Blackberry in Zone 6A — Mountain West

Blackberries offer a rewarding taste of summer in our Mountain gardens. Their intense flavor, perfect for jams, pies, or just eating fresh, makes them a worthwhile addition, especially when our cool nights enhance their sweetness. Growing your own also brings the satisfaction of harvesting sun-ripened fruit, a luxury in our short season.

While high altitude gardening presents challenges like intense sun and a compressed 153-day growing season, blackberries are manageable with careful timing. By choosing the right varieties and providing adequate care, you can enjoy a successful harvest, even with our early October frosts.

Transplant your blackberry bushes outdoors from early to late May, after the last expected frost. Before planting, harden off your bare-root canes or potted plants. This means gradually exposing them to outdoor conditions for about a week to acclimate them to the intense sun and cooler temperatures.

Space your blackberry plants 3-5 feet apart to allow for proper air circulation and growth. Keep an eye on the weather forecast, as late spring snow or hail can still occur. Providing temporary protection with row covers or burlap can help safeguard your young plants.

Blackberries need consistent moisture, especially during their fruiting period. In our dry Mountain climate, regular watering is crucial. Aim for about 1-2 inches of water per week, depending on rainfall. The "finger test" is a great way to check soil moisture: stick your finger about 2 inches into the soil near the base of the plant. If it feels dry, it's time to water.

Water deeply at the base of the plant, rather than overhead. Our low humidity minimizes the risk of fungal diseases, but watering at the base ensures the water reaches the roots where it's needed most. Signs of underwatering include wilting leaves and dry, brittle canes. Overwatering can lead to root rot, indicated by yellowing leaves and a musty smell.

Mulch heavily around your blackberry plants with organic materials like wood chips or straw. This helps retain moisture in our dry climate, suppress weeds, and regulate soil temperature.

Blackberries are vining plants that require strong support. A trellis system is the best option for most varieties, especially the erect and semi-erect types. This helps keep the canes off the ground, improving air circulation and making harvesting easier.

Install your trellis system before or at the time of planting to avoid disturbing the roots later. A simple two-wire trellis with posts spaced 8-10 feet apart works well. Train the canes to grow along the wires, tying them loosely with twine or plant tape. Thornless varieties are a great choice for easier handling and pruning.

Pruning is essential for maintaining healthy and productive blackberry plants. After harvest, remove the spent floricanes (the canes that produced fruit). These canes will not produce again and can harbor pests and diseases.

During the growing season, tip-prune new primocanes (the new, non-fruiting canes) at around 4-5 feet tall. This encourages branching, which leads to more fruit production the following year. As the first frost approaches in early October, don't prune any new growth; let it harden off for the winter.

Your first blackberry harvest in our Zone 6A Mountain gardens can be expected from late June through mid-August, depending on the variety and the weather. Blackberries are ready to harvest when they are fully black, not dark red. They should pull off the stem easily without squeezing. A dull surface, rather than a shiny one, indicates full ripeness.

Harvest regularly, every few days, to encourage continued production. Gently grasp the ripe berries and pull them from the plant. Avoid squeezing them, as they bruise easily. As the first frost approaches in early October, harvest any remaining ripe berries, even if they are slightly underripe.

Here are some common problems you might encounter with blackberries in the Mountain West:

Spotted Wing Drosophila

• What it looks like: Tiny holes in the fruit, soft and mushy berries, and small, white larvae inside.
• What causes it: This invasive fruit fly lays its eggs inside ripening fruit. Our moderate-at-altitude summer temperatures and the presence of other host plants can contribute to infestations.
• How to fix/prevent it: Use netting to exclude the flies, apply organic insecticides specifically labeled for spotted wing drosophila, and remove any overripe or fallen fruit promptly.

Cane Blight

• What it looks like: Dark brown or purple lesions on the canes, often near wounds or pruning cuts. The canes may wilt and die back.
• What causes it: A fungal disease that enters through wounds. Our intense sun can stress the plants and make them more susceptible.
• How to fix/prevent it: Prune out infected canes well below the affected area, disinfect pruning tools, and avoid injuring the canes. Ensure good air circulation around the plants.

Orange Rust

• What it looks like: Bright orange pustules on the undersides of the leaves in spring. Infected canes may be stunted and produce few or no berries.
• What causes it: A systemic fungal disease that infects the entire plant.
• How to fix/prevent it: Remove and destroy infected plants entirely, as there is no cure. Choose rust-resistant varieties.

Japanese Beetles

• What it looks like: Metallic green beetles that skeletonize the leaves, leaving a lacy appearance.
• What causes it: These beetles are attracted to the foliage and can cause significant damage.
• How to fix/prevent it: Handpick the beetles in the early morning, use Japanese beetle traps (placed away from your blackberry plants), or apply organic insecticides like neem oil.

Mountain West Specific Challenges: Our moderate-at-altitude heat and low humidity generally reduce the risk of many fungal diseases that plague blackberries in other regions. However, the intense sun can stress the plants, making them more susceptible to cane blight and other issues. Consistent watering and adequate shade during the hottest part of the day can help mitigate these problems.

Companion planting can benefit your blackberries in the Mountain West. Tansy repels many insect pests, while garlic deters Japanese beetles and other unwanted visitors. Planting green beans nearby can help fix nitrogen in the soil, benefiting the blackberry plants. Mint can attract beneficial insects, but be sure to contain it, as it can be invasive.

Avoid planting tomatoes, peppers, and potatoes near your blackberries. These plants are susceptible to similar diseases, such as verticillium wilt, which can spread to your blackberry plants. These plants also compete for the same nutrients in our often alkaline soil.