Blackberry in Zone 7A — Mountain West

Blackberries are a worthwhile addition to any Mountain West garden. Their intense, sweet-tart flavor shines in jams, pies, and fresh eating, and the satisfaction of harvesting your own berries is unmatched. Plus, our cool nights even in summer help develop a more complex, concentrated flavor in the fruit.

Our high altitude, intense sun, and short growing season (around 173 days) present unique challenges. But with careful timing and attention, you can absolutely enjoy a bountiful blackberry harvest. You'll be setting out transplants after the last frost, so success is well within reach.

Transplant your blackberry plants outdoors from mid April through mid May, after the danger of hard frost has passed. Before planting, be sure to harden off your bare-root canes or potted plants by gradually exposing them to the outdoors for about a week. This helps them adjust to the intense sun and fluctuating temperatures common in our Mountain climate.

Space your blackberry plants 3-5 feet apart to allow for adequate air circulation and growth. Keep an eye on the weather forecast around transplant time, as late spring snow or hail is always a possibility in the mountains. Protect your young plants with row covers if necessary. Blackberry care is very similar to raspberry care, so if you've grown those, you're already ahead of the game.

Blackberries need consistent moisture, especially during their fruiting period, but they don't like to sit in soggy soil. While more drought-tolerant than raspberries once established, you still need to pay attention to watering in our dry Mountain West climate. Remember, we get only 10-20 inches of rainfall annually.

During the active growing season (late spring to late summer), water your blackberry plants deeply about once a week, providing roughly 1-2 inches of water. Use the "finger test" to check the soil moisture: stick your finger about 2 inches deep into the soil near the base of the plant. If it feels dry, it's time to water. In our region's low humidity, watering at the base of the plant is preferable to overhead watering, which can encourage fungal diseases.

Signs of underwatering include wilting leaves and dry, brittle canes. Overwatering can lead to yellowing leaves and root rot. To help retain moisture and regulate soil temperature in our intense sun, mulch heavily around your blackberry plants with organic materials like wood chips or straw. This is especially crucial given our moderate-at-altitude summer heat and low humidity.

Blackberry vines are vigorous growers and need a strong trellis system to support their weight and keep them off the ground. A simple wire trellis works well, with posts set every 8-10 feet and wires strung horizontally at 2-3 foot intervals. A T-post trellis can also work well.

Install your trellis before planting, as it's much easier to do it then than after the plants have started to grow. As the canes grow, train them along the wires, tying them loosely with twine or plant tape. Thornless blackberry varieties are easier to manage on a trellis, reducing the risk of scratches and snags.

Pruning is essential for maintaining healthy and productive blackberry plants. After harvest, remove the spent floricanes (the canes that produced fruit) by cutting them back to the ground. These canes will not produce fruit again.

In late spring or early summer, tip-prune the new primocanes (the current season's growth) when they reach about 4-5 feet tall. This encourages branching, which leads to more fruit production the following year. As the first frost approaches in early October, remove any dead or diseased canes to improve air circulation and prevent the spread of disease over winter.

You can expect your first blackberry harvest from mid June through early August, depending on the variety and the specific weather conditions that year. Blackberries are ready to pick when they are fully black, not dark red, and pull easily from the plant without squeezing. A dull surface, rather than a shiny one, also indicates full ripeness.

Harvest blackberries frequently, every few days, to encourage continued production. Handle the berries gently to avoid bruising them. As the first frost approaches in early October, harvest any remaining ripe or nearly ripe berries. They won't ripen off the vine, but you can use them in jams or pies.

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

• Spotted Wing Drosophila
• What it looks like: Tiny fruit flies laying eggs in ripening fruit, causing soft spots and larvae inside the berries.
• What causes it: These flies thrive in humid conditions, but even our relatively low humidity can be enough for them to become a problem.
• How to fix/prevent it: Use traps baited with apple cider vinegar to monitor and reduce populations. Apply organic insecticides like spinosad if necessary. Netting can also provide a physical barrier.
• Cane Blight
• What it looks like: Dark brown or black lesions on the canes, often near pruning cuts or injuries.
• What causes it: A fungal disease that enters through wounds in the canes. Our intense sun can sometimes stress plants, making them more susceptible.
• How to fix/prevent it: Prune out infected canes promptly and disinfect your pruning tools between cuts. Ensure good air circulation around the plants.
• Orange Rust
• What it looks like: Bright orange pustules on the undersides of leaves and canes.
• What causes it: A systemic fungal disease that infects the entire plant.
• How to fix/prevent it: Remove and destroy infected plants immediately, as there is no cure. Choose rust-resistant varieties.
• Japanese Beetles
• What it looks like: Metallic green beetles feeding on leaves and flowers, causing skeletonization.
• What causes it: These beetles are attracted to stressed plants and can quickly defoliate them.
• How to fix/prevent it: Handpick beetles and drop them into soapy water. Use row covers to protect plants. Apply neem oil as a repellent.

Mountain West Specific Challenges: Our moderate-at-altitude heat and low humidity can actually be advantageous, reducing the incidence of some fungal diseases. However, the intense sun can stress plants, making them more susceptible to pests and diseases. Consistent watering and proper mulching are key to maintaining healthy, resilient blackberry plants in our unique climate.

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

• Tansy: Repels Japanese beetles, a common pest in our region.
• Garlic: Deters a variety of pests and helps prevent fungal diseases.
• Green Beans: Fix nitrogen in the soil, benefiting the blackberries.
• Mint: Attracts beneficial insects and pollinators, but be sure to contain it as it can be invasive.

Avoid planting blackberries near these:

• Tomatoes, Peppers, Potatoes: These belong to the nightshade family and can harbor diseases that also affect blackberries.