Sweet alyssum

Sun

Full sun to light shade; afternoon shade helps in hot-summer climates.

Water

Water moderately, keeping young plants evenly moist. Established plants tolerate brief dry spells, but flowering declines if they dry out repeatedly.

Soil

Well-drained soil, including sandy or gravelly ground; tolerates relatively poor soil but struggles in waterlogged conditions.

Height

0.25-0.75 ft (0.08-0.23 m)

Spread

0.5-1 ft (0.15-0.3 m)

Flowers

Spring through autumn in cool-summer climates, often pausing during intense heat; autumn through spring in mild-winter climates. Flowers are white, pink, lavender or purple, depending on the variety.

Foliage

Small, narrow, grey-green leaves on branching stems; foliage may persist through winter in frost-free conditions.

Growth

Fast; seed-grown plants can begin flowering within about 6-8 weeks in suitable conditions.

Care needed

Low

• Plant after hard frosts have passed, spacing plants about 0.5-1 ft (0.15-0.3 m) apart.
• Water at soil level when the surface begins to dry; check containers frequently in warm weather.
• Feed container plants lightly with a balanced liquid fertiliser every four to six weeks; avoid heavy feeding in borders.
• Keep mulch away from the crown and maintain good drainage to prevent rot.
• Remove unwanted seedlings before they flower, especially near coastal habitats.

Pruning. After a main flush of flowers, shear plants back by about one-third if they become straggly, then water to encourage fresh growth. Remove spent plants before seed ripens if you do not want them spreading.

Late winter

In cold-winter regions, sow indoors in bright light about six to eight weeks before the last expected frost; press seed onto the surface.

Spring

Harden off young plants and plant out after hard frosts, or sow directly into prepared, well-drained soil.

Early summer

Water during dry spells and lightly feed container plants.

Midsummer

Trim straggly growth after flowering. In hot climates, expect a pause in bloom rather than trying to force growth with extra fertiliser.

Early autumn

In mild-winter climates, sow a fresh crop for cool-season flowers; elsewhere, remove unwanted seedlings.

Late autumn

Remove frost-killed plants. Leave surviving plants only where drainage is good and winter temperatures are mild.

• Edge paths and small borders with a low ribbon of scented flowers.
• Let plants trail over pots, window boxes and raised-bed edges.
• Plant beneath roses or around taller annuals to cover bare soil without adding much height.
• Use white-flowered plants with lavender and silver foliage for a soft Mediterranean-style planting.
• Tuck small patches beside vegetables and herbs to provide nectar for hoverflies and other beneficial insects.

Garden styles it suits: Cottage garden, Pollinator garden, Sensory garden, White garden, Mediterranean and Small-space.

Plant it with: Lavender, Roses, Snapdragons, Calendula, Dianthus and Salvia.

Wildlife: The shallow flowers provide accessible nectar for bees, hoverflies and small parasitic wasps. Hoverfly larvae and some of these wasps help control garden pests.

• Root or crown rot in wet soil: improve drainage, keep the crown clear of mulch and replace badly affected plants.
• Flowering stops in summer heat: provide afternoon shade where practical, water consistently and trim lightly when cooler weather returns.
• Leggy growth and sparse flowers: move plants into stronger light, avoid excess nitrogen and shear back after a flowering flush.
• Aphids on soft shoots: rinse off small colonies with water and preserve ladybirds, lacewings and hoverflies.

Not known to be toxic to cats, dogs, horses or people. No part is recognised as poisonous, but it should not be treated as food; eating large amounts of plant material may cause stomach upset.

Where it spreads. Self-seeds readily and can escape cultivation. It is listed as invasive in California and is regarded as an environmental weed in parts of southern Australia, including Western Australia and South Australia, particularly in coastal habitats. Avoid planting beside dunes or native coastal vegetation in these regions.

• Evergreen candytuft (Iberis sempervirens)

  Candytuft has tougher, broader evergreen leaves and larger white flowers with noticeably unequal petals; its main display is in spring.

• Basket-of-gold (Aurinia saxatilis)

  Also sometimes called alyssum, it forms a more permanent, woody-based mound with grey foliage and bright yellow spring flowers.

The species name maritima means 'of the sea', referring to its coastal habitat, while 'sweet' describes the flowers' honey-like scent.

Propagation. Sow seed on the surface of moist seed compost or prepared soil, pressing it down without deeply covering it. It often self-seeds, although seedlings may differ from named varieties. Some vigorous hybrid varieties are propagated by cuttings rather than seed.

Accepted botanical name

Lobularia maritima

In the US and Canada

Introduced in Canada, Hawaii and the lower 48 states.

Native range

Algeria, Baleares, Corse, Egypt, France, Italy, Libya, Morocco, Portugal, Sardegna, Sicilia and Sinai.

Measured

Soil pH 7.5 to 8. Average height 16 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.