Sweet Alyssum in Zone 10B — Desert Southwest

Sweet Alyssum is a fantastic addition to any Desert Southwest garden. Its delicate, honey-scented flowers add beauty and attract beneficial insects, which are always welcome in our gardens. Plus, it acts as a living mulch, helping retain precious moisture in our arid climate.

Gardening in the Desert Southwest comes with unique challenges, but don't let that deter you from growing this rewarding plant. With our long 349-day growing season and careful timing, you can enjoy Sweet Alyssum's blooms for a good portion of the year, especially during our milder periods.

Starting Sweet Alyssum indoors in the Desert Southwest is possible, but direct sowing is often easier. If you want a head start, especially for an early bloom, start seeds indoors from mid November through early December, about six weeks before you plan to transplant.

Use seed trays with a good quality seed-starting mix. Keep the soil consistently moist (bottom watering is great for this) and provide warmth and bright light. Remember, our very-early spring character means you'll want those seedlings ready to go as soon as the weather allows.

Transplant your Sweet Alyssum seedlings outdoors from early January through mid February. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This is important to prevent shock from our intense Desert Southwest sun.

Space the seedlings 6-8 inches apart in well-draining soil. Keep an eye on the weather, as even in January and February, we can get unexpected temperature swings. Protect young transplants from frost if necessary.

Direct sowing Sweet Alyssum is a simple and effective method in our climate. You can direct sow from early January through early November, taking advantage of our two growing seasons. Just avoid the hottest part of summer.

Prepare the soil by loosening it and removing any rocks or debris. Sweet Alyssum prefers soil temperatures between 60-70°F for germination. Sow seeds 6-8 inches apart and lightly cover with soil. Keep the soil consistently moist until seedlings emerge.

Watering is critical for Sweet Alyssum's success in the Desert Southwest's arid climate. While moderately drought-tolerant once established, it needs consistent moisture, especially during its active growing periods. Remember, it goes dormant in the extreme heat, so adjust your watering accordingly.

During the cooler months (early spring and late fall), water deeply about once a week, providing about 1 inch of water. In the hotter months, increase watering to 2-3 times per week, ensuring the soil stays consistently moist but not waterlogged. Use the finger test: if the top 2 inches of soil feel 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 monsoon season.

Overwatering can lead to root rot, while underwatering will cause the plants to wilt and eventually die back. Pay close attention to your plants and adjust your watering schedule based on their needs and the weather conditions. A layer of mulch around the base of the plants will help retain moisture and regulate soil temperature.

Sweet Alyssum requires minimal pruning, but a little maintenance can keep it looking its best in our Desert Southwest gardens. When plants get leggy in midsummer due to the extreme heat, shear them back by about half.

Don't worry, fresh growth and flowers will follow quickly as temperatures cool down. Remove any dead or yellowing leaves throughout the growing season to keep the plants tidy. As the first frost approaches in late December, you can leave the plants in place as a living mulch or remove them to prepare the bed for winter crops.

Sweet Alyssum continuously flowers, so there's no specific "harvest" in the traditional sense. Instead, it serves as a living mulch and attracts beneficial insects to your Desert Southwest garden. Expect the first blooms starting in mid February if you plant in January.

Throughout the growing season, enjoy the fragrant flowers and the benefits they bring to your garden. Deadheading spent flowers can encourage continued blooming, but it's not essential. As the first frost approaches in late December, the plants will naturally decline, but they often self-seed, giving you a head start for the next growing season.

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

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: This oomycete pathogen thrives in cool, humid conditions. In the Desert Southwest, it's most likely to appear during our monsoon season or during periods of unexpected humidity.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around the plants. Water at the base, never overhead. Consider using a copper-based fungicide as a preventative measure.

May Die Back in Extreme Heat

• What it looks like: Plants wilt, leaves turn brown and crispy, and overall growth slows or stops.
• What causes it: Our extreme summer heat can be too much for Sweet Alyssum, even with adequate watering. The plants may go dormant or even die back completely.
• How to fix/prevent it: Provide afternoon shade with shade cloth essential during the hottest months. Water deeply and regularly. Shear back the plants to encourage new growth when temperatures cool down.

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. You might see small, dark beetles that jump when disturbed.
• What causes it: These small jumping beetles feed on the leaves, especially of young seedlings. They're more prevalent during warmer months.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more established. Apply kaolin clay or neem oil spray to deter the beetles.

Desert Southwest Specific Challenges: The extreme heat and arid humidity of the Desert Southwest present unique challenges for Sweet Alyssum. Sunscald can be a problem, so providing afternoon shade is crucial. While the monsoon moisture can be beneficial, it can also create conditions favorable for fungal diseases like downy mildew. Be vigilant in monitoring your plants and taking preventative measures to ensure their health and survival.

Sweet Alyssum makes a great companion plant in the Desert Southwest garden. It attracts beneficial insects that can help control pests on other crops.

Good companions include:

• Broccoli: Sweet Alyssum attracts hoverflies and other beneficial insects that prey on aphids, a common pest of broccoli.
• Potato: The beneficial insects attracted by Sweet Alyssum can help control potato beetles.
• Lettuce: Sweet Alyssum can help deter pests that attack lettuce, such as leafhoppers.

Avoid planting Sweet Alyssum near plants that are susceptible to fungal diseases, as the plant can sometimes contribute to humid conditions around the base of plants.