Celery in Zone 7A — Northern California

Growing your own celery in Northern California is a rewarding experience. The crisp, fresh taste is far superior to anything you'll find at the grocery store. Plus, it's incredibly versatile in the kitchen, adding a delicious crunch to salads, soups, and snacks. Here in Zone 7A, our long growing season gives us a great shot at success with this cool-weather crop.

Even with our long growing season, remember we're gardening in a Mediterranean climate with dry summers. Celery needs consistent moisture, so you'll need to stay on top of watering. But with a little planning and attention, you can absolutely enjoy homegrown celery from mid-summer through fall. Our 235-day growing season gives you plenty of time!

Start your celery seeds indoors in early to late January. Celery needs a long head start. Since our springs arrive early here in Northern California, getting those seeds going indoors in the dead of winter is essential. You'll want to get them started about 10 weeks before you plan to transplant them outdoors.

Use seed trays filled with a good seed-starting mix. Celery seeds are tiny and need light to germinate, so don't bury them too deeply. Keep the soil consistently moist by bottom watering. Place the trays in a warm spot (around 70-75°F) and under grow lights to ensure strong, even growth.

Transplant your celery seedlings outdoors from mid-March through mid-April. This timing takes advantage of our mild spring weather, but be sure to harden off your seedlings for about a week before planting them in the ground. Gradually expose them to outdoor conditions to prevent shock.

Plant your celery seedlings 8-10 inches apart in rows. Choose a spot that gets full sun to partial shade. Keep an eye on the forecast for any late-season frosts, which can still occur this time of year. If frost threatens, cover your young plants with row covers or blankets.

Celery is a thirsty plant, and consistent watering is absolutely critical for success in our dry Northern California climate. We have moderate-to-hot summers with low humidity and very little rainfall, so you need to be vigilant about keeping the soil consistently moist. Celery is not drought-tolerant, so it needs a lot of water.

During the warmer months, you'll likely need to water your celery every other day, or even daily, providing about 1-2 inches of water per week. Check the soil moisture by sticking your finger in 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 fungal diseases in our low-humidity environment.

Signs of underwatering include wilting leaves and bitter-tasting stalks. Overwatering can lead to root rot, so make sure the soil is well-draining. Add a layer of mulch around your celery plants to help retain moisture and suppress weeds.

You can expect your first celery harvest from mid-June through early August. This is about 85 days after transplanting. The exact timing will depend on the variety you're growing and the weather conditions.

Harvest individual outer stalks when they are at least 8 inches long, or cut the entire plant at the base when the stalks are 12 inches or more. For milder stalks, blanch them by mounding soil around the base of the plant a week or two before harvest. Celery doesn't ripen off the vine, but you can harvest continuously by taking only the outer stalks as needed.

As the first frost approaches in early November, harvest any remaining celery. You can store it in the refrigerator for several weeks.

Here are some 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.
• What causes it: Fluctuations in temperature, especially early in the season, can trigger bolting. This is common in our region with our sudden warm spells in early spring.
• How to fix/prevent it: Choose bolt-resistant varieties. Start seeds indoors early and transplant after the weather has stabilized. Provide shade during hot spells.

Hollow Stalks

• What it looks like: The inside of the celery stalks are hollow.
• What causes it: Inconsistent watering and nutrient deficiencies. Our dry summers make consistent watering a challenge.
• How to fix/prevent it: Water deeply and regularly. Fertilize with a balanced fertilizer. Ensure the soil is rich in organic matter.

Stringy Stalks from Heat

• What it looks like: The stalks become tough and stringy.
• What causes it: High temperatures. Although we don't have the brutal heat of other regions, our moderate-to-hot summers can still stress celery.
• How to fix/prevent it: Provide afternoon shade. Ensure adequate watering. Harvest promptly when stalks are mature.

Northern California Specific Challenges: Our moderate-to-hot summers, low humidity, and dry-summer rainfall pattern make consistent watering the biggest challenge for growing celery. Be prepared to water frequently and deeply, and monitor your plants closely for signs of stress.

Companion planting can help your celery thrive in Northern California.

Good companions include:

• Green beans: They fix nitrogen in the soil, which benefits celery's growth.
• Cabbage: It deters some pests that might attack celery.
• Tomatoes: Their strong scent can repel certain celery pests.
• Onions: They also deter pests and can improve soil health.

Avoid planting celery near carrots. Carrots and celery compete for the same nutrients in the soil, which can stunt the growth of both plants.