Asparagus in Zone 7B — Desert Southwest

Asparagus is a perennial vegetable that's well worth the effort in our Desert Southwest gardens. The taste of freshly harvested asparagus, grilled with a little olive oil, is unbeatable. Plus, it's incredibly versatile in the kitchen, and there's a real satisfaction in harvesting your own spears year after year.

Now, let's be real, desert gardening has its hurdles. The extreme heat and alkaline soil can be tough on plants, but asparagus thrives with the right timing and care. With our long 245-day growing season, you can absolutely grow this delicious vegetable.

Transplant your asparagus crowns outdoors in mid to late March. Before planting, give your crowns about a week to harden off. Gradually expose them to outdoor conditions to avoid shocking them.

Space your crowns 18-24 inches apart to give them plenty of room to spread. Keep an eye on the weather at transplant time. We can still get some late-season temperature swings in the Desert Southwest, so be prepared to protect your young plants if a cold snap hits. Buy 1-year-old crowns, as starting from seed takes several years before you can harvest.

Once established, asparagus needs moderate watering, but it's surprisingly drought-tolerant after a couple of years thanks to its deep roots. During our hot summers, water deeply about twice a week, providing about 1-2 inches of water each time. Use the finger test: stick your finger about 2 inches into the soil. If it feels dry, it's time to water.

During the monsoon season, let the rainfall be your guide, but supplement if needed. In the cooler spring and fall, you can usually reduce watering to once a week, or even less. Always water at the base of the plants to avoid wetting the foliage and encouraging fungal diseases in our arid climate.

If your asparagus spears are thin and spindly, it could be a sign of underwatering, especially during the heat of summer. Yellowing or wilting ferns can indicate overwatering or poor drainage. A good layer of organic mulch, like compost or wood chips, will help retain moisture and regulate soil temperature.

Asparagus pruning is minimal. The key is to let the ferns grow and flourish all summer long. 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 is usually around the time of our first frost in mid- November. Be sure not to harvest for more than 8 weeks each season, as over-harvesting weakens the plant.

Your first asparagus harvest should be about two years after planting your crowns, typically around mid March through late November. Look for spears that are 6-8 inches tall with tight, closed tips. This is when they're at their most tender and flavorful.

To harvest, snap the spears off at ground level. Avoid cutting them, as this can damage the crown. Continue harvesting as spears emerge, but stop when they start to thin out to about the width of a pencil. At this point, let the remaining spears fern out to replenish the plant's energy.

As the first frost approaches in mid- November, it's time to wrap up your harvest for the year. Leaving some spears to fern out in the fall will help ensure a strong and productive crop next spring.

Here are the top 3 issues you might encounter with 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 damage and discoloration.
• What causes it: These beetles are attracted to asparagus plants and thrive in warm weather.
• How to fix/prevent it: Handpick beetles and larvae. Use neem oil or insecticidal soap, especially during spring emergence. Encourage beneficial insects like ladybugs.

Crown Rot from Poor Drainage

• What it looks like: Yellowing or wilting ferns, stunted growth, and mushy, rotting crowns.
• What causes it: Overwatering or poorly draining soil can lead to fungal diseases that attack the crown. Our alkaline soil can exacerbate drainage problems.
• How to fix/prevent it: Ensure good drainage by planting in raised beds or amending soil with compost. Avoid overwatering, especially during monsoon season. Apply a fungicide if necessary.

Thin Spears from Over-Harvesting

• What it looks like: Spears become progressively thinner and weaker, eventually becoming unproductive.
• 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 plenty of spears to fern out and replenish the plant's energy. Fertilize with a balanced fertilizer in the spring.

Desert Southwest Specific Challenges The extreme heat and intense sun can stress asparagus plants, making them more susceptible to pests and diseases. Provide some afternoon shade during the hottest months, especially for young plants. Our arid climate can also lead to underwatering, so be sure to monitor soil moisture and water deeply when needed. The monsoon season can bring heavy rainfall and potential for crown rot, so ensure good drainage and avoid overwatering during this time.

Companion planting can really help your asparagus thrive. Tomatoes make great companions because they deter asparagus beetles with their scent, and asparagus, in turn, repels tomato root nematodes. Parsley is another good choice, attracting beneficial insects that prey on asparagus pests. Basil also helps to repel asparagus beetles and other unwanted insects, plus it thrives in similar conditions.

Avoid planting asparagus near onions or garlic, as they can inhibit asparagus growth. These alliums release compounds into the soil that can stunt the growth of asparagus and reduce its overall yield.