Eggplant in Zone 7A — Mountain West

Eggplant might seem like a challenging crop for our Mountain gardens, but the unique flavor and satisfaction of harvesting your own glossy, deep purple fruit makes it well worth the effort. The cool nights we get even in summer concentrate the flavors, giving you eggplants with a depth you won't find anywhere else. Plus, they're incredibly versatile in the kitchen.

Our high altitude, intense sun, and short growing season definitely present some hurdles. But with careful timing and a little extra attention, you can absolutely grow beautiful eggplants here. Our 173-day growing season can be enough time to produce a good crop.

Starting your eggplant seeds indoors is essential in our Zone 7A Mountain climate. Aim to start your seeds indoors in early to late March, giving them about 8 weeks to get a head start before our last frost. Use seed trays with a good seed-starting mix and provide consistent warmth, ideally around 80-85°F, using a heat mat if needed.

A sunny south-facing window often isn't enough, so supplement with grow lights to prevent leggy seedlings. It's also helpful to water from the bottom by placing the tray in a shallow dish of water, as this encourages strong root growth and prevents damping-off. Remember that spring here can be late, so don't rush things.

Transplant your eggplant seedlings outdoors from mid May through early June, after the danger of frost has passed and the soil has warmed up considerably. 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 intense sun and cooler nights of our Mountain climate.

Space your plants 18-24 inches apart to allow for good air circulation. Even in late spring, we can get unexpected cold snaps, so be ready to cover your transplants with row covers or frost blankets if necessary. Waiting until the soil is at least 65°F is key for good growth.

Eggplants need consistent moisture, especially in our dry Mountain climate. You'll need to water regularly to keep the soil evenly moist, but not waterlogged. Unlike other regions, our low humidity means that we need to be extra vigilant about watering.

During the peak of summer, you'll likely need to water deeply about 2-3 times per week, providing about 1-2 inches of water each time. Use the finger test: stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which can still lead to fungal issues even with low humidity.

Underwatering results in bitter fruit and blossom drop, while overwatering can cause root rot. Signs of underwatering include wilting leaves and stunted growth; overwatering presents as yellowing leaves and mushy stems. A good layer of mulch around your plants will help retain moisture and keep the soil cool in our intense sun.

Eggplants produce heavy fruit that can weigh down the branches, so providing support is crucial in our Mountain gardens. Staking is the best option for keeping the plant upright and preventing the fruit from touching the ground.

Install a sturdy stake, such as a bamboo or metal stake, near the base of each plant at transplant time. As the plant grows, gently tie the main stem to the stake using soft twine or plant ties. This will prevent the branches from breaking under the weight of the fruit and keep the fruit clean.

Eggplants benefit from minimal pruning to encourage good air circulation and larger fruit. Remove any suckers that grow below the first main fork of the plant. These suckers will only divert energy from fruit production.

Throughout the season, limit the plant to 5-6 main branches to focus its energy on producing larger, higher-quality fruit. As the first frost approaches in early October, pinch off any new flowers to encourage the plant to ripen the existing fruit.

You can expect your first eggplant harvest from mid July through early September, depending on the variety and the weather conditions. The key to harvesting eggplants at their peak is to look for glossy, smooth skin and a slight give when you gently press the fruit. Dull skin indicates that the eggplant is overripe and may be seedy.

Use a sharp knife or pruning shears to cut the eggplant from the plant, leaving about an inch of stem attached. Avoid pulling the fruit, as this can damage the plant. Eggplants are best used fresh and don't ripen off the vine. Regular harvesting encourages the plant to produce more fruit throughout the season. As the first frost approaches in early October, harvest any remaining mature fruit, even if they're not quite fully ripe.

Here are some common eggplant problems we see in Zone 7A Mountain gardens:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might also see small, dark beetles that jump when disturbed.
• What causes it: Flea beetles are small jumping beetles that feed on leaves. They are most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more able to withstand damage. Apply kaolin clay coating. Neem oil spray can also help. Interplant with basil or catnip. Healthy, vigorous plants outgrow damage.

Colorado Potato Beetle

• What it looks like: Yellow and black striped beetles and red larvae eating leaves.
• What causes it: These beetles are voracious eaters and can quickly defoliate eggplant plants.
• How to fix/prevent it: Handpick beetles and larvae. Spray with neem oil or insecticidal soap. Rotate crops to avoid buildup in the soil.

Verticillium Wilt

• What it looks like: Lower leaves yellow, wilt, and die, progressing upward. One side of plant may be affected first. Look for brown streaks in stem cross-section.
• What causes it: This is a soil-borne fungus that persists for years. Cooler soil temperatures favor it.
• How to fix/prevent it: There is no cure — remove infected plants immediately. Rotate with non-susceptible crops like corn or grains. Solarize the soil. Plant resistant varieties (look for 'V' on labels).

Blossom Drop

• What it looks like: Flowers fall off without setting fruit. Small fruit yellows and drops. The plant looks healthy but produces no fruit.
• What causes it: Temperature stress is the main culprit. Eggplants don't set fruit well when nights stay above 75°F or days exceed 95°F. Low humidity, excess nitrogen, or poor pollination can also contribute.
• How to fix/prevent it: Be patient – fruit set usually resumes when temperatures moderate. Provide afternoon shade during extreme heat. Keep plants well-watered. Avoid excess nitrogen fertilizer. You can also try hand-pollination.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall can create challenges for eggplant. The intense sun can stress plants, so providing afternoon shade can be beneficial. Consistent watering is essential to combat the dry climate and prevent blossom drop.

Good companions for eggplant in our Mountain gardens include green beans, peppers, spinach, and tomatoes. Green beans fix nitrogen in the soil, benefiting eggplant growth. Peppers thrive in similar conditions and don't compete for resources. Spinach provides ground cover, helping to retain moisture. Tomatoes provide some shade and support.

Avoid planting eggplant near fennel, as it inhibits the growth of many plants, including eggplant.