Celery in Zone 9A — Southern California

Celery might seem like a grocery store staple, but homegrown celery offers a crispness and flavor that's hard to beat, especially here in Southern California. It's a satisfying challenge to grow in our mild winters and long growing season, plus it's incredibly versatile in the kitchen. Imagine fresh celery sticks dipped in hummus grown from your own garden, or adding it to your soups and stir-fries.

Growing celery in SoCal does come with its challenges, particularly the need for consistent moisture during our drier months. But with a little planning and attention, you can absolutely enjoy a successful celery harvest. Our 322-day growing season gives you ample time to get it right.

Starting celery indoors is key in Southern California because it gives these slow-growing plants a head start before our spring warmth. Begin sowing your celery seeds indoors from mid November through early December, about 10 weeks before you plan to transplant them. Use seed trays filled with a good seed-starting mix and keep them consistently moist.

Celery seeds need light to germinate, so don't bury them too deeply – just gently press them into the surface of the soil. Keep the trays in a warm location, ideally around 70-75°F. Bottom watering can help prevent damping-off and keep the soil evenly moist. With our very-early springs, this head start ensures you'll have mature plants ready to go when the weather is just right.

Transplanting celery outdoors should happen from early February through early March. Before you plant, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the sun and temperature changes.

When transplanting, space your celery plants about 8-10 inches apart in rows. Southern California can still experience some cool nights during this time, so consider providing some protection if a cold snap is predicted.

Celery is notoriously thirsty, and consistent watering is crucial for a successful harvest in Southern California. Our hot summers and low-to-moderate humidity mean you'll need to pay close attention to soil moisture. Aim to keep the soil consistently wet, but not waterlogged.

During the cooler months, you might only need to water deeply a couple of times a week. But as the weather heats up from late spring through summer, you'll likely need to water daily, especially if you're inland where the heat is more intense. Use the finger test – if the top 2 inches of soil feel dry, it's time to water. Give your plants about 1-2 inches of water per week, adjusting based on rainfall. Watering at the base of the plant is ideal to avoid fungal issues in our climate.

Signs of underwatering include wilting leaves and bitter-tasting stalks. Overwatering can lead to root rot, so look for yellowing leaves. Applying a layer of mulch around your celery plants can help retain moisture in the soil and reduce the need for frequent watering, which is especially important considering our ongoing drought conditions.

You can expect your first celery harvest from late April through mid June, depending on when you transplanted. Look for outer stalks that are at least 8 inches long – these can be harvested individually as needed. Alternatively, you can cut the entire plant at the base when the stalks are 12 inches or longer.

To harvest individual stalks, simply use a sharp knife to cut them off near the base of the plant. This allows the remaining stalks to continue growing. For a milder flavor, try blanching the stalks by mounding soil around them a week or two before harvest.

As our first frost approaches around mid- December, you can harvest any remaining celery stalks. Even if they're not fully mature, they can still be used in soups and stews.

Growing celery in Southern California can present a few challenges, but understanding the potential problems can help you prevent them. Here are three common issues:

Bolting from Temperature Stress

• What it looks like: The celery plant prematurely sends up a flower stalk, making the stalks bitter and tough.
• What causes it: Bolting is triggered by temperature fluctuations, particularly heat stress. In SoCal, unexpected heat waves or prolonged periods of high temperatures can cause celery to bolt.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide shade during the hottest part of the day, especially if you're gardening inland. Consistent watering can also help reduce stress on the plants.

Hollow Stalks

• What it looks like: The center of the celery stalks becomes hollow.
• What causes it: Inconsistent watering or nutrient deficiencies. In our climate, drought conditions or infrequent watering can easily lead to hollow stalks.
• How to fix/prevent it: Ensure consistent and even watering. Amend your soil with compost before planting to provide essential nutrients. Consider using a balanced fertilizer if needed.

Stringy Stalks from Heat

• What it looks like: The celery stalks become tough and stringy, making them less palatable.
• What causes it: High temperatures and lack of moisture. The summer heat inland in Southern California can be particularly harsh on celery.
• How to fix/prevent it: Provide afternoon shade during the hottest months. Water deeply and regularly. Choose varieties known for their heat tolerance. Harvest stalks when they are young and tender.

Southern California Specific Challenges: Our region's combination of hot summers, low-to-moderate humidity, and winter-wet rainfall patterns requires careful attention to watering and temperature management when growing celery. Be prepared to adjust your watering schedule based on the weather and protect your plants from extreme heat, especially during Santa Ana wind events.

Companion planting can be a great way to improve your celery's growth and health in Southern California.

Good companions for celery include:

• Green beans: They fix nitrogen in the soil, which benefits celery.
• Cabbage: It deters some pests that might bother celery.
• Tomatoes: They provide some shade for celery, which can be helpful during our hot summer months.
• Onions: They repel celery flies.

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