How to Grow Alyssum Seeds

Grow Guide #2225
Family: Brassicaceae
Binomial name: Lobularia maritima
Life Cycle: Annual

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Alyssum (Lobularia maritima).

(Alyssum 'Mountain Gold' (Aurinia saxatilis) is a short-lived perennial and a different species botanically to alyssum. This guide is still relevant as it enjoys the same conditions and is grown in the same way as annual alyssum).

When to Sow Alyssum Seeds

Alyssum can be grown year-round in most climates. Avoid planting in extremely hot or cold weather which can affect germination and growth. Use the table below to identify the best time of year to sow alyssum in your climate.

  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Cool
Temperate
Sub-Tropical
Tropical
Arid

Preparation

Alyssum plants commonly self-seed in the garden. Self-seeding plants drop seeds onto the soil at the end of the season that may germinate and grow without help the following season. Choose a position where new plants will be welcome. If you do not want alyssum to become established in your garden, deadhead plants before they can drop seed or grow them in containers.

Alyssum plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.

Alyssum plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.

Alyssum plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 10 litres is recommended for alyssum. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.

How to Sow Alyssum Seeds

Alyssum seeds do not require any treatment (eg soaking, stratification) before sowing.

Alyssum seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.

Sow Direct

  1. Sow seeds directly in the garden 2mm deep and 20cm apart.
  2. Keep soil moist but never wet or dry.
  3. Seeds should germinate in around 7-14 days at a soil temperature of 18-22°C.
  4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

  1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
  2. Sow seeds 2mm deep.
  3. Keep soil moist but never wet or dry.
  4. Seeds should germinate in around 7-14 days at a soil temperature of 18-22°C.
  5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
  6. Plant out, spacing plants 20cm apart.

Tip: Alyssum seeds can also be sown in the less formal ‘scatter seed’ method. Simply roughen the soil, scatter seeds evenly over the surface, then smooth the soil over lightly to cover the seeds.

How to Grow Alyssum

Alyssum plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.

If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-potassium fertiliser or one formulated for flowering plants can be beneficial:

  • Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
  • Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.

Optional: To give plants room to grow, thin seedlings when they are large enough to handle. Pull out any weak or small seedlings so plants are spaced about 20cm apart.

Alyssum plants should flower in approximately 60 days.

Deadhead alyssum flowers regularly during the growing season. Using sharp secateurs or snips cut fading or dead flowers off just above a set of leaves. Removing old flowers regularly will encourage plants to produce more flowers. Learn more about deadheading flowering plants here.

Alyssum 'Mountain Gold' only - When plants have finished flowering prune them back to neaten them and encourage strong new growth. Using sharp secateurs or snips, prune the plant by about half its size.

Common Problems when Growing Alyssum

Like all plants, alyssum is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing alyssum plants:

  • Downy Mildew
    Downy mildew is a fungal disease that causes yellow to grey-brown patches on leaves, especially the undersides. Water plants at soil level (not on the leaves), remove and destroy affected leaves and do not overcrowd plants to ensure adequate air flow. If problems persist, spray with a homemade milk spray or fungicide.
  • Slugs and Snails
    Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.

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