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Sweet Alyssum
The low, honey-scented carpet of tiny flowers that's secretly the garden's best beneficial-insect magnet - a proven insectary plant that pulls in the hoverflies and wasps that control aphids and caterpillars.
Safety notes Sweet alyssum is in the mustard family (Brassicaceae) and its flowers and leaves are technically edible with a mild peppery taste - a minor garnish, not a real food crop. Non-toxic to people and pets. In coastal California and similar mild coastal regions it escapes gardens into dune, bluff and riparian habitat (Cal-IPC rates it Limited), so near a wildland edge shear or deadhead it before it sets seed. (Not the same as the yellow perennial 'basket-of-gold' alyssum, Aurinia saxatilis.)
Overview
Sweet alyssum looks like a modest edging plant - a low, spreading mat, four to eight inches high, blanketed in tiny four-petaled flowers in white, purple, pink, or apricot, with a sweet, honeyed fragrance that carries on warm air. But its real value is hidden: alyssum is one of the most effective insectary plants you can grow. Its shallow, accessible flowers are a feeding station for hoverflies, tiny parasitic wasps, lacewings, and other beneficial insects - and their larvae are voracious aphid and caterpillar predators. This is honest, researched companion value: interplanted in vegetable rows, alyssum measurably boosts aphid control.
The one thing to knowBut its real value is hidden: alyssum is one of the most effective insectary plants you can grow.
Quick facts
- Sprouts in
- 8 daysRange: 5–14 days
- Soil temperature
- 65 °FRange: 55–75 °F
- Start indoors
- 5 weeks before transplantRange: 4–6 weeks
- Height
- 5 inRange: 3–10 in
- Spread
- 10 inRange: 6–15 in
- Cold
- Takes light frostdamaged below 25°F
- Heat
- Struggles above 85°F
- Life cycle
- Annual
- Save seeds
- About 75 days after plantingRange: 60–90 days
- Self-sows
- Yes, expect volunteers
- Soil
- Well-drained
- Water
- Medium
- Plant spacing
- 8 inRange: 4–12 in
When to plant
Nothing is open today. Spring sowing opens 5 months, Mar 27 to May 1.
- Direct sow Mar 27 – May 1 Opens in 159 daysAbout 2 weeks before to 3 weeks after your last frost (Apr 10 here)Direct-sow (surface-sow, needs light) around the last frost - it takes light frost and grows fast in cool spring weather. Succession or reseed for continuous bloom.
- Direct sow Aug 16 – Sep 10 Opens in 301 daysAbout 10 weeks before to 6 weeks before your first frost (Oct 25 here)A late-summer sowing gives a fresh flush of the honey-scented carpet for fall as the heat breaks.
Frost here: last around Apr 10 (Mar 27 to Apr 24 most years), first around Oct 25. Zone averages, your own yard may run a week or two either way.
Life stages
From the first start to harvest
Follow the growing sequence. Choose a stage to see its care and signs to watch for.
Stage 1 of 5 · The growing sequence
Germination
Day 0 to 8 from sowing
Care at this stage
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Surface-sow the tiny seed - it needs light
Alyssum seed is very fine and needs light to germinate. Press it onto the surface, don't bury it, and keep evenly moist; it sprouts fast in cool-to-warm soil.
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Sow in cool weather for best growth
Alyssum germinates and grows best in the cool of spring and fall. It can be direct-sown as soon as the soil can be worked (it takes light frost) or started indoors 4-6 weeks early.
Stages can overlap; weather, variety, and growing conditions change the pace.
Watch out for
2 to know. None are high-risk for Sweet Alyssum. 2 are active in October.
Slugs & SnailsSeverity Medium PestnowSeason: Mar, Apr, May, Oct, NovIrregular ragged holes chewed out of the middle of leaves and along the edges - not the clean-edged cuts a caterpillar leaves.
A low, dense mat is exactly the cover slugs want, so alyssum gets grazed from below as well as at the seedling stage. Protect it until the mat establishes; after that it largely looks after itself.
Irregular ragged holes chewed out of the middle of leaves and along the edges - not the clean-edged cuts a caterpillar leaves. Seedlings that vanish overnight, or that are cut off at soil level with nothing left behind. Silvery dried slime trails across leaves, soil, pots, and paving in the morning: this is the giveaway that tells you it was mollusks rather than an insect. Chewed pits in ripe fruit, especially where it rests on the ground. Damage that shows up on the lowest, dampest leaves first and gets worse after rain or evening watering. Turn over a board, an upturned pot, or a clump of dense mulch during the day and look for the animals themselves sheltering in the cool underneath.
