Blackberry in Zone 5A — Mountain West

Growing blackberries in our Mountain West gardens is a rewarding experience. The intense sun here helps to develop a deep, rich flavor that you just can't get from store-bought berries. Plus, there's nothing quite like making your own jam with berries you've grown yourself, or adding them fresh to your morning oatmeal.

Our short growing season and alkaline soil present challenges for high altitude gardening, but with careful timing and a little extra attention, you can absolutely enjoy a bountiful blackberry harvest. With our 138-day growing season, starting with transplants gives your blackberries the head start they need.

You'll want to get your blackberry transplants in the ground from early May through early June, after the last threat of 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 our intense UV and variable temperatures.

Plant your blackberry bushes 3-5 feet apart to give them plenty of room to grow. Keep an eye out for late spring hail storms, which can damage young plants. Row covers can provide temporary protection.

Blackberries need regular watering, especially during the fruiting period. Our dry climate means you'll need to be more diligent than gardeners in wetter regions. While blackberries are more drought-tolerant than raspberries once established, don't let them completely dry out.

A good rule of thumb is to give your blackberry bushes about 1-2 inches of water per week, either from rain or irrigation. 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. Focus on watering at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases in some plants, although it's rarely a problem in our low humidity. Signs of underwatering include wilting leaves and dry, brittle canes. Overwatering can lead to root rot, indicated by yellowing leaves and a general decline in plant health.

Mulch heavily around your blackberry plants with straw or wood chips to help retain moisture and suppress weeds.

Blackberries are vining plants and need strong support to thrive. A trellis system works best, allowing the canes to grow vertically and receive plenty of sunlight. Install your trellis before planting to avoid disturbing the roots later on.

A simple two-wire trellis, with wires strung horizontally at 2 and 4 feet above the ground, is often sufficient. As the canes grow, train them along the wires, tying them loosely with twine or plant tape. Thornless varieties are definitely easier to manage on a trellis!

Pruning is essential for maintaining healthy and productive blackberry plants. After harvest, remove the spent floricanes (the canes that produced fruit) at the base of the plant. These canes won't produce again.

During the growing season, tip-prune new primocanes (the current year's growth) at about 4-5 feet tall. This encourages branching and more fruit production the following year. Before our first frost in late September, give your plants a final inspection, removing any dead or diseased canes.

You can expect your first blackberry harvest from early July through late August, depending on the variety and the weather conditions. Blackberries are ready to pick when they are fully black, not dark red. A ripe berry should pull off the cane easily without squeezing it. A dull surface, rather than a shiny one, also indicates full ripeness.

Harvest regularly, every few days, to encourage continued production. Handle the berries gently to avoid bruising. As our first frost approaches in late September, harvest any remaining berries, even if they aren't quite fully ripe. They won't ripen off the vine, but you can use them for jams or baking.

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

Spotted Wing Drosophila

• What it looks like: Tiny flies lay eggs in ripening fruit, causing soft spots and larvae inside the berries.
• What causes it: These pests thrive in humid conditions, although our low humidity makes them less of a problem than in other regions. They are attracted to ripe fruit.
• How to fix/prevent it: Use traps to monitor for the presence of SWD. Netting can exclude the flies from your plants. Remove any infested fruit promptly.

Cane Blight

• What it looks like: Dark brown or purple lesions appear on the canes, often near wounds or pruning cuts.
• What causes it: A fungal disease that enters through open wounds. Our dry climate helps to minimize this, but it can still occur.
• How to fix/prevent it: Prune out infected canes well below the lesion. Disinfect pruning tools between cuts. Avoid wounding the canes.

Orange Rust

• What it looks like: Bright orange pustules appear on the undersides of leaves in the spring.
• What causes it: A systemic fungal disease that infects the entire plant.
• How to fix/prevent it: Remove and destroy infected plants immediately. There is no cure for orange rust. Choose disease-resistant varieties.

Japanese Beetles

• What it looks like: Metallic green beetles that skeletonize leaves and damage fruit.
• What causes it: These beetles are attracted to a wide range of plants, including blackberries.
• How to fix/prevent it: Handpick beetles off the plants and drop them into a bucket of soapy water. Use netting to protect your plants.

Mountain West Specific Challenges: Our moderate-at-altitude summer heat and low humidity can actually be beneficial for blackberries, reducing the risk of many fungal diseases. However, our intense UV can scorch the fruit if it's not adequately shaded. Our dry rainfall means that consistent irrigation is crucial for a good harvest.

Companion planting can help improve the health and productivity of your blackberry bushes.

Good companions for blackberries include tansy, which repels insects, and garlic, which acts as a natural fungicide. Green beans can fix nitrogen in the soil, benefiting the blackberries. Mint can also deter pests, but be careful to contain it, as it can be invasive.

Avoid planting tomatoes, peppers, and potatoes near blackberries. These plants are susceptible to similar diseases and pests, which can spread between them. Also, they are heavy feeders and can compete with the blackberries for nutrients in our already alkaline soil.