” Also known as nuisance plants, noxious weeds can be invasive or introduced, but they can also be native or non-invasive. Basically, noxious weeds are simply pesky plants that grow where they aren’t wanted.

Invasive plants are problematic, non-native species that can cause harm in several ways. They tend to spread aggressively, which can be an issue on a large scale and also in the home garden.

Gardeners might be surprised to learn that some common herbs are actually invasive species. If you grow or plan to grow these herbs, consider the risks and either choose other herbs or take steps to minimize their spread.

Let's dig in to explore what herbs are invasive and what to do so they don't take over.

The Problem of Invasive Plants

To be designated as invasive, a plant must have two important characteristics:

1. Invasive plants are not native to the region in which they are invasive. They were introduced to the area, either on purpose or unintentionally.
2. Invasive plants cause economic or environmental harm, or even harm to human health.

An invasive plant often causes harm by outcompeting other plant species. They tend to grow more vigorously and spread more widely, crowding out either native plants or agricultural plants. There are several characteristics an invasive species might have that make it so successful:

• Produce and disperse a lot of seeds
• Long, spreading, and aggressive root systems
• Grow readily from disturbed soil
• Produce chemicals that inhibit the growth of other plants

Invasive plants can be a big economic issue in agriculture. Elsewhere, they cause environmental harm by overrunning and creating areas with fewer native species. In the home garden, invasive plants can take over your beds. They can also spread out of your garden and into nearby natural areas, causing harm.

What Herbs Are Invasive?

Among the many invasive plants that can be an issue in the home garden are several invasive herbs.

1. Mint

Mint is one of the most aggressive spreaders you’ll find in a garden, not just in an herb garden. Although it’s a delightful herb to grow with a nice fragrance and culinary uses, it will absolutely take over beds and your entire yard if you let it.

Mint spreads by both its persistent underground roots and its above-ground runners. Anywhere a runner touches the soil, it will put down literal roots and keep spreading. Even a small amount of root left in the soil can grow into a big, new plant that keeps spreading. Only grow mint in containers.

2. Lemon Balm

Another pleasant herb that you might not want in your beds is lemon balm. It smells delicious, and pollinators love the flowers, but it will crop up all over your garden if you’re not careful. It spreads by seeds that disperse readily.

You can avoid the invasive issue by growing lemon balm indoors. It thrives in sunny windows. If growing outdoors, remove the flowers before they have a chance to develop seeds.

3. Oregano

Oregano is popular for its many uses in the kitchen, especially in Italian dishes and on pizza. Unfortunately, it can grow quite aggressively and cause a problem in garden beds. This is a tough plant that can spread in low mats during good weather and in rich soil, but also during dry, even drought conditions.

Oregano is spread by underground rhizomes and seeds. You can grow oregano plants indoors or in containers, but take care to remove flowers before they can set seeds. If you grow it in beds, be prepared to aggressively cut back plants several times during the growing season.

4. Comfrey

Comfrey is a traditional medicinal herb with pretty purple flowers that attract pollinators to the garden. Unfortunately, it’s also an aggressive spreader that can be very difficult to eradicate once it takes root. It spreads by roots, and even a small piece left in the soil can become a new plant.

Comfrey also spreads by seed, so those pretty flowers will turn on you if you leave them in place. You can grow comfrey in a container, but also be sure to remove flowers before seeds develop. We like the garden snips from Modern Sprout, available on Amazon, for deadheading flowers and herbs.

5. Pennyroyal

Pennyroyal is an herb with traditional medicinal uses. It also has a strong smell that can be used to repel pests. Pennyroyal is easy to grow, which can make it tempting to use in any wet areas where other plants struggle, but be prepared to face an invasion.

Pennyroyal grows well in wet areas and spreads by runners, like mint. It creeps readily over soggy areas, like stream and pond banks and marshy areas, creating low, dense mats. If you have pennyroyal, you’ll need to spend some time every year pulling it out of areas where you don’t want it. A Fiskars ergo cultivator, available from Amazon, is great for pulling dense mats of roots and weeds out of the ground.

6. Fennel

Fennel is both a tasty vegetable and herb, but it can also be invasive. It spreads very readily from seeds, especially in mild climates and in soils that have been disturbed. This has made it a real issue in some areas, including California. It also cross-pollinates with dill and results in strangely flavored plants.

If you don’t live in an area where fennel has become invasive, you can probably grow it safely, but take care. If you let the seeds disperse, it might just take root in and then overtake your garden. Deadhead the flowers before they have a chance to develop seeds.

How to Grow Herbs Without Them Taking Over

Luckily, you don't have to completely write off these invasive herbs. Control invasive herbs by deadheading and cutting them back before they set seed or spread. You can contain them to reduce their aggressive impact on the rest of your garden.

Container Gardening

Container gardening for invasive herbs can be done one of two ways. You can plant individual herbs into individual containers and leave them above ground, or you can recess the containers into the ground. If you decide to recess your containers, it's best to use simple undecorated containers made of plastic, such as the ones you purchase plants and seedlings in. Don't recess the invasive herbs in the same container that you purchased them in though. Use a container that is a size or two larger to ensure that your plants have room to grow and mature.

To recess a container for invasive herbs, dig a hole large enough for the entire pot to fit into, leaving the lip (top portion) of the container sticking out approximately 1 or 2 inches (2.5-5 cm.). Be sure that your container has drainage holes. Fill the bottom of the container with gravel or Styrofoam pellets to allow proper drainage of the pot. Add potting soil and then plant your herb into the buried container. Your container-gardened herbs will need to be dug up every year or two and divided to keep them from becoming root bound.

Compartment Gardening

Compartment gardening can be done by placing borders around your invasive herbs that are planted directly into the garden. You can create separate compartments for your invasive herbs using metal or plastic edging around them. The edging must be buried fairly deeply, to keep your herbs from spreading.

Container Herb Garden Essentials

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