Asparagus in Zone 5A — Mountain West

Asparagus is a perennial vegetable that's worth the patience in our short-season Mountain gardens. The flavor of freshly harvested asparagus, especially after our cool nights, is far superior to anything you'll find at the store. Plus, a well-established asparagus patch will provide you with harvests for years to come, a real win for the high-altitude gardener.

Our intense sun and sometimes unpredictable weather can present challenges, but with careful timing and attention, you can absolutely grow asparagus here. Our growing season, around 138 days, demands we get a jump start where we can, and asparagus is no exception.

Transplant your asparagus crowns outdoors in early to mid May, once the danger of hard frost has passed. Before planting, it's crucial to harden off your crowns. Give them about a week of gradual exposure to the outdoors, increasing their time outside each day.

Space the crowns 18-24 inches apart in well-draining soil. Keep an eye on the weather forecasts around transplant time; a late cold snap or even hail can damage young plants, so be ready to cover them if necessary. Buy 1-year-old crowns for the fastest harvest.

Asparagus needs consistent moisture, especially during its first two years, to establish a strong root system. Once established, its deep roots make it fairly drought-tolerant, which is helpful in our dry Mountain climate. Aim for moderate watering, but don't let the soil become waterlogged.

During the active growing season (late spring through summer), check the soil moisture regularly. Stick your finger about 2 inches deep; if it feels dry, it's time to water. Give your asparagus patch about 1-2 inches of water per week, either through rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage, which helps prevent fungal issues in our low-humidity environment.

Signs of underwatering include wilting or yellowing fronds. Overwatering, on the other hand, can lead to crown rot, especially in heavy clay soils. To help retain moisture and suppress weeds, mulch around your asparagus plants with compost or straw. This is particularly helpful in our intense sun, which can quickly dry out the soil.

Asparagus requires minimal pruning, but proper care is essential for long-term productivity. Throughout the growing season, allow the ferns to grow and flourish. These ferns are vital for photosynthesis, which fuels the crown and ensures a good harvest the following year.

Once the ferns have died back in late fall or early spring (after our first frost around late September), you can cut them back to ground level. Be sure to remove and dispose of the dead foliage to prevent overwintering pests and diseases. Remember not to over-harvest spears during the season, allowing some to fern out and nourish the plant.

You can expect your first harvest of asparagus about two years after transplanting the crowns. In our Mountain climate, this means you might start harvesting in early May through early October. Look for spears that are 6-8 inches tall with tight, closed tips.

To harvest, snap or cut the spears off at ground level. Be careful not to damage the surrounding spears or the crown itself. Harvest regularly, every day or two, to encourage continuous production.

As the season progresses, the spears will become thinner and less productive. When the spears thin to about the width of a pencil, it's time to stop harvesting and let the remaining spears fern out. This allows the plant to replenish its energy reserves for the following year. Remember, don't harvest for more than 8 weeks per season to ensure the long-term health of your asparagus patch.

Here are a few common problems you might encounter growing asparagus in our Mountain region:

Asparagus Beetle

• What it looks like: Small, metallic blue or orange beetles and their larvae feeding on spears and ferns. You might see small, dark eggs attached to the spears.
• What causes it: These beetles are attracted to asparagus and can quickly defoliate plants. Our intense sun can stress plants, making them more susceptible.
• How to fix/prevent it: Handpick beetles and larvae. Encourage beneficial insects. In severe cases, use an organic insecticide like pyrethrin.

Crown Rot from Poor Drainage

• What it looks like: Yellowing or wilting ferns, stunted growth, and a mushy, decaying crown.
• What causes it: Overwatering or poorly draining soil creates a breeding ground for fungal pathogens. Our alkaline soil can sometimes exacerbate drainage issues.
• How to fix/prevent it: Ensure good drainage by planting in raised beds or amending the soil with compost. Avoid overwatering. Remove and destroy infected plants.

Thin Spears from Over-Harvesting

• What it looks like: Spears that are significantly thinner than usual, often pencil-thin, even early in the season.
• What causes it: Harvesting too many spears or harvesting for too long depletes the plant's energy reserves.
• How to fix/prevent it: Limit your harvest to 8 weeks per season. Allow plenty of spears to fern out and nourish the plant. Ensure adequate watering and fertilization.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall actually work in asparagus's favor. The low humidity reduces the risk of fungal diseases, and the dry climate minimizes the need for frequent watering once established. However, be vigilant about watering during dry spells and protecting plants from intense UV, which can stress them.

Companion planting can benefit your asparagus in our Mountain gardens. Tomatoes, parsley, and basil are all good companions. Tomatoes deter asparagus beetles, while parsley attracts beneficial insects that prey on asparagus pests. Basil is thought to improve asparagus flavor and vigor.

Avoid planting asparagus near onions or garlic. These plants are allelopathic, meaning they release chemicals that can inhibit the growth of asparagus. Give your asparagus plenty of space and choose companions that support its health and productivity in our unique climate.