Raspberry in Zone 7B — Desert Southwest

Growing raspberries in the Desert Southwest might seem like a challenge, but the sweet, tangy taste of fresh-picked berries is absolutely worth the effort. Imagine popping sun-ripened raspberries straight from your garden, using them in desserts, or making your own jam – a true taste of summer amidst our desert landscape.

Our extreme heat and arid conditions present unique challenges, but with careful planning and attention to watering, you can absolutely succeed. The key is understanding our two growing seasons and utilizing our long, warm fall to your advantage. With our 245-day growing season, you have time to get this right.

Transplanting your raspberry bushes outdoors should be done from mid-March through mid-April. This gives them a good start before the worst of the summer heat kicks in. 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.

Space the plants 2-3 feet apart to give them plenty of room to grow. Keep an eye on the weather forecast. Even in early spring, we can get some unexpected temperature swings, so be ready to cover your new transplants if a late cold snap threatens.

Raspberries need consistent moisture, especially in our arid climate, but they don't like soggy roots. Aim for about 1-2 inches of water per week, adjusting based on rainfall, especially during the monsoon season. Drip irrigation is your best friend here, delivering water directly to the roots and minimizing water loss from evaporation.

During the intense summer heat, you'll likely need to water more frequently, possibly every other day. Use the finger test: 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 the cooler spring and fall, you can usually reduce watering to a couple of times a week. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases, even in our dry air.

Signs of underwatering include wilting leaves and dry, brittle canes. Overwatering can lead to yellowing leaves and root rot. A good layer of mulch, like wood chips or straw, around the base of the plants will help retain moisture and keep the soil cooler.

Raspberry canes need support to keep them upright and productive. A simple two-wire trellis system works wonders. Install this at planting time or shortly after.

Run two wires horizontally, one about 2-3 feet off the ground and the other around 4-5 feet. As the canes grow, gently weave them between the wires or tie them loosely with twine. This prevents the canes from flopping over, keeps the fruit off the ground, and makes harvesting much easier.

Pruning is important for maintaining healthy and productive raspberry bushes. For summer-bearing varieties, remove the canes that fruited immediately after harvest. These canes won't produce again, and removing them encourages new growth.

For everbearing varieties, you have a couple of options. You can cut all the canes down to the ground in late winter for one large fall crop. Or, you can selectively prune the tips of the canes that fruited in the fall, leaving the rest of the cane to produce a smaller summer crop followed by a larger fall crop on the new growth. As the first frost approaches in mid- November, remove any remaining fruit and prepare the plants for dormancy.

You can expect your first harvest of raspberries from mid-May through early July, about 60 days after transplanting. The berries are ready to pick when they are deeply colored and pull easily from the core. A gentle tug should do the trick.

Check your plants every 2-3 days during peak season, as raspberries ripen quickly. To encourage continued production, harvest regularly. As the first frost approaches in mid- November, harvest any remaining mature berries.

Here are some common problems you might encounter with raspberries in the Desert Southwest:

• 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 flies thrive in humid conditions and target ripe fruit.
• How to fix/prevent it: Monitor traps, remove infested fruit promptly, and consider netting to exclude the flies.
• Cane Borer
• What it looks like: Wilting or dying canes with small holes near the base.
• What causes it: Cane borers are beetles that lay eggs in the canes, and the larvae tunnel inside.
• How to fix/prevent it: Prune and destroy infested canes below the point of entry. Keep the area around the plants clean to reduce hiding places for the beetles.
• Gray Mold
• What it looks like: Fuzzy gray mold on the fruit, especially during periods of high humidity.
• What causes it: This fungal disease thrives in moist conditions and can spread quickly.
• How to fix/prevent it: Ensure good air circulation by pruning properly and spacing plants adequately. Avoid overhead watering and remove any infected fruit immediately.
• Raspberry Crown Borer
• What it looks like: Weak or stunted plants, with swelling or galls near the base of the canes.
• What causes it: This is a moth whose larvae bore into the crown and roots of the plant.
• How to fix/prevent it: Difficult to control. Remove and destroy infested plants. Consider using beneficial nematodes to target the larvae in the soil.

Desert Southwest Specific Challenges: The extreme heat can stress raspberry plants, making them more susceptible to pests and diseases. Sunscald can also be a problem, so providing afternoon shade with shade cloth essential during the hottest months is a good idea. Our alkaline soil can also be a challenge. Amend the soil with plenty of organic matter to improve drainage and lower the pH.

Companion planting can help your raspberries thrive. Garlic, tansy, and marigolds are good companions because they deter pests with their strong scents.

Avoid planting raspberries near potatoes, tomatoes, peppers, or blackberries. These plants can attract pests and diseases that also affect raspberries. Blackberries can also compete for resources and spread diseases.