Sweet Alyssum in Zone 6A — Great Plains

Sweet Alyssum is a fantastic addition to any Great Plains garden. Its delicate, honey-scented flowers attract beneficial insects, making it a great companion plant. Plus, it thrives in our intense sunshine and adds a beautiful touch to borders, containers, and even as a living mulch.

Our region can throw some curveballs with extreme temperature swings and occasional hail, but Sweet Alyssum is surprisingly resilient. With a growing season of about 188 days, you have plenty of time to enjoy its blooms if you time your planting right.

Starting Sweet Alyssum indoors gives you a head start, especially if you're in the northern part of our zone where the growing season feels even shorter. Starting seeds indoors from mid-February through early March gives you a strong transplant.

Use seed trays with a good seed-starting mix and keep them warm—around 70°F—until germination. A simple grow light will prevent leggy seedlings. Be sure to water from the bottom to avoid damping off. This is especially useful during our variable spring weather, where indoor conditions are more stable.

Transplanting Sweet Alyssum outdoors from early April through mid-May allows you to get them established before the real heat hits. Before you put them in the ground, harden them off for about a week. Gradually expose the seedlings to outdoor conditions, starting with just a couple of hours a day.

Space the plants 6-8 inches apart to allow for their spreading growth habit. Keep an eye on the weather forecast, as those late spring cold snaps are not uncommon here. Wind protection is essential to give them the best start.

Direct sowing Sweet Alyssum is a simple and effective method, especially if you're not in a rush. Sow the seeds directly into the garden from early April through late August.

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, and keep the soil consistently moist. Thin the seedlings to 6-8 inches apart once they emerge. Direct sowing is a good option for succession planting, ensuring continuous blooms throughout the growing season.

Sweet Alyssum needs moderate watering to thrive in our Great Plains climate. While not particularly drought-tolerant, it also doesn't like soggy soil. The key is to find the right balance.

During the spring and fall, when temperatures are milder and rainfall is more frequent (though variable), aim to water deeply once a week if it hasn't rained. In the heat of summer, when temperatures can soar into the 90s, you may need to water every other day, especially if the plants are in containers. Use the finger test: stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Give them about an inch of water per week.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. Wilting leaves indicate underwatering, while yellowing leaves can signal overwatering. Applying a layer of mulch around the plants helps retain moisture and regulate soil temperature.

Sweet Alyssum requires minimal pruning, but a little attention keeps them looking their best. The main reason to prune is to rejuvenate plants that get leggy in midsummer.

When the plants start to look sparse and stop blooming as heavily, shear them back by about half. Don't worry, they'll bounce back quickly with fresh growth and more flowers. As the first frost approaches around mid-October, you can let the plants go to seed or pull them up to prevent any potential disease from overwintering.

Sweet Alyssum is primarily grown for its ornamental value and its ability to attract beneficial insects, so harvesting isn't really part of the equation. Expect the first blooms about 45 days after planting.

The flowers bloom continuously from mid-May through late October, creating a beautiful carpet of color. The plant acts as a living mulch, suppressing weeds and retaining soil moisture. As the season winds down and the first frost threatens, you can simply leave the plants to overwinter or pull them up and compost them.

Sweet Alyssum is generally easy to grow, but here are the top 3 problems you might encounter in the Great Plains:

Downy Mildew

• What it looks like: Yellow patches on the tops of leaves, with fuzzy gray-purple growth on the undersides. Leaves brown and die from the bottom up.
• What causes it: This is an oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. Different species affect different plants.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around the plants. Water at the base, never overhead. Consider using copper-based fungicides for prevention. Plant resistant varieties where available.

Heat Dieback

• What it looks like: The plant may wilt, turn brown, and appear to die back during the hottest part of summer.
• What causes it: Extreme heat, a common challenge in our Plains summers, can stress the plant beyond its limits.
• How to fix/prevent it: Provide some afternoon shade during the hottest days. Ensure consistent watering, especially during dry spells. Mulch around the plants to help retain soil moisture and keep the roots cool.

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in the leaves. You'll see small dark beetles that jump when disturbed. The worst damage occurs to young seedlings.
• What causes it: These are small jumping beetles that feed on the leaves. 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 plants are larger and better able to withstand the damage. You can also try coating the leaves with kaolin clay or spraying with neem oil. Interplanting with basil or catnip can also help deter these pests.

Great Plains Specific Challenges: The hot, dry summers and variable rainfall in the Great Plains can stress Sweet Alyssum. Consistent watering, mulching, and providing some afternoon shade during the hottest days will help keep your plants healthy and blooming. Also, our often windy conditions can dry out the soil quickly, so monitoring soil moisture is key.

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

Good companions include:

• Broccoli: The beneficial insects attracted by Sweet Alyssum can help control pests that attack broccoli.
• Potato: Sweet Alyssum can act as a living mulch around potato plants, suppressing weeds and retaining soil moisture.
• Lettuce: The low-growing habit of Sweet Alyssum makes it a good ground cover around lettuce, helping to keep the soil cool and moist.

Avoid planting Sweet Alyssum near plants that are highly susceptible to flea beetles, as it can potentially attract these pests to your garden.