Celery in Zone 7A — Pacific Northwest

Celery, with its crisp texture and refreshing flavor, is a rewarding crop to grow in the Pacific Northwest. Freshly harvested celery has a depth of flavor that store-bought simply can't match, and it adds a delightful crunch to salads, soups, and snacks. Plus, the cool nights we experience here actually enhance the sweetness of the stalks.

While celery can be a bit demanding, especially with our cool springs and tendency for late blight, it's absolutely achievable with careful timing and attention. Our 183-day growing season gives you a decent window to nurture this crop, and with a little planning, you'll be enjoying homegrown celery in no time.

To get a jump start on the season, begin sowing your celery seeds indoors from early to late February. Celery needs a good 10 weeks indoors to get a head start. Use seed trays with a good seed-starting mix, and provide consistent warmth, ideally around 70-75°F. A heat mat can be helpful, especially with our slow-warming springs.

Remember, celery seeds need light to germinate, so don't bury them too deeply. Lightly press them onto the surface of the soil. To keep the soil consistently moist without disturbing the tiny seeds, bottom watering is your best bet. Place the tray in a shallow dish of water and let the soil soak it up from the bottom.

Be patient! Celery seedlings are slow to grow, especially with our overcast spring days. But with consistent care, you'll have healthy transplants ready when the weather warms up.

Transplant your celery seedlings outdoors from mid April through mid May, after the danger of a hard frost has passed. Before transplanting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your celery plants 8-10 inches apart in a location that receives full sun to partial shade. Our mild summers mean they can handle more sun than in hotter climates. When transplanting, be mindful of the cool soil temperatures we often experience in spring. Consider using row covers to provide extra warmth and protection, especially if we're experiencing a particularly cool spell.

Celery is notoriously thirsty, and consistent moisture is key to preventing hollow, bitter stalks. In our dry-summer climate, you'll need to pay close attention to watering. During the spring, when rainfall is more frequent, aim for about 1 inch of water per week, supplementing natural rainfall as needed.

As we move into the drier summer months, increase watering to 1.5-2 inches per week. The finger test is a good way to check soil moisture: stick your finger about 2 inches deep into the soil near the base of the plant. If it feels dry, it's time to water. Water deeply at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our sometimes humid conditions. Overhead watering is fine if done early in the day, giving the leaves time to dry out before evening.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to root rot. Yellowing leaves and a general lack of vigor are indicators of overwatering. Mulching around your celery plants with straw or compost can help retain moisture in the soil, reduce evaporation, and keep the soil cool.

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

To harvest, simply cut the outer stalks at the base of the plant with a sharp knife. For a larger harvest, you can cut the entire plant at the base when the stalks are 12 inches or longer. If you prefer milder celery, blanch the stalks by hilling soil around them a week or two before harvesting.

As the first frost approaches in mid- October, harvest any remaining celery. Celery is semi-hardy and can tolerate a light frost, but a hard freeze will damage the stalks.

Here are the most common problems you might encounter growing celery in the PNW:

Bolting from Temperature Stress

• What it looks like: The celery plant prematurely sends up a flower stalk, making the stalks bitter and inedible.
• What causes it: Fluctuations in temperature, especially cold snaps after warm spells, can trigger bolting. This can be a challenge with our variable spring weather.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide consistent watering and mulching to moderate soil temperature. Use row covers during periods of unexpected cold.

Hollow Stalks

• What it looks like: The celery stalks develop hollow centers, often accompanied by a bitter taste.
• What causes it: Inconsistent watering and nutrient deficiencies, especially calcium deficiency.
• How to fix/prevent it: Ensure consistent and adequate watering, especially during dry spells. Amend the soil with compost or a balanced fertilizer before planting. Consider adding a calcium supplement like bone meal if you suspect a deficiency.

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. While our summers are mild, occasional heat waves can stress the plants.
• How to fix/prevent it: Provide afternoon shade during hot spells. Consistent watering and mulching can also help keep the soil cool. Choose varieties that are more heat-tolerant.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer climate mean that consistent watering is absolutely critical for celery. Late blight, a fungal disease, can also be a problem, so ensure good air circulation and avoid overhead watering if possible. Slugs can also be an issue, especially in wet springs. Use slug bait or traps to protect your plants.

Companion planting can help your celery thrive. Green beans are great companions because they fix nitrogen in the soil, which benefits celery's growth. Cabbage and other brassicas deter celery pests. Tomatoes provide shade during our hottest days, and onions help repel insects. Avoid planting carrots near celery, as they compete for the same nutrients in the soil.