Want More of Your Favorite Plants for Free? Divide These 7 Perennials in May to Double Your Blooms This Year

May is a month of incredible momentum in our backyards, but while much of the focus is often on planting new arrivals, the real secret to a lush, high-impact space lies in the plants you already own. Dividing perennials in May is a real treat both for you and your plants, providing you with a bounty of free plants to fill gaps in borders, while also acting as a vital reset button for the health and vigor of garden favorites.

Perennials are fantastic plants to invite into your garden because they just keep coming back. Unlike one-and-done annuals, which put all their energy into a single season, many perennials flower year after year because their roots do not die in the fall. Instead, the root ball keeps growing. Over time, a perennial plant root ball can get dense and congested. By digging these up and splitting them now, you help to refresh the plants, giving them a new lease of life. And the best bit is that you are creating new plants for your own garden, or to share with friends or neighbors.

But can you really divide perennials in May? You bet you can. While autumn is often cited as the traditional time for division, this month is better for many species, especially those that bloom in late summer and fall, as well as a few that flower in spring. Plants divided now have the entire growing season to rebuild and establish new roots before winter. So it’s smart to get stuck into dividing perennial plants in May for a chance to make more of your favorite perennials. Ready to fill your beds for free? Here are 7 key perennials to divide and conquer.

7 Best Perennials to Divide in May

This mid-spring window is a highly beneficial time for dividing key perennials, across a range of USDA hardiness zones (3-9). Being able to split plants in May allows the newly separated perennials to settle into the ground without the stresses of extreme temperatures. Dividing now doesn't just give you an easy way to fill empty spaces (although that is important), it also creates security at the root level. It’s also a great way to control how your plants look across a bed or border. By spacing out divisions, you can create rhythmic repetitions of color and texture that lead the eye through the garden, and can actually make a small yard feel bigger.

Before you start, check your soil health. Using a digital soil moisture and pH meter, such as the Yamron 4-in-1 Meter from Amazon, can tell you if your replanting spot is ready to receive its new guests. Ideally, you want moist, well-draining soil that has been enriched with organic matter. If your soil is compacted or depleted, this is the perfect moment to work in some high-quality amendments, such as a healthy dose of compost, and some finely shredded bark mulch, such as finely shredded bark mulch, like Back to the Roots Organic Premium Mulch, available from Walmart.

To divide perennials in May, you need a sharp garden spade, a dedicated dividing knife or a sturdy hori hori for precision cuts. You can buy the highly rated Hokuru Hori Hori Garden Knife from Amazon to cleanly slice through divisions without crushing surrounding plant tissue. Aim to keep as much of the root mass intact as possible, but don't be afraid to be firm: most perennials are much tougher than they look. It’s a good idea to divide your perennials every 3-4 years to keep them healthy.

1. Goldenrod

Goldenrod (Solidago spp.) is one of the most beautiful native perennial wildflowers you can grow, and if you’re lucky enough to have some, you can easily multiply your good fortune. These plants offer plumes of sunshine just when the rest of the garden starts to flag. Hardy in zones 2-8, these sunseekers bloom in late summer and keep those flowers into fall, adding an invaluable food source for pollinators. However, they grow quickly, so they should be divided every few years to control their spread.

Dividing goldenrod in May is easy. Dig up the entire clump, and use a sharp spade or a serrated knife to slice the root mass into 3-4 healthy sections. Each section should have several vigorous shoots and a good portion of roots. Replant your divisions in a sunny spot with well-drained soil. Add a little slow-release fertilizer in the planting hole, such as Espoma ​​Organic Flower-tone Fertilizer from Walmart. After replanting, give them a good soak and a layer of mulch to keep roots cool as they re-establish. Within a few weeks, you should see them surging upward.

2. Hosta

Hostas (Hosta spp.) are some of the flashiest perennials you can grow in shade (partial to full shade), offering bold texture and cool colors, from lime green to cool blue foliage. But after a few years, plants can start looking thin or die out at the center, and dividing your hosta plants is a great way to rejuvenate them. May is the perfect moment, ideally as the pointed leaf buds (eyes) are poking through the soil, but before leaves fully unfurl.

Simply dig up the root ball, cut into pieces, then replant each separately. As you are dividing the plant roots, toss out the central portion if it is thin or bare. You can pull smaller clumps apart by hand, or use a hori hori knife to cut through denser centers of older specimens. Relocating divisions is one of the quickest ways to brighten up a dark corner or line a shady pathway (just make sure your new spots are safe from the afternoon sun). Check the crown of the plant is level with the soil surface. They love rich, moisture-retentive soil, so don't be shy with the compost during replanting.

