Sweet Alyssum in Zone 7A — Pacific Northwest

Sweet Alyssum is a delightful addition to any Pacific Northwest garden. Its delicate fragrance, charming blooms, and ability to attract beneficial insects make it a winner. Plus, it's edible, adding a touch of sweetness to salads.

While our wet springs and relatively short stretches of warm weather can present challenges, Sweet Alyssum thrives with proper timing. With a 183-day growing season, you'll have plenty of time to enjoy its beauty and benefits.

Starting Sweet Alyssum indoors gives you a head start, especially with our cool spring soil temperatures. If you're eager to see blooms as early as possible, consider starting seeds indoors from mid-February through early March, roughly six weeks before you plan to transplant.

Use seed trays filled with a good seed-starting mix. Keep the trays warm (around 70°F) and provide plenty of light, either from a sunny windowsill or a grow light. A little trick I find helpful is to bottom-water the trays to prevent damping off.

Once the danger of frost has passed, typically from early April through mid-May, it's time to transplant your Sweet Alyssum seedlings outdoors. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space the plants 6-8 inches apart in a sunny or partially shaded location. Keep an eye on the weather forecast – those overcast spring days can still bring unexpected chills.

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

Prepare the soil by loosening it and removing any weeds. Sweet Alyssum prefers soil temperatures around 60-70°F for optimal germination. Space the seeds 6-8 inches apart and cover them with a thin layer of soil.

Sweet Alyssum needs moderate watering, but it's important to get it right in our unique Pacific Northwest climate. During our wet springs, you may not need to water at all, relying on natural rainfall. Once our dry summer months arrive, you'll need to water more regularly.

A good rule of thumb is to check the soil moisture about two inches deep – if it feels dry to the touch, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our sometimes humid conditions.

Overwatering can lead to root rot, while underwatering can cause the plants to wilt and become stressed. Mulching around the plants with compost or bark chips helps retain moisture and suppress weeds, which is always a bonus. If the alyssum goes dormant due to extreme heat, don't panic, it will return when temperatures cool down.

Sweet Alyssum requires minimal pruning, but a little attention can keep it looking its best. The main thing you'll want to do is shear back the plants by about half when they start to get leggy, usually in midsummer.

This encourages fresh growth and a new flush of flowers. Don't be afraid to be a bit aggressive – Sweet Alyssum is quite resilient. As the first frost approaches around mid-October, you can let the plants go to seed or pull them up if you prefer.

While you don't "harvest" Sweet Alyssum in the traditional sense, you can enjoy its benefits throughout the growing season. Expect the first blooms to appear roughly 45 days after planting, which means late May if you direct sow in early April.

Sweet Alyssum flowers continuously, attracting beneficial insects to your garden. You can also use the flowers as a living mulch, suppressing weeds and adding beauty to your beds. As the season winds down and the first frost approaches in mid-October, let the plants go to seed to encourage self-sowing for next year, or simply enjoy the last blooms before winter sets in.

Here are a few common problems you might encounter with Sweet Alyssum in the Pacific Northwest:

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 thrives in cool, humid conditions, which we often experience in our spring and fall. Spores spread easily by wind. *How to fix/prevent it:* Remove affected leaves promptly. Improve air circulation by spacing plants adequately. Water at the base of the plants, avoiding overhead watering. For prevention, consider a copper-based fungicide. Look for resistant varieties when purchasing seeds.

May Die Back in Extreme Heat Sweet Alyssum may go dormant during brief periods of extreme heat, but will bounce back when temperatures cool down.

Flea Beetles *What it looks like:* Tiny round holes (shot-hole pattern) in the leaves, especially on young seedlings. You might also see small, dark beetles that jump when disturbed. *What causes it:* Flea beetles are small jumping beetles that feed on leaves. They're most damaging to small, young plants. *How to fix/prevent it:* Protect seedlings with row covers during their vulnerable stage. Delay planting until 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 may also help deter them.

Pacific Northwest Specific Challenges: Our mild summers and dry-summer humidity, coupled with dry-summer rainfall, generally favor Sweet Alyssum. However, be vigilant for downy mildew during periods of prolonged wet weather. Also, be aware that slugs can be an issue, especially for young plants, so take appropriate control measures.

Sweet Alyssum makes a great companion plant for several vegetables in the Pacific Northwest garden. It attracts beneficial insects that can help control pests on your broccoli, potato, and lettuce.

• Broccoli: The beneficial insects attracted by Sweet Alyssum can prey on aphids and other pests that commonly attack broccoli.
• Potato: Sweet Alyssum can help deter potato beetles.
• Lettuce: It provides ground cover, helping to retain moisture and suppress weeds around lettuce plants.

I wouldn't recommend planting it near anything that's highly susceptible to flea beetles, as it might attract more of those pests to your garden overall.