Hand-picking works and costs nothing: go out an hour after dark with a headlamp, drop what you find into soapy water, and repeat nightly for a week or two - persistence is what wins, not any single product. Shallow beer traps sunk to soil level catch them too, but need emptying and refilling daily to be worth anything. Iron-phosphate bait is the standard control and is far lower-risk around pets and wildlife than the old metaldehyde products, but it is not harmless: many formulations include EDTA, and a dog that eats a quantity of pellets can develop iron toxicosis. Scatter it thinly per the label, never in piles, and keep dogs off a baited bed. Clear fallen foliage and debris in autumn, where the eggs are laid. In a wet climate this is a population you manage each season rather than one you eradicate - and on most established plants light grazing is cosmetic and needs nothing at all.
Take away the daytime shelter first: lift boards and upturned pots, clear piles of debris, keep dense mulch pulled back from crowns and stems, and give crowded plantings enough airflow to dry out. Water in the morning rather than the evening so the surface is dry by the time they come out. Copper tape around containers and raised beds gives them a shock they will not cross, and it is the one barrier that reliably works. Get plants past the vulnerable stage quickly - start seedlings in pots and set them out at a decent size rather than direct-sowing into a cold wet bed, since most plants stop being worth defending once the leaves toughen. Leave the ground beetles, frogs, toads, and ground-feeding birds alone, because they eat mollusks all night for free and broad-spectrum slug pellets kill them too. Where thick-leaved or resistant varieties exist for what you are growing, they take far less damage.
Slugs and snails are nocturnal mollusks that rasp ragged holes in soft leaves, shear off seedlings at ground level, and chew into ripe fruit that touches the soil. They feed at night and in the early morning and spend the day hidden under boards, pots, dense mulch, leaf litter, and low foliage, becoming active in exactly the cool, damp, shaded conditions that suit young plants. Damage is heaviest in wet spells and on tender spring growth: a single wet week can erase a row of seedlings while an established, tough-leaved plant of the same species is barely marked. They lay clusters of small pearly eggs in damp soil and under debris, so a garden with plenty of cover carries a resident population year after year rather than being invaded from outside.
AphidsSeverity Low PestnowSeason: Apr, May, Jun, Sep, OctDense clusters of tiny insects packed onto shoot tips, flower buds, and the undersides of young leaves.
Alyssum is grown as an insectary plant, so aphids on it are largely a feature - they feed the hoverflies, lady beetles and parasitic wasps it is there to attract. Do not spray it: that kills the beneficials and defeats the point of the planting. Hose them off only if a young planting is genuinely overrun.
Dense clusters of tiny insects packed onto shoot tips, flower buds, and the undersides of young leaves. Curled, cupped, or distorted new growth that never opens properly. A sticky shine on the leaves - and on whatever sits under the plant - that later goes black with sooty mold. Tiny white cast skins left behind where a colony has been feeding. Ants running steadily up and down the stems, which is often the first thing you notice. Mottled, streaked, or misshapen leaves that do not grow out can mean a virus the aphids brought with them rather than the feeding itself.
Knock the colonies off with a hard jet of water and repeat every few days - on most plants that alone ends it. Pinch out or prune off the worst-infested tips rather than treating the whole plant. If colonies keep rebuilding, spray insecticidal soap or horticultural oil directly onto the insects, covering leaf undersides, and repeat weekly until they are gone; treat early or late in the day, and never spray a wilted or heat-stressed plant. Avoid broad-spectrum insecticides - they kill the ladybugs, lacewings, and parasitic wasps that were about to solve the problem for you, and aphid numbers usually come back worse afterward. Anything you spray must be labeled for the plant you are treating; follow that label and observe its pre-harvest interval. On anything you eat, wash leaves, heads, and buds well before use, since aphids hide down in crowns, folds, and tight growth.