3. Beebalm

Beebalm (Monarda didyma) is a stunning plant with big, shaggy blossoms. It attracts all kinds of pollinators, and thrives in full sun or partial shade. This is one plant that flowers in spring and summer, yet should be divided in spring, because it spreads quickly. Dividing in May keeps the size in check and reduces overcrowding. This reduces the risk of powdery mildew and allows companion plants breathing room.

The key to division: toss out the center of the plant. Dig around the perimeter of the clump and replant the younger, more vigorous outer sections. By giving them fresh soil and more space, you improve air circulation, protecting against the powdery mildew that often plagues this species. Keep new divisions well-watered for 2 weeks. It’s also wise to add a little bio-fungicide to divisions. You can buy Arber Organic Bio-Fungicide from Walmart to help keep powdery mildew at bay.

4. Dianthus

Known affectionately as pinks, dianthus (Dianthus spp.) provides intoxicating scents in spring, and plenty of enchanting ruffles. But if you are growing carnations or pinks, you know how quickly these beauties spread. At the same time, the overcrowding of dianthus can negatively impact the quality of the plant, and you might see it clumping or looking thin at the edges. You can solve these issues by dividing every year or two. Yes, it’s a summer-flowering plant, but it divides best in spring.

Dividing in May, right as they are gearing up for their main show, is a fantastic way to refresh the foliage and double your fragrance for free. Dianthus often has a shallow root system, so a sturdy hand fork is often enough to lift the clumps. Gently pull the sections apart, ensuring each piece has a good bit of root and some healthy growth. Dianthus divisions just need excellent drainage and full sun. Add a handful of fine grit or add crushed eggshells to the planting hole. These beauties will reward you with a second flush of flowers if you deadhead through summer.

5. Asters

This is a classic fall-flowering perennial to divide in May. Let aster (Symphyotrichum spp.) plant growth determine how often to divide. If your asters are truly vigorous, divide every year. Slightly calmer plants can be divided every couple of years. If you leave an aster clump alone for too long, the stems become weak and the plant often flops over under the weight of its own blooms. By dividing every year or two, you create sturdier, self-supporting plants that thrive in full sun or part shade (zones 3-9).

Use a sharp spade to chop the clump into quarters. You can be quite aggressive, as asters are tough as nails and will bounce back with enthusiasm. When replanting, give them plenty of room (18 inches/45cm apart) to allow for air movement. Ensure they are in a spot that gets at least 6 hours of sun. You can buy Jobe’s Organics All-Purpose Fertilizer Spikes from Amazon to nourish these fast-growing bloomers.

6. Garden Phlox

Garden phlox (Phlox paniculata), with their erect, domed clusters of flowers, wake up your landscape with color and fragrance from mid-summer to fall. However, this sun-loving perennial is also a magnet for powdery mildew if it gets too crowded. Dividing in May is the best way to keep phlox healthy, while filling more of your yard with this pollinator favorite. Like beebalm, phlox gets tired in the center. Dig up the clump and use a sharp knife to take 4-inch (10cm) sections from the outer ring.

Replanting these fresh starts will result in larger flower panicles, and it’s an easy way to turn one plant into 3-4 healthy superstars. Phlox loves plenty of organic matter and consistent moisture. When replanting your divisions, choose a spot with full sun, plus some afternoon shade if you live in a very hot climate. After replanting, apply a thick layer of organic mulch, like shredded bark or leaf mold, to keep roots cool and moist, exactly what phlox needs to produce those iconic, domed flower heads.

7. Hardy Mums

Hardy garden mums (Chrysanthemum spp), aka old-fashioned mums, are perennial treasures that can return year after year in zones 4-9. However, they are short-lived if they aren't divided regularly, and May is the ideal time to make that split. Do it now, and you allow the divisions to develop a massive root system before they need to produce flowers in fall. Dig up the clump and look for new runners. These are your new plants. Simply snip them off with a bit of root attached and you’re ready to go.

Replant only the healthiest sections taken from the outside of the clump. Replant in a sunny, well-drained spot. Because mums are heavy feeders, they will appreciate a balanced liquid fertilizer every few weeks in early summer. Add a splash of seaweed fertilizer to boost mum growth. You can buy Neptune's Harvest Fish & Seaweed Fertilizer from Walmart. It’s also good to pinch off the tips of stems every few weeks until July. This forces the plant to branch out, resulting in a carpet of flowers in fall.

Shop Perennial Care in May

Ready to multiply your garden? Having the right gear makes the job faster, easier, and healthier for the plants. From precision cutting tools that protect delicate crowns to the rich soil amendments that help new babies thrive, these curated items will help you divide and conquer your borders.

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