Asparagus in Zone 9B — Desert Southwest

Asparagus is a true gourmet treat, and growing your own in the Desert Southwest is absolutely worth the effort. The flavor of freshly harvested asparagus, grilled or roasted, is far superior to anything you'll find in the store. Plus, asparagus is a perennial, so once established, you'll have a reliable spring harvest for years to come.

Our desert climate presents unique challenges, but with careful timing and attention to watering, you can successfully grow asparagus here. Our long, 313-day growing season gives these plants plenty of time to mature and establish strong root systems, setting you up for years of delicious harvests.

Transplant your asparagus crowns outdoors in early to mid-February. This gives them a chance to settle in before the extreme heat arrives. Before planting, harden off your crowns by gradually exposing them to outdoor conditions for about a week.

Plant your crowns 18-24 inches apart in well-draining soil. Keep an eye on the weather forecast, as we can still get some late frosts or unexpected cold snaps during this time. Cover the crowns if frost threatens. Remember, you're planting one-year-old crowns, not seeds. It takes years to get a harvest from seed!

Asparagus appreciates consistent moisture, especially during its first two years. Once established, it's surprisingly drought-tolerant, thanks to its deep root system. However, in our arid Desert Southwest climate, "drought-tolerant" doesn't mean "no water."

During the active growing season (spring and fall), water deeply about once a week, providing roughly 1-2 inches of water. Use the finger test: stick your finger into the soil about two inches deep. If it feels dry, it's time to water. During the monsoon season, let the rains do the work, but supplement if rainfall is insufficient. Avoid overhead watering as much as possible to minimize fungal issues in our warm climate; water at the base of the plants.

Signs of underwatering include wilting or yellowing ferns. Overwatering can lead to crown rot, indicated by mushy, brown roots and a foul odor. A layer of organic mulch, like compost or shredded leaves, helps retain moisture in our dry air and regulates soil temperature, but avoid piling it directly against the crown.

Asparagus requires minimal pruning, which is good news for us Desert Southwest gardeners who want easy-care plants. The most important thing is to let the ferns grow and flourish all summer long. These ferns are essential for feeding the crown and ensuring a good harvest the following year.

In late fall or early spring, after the ferns have died back (usually after our first frost around mid- December), you can cut them back to the ground. Be sure to remove all the dead foliage to prevent disease. During the harvest season, don't harvest more than 8 weeks to avoid weakening the plant.

You can expect your first asparagus harvest about two years after transplanting your crowns, typically from early February through late December in our long growing season. Look for spears that are 6-8 inches tall with tight, closed tips. These are the most tender and flavorful.

To harvest, snap the spear off at ground level. Avoid cutting, as this can damage the crown. Continue harvesting until the spears start to become thin and pencil-like. This indicates that the plant needs to rest and replenish its energy reserves.

As the weather cools down in late fall, and the first frost approaches (around mid- December), stop harvesting and let the remaining spears fern out. This will help the plant store energy for the winter and ensure a bountiful harvest next spring.

Here are some common problems you might encounter growing asparagus in the Desert Southwest:

Asparagus Beetle

• What it looks like: Small, elongated beetles, often orange or yellow with dark markings, and their larvae are seen feeding on spears and ferns.
• What causes it: Beetles are attracted to asparagus plants, especially in warmer weather. They lay eggs on the spears, and the larvae can cause significant damage.
• How to fix/prevent it: Handpick beetles and larvae when you see them. Encourage beneficial insects like ladybugs. In severe infestations, use insecticidal soap or neem oil, being mindful of application during our intense sun.

Crown Rot

• What it looks like: Yellowing or wilting ferns, stunted growth, and mushy, brown roots with a foul odor.
• What causes it: Poor drainage, heavy soils, and overwatering create conditions favorable for fungal pathogens that cause crown rot. Our alkaline soils and caliche layers can exacerbate drainage issues.
• How to fix/prevent it: Plant asparagus in well-draining soil amended with plenty of organic matter. Avoid overwatering, especially during the monsoon season. Ensure proper drainage by planting on raised beds if necessary.

Thin Spears (Over-Harvesting)

• What it looks like: Spears that are significantly thinner than usual, often pencil-thin or even smaller.
• What causes it: Harvesting too many spears for too long depletes the plant's energy reserves.
• How to fix/prevent it: Limit your harvest to 6-8 weeks per season. Allow the remaining spears to fern out to replenish the plant's 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 lead to rapid drying of the soil, requiring careful monitoring of watering. Even monsoon moisture needs to be managed to prevent root rot. Providing afternoon shade during the hottest months can help mitigate heat stress.

Companion planting can be a helpful strategy in our Desert Southwest gardens. Tomatoes make good companions for asparagus because they deter asparagus beetles. Parsley is another good choice as it attracts beneficial insects that prey on asparagus pests. Basil can also be a helpful companion, as its strong scent may repel asparagus beetles.

Avoid planting asparagus near onions or garlic. These plants are allelopathic, meaning they release substances that can inhibit the growth of asparagus. In our challenging climate, we want to give our asparagus every advantage possible, so keep these bad companions far away.