Celery in Zone 8A — Northern California

Growing your own celery here in Northern California is incredibly rewarding. The taste is far superior to anything you'll find at the grocery store, and it's a staple in so many dishes, from soups and salads to snacking with peanut butter. Plus, with our long growing season, you can often get multiple harvests.

Sure, we face challenges like drought and those unpredictable temperature swings, but with careful planning and water-wise gardening techniques, you can absolutely grow delicious celery. Our 255-day growing season gives you plenty of time to get it right.

Starting celery from seed indoors is the way to go in our region. You'll want to get those tiny seeds going late December through mid January, giving them about 10 weeks indoors before transplanting. Celery seeds are notoriously slow to germinate, so be patient!

Use seed trays with a good seed-starting mix and provide consistent warmth, ideally around 70-75°F. A heat mat can be a lifesaver. Don't bury the seeds too deep, as they need light to germinate. I like to bottom-water my seed trays to keep the soil consistently moist without disturbing the delicate seedlings. Given our early springs here in Northern California, this head start is crucial.

Once the danger of frost has passed, usually early March through early April, it's time to transplant your celery seedlings outdoors. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sunlight and temperature fluctuations.

Choose a spot with full sun to partial shade. Space the seedlings about 8-10 inches apart. Keep an eye on the weather; those late-season cold snaps can still happen. If a frost is predicted, cover your young plants with frost cloth.

Celery is a thirsty plant, and keeping it consistently watered is critical, especially with our dry summers. Aim to water deeply and regularly, providing at least 1-2 inches of water per week, depending on the weather. Use the "finger test" – stick your finger about 2 inches into the soil; if it feels dry, it's time to water.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases. While our humidity is generally low, it's still a good practice. 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 good layer of mulch, like straw or wood chips, will help retain moisture and keep the soil cool during those moderate-to-hot summer days.

In the heat of summer, you might need to water every day, especially if you're growing in containers. As the weather cools down in the fall, you can reduce watering frequency.

You can expect your first celery harvest early June through late July, about 85 days after transplanting. Look for stalks that are at least 8 inches tall. You can harvest individual outer stalks as needed, allowing the inner stalks to continue growing.

For a larger harvest, you can cut the entire plant at the base when the stalks are 12 inches or more. If you prefer a milder flavor, blanch the stalks by mounding soil around them a week or two before harvest. To encourage continued production, don't harvest all the stalks at once. As our first frost approaches around mid- November, harvest any remaining celery to prevent frost damage.

Celery, while delicious, can be a bit finicky. Here are some common problems we see in Northern California.

Bolting from Temperature Stress

• What it looks like: The plant prematurely sends up a flower stalk, making the stalks tough and bitter.
• What causes it: Wide temperature fluctuations, especially early in the season, can stress the plant and trigger bolting. Those temperature swings we often get in spring can do it.
• How to fix/prevent it: Choose bolt-resistant varieties, provide consistent watering, and protect young plants from sudden temperature drops with row covers or frost cloth.

Hollow Stalks

• What it looks like: The celery stalks develop hollow centers, making them less desirable.
• What causes it: Inconsistent watering or nutrient deficiencies, particularly a lack of boron, can cause hollow stalks.
• How to fix/prevent it: Maintain consistent soil moisture and amend the soil with compost or a balanced fertilizer. A soil test can help determine if a boron supplement is needed.

Stringy Stalks from Heat

• What it looks like: The celery stalks become tough and stringy, making them less palatable.
• What causes it: Prolonged exposure to high temperatures can cause the stalks to become stringy.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day, especially during our dry summers. Consistent watering and mulching can also help keep the soil cool.

Northern California Specific Challenges: Our moderate-to-hot summers, low humidity, and dry-summer rainfall pattern mean that water management is absolutely crucial for growing celery. Inconsistent watering is the biggest culprit for most celery problems.

Companion planting can really give your celery a boost! Green beans are great companions because they fix nitrogen in the soil, which celery loves. Cabbage benefits from celery's pest-repelling properties. Tomatoes also benefit, as celery can deter some common tomato pests. Onions deter celery fly and other pests.

Avoid planting carrots near celery. Carrots and celery compete for the same nutrients in the soil, so they can stunt each other's growth.