Asparagus in Zone 7B — Northern California

Asparagus is a true taste of spring in Northern California. The crisp, slightly grassy flavor is a world away from anything you'll find in the grocery store. Plus, its perennial nature means you'll enjoy harvests for years to come, a rewarding prospect for any NorCal gardener.

Our Mediterranean climate, with its dry summers and mild winters, does present challenges like drought and water restrictions. However, asparagus is surprisingly resilient once established. With our long 245-day growing season, you'll have ample opportunity to nurture your asparagus patch.

Transplant your asparagus crowns outdoors from mid to late March. This gives them a good head start before our dry summers arrive. Before planting, be sure to harden off your crowns by gradually exposing them to outdoor conditions for about a week.

Plant the crowns 18-24 inches apart in well-draining soil. Keep an eye on the weather forecast – a late frost could damage new growth, so be prepared to cover your plants if necessary. Remember, buying 1-year-old crowns is the fastest route to a good harvest, saving you years compared to starting from seed.

While asparagus is drought-tolerant once established, proper watering is crucial, especially in our dry Northern California climate. During the first two years, consistent watering is key to developing a strong root system. After that, you can ease up a bit.

During the growing season (spring and summer), aim to water deeply about once a week. Give them about 1-2 inches of water per week, depending on rainfall. 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. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our low-humidity environment.

Signs of underwatering include yellowing or wilting ferns. Overwatering, on the other hand, can lead to root rot. To help retain moisture and suppress weeds, mulch around your asparagus plants with compost or wood chips.

Asparagus requires minimal pruning, which is great for busy Northern California gardeners. The most important thing is to let the ferns grow and flourish throughout the summer and fall. These ferns are essential for feeding the crown and ensuring a good harvest next year.

Once the ferns turn brown and die back in late fall or early spring (after our first frosts in mid- November), you can cut them back to the ground. Avoid harvesting spears for more than 8 weeks each season.

The first harvest from your asparagus patch typically arrives from mid March through late November, about two years after planting 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. Be careful not to damage the surrounding spears or the crown. Continue harvesting regularly, every day or two, as new spears emerge. Stop harvesting when the spears become thin and pencil-like. This signals that the plant needs to conserve energy for the following year. As fall approaches and our first frosts arrive around mid- November, let the remaining spears fern out to strengthen the plant for the winter.

Here are some common problems Northern California asparagus growers might face:

Asparagus Beetle

• What it looks like: Small, elongated beetles (often reddish-orange or bluish-black) and their larvae feeding on spears and ferns. You might see small, dark eggs attached to spears.
• What causes it: These beetles are attracted to asparagus plants and thrive in our moderate-to-hot summer temperatures.
• How to fix/prevent it: Handpick beetles and larvae. Encourage beneficial insects like ladybugs. In severe cases, use insecticidal soap or neem oil, following label instructions carefully.

Crown Rot from Poor Drainage

• What it looks like: Yellowing or wilting ferns, stunted growth, and mushy, brown roots.
• What causes it: Overwatering or poorly draining soil, especially during our wet winter months, can lead to fungal diseases that rot the crown.
• How to fix/prevent it: Ensure your asparagus bed has excellent drainage. Amend heavy clay soils with compost and other organic matter. Avoid overwatering, especially during the dormant season.

Thin Spears from Over-Harvesting

• What it looks like: Spears that are consistently thin and pencil-like, even at the beginning of the harvest season.
• What causes it: Harvesting too many spears or harvesting for too long weakens the plant and depletes its energy reserves.
• How to fix/prevent it: Limit your harvest to 6-8 weeks per season. Let plenty of spears fern out to replenish the plant's energy. Ensure the plants receive adequate water and nutrients.

Northern California Specific Challenges: Our dry summers and potential water restrictions mean you need to be vigilant about watering, especially during the first few years. Mulching is key to retaining moisture and reducing water needs. Also, be aware of microclimates in your area – some spots might be hotter and drier than others, requiring adjustments to your watering schedule.

Good companion plants for asparagus in Northern California include tomatoes, parsley, and basil. Tomatoes provide shade that can help protect asparagus from the intense summer sun. Parsley attracts beneficial insects that prey on asparagus pests. Basil can help repel asparagus beetles with its strong scent.

Avoid planting asparagus near onions and garlic. These plants can inhibit asparagus growth and may compete for resources in your garden.