Asparagus in Zone 8B — Desert Southwest

Asparagus is a worthwhile addition to any Desert Southwest garden. The taste of fresh-picked asparagus is far superior to anything you'll find in the store, and it's incredibly versatile in the kitchen. Plus, there's a unique satisfaction in harvesting spears from a plant you've nurtured for years, especially in our challenging climate.

Growing asparagus here in Zone 8B does present some hurdles, like our extreme summer heat and alkaline soil. But with careful planning and proper techniques, you can successfully grow asparagus and enjoy a bountiful harvest during our long, 279-day growing season.

Transplant your asparagus crowns outdoors in late February through early March. This timing allows the plants to establish themselves before the extreme heat hits. Before planting, harden off the crowns by gradually exposing them to outdoor conditions for about a week.

When you're ready to plant, space the crowns 18-24 inches apart. Remember, you're planting for the long haul with asparagus, so choose your location carefully.

Watering asparagus correctly is key, especially in our arid Desert Southwest climate. While established asparagus is fairly drought-tolerant, consistent moisture is crucial, especially during the first two years. The monsoon season can be tricky; just because it rained doesn't mean the soil is adequately watered.

During the cooler spring and fall, water deeply about once a week, providing roughly 1-2 inches of water each time. Use the "finger test" – stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. In the extreme heat of summer, increase watering to 2-3 times a week, or more if the soil dries out quickly.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases even in our dry climate. Signs of underwatering include wilting and yellowing leaves. Overwatering can lead to root rot, indicated by stunted growth and mushy roots. Mulching around your asparagus with compost or straw will help retain moisture and regulate soil temperature.

Asparagus requires minimal pruning, which is great for us Desert Southwest gardeners who want low-maintenance plants. During the growing season, let the ferns grow freely. These ferns are essential for feeding the crown and ensuring a good harvest next year.

In late fall or early spring, after the ferns have died back and turned brown, cut them down to the ground. This helps remove potential overwintering sites for pests and diseases. Remember not to harvest for more than 8 weeks each season to allow the plant to replenish its energy reserves.

You can expect your first asparagus harvest in late February through mid December, about two years after planting the crowns. Look for spears that are 6-8 inches tall with tight, closed tips. These are the most tender and flavorful.

To harvest, snap the spears off at ground level. Avoid cutting them, as this can damage the crown. Continue harvesting until the spears become thin, about the width of a pencil. At that point, stop harvesting and allow the remaining spears to fern out.

As the first frost approaches around early December, stop harvesting and allow the plant to rest for the winter. This allows the crown to store energy for the next growing season.

Here are the top three problems you might encounter growing asparagus in the Desert Southwest:

Asparagus Beetle

• What it looks like: Small, metallic blue or orange beetles and their larvae feeding on spears and ferns, causing defoliation and stunted growth.
• What causes it: These beetles thrive in warm weather and can quickly infest asparagus patches.
• How to fix/prevent it: Handpick beetles and larvae. Encourage beneficial insects. Use insecticidal soap as a last resort, following label instructions carefully.

Crown Rot from Poor Drainage

• What it looks like: Yellowing and wilting ferns, stunted growth, and mushy, decaying roots.
• What causes it: Asparagus prefers well-drained soil. Our alkaline soil and occasional caliche layers can lead to poor drainage, especially during monsoon season.
• How to fix/prevent it: Ensure good soil drainage by amending with plenty of organic matter and planting in raised beds if necessary. Avoid overwatering.

Thin Spears from Over-Harvesting

• What it looks like: Spears become progressively thinner and weaker over time.
• What causes it: Harvesting too many spears for too long depletes the plant's energy reserves.
• How to fix/prevent it: Limit harvesting to 8 weeks per season. Allow the plant to fern out and replenish its energy stores.

Desert Southwest Specific Challenges: The extreme heat of our summers can stress asparagus plants, making them more susceptible to pests and diseases. The arid humidity can also lead to rapid soil drying, requiring careful monitoring and watering. The monsoon rainfall can be a blessing and a curse, providing much-needed moisture but also increasing the risk of crown rot in poorly drained soils.

Companion planting can be a helpful strategy for growing asparagus in the Desert Southwest. Tomatoes, parsley, and basil are all good companions for asparagus. Tomatoes provide shade during the hottest part of the day, protecting the asparagus from sunscald. Parsley attracts beneficial insects that prey on asparagus beetles. Basil repels asparagus beetles and other pests.

Avoid planting asparagus near onions or garlic. These plants can inhibit asparagus growth and attract harmful pests. By choosing the right companions, you can create a thriving and productive asparagus patch in your Desert Southwest garden.