Celery in Zone 7A — Mountain West

Celery might seem like a grocery store staple, but homegrown celery in our Mountain West gardens offers a flavor you just can't buy. The cool nights we get, even in summer, concentrate sugars and create a crisp, refreshing taste that's perfect in salads, soups, or as a crunchy snack. Plus, there's a real satisfaction in coaxing this water-loving plant to thrive in our challenging climate.

We're dealing with high altitude, intense sun, and a short growing season up here. But by starting celery indoors early and paying close attention to its needs, especially water, you can definitely enjoy a successful harvest. With a 173-day growing season, timing is everything!

Start your celery seeds indoors in early to late February, about 10 weeks before you plan to transplant. Celery is a slow grower, so giving it a head start is crucial in our short season. You'll need seed trays, a good seed-starting mix, and a warm location, ideally around 70-75°F. A heat mat can really help with germination.

Celery seeds need light to germinate, so don't bury them too deeply; just gently press them into the soil surface. Keep the soil consistently moist. Bottom watering is a great technique to avoid disturbing the tiny seeds. Given our late springs here in the Mountain West, starting indoors is really the only way to go.

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

Space your celery plants 8-10 inches apart in a sunny to partly shaded spot. Remember our intense sun can be tough on young plants. Keep an eye on the weather forecast; even in late spring, we can get unexpected cold snaps. Be ready to cover your young plants if needed.

Celery is a thirsty plant, and consistent watering is key to preventing hollow, bitter stalks. In our dry Mountain West climate, this means you'll need to be diligent. Aim to keep the soil consistently moist, but not waterlogged.

During the hotter summer months (late June through August), you'll likely need to water deeply every 2-3 days. Use the finger test: stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Give them about 1-2 inches of water per week, depending on rainfall. Water at the base of the plants to avoid splashing soil onto the leaves, which can help prevent disease in our low-humidity environment.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. A good layer of organic mulch, like straw or wood chips, can help retain moisture in the soil and regulate soil temperature during our hot days and cool nights.

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 with a sharp knife. Alternatively, you can cut the entire plant at the base when the stalks are 12 inches or longer. Some gardeners blanch their celery by mounding soil around the stalks a few weeks before harvest; this reduces bitterness and creates a milder flavor.

As our first frost approaches in early October, harvest any remaining celery. Celery is semi-hardy, so it can withstand a light frost, but a hard freeze will damage the stalks.

Here are three common problems you might encounter growing celery in the Mountain West:

Bolting from Temperature Stress

• What it looks like: The celery plant prematurely sends up a flower stalk, and the stalks become bitter and tough.
• What causes it: Bolting is triggered by temperature fluctuations, especially cool spells followed by warm weather. This can happen in our unpredictable Mountain climate.
• How to fix/prevent it: Choose bolt-resistant varieties. Provide consistent moisture and shade during hot spells. Use row covers during unexpected cold snaps.

Hollow Stalks

• What it looks like: The celery stalks develop hollow centers, making them less crisp and flavorful.
• What causes it: Inconsistent watering and nutrient deficiencies, especially calcium deficiency, can cause hollow stalks. Our alkaline soil can sometimes make it harder for plants to absorb nutrients.
• How to fix/prevent it: Water deeply and regularly. Amend your soil with compost to improve nutrient availability. Consider adding a calcium supplement if your soil is particularly alkaline.

Stringy Stalks from Heat

• What it looks like: The celery stalks become tough and stringy, making them unpleasant to eat.
• What causes it: Prolonged exposure to high temperatures can cause celery stalks to become stringy. Even our moderate-at-altitude summer heat can be tough on celery.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Ensure adequate watering to keep the plants cool. Choose heat-tolerant varieties.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry conditions mean you need to be extra vigilant about watering and providing shade for your celery. Consistent moisture is key to avoiding many of these problems.

Companion planting can help your celery thrive in the Mountain West.

Good companions for celery include:

• Green beans: They fix nitrogen in the soil, which benefits celery's growth.
• Cabbage: It deters cabbage white butterflies, which can sometimes bother celery.
• Tomatoes: They provide shade and protection from intense sun, which celery appreciates.
• Onions: They repel certain pests that might attack celery.

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