Sweet Alyssum in Zone 6A — Mid-Atlantic

Sweet Alyssum is a charming addition to any Mid-Atlantic garden. Its delicate, honey-scented flowers attract beneficial insects, making it a valuable companion plant for vegetables. Plus, it thrives in our four seasons, providing a carpet of color from spring through fall.

Don't let our humid summers or the occasional deer pressure deter you. With a little planning and attention to timing, Sweet Alyssum is easy to grow during our 188-day growing season. You'll find success with this rewarding flower.

Starting Sweet Alyssum indoors is an option, especially if you want a head start on blooms. Sow seeds indoors from mid-February through early March, about six weeks before the last expected frost. Use seed trays filled with a good seed-starting mix, and keep them warm and well-lit.

Bottom watering helps prevent damping-off, a common problem in our sometimes-damp Mid-Atlantic springs. It also encourages strong root growth. Keep the soil consistently moist, but not soggy.

Transplant your Sweet Alyssum seedlings outdoors from early April through mid-May, after the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Mid-Atlantic's variable spring weather.

Space the plants 6-8 inches apart in a sunny or partially shaded spot with well-drained soil. Watch for late frost and cover the plants if necessary.

Direct sowing Sweet Alyssum is a simple and effective method, especially since our rainfall is reliable. Sow seeds directly into the garden from early April through late August. This gives you a long window to plant and enjoy continuous blooms.

Prepare the soil by loosening it and removing any weeds. Gently press the seeds into the soil, spacing them 6-8 inches apart. Keep the soil consistently moist until the seedlings emerge.

Sweet Alyssum needs moderate watering, especially during our humid summers. Aim for about 1 inch of water per week, either from rainfall or irrigation. Use the finger test to check soil moisture: if the top 2 inches feel dry, it's time to water.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Overhead watering is fine, but do it early in the day so the leaves can dry before nightfall. Mulching around the plants helps retain moisture and suppress weeds.

Signs of underwatering include wilting leaves and dry soil. Overwatering can lead to yellowing leaves and root rot. Sweet Alyssum may go dormant during periods of extreme heat, but it will revive when temperatures cool down.

Sweet Alyssum requires minimal pruning. The main goal is to keep the plants tidy and encourage continued blooming.

Shear back the plants by about half when they start to look leggy, usually in midsummer. This will stimulate fresh growth and a new flush of flowers. As the first frost approaches around mid-October, you can let the plants go to seed or pull them up to prepare the bed for fall planting.

Sweet Alyssum is primarily grown for its ornamental value and as a beneficial insect attractant, so there's no need for traditional harvesting. The plants will flower continuously from mid-May through late October, about 45 days after planting.

Instead of harvesting, enjoy the fragrant blooms and the beneficial insects they attract to your garden. Deadheading spent flowers can encourage more blooms, but it's not essential. As the first frost approaches in mid-October, you can collect seeds from dried flower heads for next year's planting.

Here are some common problems you might encounter with Sweet Alyssum in the Mid-Atlantic:

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. Our humid springs and summers can create ideal conditions for this disease.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation by spacing plants properly. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Dieback in Extreme Heat

• What it looks like: Plants stop blooming, leaves turn brown, and overall growth slows or stops.
• What causes it: While Sweet Alyssum prefers full sun, our moderate-to-hot summers can be stressful. Especially if coupled with humidity.
• How to fix/prevent it: Provide some afternoon shade during the hottest part of the day. Ensure adequate watering and mulch to keep the soil cool. The plants will usually recover when temperatures cool down.

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. Small dark beetles that jump when disturbed. Worst damage to young seedlings.
• What causes it: Small jumping beetles that feed on leaves of brassicas, eggplant, and other crops. Most damaging to small, young plants.
• How to fix/prevent it: Row covers protect seedlings during the vulnerable stage. Delay planting until plants are larger. Kaolin clay coating. Neem oil spray. Interplant with basil or catnip. Healthy, vigorous plants outgrow damage.

Mid-Atlantic Specific Challenges: The combination of moderate-to-hot heat, humid humidity, and even rainfall in the Mid-Atlantic can create challenges for Sweet Alyssum. Proper watering, good air circulation, and preventative measures against fungal diseases are essential for success. Also, deer like it, so protect accordingly.

Sweet Alyssum makes a great companion plant in the Mid-Atlantic vegetable garden. It attracts beneficial insects like hoverflies and lacewings, which prey on aphids and other pests. Plant it near broccoli to help protect it from cabbage moths. Its low, spreading habit also makes it a good living mulch around taller plants like potatoes, helping to suppress weeds and retain moisture.

Sweet Alyssum also works well with lettuce, providing ground cover to keep the soil cool and moist. Avoid planting it near anything that requires extremely dry soil, as its moderate watering needs might create overly moist conditions for those plants.