Celery in Zone 8B — Northern California

Growing your own celery in Northern California is incredibly rewarding. The taste is far superior to anything you'll find at the store, and it's a versatile addition to soups, salads, and snacks. Plus, the satisfaction of harvesting crisp, homegrown celery in our Mediterranean climate is hard to beat.

We definitely face some challenges here in NorCal, including drought and occasional heat waves, but with careful planning and attention, you can absolutely grow delicious celery. Our long, 269-day growing season gives you plenty of time to get it right.

Starting celery indoors is the way to go in our region, as it needs a long head start. Begin sowing your celery seeds from mid December through early January, roughly 10 weeks before you plan to transplant. Celery seeds are tiny and need light to germinate, so don't bury them too deeply.

Use seed trays filled with a good seed-starting mix, and keep them consistently moist. Bottom watering is a great trick to prevent disturbing the delicate seeds. Place the trays in a warm spot, ideally around 70-75°F, and provide plenty of light, especially with our early spring character. A grow light is your best bet.

Transplant your celery seedlings outdoors from early to late March, once they have a few true leaves and the weather has settled a bit. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Choose a spot with full sun to partial shade, and space the seedlings about 8-10 inches apart. Keep an eye on the weather, as we can still get some unexpected cold snaps. Cover the seedlings if frost is predicted.

Celery is a very thirsty plant, and consistent watering is crucial, especially during our dry summers. You'll need to pay close attention to soil moisture to avoid problems. Our moderate-to-hot summers and low humidity mean you'll likely need to water more frequently than gardeners in other regions.

A good rule of thumb is to aim for about 1-2 inches of water per week, depending on the weather. Use the "finger test" – stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can encourage disease in some areas.

Signs of underwatering include wilting leaves and bitter-tasting stalks. Overwatering can lead to root rot, so make sure the soil is well-draining. A layer of mulch around the plants can help retain moisture and keep the soil cool, which is especially helpful during our warmer months.

You can expect your first celery harvest from late May through mid July, about 85 days after transplanting. Look for outer stalks that are at least 8 inches long. You can harvest individual stalks as needed, or cut the entire plant at the base when the stalks are 12+ inches tall.

For a milder flavor, blanch the stalks by mounding soil around them a week or two before harvesting. To encourage continued production, harvest outer stalks first, leaving the inner ones to mature. As our first frost approaches in late November, harvest any remaining celery, as it won't tolerate freezing temperatures.

Here are three common problems you might encounter growing celery in Northern California:

Bolting from temperature stress

• What it looks like: The plant sends up a flower stalk prematurely, and the stalks become bitter and tough.
• What causes it: Fluctuating temperatures, especially periods of cold followed by sudden warmth, can trigger bolting. This can happen during our spring temperature swings.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide consistent watering and mulch to moderate soil temperature. Shade cloth can help during heat waves.

Hollow stalks

• What it looks like: The stalks develop a hollow center, and the texture becomes spongy.
• What causes it: Inconsistent watering and nutrient deficiencies, especially calcium, can cause hollow stalks.
• How to fix/prevent it: Ensure consistent watering, especially during hot weather. Amend the soil with compost or bone meal to provide essential nutrients.

Stringy stalks from heat

• What it looks like: The celery stalks become tough and stringy, making them unpleasant to eat.
• What causes it: High temperatures, especially during our dry summers, can cause the stalks to become stringy.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Ensure adequate watering. Choose varieties that are more heat-tolerant.

Northern California Specific Challenges: Our moderate-to-hot heat, low humidity, and dry-summer rainfall create unique challenges for growing celery. Consistent watering is absolutely crucial, and providing shade during the hottest part of the day can help prevent bolting and stringy stalks. Pay attention to microclimates in your yard.

Companion planting can be a great way to improve your celery crop. Green beans are good companions because they fix nitrogen in the soil, which benefits celery's growth. Cabbage family plants help deter some pests that might bother your celery.

Tomatoes offer some shade to the celery, which can be beneficial during our warmer months. Onions also deter pests. Avoid planting carrots near celery, as they compete for the same nutrients in the soil.