Go easy on nitrogen: the soft, lush growth that heavy feeding produces is exactly what aphids breed on. Check new growth once a week through spring and early summer so you catch colonies while they are still small, and rub the first few out with your fingers. Leave flowering plants nearby and skip broad-spectrum sprays - ladybugs, lacewings, hoverflies, and parasitic wasps do most of this work for free, and they only stay if there is something for them to eat. Keep ants off the plant where you can, since they protect aphids from those predators. Water steadily so plants are not stressed, and check any new plant over before you bring it home or move it indoors, since aphids usually arrive on something else.
Aphids are small soft-bodied sap-suckers - green, black, gray, pink, or waxy white, and mostly wingless - that gather in dense colonies on the tenderest new growth: shoot tips, buds, and the undersides of young leaves. They breed extremely fast in mild weather, so a few can become hundreds inside a week. Their feeding curls and distorts soft growth, and the sticky honeydew they excrete coats everything below and turns black with sooty mold. Ants often farm and defend the colonies for that honeydew. A few aphids are normal on almost any plant and a healthy plant shrugs them off; only dense, persistent colonies do real damage, and some aphids also spread plant viruses as they feed.
Good & bad neighbors
Plant nearby
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A researched insectary pairing: alyssum interplanted in lettuce draws hoverflies whose larvae eat lettuce aphids - field trials show measurably better aphid control. One of the best-supported companion relationships in the catalog.
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Alyssum strips among brassicas pull in hoverflies and parasitic wasps that attack aphids and cabbage caterpillars; a strong, evidence-backed beneficial-insect companion.
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Same brassica-family insectary benefit - the honey-scented flowers feed aphid and caterpillar predators; both also share cool-season timing.
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Interplanted with cucurbits to attract hoverflies, parasitic wasps, and pollinators - better pest control plus more bee visits for fruit set.
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A low insectary carpet at the feet of peppers draws beneficials that prey on aphids while the flowers pull in pollinators.
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Underplanted among tomatoes as a living mulch and insectary flower - shades the soil, draws hoverflies and pollinators, and feeds aphid predators.
- Traditional pairings, thin evidence
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A cool-season ornamental pairing: alyssum's low carpet fills the ground layer beneath snapdragon spikes and draws beneficial insects to the bed.
Varieties · 7
You pick one when you add Sweet Alyssum to your garden. Its days to maturity set your harvest window.
Carpet of Snow
The classic pure-white sweet alyssum: a low, spreading 3-4 inch carpet smothered in tiny honey-scented white flowers.
Variety details for Carpet of Snow
A dense low mat of tiny four-petaled pure-white flower clusters.
whitecarpetheirloomself-seedingThe standard edging and ground-cover type, a reliable self-sower, and a top beneficial-insect plant. Open-pollinated and easy from seed.
Royal Carpet
The deep violet-purple sweet alyssum: the same low fragrant carpet as Carpet of Snow but in rich purple, making a striking edging and a strong pollinator and hoverfly draw.
Variety details for Royal Carpet
Low mat of tiny deep violet-purple honey-scented flower clusters.
purplecarpetheirloomfragrantAn old favorite and dependable self-sower.
Snow Princess
A breakthrough heat-tolerant hybrid (a vegetative, cuttings-grown, largely sterile Lobularia): far more vigorous and heat-resistant than seed types, it blooms nonstop from spring to frost without slumping in summer and spreads to a couple of feet.
Variety details for Snow Princess
Vigorous spreading mounds covered in fragrant white flowers all season.
whiteheat-tolerantvegetativesterileSpace it 18-24 inches apart, not at the species' 4-12 inches, or the plants smother each other and mildew. Sold as plants; the top choice for season-long bloom and beneficial-insect support.
Easter Bonnet
An early, uniform, compact series in a wide color range (white, lavender, deep violet, pink, and mixes) - fast to bloom and tidy, a popular bedding and container alyssum.
Variety details for Easter Bonnet
Compact mounds of tiny flowers in white, lavender, violet, and pink.
seriesmixcompactearlyClear Crystal
A large-flowered series (white, purple, and lavender) with bigger blooms and a stronger honey fragrance than most - showier for containers and edging while still feeding beneficial insects well.
Variety details for Clear Crystal
Larger-than-usual flower clusters in white, lavender-shades, and deep purple.
serieslarge-floweredmixfragrantSnow Crystals
An All-America Selections white type with unusually large flowers and good heat tolerance for a seed-grown alyssum - vigorous, fragrant, and long-blooming.
Variety details for Snow Crystals
whitelarge-floweredheat-tolerantvigorous
Grower tips
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