The “Allison plant” is commonly known as Sweet Alyssum (Lobularia maritima), a low-growing annual or short-lived perennial. It produces clusters of small, fragrant flowers, reaching 3 to 10 inches tall and spreading 5 to 48 inches. Its narrow, lance-shaped, gray-green leaves provide a subtle backdrop for the abundant flowers.
Key Features and Garden Uses
Sweet Alyssum is prized for its sweet, honey-like fragrance, intensifying in warm weather. Its tiny, four-petal flowers appear in colors including white, pink, purple, lavender, and yellow. It makes an excellent groundcover, suppressing weeds and protecting soil from erosion.
It also functions effectively as a border plant along pathways, a filler in containers and hanging baskets where its blooms can cascade, or nestled into rock gardens. Beyond its visual appeal, Sweet Alyssum attracts beneficial pollinators like bees and butterflies, and beneficial insects such as hoverflies and ladybugs, which help control garden pests.
Planting and Site Selection
When to Plant
Sweet Alyssum is a cool-season flower, planted in early spring after the last frost has passed. In milder climates, it can also be sown in the fall for blooms that may last through winter. Transplanting starts in spring is recommended.
Sunlight Requirements
Sweet Alyssum thrives in full sun. In particularly hot climates, providing some partial or afternoon shade can help the plant perform better and prevent wilting. Too much shade can lead to leggy growth and reduced flower production.
Soil Preferences
This plant prefers moist, well-draining soil and can tolerate a range of soil types, including sandy conditions. Moderately fertile soil with a neutral to slightly acidic pH, between 6.0 and 7.0, is preferred for optimal growth. Improving heavy or compacted soil with organic matter like compost can enhance drainage.
Planting from Seed
Sweet Alyssum is easy to grow from seed. For indoor starting, sow seeds six to eight weeks before the last expected frost. When direct sowing outdoors, scatter seeds on the soil surface and lightly press them in, as they require light to germinate. Keep the soil consistently moist until germination occurs, typically in 7 to 15 days.
Transplanting
When transplanting Sweet Alyssum seedlings, ensure the threat of frost has passed. Water the plants thoroughly before transplanting to reduce stress. Space them about 6 inches apart for a dense carpet effect, or 8 to 12 inches apart for larger plantings, firming the soil gently around the roots after placement.
Ongoing Care
Watering
Sweet Alyssum prefers consistently moist, but not waterlogged, soil. During the peak growing season, it requires about one inch of water per week, often two to three times weekly. Plants in containers tend to dry out faster and may need more frequent watering, possibly every other day in hot weather. Water in the early morning or late afternoon to allow foliage to dry before nightfall, helping prevent fungal issues.
Fertilizing
In-ground Sweet Alyssum does not require heavy fertilization unless the soil is poor. Over-fertilizing can lead to lush foliage at the expense of flower production. If fertilization is desired, an annual application of a well-balanced, slow-release fertilizer or working compost into the soil in spring can be beneficial. Container-grown plants, however, benefit from monthly feedings with a water-soluble, balanced fertilizer, as nutrients leach out more quickly. A fertilizer with a higher phosphorus content can promote blooming.
Deadheading and Pruning
Deadheading, the removal of spent blooms, encourages continuous flowering and can prevent unwanted self-seeding. For large plantings, shearing the entire plant back by about one-third to one-half can rejuvenate it, promote new growth, and encourage a fresh flush of blooms, particularly if the plant becomes leggy or stops flowering in heat. This pruning helps the plant revive and continue blooming into cooler temperatures.
Common Problems and Solutions
Pests
Sweet Alyssum is problem-free, but it can be affected by pests such as aphids and spider mites, especially when the plant is under stress. Beneficial insects attracted by Sweet Alyssum help control these pests. Severe infestations might require treatment. If cyclamen mites cause curled leaves, insecticidal soap or neem oil can be effective.
Diseases
Sweet Alyssum is resilient to diseases, but issues like downy mildew, stem rot, and crown rot can occur, particularly in poorly draining or overwatered soil. Symptoms of root rot include yellowing, wilting, and collapse of the plant. Ensuring good air circulation and avoiding overwatering, especially around the plant’s crown, can help prevent these fungal problems.
Environmental Stress
Sweet Alyssum may show signs of stress from environmental factors. Wilting can occur due to insufficient water or excessive heat. Providing extra water during hot periods and ensuring good drainage can alleviate wilting. Leggy growth indicates insufficient light, while poor blooming can result from excessive heat or overly rich soil. If plants decline in summer heat, a good pruning and watering can revive them when cooler temperatures return.