Ornamental · Brassicaceae
Sweet Alyssum
Lobularia maritima
A low carpet of honey-scented bloom that flowers spring to fall and brings in the helpful bugs.
Full sun
42–56 days
USDA 5–9
3–10 in · 8–25 cm
Overview
Want an easy flower for a path edge or a wall to spill over? Sweet alyssum is it. Its low mounds pretty much vanish under tiny honey-scented flowers, and it's part of the cabbage family, believe it or not. It's simple to grow and keeps white, pink, or purple bloom coming from spring right through fall.
Here's the thing: it's a cool-season annual, so it's happiest in the mild weather of spring and fall. When summer really heats up it tends to sulk and slow its bloom, but cooler days snap it back. Most plants stay under 10 inches tall and about a foot across, so instead of climbing they just spread into a tidy carpet.
And there's a bonus that farmers already know about. The flowers feed hoverflies and parasitic wasps, whose young make a meal of aphids, so a strip of alyssum is basically a tiny pest-control crew working your garden for nothing.
Care
The short version: full sun, average soil that drains well, and an easy hand with water and food. When summer heat stalls the flowers, shear it back and it'll bounce right back in fall.
Light
Full sun is what it wants for the most flowers, though a bit of afternoon shade helps out where summers get brutal. The more sun it gets in spring and fall, the fuller the bloom.
Water
Water it regularly while it's getting established, then you can ease way off, because it's drought tolerant once it's settled. The one thing it hates? Wet feet. So let the soil dry between drinks and don't leave it sitting in water.
Soil
Average well-drained soil is plenty, and honestly it'll put up with poor ground too. What it won't forgive is soggy soil, since that's what rots the crown, so sharp drainage is the deal-breaker.
Humidity
Regular outdoor air is all it asks for, so there's no number to worry about. What matters more is good airflow, because damp, crowded plants are an open invitation to downy mildew.
Feeding
Feed it lightly during the growing season, about once a month, and leave it at that. Overdo the fertilizer and you'll get leaves instead of flowers, so a light hand keeps the bloom going.
Pruning
Deadhead the spent flowers and new ones keep coming, and snip off anything damaged or diseased while you're at it. When summer heat stalls the plant, a harder shear resets it for a fresh round of fall flowers.
Size & spacing
It stays low, running 3 to 10 inches (8 to 25 cm) tall and 6 to 12 inches (15 to 30 cm) wide. Set the plants close enough to knit into a carpet, but give them a little breathing room so air can move through.
When to plant
Sweet alyssum runs on the cooler parts of the year, so timing's pretty forgiving. Start seeds indoors 6 to 8 weeks before the last frost, or just sow them outside a few weeks before that, and you'll get bloom from spring through fall with a quiet spell in the summer heat. Got mild winters? You can sow in fall too.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before the last spring frost
- Plant: A few weeks before to around the last spring frost; can also sow in fall in mild climates
- Harvest: Spring through fall, flushing in spring and fall and slowing in peak summer heat
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Most of what goes wrong with sweet alyssum comes down to heat or too much water, and neither is a disaster. Catch the early signs below and it's easy to step in before a slow patch turns into a goner. Just match what you're seeing, then act.
Wilting plants with rot at the stem and crown
This one's about soggy ground. Stem and crown rot shows up when the soil stays wet or water pools at the base, and the plant wilts even though its roots are basically drowning. Pull the affected plants, sort out the drainage, and back off the watering.
Fix:
- Improve soil drainage
- Avoid overwatering and standing water
- Remove affected plants
Yellow leaves with fuzzy stuff underneath
See fuzzy growth on the undersides of the leaves with yellowing showing through on top? That's downy mildew. It moves in during cool, wet spells when the leaves stay damp. Open the plants up for better airflow, water at the base instead of overhead, and clear out any infected debris.
Fix:
- Improve air circulation
- Avoid overhead watering
- Remove and discard infected plant debris
Flowers quit and plants look ragged in midsummer
Don't panic, this is just heat stress, not the end. Sweet alyssum's a cool-season annual, so it naturally slows its growth and flowering once summer gets hot. Shear the plants back by about half, give them water and a light feed, and they'll flush again once fall cools things off.
Fix:
- Shear plants back by about one-half
- Water and lightly fertilize to encourage a new flush
- Allow plants to rebound in cooler fall weather
Toxicity
Good news if there are animals in the house: sweet alyssum is non-toxic. Cats, dogs, and everyone else can hang around it, nibble it, even flop down in it without any harm. And those honey-scented flowers? Totally safe for curious kids to handle.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are totally fine. A curious nibble of the leaves or flowers won't poison them.
Dogs None
Nothing to worry about with dogs either, since it's non-toxic and a stray mouthful is no big deal.
Horses Safe
Horses can graze right next to it without harm, because there's nothing in the plant that affects them.
Rabbits Safe
Rabbits can nibble the leaves and flowers safely, though it's smart to offer any new green in small amounts.
Livestock Safe
Cattle, goats, and sheep are in the clear too, since nothing in the plant bothers grazing animals.
Birds Safe
Birds are fine around it, and the flowers pull in bees and butterflies that birds might go after anyway.
People Safe
It's harmless to people, so those honey-scented flowers are perfectly safe for kids to pick and handle.
Varieties
There's a handful of named types worth knowing, and they mostly sort out by flower color and how well they shrug off heat.
Carpet of Snow
It's a compact, low-spreading pick that stays around 3 to 4 inches tall and disappears under white flowers.
Royal Carpet
A 1953 All-America Selections winner with violet-purple flowers that stays about 3 inches tall.
Snow Princess
A tough, sterile white hybrid that just keeps flowering through the heat, way better than the older types do.
Snow Crystals
A tetraploid with bigger white flowers and better heat tolerance too.
Easter Bonnet
An early bloomer that's sold as a mix of colors.
Companions
Sweet alyssum earns its place beside vegetables by drawing in the insects that hunt aphids, which is why it's grown in flower strips next to crops like lettuce.
Plant near
Lettuce: Planted as insectary flower strips, sweet alyssum attracts hoverflies (syrphid flies) and parasitic wasps whose larvae prey on aphids, providing biological aphid control in lettuce and other vegetable crops
How to propagate
Sweet alyssum practically spreads itself, so whether you're sowing a seed packet or snipping cuttings off a hybrid you love, it's easy going.
SeedEasy
Direct sow several weeks before the last spring frost, or start indoors 6 to 8 weeks before transplanting; can also sow in fall in mild climates · Blooms about 6 to 8 weeks from seed
Seed's the easy way to go. Scatter it on the surface and barely cover it, because the seeds need light to sprout, either outside a few weeks before the last frost or indoors 6 to 8 weeks before you plant out. You'll see flowers in about 6 to 8 weeks, and once it's happy it self-sows all on its own.
Stem cuttingsModerate
During active growth · A few weeks to root
Cuttings are how the sterile hybrids keep going, since cultivars like Snow Princess barely set seed. Take them while the plant's actively growing and they'll root in a few weeks into new plants that match the parent.
Myths
If sweet alyssum browns and stops blooming in summer, it's a goner.
Nope, it's a cool-season annual that's usually just slowing down in the heat. Shear it back, keep it watered, and the cooler days of fall bring it right back into flower. A ragged midsummer plant is resting, not dead.
Sweet alyssum needs lots of feeding to flower well.
Load it up with fertilizer and you'll grow a leafy plant with hardly any flowers. A light feed gets you way better bloom, since this one flowers best when it isn't pushed.