Sweet Alyssum in Zone 6B — Southeast

Sweet Alyssum is a fantastic addition to any Zone 6B Southeast garden. Its delicate, honey-scented flowers attract beneficial insects, making it a wonderful companion plant for your vegetables. Plus, it thrives in our long summer, providing continuous blooms from spring until frost.

While we do face challenges like humidity and fungal diseases, Sweet Alyssum's relatively short maturity time allows you to get a head start and enjoy its benefits throughout our 208-day growing season. Proper timing and a few preventative measures will help ensure success.

Starting Sweet Alyssum indoors in the Southeast is possible, but direct sowing is often easier. If you want a really early start, you can sow seeds indoors from early to late February, about six weeks before you plan to transplant.

Use seed trays filled with a good seed-starting mix, and keep them warm and consistently moist. Bottom watering helps prevent damping off, which can be a problem in our humid climate. Place the trays under grow lights, because our spring weather can be surprisingly moderate and overcast.

Transplant your Sweet Alyssum seedlings outdoors from late March through early May. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Southeast's fluctuating spring temperatures.

Space the plants 6-8 inches apart in well-draining soil. Keep an eye on the weather forecast, as a late frost can still occur during this time. Cover the seedlings if frost is predicted.

Direct sowing Sweet Alyssum is a simple and effective method in the Southeast. Sow seeds directly into the garden from late March through early September. This gives you a long window to establish plants.

Prepare the soil by loosening it and removing any weeds. Sweet Alyssum prefers soil temperatures around 60-70°F for optimal germination. Sow seeds thinly and lightly cover them with soil. Keep the soil consistently moist until the seedlings emerge, usually within a week or two. Thin seedlings to 6-8 inches apart.

Sweet Alyssum needs moderate watering to thrive in the Southeast. During the spring and fall, when temperatures are milder, water deeply once or twice a week, providing about an inch of water each time. Use the "finger test" – if the top two inches of soil feel dry, it's time to water.

In the heat of summer, especially during dry spells, you might need to water more frequently. Sweet Alyssum can go dormant in extreme heat, but it will bounce back when temperatures cool. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Overwatering can be just as detrimental as underwatering. Signs of overwatering include yellowing leaves and wilting, even when the soil is wet. Signs of underwatering include dry, crispy leaves and stunted growth. Mulching around the plants with pine straw or shredded bark helps retain moisture and suppress weeds, which is beneficial in our wet-summer climate.

Sweet Alyssum requires minimal pruning, but a little maintenance can keep it looking its best in the Southeast. During the long summer, plants may get leggy and stop blooming profusely. When this happens, shear them back by about half.

Use sharp garden shears to remove the spent flowers and trim back any long, straggly stems. This encourages fresh growth and a new flush of blooms. Don't worry about being too precise; Sweet Alyssum is quite forgiving. As the first frost approaches in late October, you can leave the plants in place, as they may provide some winter interest or reseed themselves.

Sweet Alyssum is primarily grown for its ornamental value and its ability to attract beneficial insects, so there's no need for traditional harvesting. You can expect the first blooms about 45 days after sowing, from early May through early November.

The plants will flower continuously throughout the growing season, providing a constant source of nectar for pollinators. Simply enjoy the blooms and the benefits they bring to your garden. To encourage continued production, deadhead spent flowers occasionally, although this isn't strictly necessary. As the first frost approaches in late October, the plants will naturally begin to decline.

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 a fuzzy gray-purple growth on the undersides. Leaves brown and die from the bottom up.
• What causes it: This is an oomycete pathogen that thrives in cool, humid conditions. The spores spread easily via wind, and our humid springs and falls are perfect breeding grounds for it.
• How to fix/prevent it: Remove affected leaves immediately to prevent further spread. Improve air circulation around the plants by spacing them properly. Water at the base, avoiding overhead watering. Copper-based fungicides can be used as a preventative measure. Plant resistant varieties if available.

Dieback in Extreme Heat

• What it looks like: The plants may wilt, turn brown, and appear to die back during the hottest part of the summer.
• What causes it: Sweet Alyssum prefers cooler temperatures and can struggle in our intense summer heat.
• How to fix/prevent it: Provide some afternoon shade during the hottest months. Water deeply and regularly to help the plants cope with the heat stress. Mulch around the plants to help retain moisture and keep the soil cool. Don't worry too much; they often recover when the weather cools down.

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 are 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 able to withstand the damage. You can also try coating the plants with kaolin clay or spraying them with neem oil. Interplanting with basil or catnip can help repel flea beetles. Healthy, vigorous plants will often outgrow the damage.

Southeast Specific Challenges: The hot heat and humid humidity of the Southeast create a perfect environment for fungal diseases like downy mildew. Our wet-summer rainfall can also exacerbate these problems. Proper spacing, watering practices, and preventative measures are essential for growing healthy Sweet Alyssum in our region.

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

Good companions include broccoli, potato, and lettuce. Broccoli benefits from the pest control provided by the beneficial insects attracted to Sweet Alyssum. Potatoes benefit from the living mulch effect, which helps suppress weeds and retain moisture in our clay soil. Lettuce also benefits from the shade and moisture retention provided by Sweet Alyssum, especially during the heat of summer. Avoid planting Sweet Alyssum near plants that are highly susceptible to flea beetles, as it can sometimes attract these pests.