6 Slow-Growing Flowers You Need to Start Early – Or They Won’t Bloom This Year (They’re Totally Worth the Wait)
Some of the most breathtaking performers refuse to be rushed. From the rose-like lisianthus to the honey-scented heliotrope, give these 6 slow-growing flowers a head start now to ensure your garden is draped in summer color
They say timing is everything – and this can certainly be true when it comes to gardening. If you miscalculate the lead time for certain slow growing plants for flowers, they might not even be budding by the time the first killing frosts of fall arrive. So you’ll be left with lingering "what ifs" instead of summer beds and borders filled with gorgeous blooms. In these cases, it pays to play the long game.
The shorter your growing season, the more likely it is that sowing seeds in the ground in spring will not get you where you want to go. And the more vital it is to ignore the calendar on the wall and look at the one in your seed packets. Sowing seeds directly into the soil in May is fine for zinnias, but for the garden’s "slow-burn" divas, it’s too late. Certain flowering beauties need time to make their entrance, and they don’t like to be rushed!
By starting seeds indoors now for slow growing flowers, you are buying time. You’re giving these ornamentals a protected, climate-controlled environment to navigate their awkward teenage phase, so that when the soil warms, they are established and ready to make their big appearance. These slow-growing superstars may take their time, but they will stun you with their beauty when they do arrive.
Grab Your Sowing Essentials
Make sure you’re equipped to care for these slow-movers with kit that maintains consistency and quality as they grow.
Great for developing root systems, as you can plant the whole pot out and avoid disturbing sensitive roots. These pots are deeper than other eco pots.
Excellent eco-conscious formula for starting flowers. Includes worm casts, mycorrhizae and pine bark fines.
Covered multi-tier plant stand with easy-to-assemble grow light system. Give slow starters a rich energy rich cocktail and ensure they have the best start.
6 Slow-Growers with Staying Power
These slow flowers have been selected because they provide textures, scents, and forms that fast flowers can't replicate. Whether you have a tiny urban balcony or a sprawling cottage garden, these selections hit different niches, from the vertical drama of the clambering vine to the shade-brightening glow of a begonia. That said, they all deliver beautiful summer blooms that are well worth the wait.
Early seed starting is an exercise in micro-management. Because these plants sit in their pots for months rather than weeks, they face unique challenges like damping off (a fungal disease) or becoming root-bound. Furthermore, you’ll need to adapt your methods based on your hardiness zone and growing region. But starting early means you have that little pocket of insurance – and time to intervene if needs be.
When starting slow growers, use a sterile, soilless seed starting mix. One of our team’s go-to recommendations for healthy germination and root growth is Burpee’s Organic Coconut Coir Seed Starting Mix from Amazon, which comes in handy bricks that expand with water. Since these plants will be indoors for a long while, cheap garden soil can introduce gnats and pathogens that will thrive and take over long before the plants ever see the sun. So go for the good stuff, and start your engines.
1. Lisianthus
Remember the Shakespeare quote about a rose by any other name smelling just as sweet? That describes lisianthus (Eustoma grandiflorum), a tender perennial with elegant flowers that look just like vibrant roses. Delicate rose-like flowers (in shades ranging from white to purple and red) grow on upright stems. You can buy a ‘Romantic Mix’ Lisianthus Seed Pack from Amazon, for pinks, whites, lilacs, and even pale greens. They are happy in USDA zones 8-10.
Alas, these cottage garden classics can take up to 5 months from seed germination to blossom. By starting lisianthus seeds indoors, you can be sure to be basking in their gorgeous blooms before mid-summer. Check the last expected spring frost date and start lisianthus seeds indoors 10-12 weeks before that date.
Keep them in a warm spot with lots of light. They should germinate in 10-20 days, but require at least 3 months of growth before transplant. Seeds are microscopic, so don’t cover them with soil, as they need light to wake up. Also, take care when watering, as a can may disperse seeds. Instead, use a mister to soak the potting mix in a gentle way. Buy a Lianshi Brass Plant Mister from Amazon for gentle hydration.
2. Heliotrope
This slow burner is called the cherry pie plant, due to its vanilla-cherry fragrance. Heliotrope adds a rare, deep purple hue and a vintage feel to containers. There are hundreds of species, most with clusters of tiny flowers that follow the sun. That explains their genus name – helios meaning ‘sun’ in Greek, tropos meaning ‘to turn’.
I’m a big fan of the ‘Princess Marina’ cultivar (H. arborescens), which stays compact and offers lovely pinky purple blooms. But if you’re in the mood for a lush, sultry violet, you can buy EpicGlobalSeeds Heliotrope ‘Marine’ Seeds from Etsy.
Sow indoors 10-12 weeks before the last frost in spring. Seeds need a warm area to germinate. Keep the temperature between 70-75°F (21-24°C). Use a seedling heat mat, like the Vivosun Heat Mat from Amazon, to maintain that steady temp. Expect to see flowers 12-14 weeks after planting. These slow bloomers are happy in zones 9-11.
3. Tuberous Begonias
While many types of begonias (Begonia spp.) are grown for their foliage, tuberous begonias stand out for their enormous, jewel-toned flowers. They bring vibrant color to shaded porches and patios, and, with their trailing habit they work well in hanging baskets. Buy Park Seed Non Stop Joy ‘Peaches & Dreams’ Begonia Seeds from Amazon for golds, rose picotees and apricots. They are happy in zones 9-11.
