Sweet Alyssum in Zone 8B — Southeast

Sweet Alyssum is a winner in our Southeast gardens. The honey scent is lovely, it attracts beneficial insects to help manage pests, and it fills in nicely around other plants. Plus, it keeps blooming through our long summer and even into fall.

We do have to deal with the hot, humid summers and clay soil here in the Southeast, which can make gardening a challenge. But with a little planning and attention to timing, you can easily enjoy Sweet Alyssum in your garden, taking advantage of our 255-day growing season.

Starting Sweet Alyssum indoors gives you a head start, especially if you want blooms early. Begin in early to late January, about six weeks before you plan to transplant. It's not essential, but it can be nice.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, either with a grow light or a sunny window. Bottom watering is a great way to keep the soil moist without encouraging fungal diseases. Our spring here in the Southeast can be moderate, so getting a jump on the season indoors helps.

Transplant your Sweet Alyssum seedlings outdoors in late February through early April. Before you do, harden them off for about a week by gradually exposing them to outdoor conditions. This helps them adjust to the Southeast's sun and temperature.

Space the plants 6-8 inches apart, giving them room to spread. Keep an eye on the weather forecast; a late frost is always possible during this time, so be ready to cover your plants if needed.

Direct sowing Sweet Alyssum is easy, especially with our long growing season. Sow seeds directly into the garden from late February through late September. This gives you a wide window to work with.

Prepare the soil by loosening it and adding some compost. Sweet Alyssum prefers soil temperatures around 60-70°F for germination. Direct sowing is convenient, but be aware that seedlings may be more vulnerable to pests and weather fluctuations than transplants.

Sweet Alyssum needs moderate watering, which can be tricky in our Southeast climate. During the spring and fall, when temperatures are milder, aim for about 1 inch of water per week, either from rainfall or irrigation. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water.

In the heat of the summer, especially during dry spells, you might need to water more frequently. However, avoid overwatering, as our humid conditions can lead to fungal problems. Water at the base of the plants to keep the foliage dry and reduce disease pressure.

Look out for signs of under- or overwatering. Wilting leaves indicate not enough water, while yellowing leaves can mean too much. A layer of mulch helps retain moisture and suppress weeds, but avoid piling it against the stems, which can encourage rot in our humid climate.

Sweet Alyssum doesn't need a lot of pruning, but a little maintenance keeps it looking its best. When the plants get leggy in midsummer, shear them back by about half. This encourages fresh growth and more blooms.

Use clean pruning shears to make the cuts. Don't be afraid to cut back quite a bit; Sweet Alyssum is resilient. As our first frost approaches in mid- November, you can leave the plants in place. They may survive the winter or reseed themselves for next year.

Sweet Alyssum isn't really a plant you "harvest" in the traditional sense. It flowers continuously from early April through late November, providing beauty and attracting beneficial insects. Instead of harvesting, think of it as a living mulch and a pollinator magnet.

The flowers will bloom profusely without any deadheading. Just enjoy the show! As the season winds down and the first frost approaches, you can let the plants go to seed, allowing them to self-sow for the following year.

Here are some common problems you might encounter with Sweet Alyssum in the Southeast:

Downy Mildew

• What it looks like: Yellow patches on the tops of leaves, with fuzzy gray-purple growth on the undersides. The leaves will brown and die, starting from the bottom of the plant.
• What causes it: This is an oomycete pathogen that thrives in cool, humid conditions. The spores are carried by the wind, and different species affect different plants. Our humid Southeast climate is perfect for this disease.
• How to fix/prevent it: Remove any affected leaves immediately to prevent the spread. Improve air circulation around your plants. Water at the base, never overhead. Consider using a copper-based fungicide as a preventative measure. If possible, choose disease-resistant varieties.

May die back in extreme heat

• What it looks like: The plant may appear wilted, stunted, or may even die back in the hottest part of summer.
• What causes it: Prolonged exposure to high temperatures can stress Sweet Alyssum, especially when combined with high humidity. While it can tolerate some heat, extreme conditions can cause it to go dormant or even die.
• How to fix/prevent it: Provide some afternoon shade during the hottest part of the day. Ensure adequate watering, but avoid overwatering in humid conditions. Mulch can help retain moisture and regulate soil temperature.

Flea Beetles

• What it looks like: Tiny, round holes (shot-hole pattern) in the leaves. You might also see small, dark beetles that jump when disturbed. The damage is usually worst on young seedlings.
• What causes it: These are small jumping beetles that feed on the leaves of various plants. They're most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until the plants are larger and more resilient. You can also try coating the leaves with kaolin clay or spraying with neem oil. Interplanting with basil or catnip can help repel them.

Southeast Specific Challenges: The hot and humid summers in the Southeast, combined with our wet-summer rainfall, create ideal conditions for fungal diseases like downy mildew. Be vigilant about watering practices, air circulation, and choosing disease-resistant varieties to keep your Sweet Alyssum healthy and thriving.

Sweet Alyssum makes a great companion plant in the Southeast garden. It attracts beneficial insects like hoverflies and ladybugs, which prey on pests.

Good companions include:

• Broccoli: Sweet Alyssum attracts beneficial insects that help control broccoli pests like aphids.
• Potato: The flowers attract pollinators, potentially increasing potato yields.
• Lettuce: Sweet Alyssum acts as a living mulch, helping to keep the soil cool and moist, which lettuce appreciates, especially as the weather heats up here.

I wouldn't recommend planting it near anything that requires very dry soil, since Sweet Alyssum likes moderate moisture.