Sweet Alyssum in Zone 7A — Midwest

Sweet Alyssum is a winner in the Midwest garden. It's not just pretty with its delicate flowers and sweet scent, but it also attracts beneficial insects to your vegetable patch. Plus, it thrives in our fertile soil and offers a long bloom season, bringing beauty to your garden from mid-spring all the way into late fall.

Our Midwest weather can be unpredictable, with cold winters and the occasional summer heat spells. But with a little planning and attention to timing, Sweet Alyssum is easy to grow here. Our long 193-day growing season gives you plenty of time to enjoy its benefits.

Starting Sweet Alyssum indoors isn't strictly necessary, but it can give you a head start, especially if you're eager for early blooms. If you want to get going early, start your seeds indoors in early to late February, about six weeks before you plan to transplant them outside.

Use seed trays filled with a good seed-starting mix. Keep the trays warm and provide plenty of light, either with a grow light or a sunny windowsill. Consider bottom watering to keep the seedlings consistently moist without soaking the foliage. Since our springs can be moderate-to-late, this indoor start ensures you have blooms ready as soon as the weather cooperates.

Transplant your Sweet Alyssum seedlings outdoors in late March through early May, after the danger of a hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest weather.

Plant them 6-8 inches apart in well-drained soil. Keep an eye on the weather forecast as you approach transplant time. We sometimes get a late frost that can damage young plants, so be ready to cover them if needed.

Direct sowing Sweet Alyssum is a simple and effective method, especially for later blooms. Sow seeds directly into your garden beds from late March through late August. This gives you a long window for successive sowings and continuous blooms.

Prepare the soil by loosening it and removing any weeds. Sweet Alyssum seeds need light to germinate, so just press them gently into the soil surface. Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 6-8 inches apart. Direct sowing works well, but keep in mind that germination can be slower than starting indoors, especially in cooler soil.

Sweet Alyssum needs moderate watering to thrive in our Midwest climate. While we get good rainfall, consistent moisture is key, especially during those summer heat spells. Aim for about 1 inch of water per week, whether from rain or irrigation.

Check the soil moisture by using the "finger test." Stick your finger into the soil about 2 inches deep. If it feels 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 moderate-to-humid climate.

Watch for signs of underwatering, such as wilting leaves, or overwatering, such as yellowing leaves. A layer of mulch around your plants helps retain moisture and suppress weeds. In the Midwest, organic mulches like shredded bark or straw work well.

Sweet Alyssum requires minimal pruning, but a little attention can keep your plants looking their best. When the plants get leggy in midsummer, shear them back by about half. Don't worry, fresh growth and flowers will follow quickly.

Use sharp scissors or pruning shears to make clean cuts. Leave the healthy, green growth intact. As the first frost approaches around mid- October, you can let the plants go to seed or pull them up. They might self-sow, giving you a head start next spring.

Sweet Alyssum is primarily grown for its beauty and its ability to attract beneficial insects, so there's no need to "harvest" in the traditional sense. The plants will flower continuously from mid May through late October, providing a constant display of color.

Because it's a living mulch and beneficial insect attractant, you're really harvesting the benefits it brings to the garden ecosystem. No specific signs of ripeness needed. Just enjoy the blooms and the activity around your plants.

As the first frost approaches in mid- October, you can leave the plants to self-seed or pull them up. If you let them self-seed, you might find new plants popping up in the spring.

Here are three common problems you might encounter with Sweet Alyssum in the Midwest:

Downy Mildew

• What it looks like: Yellow patches on the tops of the leaves, with fuzzy gray-purple growth on the undersides. Leaves start to brown and die from the bottom up.
• What causes it: This is caused by an oomycete pathogen that thrives in cool, humid conditions. The spores are spread by wind.
• How to fix/prevent it: Remove any affected leaves immediately. Improve air circulation around your plants. Water at the base, never overhead. You can also use copper-based fungicides for prevention.

Die Back in Extreme Heat

• What it looks like: The plants may wilt, brown, and appear to die back during periods of intense heat.
• What causes it: Sweet Alyssum prefers moderate temperatures and can struggle during our summer heat spells.
• How to fix/prevent it: Provide some afternoon shade during the hottest part of the day. Water deeply during heat waves. The plants will often recover when temperatures cool 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.
• What causes it: These are small jumping beetles that feed on the leaves. They are most damaging to young seedlings.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. You can also delay planting until the plants are larger. Try a kaolin clay coating or neem oil spray. Interplanting with basil or catnip can also help.

Midwest Specific Challenges: Our moderate-to-hot summers, moderate-to-humid humidity, and wet-summer rainfall can create conditions favorable for fungal diseases like downy mildew. Keep an eye on your plants and take preventive measures to keep them healthy.

Sweet Alyssum makes a great companion plant in the Midwest garden.

Good companions:

• Broccoli: Sweet Alyssum attracts beneficial insects that prey on broccoli pests, like aphids and cabbage worms.
• Potato: The sweet scent of Alyssum can deter potato beetles.
• Lettuce: Alyssum acts as a living mulch, keeping the soil cool and moist for lettuce.

Avoid planting it near anything extremely heat-sensitive, as Alyssum itself can struggle in extreme heat, and you don't want to exacerbate the issue for its neighbors.