Few annuals give back as much for as little effort as alyssum. Sow a pinch of seed on bare soil in spring, barely press it in, and within a few weeks you have a low, spreading carpet of tiny four-petaled flowers in white, lavender, pink, or purple, each one releasing a warm honey scent that drifts across the whole bed. It edges paths, spills over container rims, knits together a rock garden, and quietly pulls in the very insects that keep aphids off your vegetables. Sweet alyssum (Lobularia maritima) is one of the easiest flowers any gardener can grow, and once you understand its one quirk, the summer heat slump, you can keep it blooming from the last spring frost right through fall.
What sweet alyssum is and where it grows
Sweet alyssum is a low-growing member of the mustard family (Brassicaceae), native to the Mediterranean and the Canary Islands. It forms a rounded or sprawling mound 3 to 10 inches tall and 5 to 12 inches wide, sometimes wider, smothered in clusters of fragrant blossoms barely a quarter inch across. The fine, hairy, gray-green leaves all but disappear under the flowers at peak bloom.
Most gardeners treat it as a cool-season annual, and it is sold and grown that way across USDA Zones 3 through 8. But it is technically a short-lived perennial, and in the mild winters of Zones 9 to 11, often coastal or Mediterranean-type climates, it can overwinter and return for a second or third year. Even outside that range it has a way of seeming perennial: plants that are allowed to set seed reseed themselves so freely that fresh seedlings pop up in the same spot the following spring, creating the illusion that the original plant came back.
Bloom time runs from spring until the first hard frost, with one important interruption in the heat of midsummer that we will get to below.
Sweet alyssum is not basket-of-gold, and the difference matters
Walk into a nursery and you may find two very different plants labeled “alyssum,” and confusing them leads to disappointment. Sweet alyssum is Lobularia maritima, the soft mounding annual with white, pink, or purple flowers described throughout this guide.
Basket-of-gold is a completely separate plant: Aurinia saxatilis, also sold as gold-dust, golden tuft, or yellow alyssum. It was once classified in the genus Alyssum, which is the root of the lingering confusion, but it is a true hardy perennial, not an annual. The two differ in almost every way that affects how you use them:
- Basket-of-gold blooms in a single flush of bright yellow flowers in mid-spring, then is done; sweet alyssum blooms in white, pink, lavender, or purple over a long season.
- Basket-of-gold is a woody-based evergreen perennial that returns reliably for years in Zones 3 to 7; sweet alyssum is grown as an annual.
- Basket-of-gold wants sharp drainage, lean soil, low humidity, and sunny slopes or rock walls, where it can be short-lived if it sits wet; sweet alyssum is more forgiving of average garden soil and regular water.
If you want a low yellow carpet for a spring rock garden that comes back on its own, buy Aurinia saxatilis. If you want a season-long honey-scented edging in white or pastels, buy Lobularia maritima. The rest of this guide is about the latter.
Giving alyssum the sun and soil it wants
Sweet alyssum flowers best in full sun, meaning at least six hours of direct light a day. In cooler northern gardens, give it all the sun you can; more light means more flowers and a tighter, less leggy habit. In hot-summer regions, the calculation flips: a spot that gets some shade during the worst of the afternoon helps the plant push through summer without burning out.
For soil, the single most important quality is good drainage. Sweet alyssum is genuinely adaptable and will grow in neutral to slightly acidic ground, in average fertility, even in poorer soils where fussier annuals sulk. What it will not tolerate is sitting in cold, soggy ground, which invites root and stem rot. In beds, loosen heavy soil and work in some compost for structure rather than richness. In containers and hanging baskets, use a quality all-purpose potting mix and make sure every pot has drainage holes.
Resist the urge to plant it in overly rich, heavily fertilized soil. Like many flowering annuals in the mustard family, alyssum responds to a glut of nitrogen by growing lush green foliage and producing very few flowers, exactly the opposite of what you want.
Watering and feeding without overdoing it
Newly sown seed and young transplants need consistently moist soil to establish. After that, sweet alyssum is fairly drought tolerant once its roots are down, though it is not a true desert plant. A reasonable target is about an inch of water per week from rain or irrigation, with extra spot-watering during the hottest, driest stretches of summer. Let the surface dry slightly between waterings rather than keeping the soil permanently wet.
Containers are the exception. Pots and baskets dry out fast, especially in heat and wind, so check them daily in summer and let only the top inch or two of mix dry before watering again.
