Celery in Zone 6B — Mountain West

Celery might seem like a grocery store staple, but homegrown celery in the Mountain West offers a flavor you just can't buy. The cool nights even in summer concentrate the sugars, giving you a sweeter, more aromatic stalk perfect for snacking, soups, or even juicing. Plus, there's a real satisfaction in coaxing this water-loving plant to thrive in our challenging climate.

Growing celery at high altitude presents some unique challenges. The intense sun, alkaline soil, and short growing season demand careful planning. But with a head start indoors and consistent watering, you can absolutely enjoy fresh, crisp celery from your garden within our 163-day growing season.

Starting celery indoors is essential in our Zone 6B Mountain gardens. You'll want to get those tiny seeds going in early to late February, giving them about 10 weeks to develop before transplanting. This head start is crucial to beat the short season.

Use seed trays with a good seed-starting mix. Celery seeds are tiny and need light to germinate, so don't bury them too deeply – just barely press them into the soil surface. Keep the soil consistently moist, and consider bottom watering to avoid disturbing the delicate seeds. Place the trays in a warm spot, ideally with a heat mat, and provide plenty of light, especially given our region's late spring start.

Transplant your celery seedlings outdoors late April through late May once the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the intense sun and cooler temperatures.

Space the seedlings 8-10 inches apart in well-amended soil. Be mindful of potential late frosts, which can still happen this time of year in the mountains. Having frost cloth on hand is always a good idea!

Celery is a very thirsty plant, and consistent moisture is key to preventing hollow, bitter stalks. Especially in our dry Mountain West climate, you need to be diligent.

During the peak of summer, when temperatures reach around 85°F, you'll likely need to water deeply every other day, providing at least 1-2 inches of water per week. Use the finger test: stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can lead to fungal issues in more humid climates (though it's less of a concern here).

Signs of underwatering include wilting leaves and stunted growth, while yellowing leaves and soggy soil can indicate overwatering. Add a layer of organic mulch around your celery plants to help retain moisture and suppress weeds. This is crucial with our low humidity and dry rainfall.

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. These can be harvested individually as needed.

For a larger harvest, you can cut the entire plant at the base when the stalks are 12 inches or longer. If you want milder stalks, try blanching them by mounding soil around the base of the plants a week or two before harvest. To encourage continued production, harvest outer stalks first. As the first frost approaches in early October, harvest any remaining celery, as it won't tolerate freezing temperatures.

Celery can be a bit finicky, and here in the Mountain West, we often see a few common problems: bolting from temperature stress, hollow stalks, and stringy stalks from heat.

Bolting from Temperature Stress

• What it looks like: The 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 is particularly relevant with our temperature swings.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide consistent watering and mulch to moderate soil temperature. If a cold snap is predicted, cover your plants with frost cloth.

Hollow Stalks

• What it looks like: The center of the celery stalk is empty or has large air pockets.
• What causes it: Inconsistent watering, especially during hot weather, stresses the plant. Our low humidity makes this worse.
• How to fix/prevent it: Water deeply and regularly, ensuring the soil stays consistently moist. Mulch around the plants to retain moisture.

Stringy Stalks from Heat

• What it looks like: The celery stalks become tough and fibrous.
• What causes it: High temperatures and intense sun can cause the plant to develop more fiber.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Consistent watering also helps. Consider planting in a location that gets morning sun but is protected from the harshest afternoon rays.

Mountain West Specific Challenges: Our moderate-at-altitude heat, combined with low humidity and dry rainfall, makes consistent watering absolutely critical for celery. The intense sun can also exacerbate problems like stringy stalks, so providing some shade is beneficial.

Companion planting can give your celery a boost. Green beans help fix nitrogen in the soil, benefiting celery's growth. Cabbage family plants deter pests. Tomatoes provide shade during the hottest part of the day, which helps prevent stringy stalks. Onions deter celery flies and other pests. Avoid planting carrots near celery, as they compete for the same nutrients and can stunt each other's growth.