Alyssum: Direct Sow or Potted Plant Annual
How to Sow and Plant
Alyssum may be sown directly in the garden after frost or planted as a potted plant.
Sowing Directly in the Garden:
- Direct sow seeds in average soil in full sun to part shade after danger of heavy frost.
- Sow seeds 6 inches apart and barely press in; light aids germination.
- Firm soil lightly and keep evenly moist.
- Seedlings will emerge in 8-10 days.
Planting Potted Plants:
- Select a location in full sun with good rich moist organic soil.
- Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
- Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
- Dig a hole for each plant large enough to amply accommodate the root ball.
- Set level with the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand leaving a slight depression around the plant to hold water.
- Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.
- Use the plant tag as a location marker.
How to Grow
- Keep soil evenly moist but not wet
- Shear plants back by one-half after the first flush of flowers has ended to encourage new buds to form.
- Plants self-sow so allow some to set seeds.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
- Remove plants after they are killed by heavy frost in fall to avoid disease issues the following year.
- Alyssum performs best in areas with relatively cool summers, but can grow anywhere.
- Alyssum makes a great temporary ground cover and grows nicely with dianthus, violets, and thyme. Plant alyssum between stepping stones or in paving cracks, or grow it in containers. Alyssum also makes a great addition to a butterfly or seaside garden.
- Alyssum has a sweet fragrance. Plant where you can enjoy this, such as in a windowbox. Because of the fragrance it will also attract bees, butterflies and many beneficial insects such as lady bugs.
Common Disease Problems
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. This can be a problem if alyssum is grown in overly wet areas. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Clubroot: Leaf symptoms include stunting, yellowing and wilt. When the plants are removed from the soil the roots may have galls, swelling or be distorted. Burpee Recommends: Test the soil pH as clubroot is most common in acid soil. Add lime to raise the pH. Avoid planting where brassica plants were grown the previous year.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Fasciation: Fasciation is an abnormal flatting of stems, which may cause them to have a fused appearance. Distortion often develops at the base of the plant. It is usually caused by a bacteria or virus and enters through a wound in the plant. Burpee Recommends: Be very careful when handling plants. Remove and destroy any plants that show signs of the disease.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Aphids are only a problem if the plants are stressed. Alyssum is used as a trap crop for lettuce. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cyclamen Mite: These mites damage plants by sucking juice from stems and leaves. They multiply rapidity in hot, dry weather. They can only be seen using a magnifying glass. Plants will look distorted and stunted, and may not bloom. Flowers will be distorted, streaked and blotched. Leaves can become cupped, curled, dwarfed and thickened. Burpee Recommends: Discard plants that are severely infested. Avoid working with infested plants. Keep plants watered in dry weather. For heavy infestations consult your Cooperative Extension Service for insecticide recommendations.
Edema (Oedema): Leaves become distorted due to excess moisture in the soil. Plants absorb more water than they can use. Burpee Recommends: Do not overwater plants, keep the soil moist but not wet. If drainage is poor add compost or peat moss to improve drainage.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage. Sanitation is important so be sure to remove all debris at the end of the season.
Root Knot Nematodes: Microscopic worm-like pests that cause swellings (galls) to form on roots. Plants may wilt or appear stunted. This is a serious problem in many Southern states. Burpee Recommends: Do not plant into infested soil. Try planting ‘Nema-Gone’ marigolds around your plants.
Can I grow alyssum in containers? Alyssum is perfect for the edges of containers combined with other flowers. Raise the container to a wall or table, or plant in hanging baskets, so you can enjoy the fragrance.
Is alyssum toxic to pets? Alyssum is non-toxic to dogs and non-toxic to cats.
How can alyssum be used as a companion plant? Alyssum is a great companion to many plants and will attract aphids from lettuce.
Why didn’t my seeds germinate? Alyssum needs light to germinate, just press them into the top of the soil and do not burry them. Keep the soil evenly moist but not wet.
Can I start seeds inside? Alyssum is very easy to start outside and does not need to be started inside, however you can start them inside 6-8 weeks before the last frost.