Most raspberry varieties will survive a mild frost. However, providing cover during cold weather is very beneficial, especially if temperatures drop well below freezing, remain cold for an extended period, or if frost occurs often in a short period of time. Some of the best ways to protect your raspberries from frost include the use of a plant tarp, using heat lamps, building a protective layer of hay mulch, or bundling your raspberries under the soil until spring.
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The 4 Best Ways to Protect Raspberries from Frost
If you enjoy growing raspberries, frost probably crosses your mind at the season’s end. This is because most berries need some protection from frigid temperatures. Below are 4 highly effective ways to protect your raspberries from frost:
Create a Barrier With Hay Mulch
Mulch provides an extra layer of protection from the cold. Hay mulch is the best choice when using this technique. Create a mound of mulch 3–5 inches high (7.5–13 cm) around the base of your plants. This will help to trap warmth in the soil, preventing serious root damage to your raspberry canes.
- Build a barrier of hay mulch 3–5 inches high (7.5–13 cm) around the bottom of your plants.
- Don’t use this technique too early in the season, or your plants may be smothered.
- Remove the mounds early in the spring.
Wait until you are well into fall frost season to mulch your raspberries in this way. If you implement this technique too early, you risk smothering your plants. For the same reason, it’s also important to remove the hay mulch mounds and spread them out evenly in early spring.
Invest in Heat Lamps or Break Out Your Holiday Lights Early
If you have a large raspberry patch and it’s located in proximity to a power source, consider investing in heat lamps, which you can turn on and off at will whenever frost is predicted. A good set of heat lamps provide warmth to your outdoor plants and completely prevents frost damage.
- Consider investing in these heat lamps if you have a large raspberry patch.
- Strings of ordinary Christmas lights can be used as heat lights for raspberries
- Do not allow the lights to come in contact with the plants—they may cause damage.
- Position heat lamps on the ground or string lights along stakes to keep them at a safe distance.
- Keep lights 5 inches (13 cm) from your raspberries for the best results.
- Only use heat lamps or lights when a frost is predicted.
If you’re on a budget and you’re not concerned about appearance, standard Christmas lights can also be used in this way. Make sure you string them up in such a manner that they are in no danger of coming in contact with the plants themselves, and only use them when a frost is predicted. You can set lights up near round level, or string them between stakes 5 inches (13 cm) from your plants.
Bundle Your Raspberry Plants Under the Soil
Another way to protect your raspberries from frost is by bundling them and covering them with soil. After you’ve harvested the last berries for the season, prune off all raspberry canes that are two years old. Once a raspberry cane produces berries in its second year of growth, it will not produce berries again. So, you can remove these old canes.
- Protect your raspberry plants by bundling them under the soil.
- Harvest your raspberry plants and remove all 2-year-old canes.
- Cut the remaining canes back to 12 inches (30 cm) in height.
- Gently bend the pruned canes to the ground and cover them with 3 inches (7.5 cm) of soil.
After you’ve removed all the two-year-old canes, cut any one-year-old canes back to a height of 12 inches (30 cm), and bend them to the ground. Cover these canes with 3 inches (7.5 cm) of soil This will protect your raspberry plants from frost and winter damage. Once spring arrives, remove the soil layer and allow your raspberry canes to produce vibrant new growth.
Cover Your Raspberries With Plant Tarps or Homemade Coverings
A highly recommended way to protect your raspberry plants from frost is to use plant tarps, blankets, or sheets to cover your raspberries anytime a frost is predicted. You can also use emergency thermal blankets when using this technique.
- Invest in plant tarps, or everyday blankets to protect your raspberries from frost.
- Don’t allow the coverings to touch the plants. Support them on these hoops.
- If the coverings touch your raspberries, then the plants can be damaged by frost and fungus.
- Put your coverings in place before nightfall.
Don’t allow the blankets to touch the raspberries, as this can allow fungus-based plant diseases to take hold when the frost is over. Never wait until the last minute to cover your plants. Rather, put the coverings in place at dusk when frost is in the forecast.
Does Frost Hurt Raspberries?
Frost can be harmful to raspberries. The level of damage is often directly related to the temperature and how many times your plants were caught in a frost. Long periods of cold, repeated nightly frosts, or a harsh cold snap several degrees below freezing are especially damaging.
- Frost can be very harmful to raspberries.
- The amount of frost damage depends on how many times your raspberries were exposed to freezing temperatures and how harsh the frost was.
- The Caroline Raspberry can withstand freezing temperatures.
One variety, the Caroline Raspberry, can withstand freezing temperatures with little or no protection. So, it’s a good choice if you are growing in a climate with harsh winters. However, the most commonly grown variety of raspberry, the Floricane, needs some cover from frost or the plants may suffer.
When Should You Protect Raspberries from Frost?
Generally speaking, raspberries should be protected from frost as soon as the first freeze occurs. There is one exception to this rule, however. If a mild frost is predicted, you can allow your raspberries to remain exposed, and from then on, offer a covering from frost.
- Allowing your raspberries to go through one mild, short frost is not dangerous and may even be beneficial.
- If temperatures dip below 30℉ (-1℃) your raspberries need protection from frost.
Sometimes, exposure to a short, mild frost can actually improve the health of your raspberry canes. On the other hand, if temperatures are predicted to drop below 30℉ (-1℃) or a harsh winter is on the horizon, protect them from the first frost onward.
How to Cover Raspberries from Frost
Most raspberries will withstand mild frost, but it is necessary to protect them from harsh freezes and repeated cold temperatures.
- Other than mild frosts, raspberries need protection from winter temperatures.
- The harsher the frost, the more damage it will do to your raspberries.
- Building a protective layer of hay mulch is an effective way to keep your raspberries safe from frost.
- Heat lamps are a good investment if you have a large raspberry patch.
- You can bundle your raspberries and cover them with 3 inches (7.5 cm) of soil to protect them from frost damage.
- Using a thermal blanket, plant tarp, or simple homemade covering is an easy way to keep your raspberries safe from frost.
By using a row cover, mulching techniques, heat lamps, or bundling you can keep your raspberries safe until warmer temperatures arrive. Once spring weather returns, these hardy plants will impress you with their quick growth rate.