Celery in Zone 8B — Pacific Northwest

Celery, with its crisp texture and refreshing flavor, is a rewarding addition to any Pacific Northwest garden. The cool nights and mild summers of our region actually enhance its sweetness, making homegrown celery far superior to anything you'll find at the store. Plus, it's incredibly versatile, adding a satisfying crunch to salads, soups, and snacks.

While celery can be a bit demanding, especially with our cool, wet springs, success is achievable with careful timing. Our long, mild fall gives you a buffer, and the 210-day growing season is just enough to bring this crop to harvest.

Starting celery indoors is essential in the PNW to get a head start on our relatively short growing season. Begin sowing your seeds indoors from mid-January through early February, roughly 10 weeks before you plan to transplant them outdoors. Celery seeds are tiny and need light to germinate, so don't bury them too deeply; gently press them onto the surface of a seed-starting mix.

Use seed trays with a humidity dome and provide consistent warmth (around 70-75°F) using a heat mat. Bottom watering is ideal to prevent damping off and keep the soil consistently moist without disturbing the delicate seeds. Be patient, as germination can be slow, especially with our overcast spring days.

Transplant your celery seedlings outdoors from early April through early May, once the danger of hard frost has passed and the soil has warmed up a bit. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Plant your celery seedlings 8-10 inches apart in well-prepared soil. Even though we get plenty of rain in spring, the soil can still be cool which will slow growth. Protect young plants from slugs, which are always eager to munch on tender seedlings in our wet springs.

Celery is *thirsty*. In our dry-summer climate, consistent watering is critical for preventing hollow, bitter stalks. Aim to keep the soil consistently moist, but not waterlogged, throughout the growing season.

During our typically wet springs, you may only need to supplement rainfall with an inch of water per week, but during the dry summer months, increase that to 1.5-2 inches per week, depending on rainfall. Use the finger test – if the top 2 inches of soil feel dry, it's time to water. Water deeply at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases, even with our dry summers.

Keep an eye out for drooping leaves, which indicate underwatering, and yellowing leaves, which can signal overwatering. A layer of mulch around your celery plants will help retain moisture and suppress weeds.

You can expect your first celery harvest from late June through mid-August, about 85 days after transplanting. Celery is ready to harvest when the outer stalks are at least 8 inches long. You can harvest individual stalks as needed, allowing the inner stalks to continue growing, or you can cut the entire plant at the base when the stalks reach 12 inches or more.

For a milder flavor, blanch the stalks by mounding soil around them a couple of weeks before harvest. As the first frost approaches in early November, harvest any remaining celery, even if it’s not fully mature, to prevent frost damage. It's best to get it inside before the cold weather hits.

Here are a few common issues you might encounter when growing celery in the Pacific Northwest:

Bolting from Temperature Stress

• What it looks like: The celery plant sends up a flower stalk prematurely, making the stalks bitter and inedible.
• What causes it: Fluctuations in temperature, especially cold snaps during our cool springs, can trigger bolting.
• How to fix/prevent it: Choose bolt-resistant varieties. Start seeds indoors early to avoid temperature stress. Protect young plants with row covers during unexpected cold spells.

Hollow Stalks

• What it looks like: The inside of the celery stalks are hollow instead of solid.
• What causes it: Inconsistent watering and nutrient deficiencies, especially calcium, are the main culprits.
• How to fix/prevent it: Maintain consistent soil moisture by watering deeply and regularly. Amend the soil with compost or a calcium supplement like bone meal before planting.

Stringy Stalks from Heat

• What it looks like: The celery stalks become tough, fibrous, and stringy.
• What causes it: Excessive heat and lack of consistent moisture during our dry summer months.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Ensure consistent watering and mulch around the plants to retain moisture.

Pacific Northwest Specific Challenges: Late blight can be a concern in our region, especially during wet springs. Ensure good air circulation around plants and avoid overhead watering to minimize the risk. Slugs can also be a problem, particularly for young seedlings. Use slug bait or traps to protect your plants.

Celery thrives when planted alongside beneficial companions. Green beans help fix nitrogen in the soil, benefiting celery's growth. Cabbage family members like broccoli and kale deter pests that might target celery. Tomatoes provide shade and support, while onions repel celery flies.

Avoid planting celery near carrots, as they compete for the same nutrients in the soil, hindering the growth of both plants. Proper companion planting can improve your celery's health and productivity in the PNW.