Sweet alyssum

Sweet alyssum: how do you recognise it?

Habit

Low, cushion-forming to trailing plant 10–15 cm tall and up to 30 cm wide, with many branching stems.

Leaves

Small, narrow and lance-shaped, greyish green and slightly hairy.

Flower

Tiny four-petalled flowers in dense, rounded clusters that gradually lengthen, from May to October.

Scent

Sweet, like honey, especially on warm, sunny days.

Colour

White; there are also cultivars in pink, lilac and purple.

Seed

Small, flat, round pods with fine seed; it self-seeds easily.

Flowering: May–October · Sowing: March–May · Plants: May · Pruning: July

Why grow it?

• Flowers from May to October, especially if you cut it back in midsummer.
• A sweet honey scent that you can smell from a distance on warm days.
• Attracts bees, butterflies and hoverflies, whose larvae eat aphids.
• Fast, low ground cover for edges, between paving, in rock gardens, pots and hanging baskets.
• Cheap and easy from seed, and often self-seeds.
• Quickly fills gaps between perennials or after spring bulbs.

Sweet alyssum: where does it grow best?

• Full sun is ideal; in partial shade it still flowers, but less freely.
• Light to average, well-drained soil: sand, loam or clay, neutral to chalky.
• Dry rather than wet: it copes with a dry spell, but not with waterlogged soil.
• Plant 20–25 cm apart; each plant spreads to about 30 cm.
• Ideal for the front of the border, between paving, in wall crevices and in pots and hanging baskets.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

0.15 m tall, 0.3 m wide

Hardiness

Tolerates light frost (to -5 °C)

Goes well with

• Lobelia: Little blue flowers next to white ones: the classic pairing for edges, pots and hanging baskets.
• Lavender: Also for sun and dry soil; white and purple together attract lots of bees.
• Pelargonium: A white carpet at the feet of pelargoniums in window boxes and pots.
• Mealy sage: Blue spikes above a white carpet; both flower until autumn.
• Lettuce: Among vegetables it attracts hoverflies that clear up aphids.

Sweet alyssum: when and how to plant it?

Plant in May.

1. Sow indoors in March–April at 15–20 °C: scatter the fine seed thinly on moist seed compost, press it in and cover it with no more than a very thin layer.
2. Prick out the seedlings in groups of 3–4 per pot or cell; this quickly gives full, bushy plants.
3. Or sow directly outdoors from April in an edge or between paving and later thin the seedlings to 20 cm.
4. Harden off indoor-sown plants outside for a week and plant them out in May, 20–25 cm apart and at the same depth as in the pot.
5. Water straight away and keep the soil moist until the plants are established.

Care

Water

Little needed in open ground once established. In pots and hanging baskets water regularly, but avoid waterlogging. In a long drought flowering stops.

Feeding

Little needed: soil that is too rich gives lots of leaves and fewer flowers. In pots, a little liquid feed every three to four weeks.

Cutting back

If flowering slows in summer, cut the plants back by half with scissors; they flower again after 2–3 weeks.

Weeding

Keep young seedlings free of weeds until they cover the ground.

Self-seeding

Let a few plants set seed in late summer if you want new plants to come up by themselves next year.

Tip: Put a few plants among your vegetables or along the edge of the vegetable patch: the flowers attract hoverflies, whose larvae eat aphids.

Sweet alyssum: when to prune it?

Pruning months: July.

When: Cut the plants back by about half in July, after the first big flush of flowers. They will then flower again until autumn.

How:

• Cut all the stems back by about half with scissors or shears, even if there are still a few flowers.
• Then water and, in a pot, give a little liquid feed.
• New flower clusters appear after 2–3 weeks.
• Clear the plants away in late autumn, or leave them if you want them to self-seed.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Indoors in March–April at 15–20 °C, or outdoors in April–May. The seed usually germinates within 1–2 weeks.

Self-seeding

Let a few plants form seed in late summer; in spring seedlings often appear that you can move.

Cuttings

In summer, insert 5 cm cuttings from non-flowering shoots in moist cutting compost. This way you keep a favourite colour.

Sweet alyssum: how does it get through the winter?

Hardy to −5 °C: protect in harsh winters.

• An annual: it tolerates light frost to about −5 °C and often flowers on into November, but does not survive hard frost.
• In a mild winter in a sheltered spot a plant sometimes survives, but usually you start again in spring.
• Let a few plants set seed: in spring the seedlings often come up by themselves.
• Store collected seed dry and cool until spring.

Diseases and pests

• Flea beetles: Small jumping beetles that eat round holes in the leaves of young plants, especially in warm, dry weather. Keep the soil moist; older plants grow away from the damage.
• Downy mildew: Yellow patches on the leaves with grey fuzz underneath, especially in cool, damp weather. Do not plant too densely and remove affected plants.
• Damping off: Seedlings collapse at the base because of a fungus. Sow thinly in clean seed compost, do not overwater and give fresh air.
• Slugs: Strip young seedlings bare. Pick them off in the evening and protect young plants.
• Flowering stops: In heat and drought flowering stops and the stems go bare. Cut back by half and water.

Through the year

• March: Sow indoors at 15–20 °C.
• April: Sow indoors and prick out. Sow outdoors in edges and between paving.
• May: Harden off and plant out, 20–25 cm apart. Sow outdoors. First flowers.
• June: Full flower. Water pots and hanging baskets.
• July: After the first flush, cut back by half. Water.
• August: Flowering again. Take cuttings.
• September: Flowering. Let a few plants set seed.
• October: Last flowers. Collect seed.
• November: Clear plants away after hard frost.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• Sweet alyssum belongs to the cabbage family, like cabbage and mustard: its four petals form a cross.
• It used to be called Alyssum maritimum, which is why it is still often sold as alyssum.
• In the wild it grows on dunes, rocks and walls close to the sea: hence the scientific name maritima.