Asparagus in Zone 6B — Mountain West

Asparagus is a true treat in our Mountain gardens. Its unique, slightly sweet flavor is unmatched by store-bought versions, and those early spring spears are a welcome sign after a long winter. Plus, asparagus is a perennial – plant it once, and with a little care, you'll enjoy harvests for years to come.

Our high altitude, intense sun, and short growing season present challenges, but asparagus is surprisingly well-suited to our climate. The cool nights even in summer actually improve its flavor. With careful timing and attention, you can absolutely grow delicious asparagus within our 163-day growing season.

Transplant your asparagus crowns outdoors from late April through early May, after the last expected frost. Before planting, be sure to harden off your asparagus by gradually exposing them to the outdoor elements for about a week. This will help them adjust to the intense sun and cool nights that are common in our Mountain region.

Space the crowns 18-24 inches apart, giving them plenty of room to spread their roots. At this time of year, keep an eye out for late-season snow or hail, which can damage young transplants. You'll want to buy 1-year-old crowns for transplanting, as starting from seed can add several years before your first harvest.

Asparagus needs moderate watering, especially during its establishment phase. Once established (after about two years), it becomes fairly drought-tolerant thanks to its deep root system.

During the first year, water deeply about once a week, providing roughly 1 inch of water. Use the "finger test" – stick your finger about 2 inches into the soil near the plant. If it feels dry, it's time to water. Because our humidity is so low, watering at the base of the plant is ideal to avoid fungal issues. In the Mountain West, our dry climate means overhead watering isn't as risky as it is in more humid regions.

Signs of underwatering include yellowing or wilting ferns, while overwatering can lead to crown rot (more on that later). A layer of mulch, like straw or wood chips, can help retain moisture and regulate soil temperature, which is especially helpful in our climate with intense sun and cool nights.

Asparagus pruning is minimal but important. During the growing season, let the ferns grow freely – they're 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 and turned brown, cut them down to the ground. Make sure you don't harvest for more than 8 weeks in a season, or you will weaken the plant.

You can expect your first harvest of asparagus in late April through mid October, about two years after transplanting the crowns. Look for spears that are 6-8 inches tall with tight, unopened tips.

To harvest, snap the spear off at ground level – you can also use a sharp knife. Be careful not to damage the surrounding spears. Continue harvesting until the spears start to become thin, about the width of a pencil. This signals that it's time to let the remaining spears fern out and focus on storing energy for next year's crop.

As the first frost approaches in early October, stop harvesting altogether and allow the remaining ferns to grow. This will help the plant build up its reserves for the winter.

Here are some common problems you might encounter with asparagus in the Mountain West:

Asparagus Beetle *What it looks like:* Small, metallic blue or black beetles and their larvae feeding on spears and ferns, causing damage and discoloration. *What causes it:* These beetles are attracted to asparagus plants. Our intense UV can actually worsen infestations by weakening the plants. *How to fix/prevent it:* Handpick beetles and larvae, use insecticidal soap, or introduce beneficial insects like ladybugs. Row covers can also help prevent beetles from reaching your plants.

Crown Rot *What it looks like:* Yellowing or wilting ferns, stunted growth, and a mushy, decaying crown. *What causes it:* Poor drainage and overly wet soil create conditions for fungal diseases to thrive. Alkaline soil may also contribute to fungal issues. *How to fix/prevent it:* Ensure good drainage by planting in well-draining soil and avoiding overwatering. Amend heavy clay soils with compost. Consider raised beds if your soil is particularly problematic.

Thin Spears from Over-Harvesting *What it looks like:* Spears that are much thinner than usual, often pencil-thin or smaller. *What causes it:* Harvesting too many spears for too long depletes the plant's energy reserves. Our short growing season means the plant has less time to recover. *How to fix/prevent it:* Limit your harvest to 6-8 weeks per season, and stop harvesting when the spears start to thin out. Allow the remaining spears to fern out and replenish the plant's energy.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall can actually be beneficial for asparagus, reducing the risk of fungal diseases compared to more humid climates. However, the intense sun can stress the plants, so adequate watering and mulching are essential.

Good companion plants for asparagus in the Mountain West include:

• Tomato: Tomatoes deter asparagus beetles and thrive in similar conditions of full sun.
• Parsley: Parsley attracts beneficial insects that prey on asparagus beetle larvae.
• Basil: Basil repels asparagus beetles and improves the flavor of asparagus.

Avoid planting asparagus near:

• Onion and Garlic: These plants can inhibit asparagus growth due to allelopathic compounds they release into the soil.