Growing tuberous begonias isn’t hard, but you’ll want to get them blooming early, so you have more time to appreciate them. To grow these begonias from seed, start them indoors 14-16 weeks before the last frost date. Keep the temperature around 75°F (24°C), as these slow flowering plants are serious heat lovers.
If your indoor starting area is drafty, use a seedling heat mat and a humidity dome. Buy Jiffy Seed Starting Tray Kits from Amazon, which come with their own humidity domes. Press their tiny seeds into the seed starting medium and keep them moist until they germinate, usually 15-21 days later. Flowers appear within 12-14 weeks.
4. Snapdragons
The brilliant hues of snapdragons (Antirrhinum majus) catch everyone’s attention. There are many varieties to choose from, which work well in sunny borders, but you can also cultivate sensational snaps as part of an imaginative container garden. You can buy some Stunning Snapdragon Seeds from Burpee, such as ruffled ‘Madame Butterfly’ and bee-friendly ‘Opus Appleblossom’ varieties.
Though admittedly gorgeous, snapdragons are slow-growing plants. Their seeds should be started indoors 6-12 weeks before the last spring frost date. You’ll need to keep them warm. Snapdragons are major light-seekers, so cater for seedlings in low light with a grow light such as the SoLigt Full Spectrum Grow Light from Amazon.
Expect germination in 1-2 weeks, but count on several months before flowering. These are cool-season growers, so they can go out earlier than the others on this list. To get a bushier plant with more flower spikes, pinch the tips once seedlings reach 3-4 inches (8-10 cm) tall. It feels wrong, but it doubles bloom count. Snaps are happy in USDA zones 7-11.
5. Petunias
These trumpet-shaped flowers seem to bloom forever, and come in almost every color of the rainbow. Some petunias (Petunia spp.) are fragrant, some are mounding while others are cascading. All make spectacular container plants and flowers for hanging baskets in zones 10-11. There are some unique Petunia Seed Options at Etsy, including butterfly ‘Night Sky’ and ‘Crazytunia Black Mamba’ varieties.
To grow from seed indoors, get them started 10-12 weeks before your area’s last spring frost date. Keep the seeds in a warm place, and you’ll see them germinate in 7-10 days. Petunias usually start to bloom 8-10 weeks after germination. Once they get going in your stylish planter of choice, they will produce flowers all season long.
Bear in mind petunias are heavy feeders. They will likely exhaust the nutrients in the seed mix before they come out. Start a half-strength liquid fertilizer regimen once they have 3 sets of true leaves. Use an organic multivitamin like GS Plant Foods Liquid Fish & Kelp Fertilizer from Amazon.
6. Cup and Saucer Vine
It’s got an unusual name, but this fast-growing climbing vine is a beautiful plant, with oblong leaves and bell-shaped flowers. The blossoms of Cobaea scandens are pale green when they first appear, but they turn a deep purple as they mature and have a sweet fragrance. Although the bright green foliage seems lightweight, the vine grows rapidly up to 30 feet (10 m). It thrives in zones 9-11.
Start seeds indoors 6-8 weeks before the last expected spring frost. Seeds are flat and large. Plant them on their edge rather than flat. This prevents the seed from rotting. Sowing in eco pots means you can plant outside without lifting out of cells. You can buy Daniel’s Plants 4inch Naked Starter Pots from Amazon.
The plant will take 14-28 days to germinate. It takes longer for the cup and saucer vine to bloom, up to 12 weeks from germination to flower, but the foliage grows quickly and spreads out to create a green screen. You can buy Purple Cup and Saucer Vine Seeds from Burpee.
How to Nudge Nature Along
If you feel you’ve started a week or two late, don’t panic. There are ways to nudge things along. The biggest bottleneck for indoor seedlings is light. A sunny windowsill in February rarely provides enough lumens for a slow grower, so they become leggy. Using a full-spectrum LED grow light, like the Glowrium Height Adjustable Grow Light from Amazon, can shave two weeks off the development time of a Lisianthus.
Another growth hack is the use of humidity domes. By keeping the air moist around the emerging leaves, the plant doesn't have to work as hard, allowing it to put all its energy into root development. For smart watering, once your slow-growing flowers have sprouted, shift to bottom-watering. Place your seed tray in an inch of water for 15 minutes and let the soil wick the moisture up. This keeps the delicate stems dry and encourages the roots to grow deep and strong in search of water.
Finally, once the plants have established roots, a phosphorus-heavy bloom booster fertilizer like Scotts Super Bloom from Amazon can signal to the plant that it's time to stop making leaves and start making buds.
Don’t Forget for a Summer of Color
Once you've got your slow-starters under way, keep these care essentials close to give those flowers a helping hand…
This is a reliable organic multivitamin for your petunias once they hit the 6-week mark. It's the ideal way to support plant growth & flower power. Add every few weeks during the growing season.
Trust me, when you're waiting months for blooms, you will forget which variety is which! So why not get something pretty?
Not only does it provide the cloud of moisture small seeds crave, but it looks beautiful sitting on a windowsill while you wait for summer blooms.
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