Raspberry in Zone 5A — Mountain West

Raspberries are a rewarding addition to any Mountain West garden. Their sweet-tart flavor shines in jams, desserts, or just eaten fresh off the cane. Plus, they are fairly easy to grow in our high altitude climate, and the cool nights even in summer enhance their flavor.

Our short growing season and alkaline soil present some challenges, but careful timing and soil preparation make growing raspberries entirely achievable. With a growing season of around 138 days, we need to make the most of our warm months.

Transplant your raspberry plants outdoors from early May through early June. Choose bare-root canes or potted plants from your local nursery. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

When transplanting, space the plants 2-3 feet apart to allow for adequate growth and air circulation. Keep an eye on the weather; a late frost or unexpected hail can damage new growth.

Raspberries need consistent moisture, especially in our dry Mountain climate. Aim for about 1-2 inches of water per week, which can be a lot to deliver in one go. Since our humidity is low, watering at the base of the plant is ideal to avoid fungal issues. Drip irrigation works best to deliver water directly to the roots.

In the spring, as the plants are establishing, check the soil moisture regularly. Use the finger test: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. During the moderate-at-altitude summer heat, you may need to water more frequently.

Underwatering can lead to stunted growth and dry, crumbly berries. Overwatering, on the other hand, can cause root rot, so make sure the soil is well-draining. Mulching around the base of the plants with wood chips or straw helps retain moisture and regulate soil temperature.

Raspberry canes need support to keep them upright and prevent the fruit from touching the ground. A simple two-wire trellis system works well. Install the trellis at planting time, running two wires parallel to the ground, one at about 2 feet and another at 4 feet.

As the canes grow, gently weave them between the wires to provide support. This not only keeps the plants tidy but also improves air circulation and makes harvesting easier.

Pruning is essential for maintaining healthy and productive raspberry plants. For summer-bearing varieties, remove the spent canes after they finish fruiting. These canes, which produced fruit that year, will turn brown and woody. Cut them back to the ground.

For everbearing raspberries, you have two options. You can either cut all the canes to the ground in late winter for one large fall crop, or you can selectively prune to get two harvests. To get two harvests, prune only the top portion of the canes that fruited in the fall, leaving the lower portion to produce a summer crop. Regardless, always remove any weak or damaged canes.

As the first frost approaches in late September, remove any late-fruiting canes that won't have time to ripen. This will encourage the plant to focus its energy on root development for the following year.

Your first raspberry harvest can be expected from early July through late August. The berries are ready to pick when they are deeply colored and pull easily off the core. Ripe berries will release with a gentle tug.

Pick every 2-3 days during peak season to prevent overripe fruit and encourage continued production. Handle the berries gently to avoid bruising.

As the first frost approaches in late September, harvest any remaining ripe or nearly ripe berries. Even slightly underripe berries can be used for jams or sauces.

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

Spotted Wing Drosophila

• What it looks like: Tiny flies laying eggs inside ripening fruit, causing soft spots and decay.
• What causes it: These pests thrive in humid conditions, though even our low humidity can't completely eliminate them.
• How to fix/prevent it: Use netting to exclude the flies, prune plants for good air circulation, and remove overripe fruit promptly.

Cane Borer

• What it looks like: Wilting or dying canes with small holes.
• What causes it: Cane borers lay eggs in the canes, and the larvae tunnel through them.
• How to fix/prevent it: Prune and destroy infested canes below the lowest hole as soon as you see the damage.

Gray Mold (Botrytis)

• What it looks like: Gray, fuzzy mold on berries and canes.
• What causes it: Fungal disease that thrives in wet conditions.
• How to fix/prevent it: Improve air circulation by pruning, avoid overhead watering, and remove infected plant parts.

Raspberry Crown Borer

• What it looks like: Weakened plants with swellings at the base of the canes.
• What causes it: Larvae bore into the crown and roots of the plant.
• How to fix/prevent it: Remove and destroy infested plants. Use beneficial nematodes to target the larvae in the soil.

Mountain West Specific Challenges: Our moderate-at-altitude heat and low humidity can help reduce some disease pressure, but the intense UV radiation can stress plants if they're not properly acclimated. Dry rainfall means consistent irrigation is crucial for success with raspberries.

Good companions for raspberries include garlic, tansy, and marigolds. Garlic and tansy are natural pest repellents, helping to keep away harmful insects. Marigolds attract beneficial insects that can help control pests and also deter nematodes in the alkaline soil.

Avoid planting raspberries near potatoes, tomatoes, peppers, or blackberries. Potatoes, tomatoes, and peppers can harbor diseases that can spread to raspberries. Blackberries compete for nutrients and can also spread diseases.