Growing sweet alyssum from seed is a lot cheaper than purchasing flats of seedlings each year—it’s one of those plants where you don’t really buy just one! I love the versatility of this hardy annual—lobularia maritima—a member of the cabbage family that is the perfect filler and spiller for container arrangements. Mature plants produce a profusion of delicate blooms that cascade over the side of a pot. In the garden, it can be planted as a beautiful annual groundcover or edging plant. Sweet alyssum plants grow so densely they help keep the weeds down!
But sweet alyssum is no mere filler. Its dozens of tiny white or purple blooms will attract important beneficial insects to the garden.
In her new book, Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden, Jessica devotes a page to the benefits of growing sweet alyssum. The plants can be used as natural pest control in the vegetable garden to manage aphid infestations. Parasitic wasps and syrphid flies consider alyssum pollen and nectar to be a tasty food source. The larvae of the latter feed on aphids, while the former will lay one tiny egg in an aphid.
Whether you give them a head start indoors or head out to the garden with a seed packet come spring, here are some tips for growing sweet alyssum from seed.
Growing sweet alyssum from seed indoors
You can’t really go wrong when choosing sweet alyssum seeds. There are a few varieties to choose from, but they all look pretty much the same except their colour. Many have white blooms, some are mauve or violet hues, and I’ve even seen peach-coloured alyssum flowers.
If you’re starting alyssum seeds indoors, count back about six to eight weeks from your last frost-free date. Grab a seed tray with cell inserts filled with a seed-starting mix. I use a little tray with a humidity dome cover, which I’ll remove after the seeds have germinated. With alyssum, it takes about one to two weeks. Or, consider using a heat mat, which can help with germination if your setup is in a cold room.
The seeds are so tiny, you don’t need to cover them with soil. Simply scatter them in each cell and use a plant mister when you water so the seeds don’t wash away. Place the tray under your grow lights or in a very bright, warm south-facing window. Once seedlings start to appear, gently thin so seedlings are about six inches (15 cm) apart.
Planting alyssum seedlings in the garden
I add sweet alyssum to the edges of my raised beds, in my ornamental containers, and any leftover seedlings usually fill any other holes I have in the garden among my perennials and any annuals I may have planted. Alyssum is easy to grow and is often still in bloom, well through the fall months—plants are usually among the last to remain in bloom!
When you’re ready to plant seedlings in the garden, choose sunny, well-draining spot (a bit of partial shade is okay, too) and amend the area with compost. Even though they’re pretty small at this point, you’ll want to give your alyssum seedlings lots of room. Plant them about eight to 12 inches (20 to 30 cm) apart.
Add sweet alyssum to your raised beds
I always plant a healthy percentage of flowers in my raised beds, not only for summer bouquets, but also to attract pollinators and beneficial insects. And to add to their visual interest! Alyssum isn’t going to make it into your seasonal vases, but it’s a gorgeous addition to the garden that can help with the aforementioned natural pest management. In the summer, plants are always abuzz.
Because it’s low growing, you don’t have to worry about sweet alyssum shading anything out (something that’s happened to me when I haven’t read the seed packet on taller blooming annuals). Tuck plants in the corners or between plants, or right at the edge of your raised bed, where it can cascade over the side.
Growing sweet alyssum from seed by sowing directly in the garden or in pots
If your seed-starting setup only has room for veggies, that’s okay, you can direct-sow alyssum seeds right in your garden, once temperatures have warmed up a little in the spring. Plant alyssum seeds after all threats of heavy frosts have passed. A little light frost is okay. You don’t really have to make a hole, simply loosen up the soil and scatter the seeds. Keep the soil moist until seeds germinate (usually in about eight to 10 days). A hose or watering can may cause seeds to wash away (though you can’t prevent a good spring downpour). But you may want to lightly mist the soil until a seedling appears. Thin your plants so they’re about six inches (15 cm apart) because they will spread!
Don’t be alarmed if plants go dormant in the heat of summer. They’ll perk back up again when temperatures cool closer to fall.
If you are planting up a spring arrangement, add alyssum seeds among the spring bulbs and/or blooms. By the time you’re ready to remove spent plants for your summer arrangement, the alyssum will have started to fill in.
In my first home, a dependable carpet of alyssum would appear each spring if I didn’t inadvertently rip out the seedlings. Not clearing away the plants meant they would reseed for me. So leave your plants in the ground this fall and see if you are rewarded with plants next spring!
More flowers to start from seed
- Growing angel trumpet from seed
- Growing Bells of Ireland from seed
- Milkweeds and how to grow them from seed