Ornamental · Brassicaceae
Sweet Alyssum
Lobularia maritima
A soft carpet of honey-scented bloom that keeps flowering spring to fall and welcomes the helpful bugs.
Full sun
42–56 days
USDA 5–9
3–10 in · 8–25 cm
Overview
If you are just starting out, sweet alyssum is a kind place to begin. It settles along a path edge or tumbles over a low wall, and before long its soft mounds vanish under tiny honey-scented flowers. This one belongs to the cabbage family, it forgives beginners, and it carries white, pink, or purple bloom from spring all the way through fall.
Think of it as a cool-season annual that feels happiest in the mild days of spring and fall. When high summer arrives it often slows down and looks tired, but that is normal and easy to fix, and cooler weather brings the flowers back. Most plants stay under 10 inches tall and about a foot wide, so they settle into a neat carpet instead of climbing.
Here is a lovely bonus: farmers grow it on purpose. Its flowers feed hoverflies and parasitic wasps, and their young go after aphids, so a ribbon of alyssum quietly works as a little pest patrol for the whole garden.
Care
The short version: give it full sun, average soil that drains well, and a gentle hand with water and feed. When summer heat stalls the flowers, shear it back and it comes back for you in fall.
Light
For the fullest bloom, give sweet alyssum full sun, and if your summers turn hot a little afternoon shade is kind to it. The more sun it soaks up in spring and fall, the thicker its flowers come.
Water
Water it on a regular schedule while it roots in, then relax, because it grows drought tolerant once settled. The thing it truly cannot bear is wet feet, so let the soil dry between drinks and never leave it standing in water.
Soil
Ordinary well-drained soil makes it happy, and it will even forgive poor, thin ground. The one thing it asks for is sharp drainage, since soggy soil is what leads to crown rot.
Humidity
Plain outdoor air is all this plant wants, so there is no number to fuss over. What matters more is good airflow, because crowded, damp plants can invite downy mildew.
Feeding
Feed it lightly through the growing season, about once a month, and that is plenty. Overdo it and you trade flowers for leaves, so a light touch keeps the bloom going.
Pruning
Deadhead the faded flowers to coax new ones along, and snip away anything damaged or diseased. When summer heat stalls the plant, a firmer shear resets it for a fresh flush of fall flowers.
Size & spacing
These plants stay low, reaching 3 to 10 inches (8 to 25 cm) tall and 6 to 12 inches (15 to 30 cm) across. Set them close enough to weave into a carpet, while still leaving a little room for air to move between them.
When to plant
Sweet alyssum leans on the cooler ends of the year, and it makes life easy. Start seeds indoors 6 to 8 weeks before the last frost, or sow them right in the ground a few weeks before that date, and you will have bloom from spring through fall with a quiet spell in the summer heat. Where winters stay mild, a fall sowing works 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
Almost every hiccup with sweet alyssum comes down to heat or too much water, and both are recoverable. Watch for the early signs below and you can step in gently before a tired patch slips away. Match what you see, then take the small step that fixes it.
Wilting plants with soft rot at the base
The trouble here is soggy ground. Stem and crown rot creeps in when the soil stays wet or water gathers around the base, and the plant wilts even while its roots are drowning. Pull the affected plants, sort out the drainage, and ease back on the watering.
Fix:
- Improve soil drainage
- Avoid overwatering and standing water
- Remove affected plants
Yellowing leaves with soft fuzz on their undersides
When the undersides of the leaves grow fuzzy and yellowing shows through on top, that points to downy mildew. It settles in during cool, wet stretches when the foliage stays damp. Open the plants up for better airflow, water at the base rather than overhead, and clear away any infected debris.
Fix:
- Improve air circulation
- Avoid overhead watering
- Remove and discard infected plant debris
Flowers fade and the plants look tired in high summer
Take heart, this is simple heat stress and not the end. Sweet alyssum is a cool-season annual, so it naturally eases off its growth and flowering once summer turns hot. Shear the plants back by about half, water and feed them lightly, and they flush again as fall cools down.
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
Here is reassuring news for animal-loving homes: sweet alyssum is non-toxic. Cats, dogs, and the rest can wander through it, nibble a leaf, even nap in it without harm. The honey-scented flowers are safe for curious little hands to touch too.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are safe with it, and a curious nibble of the leaves or flowers will not bring on poisoning.
Dogs None
Dogs have nothing to fear here, since the plant is listed as non-toxic and a stray mouthful will do no harm.
Horses Safe
Horses can graze nearby without worry, as the plant holds no toxins that trouble them.
Rabbits Safe
Rabbits may sample the leaves and flowers safely, though it is kind to offer any new green in small amounts.
Livestock Safe
Cattle, goats, and sheep are in no danger from it, with nothing in the plant to upset grazing animals.
Birds Safe
Birds are perfectly fine around it, and the flowers draw bees and butterflies that birds may hunt in turn.
People Safe
People have nothing to worry about either, and the honey-scented flowers are safe for children to pick and handle.
Varieties
Sweet alyssum comes in a friendly handful of named types worth knowing, grouped mostly by flower color and how gracefully they handle heat.
Carpet of Snow
This compact, low-spreading pick stays around 3 to 4 inches tall and covers itself in white flowers.
Royal Carpet
A 1953 All-America Selections winner, this one carries violet-purple flowers and holds to about 3 inches tall.
Snow Princess
A vigorous sterile hybrid in white that keeps flowering through heat far better than the older types.
Snow Crystals
A tetraploid with larger white flowers and improved heat tolerance.
Easter Bonnet
An early-blooming series sold as a cheerful 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 does most of the multiplying for you, whether you open a fresh seed packet or take a few cuttings from a hybrid you love.
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 is the gentle way to start. Scatter it on the surface and barely cover it, since the seeds need light to wake up, either outdoors a few weeks before the last frost or indoors 6 to 8 weeks before you plant out. Flowers follow in about 6 to 8 weeks, and once it feels at home it self-sows with ease.
Stem cuttingsModerate
During active growth · A few weeks to root
Cuttings are how the sterile hybrids keep going, since cultivars like Snow Princess set little or no seed. Take them while the plant is growing and they root in a few weeks into new plants just like the parent.
Myths
Once sweet alyssum stops blooming and browns in summer, it has died for good.
Not so, and this is a relief: it is a cool-season annual that usually just slows down in the heat. Shear it back, keep it watered, and the cooler days of fall coax it right back into flower. A ragged midsummer plant is resting, not dead.
Sweet alyssum needs heavy feeding before it will flower well.
Pile on the fertilizer and you will grow a lush, leafy plant with hardly any flowers. A light feed gives you far better bloom, because this plant flowers best when it is not pushed too hard.