Celery in Zone 6A — Pacific Northwest

Celery, with its crisp stalks and refreshing flavor, is a rewarding challenge for the Pacific Northwest gardener. Nothing beats the taste of fresh, homegrown celery in soups, salads, or as a crunchy snack, especially when you know the cool nights here contribute to its sweetness. Plus, you'll have the satisfaction of mastering a crop that appreciates our mild summers.

While celery can be a bit demanding, don't let that deter you. Our 148-day growing season gives you a reasonable window to get it done, especially with a little planning. We may have to contend with cool springs and the risk of late blight, but careful timing and a few clever tricks will help you succeed.

Starting celery indoors is essential here in the PNW. You'll want to sow those tiny seeds from late February through mid March, giving them about 10 weeks indoors before transplanting. Celery seeds are notoriously slow to germinate, so patience is key.

Use seed trays with a good seed-starting mix and provide consistent warmth – a heat mat can be a lifesaver. Don't bury the seeds too deeply; they need light to germinate. Bottom watering is ideal to avoid disturbing the delicate seedlings. Given our overcast spring days, supplemental lighting can really boost germination and early growth.

Transplant your celery seedlings outdoors from early May through early June, once the danger of hard frost has passed. 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, preventing transplant shock.

Plant seedlings 8-10 inches apart in well-prepared soil. Keep an eye on the weather forecast – a late cold snap can set them back, so be ready to cover them if needed.

Celery is a water hog, and consistent moisture is absolutely critical for a successful harvest here in the dry-summer Pacific Northwest. You really can't let it dry out, even briefly. A good rule of thumb is to aim for at least 1-2 inches of water per week, depending on rainfall.

During our drier summer months, you'll likely need to water deeply every few days. Use the finger test – stick your finger about 2 inches into the soil, and 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 region.

Underwatering will lead to hollow, bitter stalks, while overwatering can cause root rot. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A layer of mulch can help retain moisture and regulate soil temperature.

You can expect your first celery harvest from early August through late September, roughly 85 days after transplanting. Look for stalks that are at least 8 inches long; you can harvest individual outer stalks as needed, allowing the plant to continue producing.

Alternatively, if you want to harvest the entire plant, wait until the stalks are at least 12 inches tall and cut the whole thing off at the base. For milder-tasting celery, blanch the stalks by mounding soil around them a few weeks before harvest. As our first frost approaches in early October, harvest any remaining celery, as it won't tolerate freezing temperatures.

Here are three common problems you might encounter growing celery in the Pacific Northwest:

Bolting from Temperature Stress

• What it looks like: The plant sends up a flower stalk prematurely, making the stalks bitter and tough.
• What causes it: Fluctuations in temperature, especially cold spells followed by warm weather, can trigger bolting. This can be an issue with our variable spring weather.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide consistent moisture and protection from temperature swings with row covers or shade cloth.

Hollow Stalks

• What it looks like: The center of the celery stalks is empty or has large air pockets.
• What causes it: Inconsistent watering and nutrient deficiencies, especially calcium deficiency.
• How to fix/prevent it: Ensure consistent, even watering. Amend the soil with compost and consider adding a calcium supplement if needed.

Stringy Stalks from Heat

• What it looks like: The celery stalks are tough and fibrous, with prominent strings.
• What causes it: High temperatures and dry conditions during the growing season. Even though our summers are mild, periods of above-average heat can stress the plants.
• How to fix/prevent it: Provide afternoon shade during hot spells. Ensure consistent watering and mulch around the plants to keep the soil cool.

Pacific Northwest Specific Challenges: Late blight can be a concern, especially with our wet springs. Monitor your plants regularly and provide good air circulation. Slugs also love celery, so use your preferred slug control methods.

Celery benefits from several companion plants in the Pacific Northwest garden. Green beans help fix nitrogen in the soil, providing celery with a nutrient boost. Cabbage family members like broccoli and kale deter celery pests, while their differing growth habits allow them to share space efficiently. Tomatoes offer some shade during hotter periods, and celery repels tomato hornworms. Onions deter many common pests and have shallow roots that don't compete with celery. Avoid planting carrots nearby, as they attract the same pests, increasing the risk of damage to both crops.