Feeding should be modest. Plants in decent garden soil often need nothing at all. If you do feed, a single application of a balanced, slow-release fertilizer at planting time is plenty for the season. The most useful time to feed is after the midsummer shearing described below, when a dose of liquid or water-soluble fertilizer helps the plant rebuild and rebloom. Container plants, which leach nutrients with every watering, benefit from a light monthly feeding through the growing season.
A useful distinction: this restraint applies most to the old-fashioned seed-grown Lobularia maritima. The newer sterile hybrids (see below) are bred to grow large and bloom hard all season, and they are hungrier and thirstier, needing both more water and more regular feeding to live up to their billing.
Why alyssum stops blooming in summer, and the shear-by-a-third fix
The one thing that surprises new alyssum growers is the midsummer slump. Sweet alyssum is a cool-season bloomer. It flowers enthusiastically in the mild weather of spring, then, when daytime highs climb and stay high, it slows down, gets leggy and stretched, and may stop blooming altogether. The plant is not dead and it is not diseased; it is conserving energy and waiting out the heat. White-flowered varieties tend to take the heat a little better than colored ones, but nearly all seed-grown types pause.
The fix is one of the most satisfying maintenance jobs in the garden. In midsummer, when the plant looks tired and the flowers thin out, shear the whole thing back by a third to a half with scissors or hedging shears. Don’t be timid; you are cutting off the spent, leggy growth to force a flush of fresh stems. Water it in and give it a dose of fertilizer, and within a couple of weeks you will see new growth, followed by a second wave of bloom that carries the plant through fall as temperatures ease back down. This same shearing also prevents the plant from setting seed and going dormant, and it keeps a container or edging looking neat instead of straggly.
If you would rather not shear, you can also extend bloom by siting plants where they get afternoon shade in hot climates, and by deadheading lightly to encourage new buds. But the all-over shear is the single most effective tool for a strong fall rebloom.
Putting alyssum to work in beds, edges, and containers
Few annuals are as flexible. Sweet alyssum’s low, spreading, fast-filling habit suits it to a long list of jobs:
- Edging and borders. Planted along paths, porches, and bed lines, it forms a soft, fragrant ribbon. Position it near walkways, doorways, and seating areas where the honey scent can be enjoyed up close.
- Between pavers and stepping stones. Compact, low varieties tuck into the gaps and soften hardscape without flopping into the walking surface.
- Groundcover and weed suppression. Massed in beds or vegetable rows, its dense mat shades the soil and blocks many weed seeds from sprouting, a living mulch that also flowers.
- The “spiller” in mixed containers. In the classic “thriller, filler, spiller” container recipe, trailing alyssum is an ideal spiller, draping gracefully over the rim of pots, window boxes, and hanging baskets without going leggy or pendulous the way some trailing plants do.
- Filling gaps in perennial beds and rock gardens. It slots between established perennials such as black-eyed Susans, lavender, thyme, sedums, and columbine to fill bare pockets with temporary, scented color.
It also combines beautifully with other cool-season and bedding companions for color and contrast, including pansies, violas, dianthus, snapdragons, geraniums, salvia, catmint, dusty miller, and osteospermum. White alyssum is a classic choice for a moon garden, where pale flowers glow along pathways at dusk. As a bonus, deer tend to avoid it; its strong scent overwhelms their sense of smell.
Alyssum as a pollinator and aphid-control workhorse
This is where sweet alyssum earns its place in the vegetable garden, not just the flower bed. Its abundant, easily accessible little flowers are a magnet for bees, butterflies, and even hummingbirds. But the most valuable visitors are the ones gardeners overlook: hoverflies, also called syrphid flies.
Here is the mechanism that makes alyssum such an effective companion plant. Adult hoverflies feed on nectar and pollen, and they need that floral fuel to mature their eggs and to lay them. Alyssum’s shallow, open flowers are perfectly shaped for these short-tongued insects, making it one of the most attractive nectar sources you can plant for them. Once well fed, the female hoverflies lay eggs among aphid colonies on nearby plants, and the hoverfly larvae that hatch are voracious aphid predators, each one eating hundreds of aphids before it pupates. Alyssum also draws in parasitoid wasps that lay their eggs inside aphids.
This is not folk wisdom; it is documented conservation biological control. Strips of sweet alyssum interplanted in commercial lettuce fields have been shown to increase hoverfly egg-laying and reduce aphid numbers, and alyssum grown in apple orchards has boosted hoverfly populations and cut down woolly apple aphid on the trees. For the home gardener the takeaway is simple: tuck sweet alyssum among your lettuce, brassicas, cucumbers, and other aphid-prone crops, and you are building a standing army of beneficial insects that suppresses pests for free, reducing or eliminating the need for sprays. Sown between vegetable rows it does double duty, suppressing weeds while feeding the good bugs.
Starting sweet alyssum from seed and by cuttings
Alyssum is so easy from seed that buying nursery six-packs is almost unnecessary, though they are handy for instant impact. Seeds germinate in about a week under good conditions and plants reach maturity in roughly six to eight weeks.
Direct sowing. After the last hard frost, scatter seed over prepared, well-drained soil. Because the seed needs light to germinate, do not bury it; simply press it lightly into the surface so it makes contact with the soil, and keep it evenly moist until it sprouts (7 to 20 days). Thin or space plants 6 to 10 inches apart so each can mound out. In Zones 9 to 11 you can also sow in September for fall and winter flowers.
Starting indoors. For a head start, sow 6 to 8 weeks before your last expected frost. Press seed onto the surface of a moist seed-starting mix, do not cover, and keep it warm and bright. Transplant seedlings out once they have two sets of true leaves and have been hardened off to outdoor conditions.
Self-seeding. Left to flower and set seed, open-pollinated and heirloom alyssum reseeds freely and comes back year after year in the same area. This is welcome in informal and cottage-style plantings; in tidy, formal gardens you may need to deadhead or shear before seed sets to keep it from wandering. One caveat with letting it reseed: each successive self-sown generation tends to be a little weaker and less vigorous than the last, so many gardeners refresh their planting with new seed or plants every couple of years.
Cuttings. Alyssum can also be propagated from stem cuttings. This is mainly useful for the sterile hybrid types, which set little or no viable seed and therefore cannot be grown from seed at all; cuttings are the only way for a home gardener to multiply them.
Choosing between seed-grown alyssum and the modern hybrids
It helps to know that “sweet alyssum” now covers two distinct groups of plants, and which you choose changes how you grow it.
The classic group is the seed-grown Lobularia maritima: old favorites such as ‘Carpet of Snow’ and ‘Snow Crystals’ (white), ‘Tiny Tim’ (a tiny 3-inch groundcover), ‘Tall White’, ‘Rosie O’Day’ and ‘Royal Carpet’ (purple and pink), and mixes like the ‘Wonderland’, ‘Easter Bonnet’, and ‘Magic Circle’ series. These are cheap and easy from seed, self-sow, are more cold hardy and more drought tolerant, and bloom best in spring and fall with the midsummer lull described above.
The newer group is the sterile Lobularia hybrids, sold under trademarked names such as Snow Princess, White Stream, and Lavender Stream. Bred for vigor and size, they grow much larger (up to about a foot tall and 2 to 3 feet wide) and bloom nonstop right through summer heat without the slump, needing little or no deadheading. The trade-offs: they are not available as seed, so you buy them as plants propagated from cuttings, they need more water and more regular feeding, and they are less drought tolerant. Choose seed-grown types for self-sowing carpets, edging, and budget plantings; choose the hybrids when you want one big, foolproof, all-summer mound that never quits.
Heading off alyssum’s few problems
Sweet alyssum is largely trouble-free, and most of the issues it does get trace back to one cause: too much moisture, especially in poorly drained or shady sites.
Root and stem rot. Cold, soggy soil and overwatering are the classic killers. Plant in well-drained soil, avoid heavy clay that stays wet, give containers ample drainage holes, and don’t keep the soil saturated. A spot that is sunny and airy is far less likely to rot than one that is shaded and damp.
Downy mildew. The most common true disease of alyssum is downy mildew, caused by a fungus-like organism (Hyaloperonospora parasitica, also called Peronospora parasitica). It shows up in cool, wet, humid conditions as discoloration and decline, and it is a known problem in dense, crowded, or poorly ventilated plantings. Prevent it by spacing plants for airflow, watering at the base rather than overhead, and avoiding the prolonged leaf wetness it needs to spread.
Damping-off. Seedlings, like those of many annuals, can collapse from damping-off if started in cold, overly wet conditions. Use clean containers and fresh mix, provide good air circulation, and don’t overwater seed flats.
Aphids. Aphids can occasionally settle on alyssum itself. The irony is that a healthy stand of alyssum is one of the best aphid solutions in the garden, because it recruits the hoverflies and parasitoid wasps that hunt aphids down. Skip the insecticides, which would kill those beneficial insects too, and let the system balance itself; a strong blast of water knocks down any heavy clusters in the meantime.
Get the site right, sun, drainage, and airflow, and sweet alyssum asks for almost nothing in return. Slip it along an edge, into a pot, or between the lettuce rows this season, shear it back when the heat hits, and you will have fragrant flowers and a yard full of helpful insects from spring until frost.