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Rhododendrons - the beautiful, evergreen shrubs that provide a magnificent display of color in many gardens. But especially in winter, these plants can suffer from cold temperatures and dry winds. To ensure that your rhododendrons get through the winter healthy and strong, you should follow a few simple but important care steps.
Why rhododendrons need protection in winter
AlthoughRhododendrons are robust plants, they are sensitive to cold, especially in winter. The problem? It's not cold alone, but the combination of icy winds and dry ground. Cold winds remove moisture from the leaves, and if the ground is frozen, the plant cannot draw in water. The result? The leaves wilt and, in extreme cases, entire branches may die.
Is it ideal to plant the rhododendron in a protected place? Partial shade in winter and sun in spring are perfect. A location shielded from cold winds greatly reduces the risk of frost damage.
Why rhododendron leaves droop and curl
A common phenomenon with rhododendrons in winter is drooping and curling of the leaves. Many garden owners wonder whether this is a...Signs of disease or pest infestationis ? But don't worry, it's a natural protective mechanism of the plant. The leaves begin to droop slightly at temperatures around 2 °C. If the temperature drops to freezing point (0 °C), the leaves curl up at the edges. At temperatures below -4 °C the leaves are tightly rolled up.
This process, also calledthermonastic leaf movementknown, helps the plant to protect itself from cold and water loss. Cold, dry winds can cause too much moisture to be removed from the leaves without enough water coming in from the frozen ground. By curling its leaves, the rhododendron reduces the surface area over which water can evaporate, minimizing damage.
Interestingly, not all rhododendron species exhibit this behavior. While that atRhododendron catawbienseoccurs frequently, for example reactsRhododendron ponticusless sensitive to the cold and does not show this reaction.
So if you notice that your rhododendron leaves are drooping or curled in winter, shouldn't you worry? As soon as the temperatures rise again, the leaves recover on their own.
Root activity in winter – what happens underground?
While the above-ground parts of the rhododendron go into a kind of dormant state in winter, the roots remain active. Yes, you heard that right! The roots are not completely inactive during the winter months. If the soil does not drop below -7°C, they can even continue to grow. As soon as the ground thaws slightly and reaches temperatures between 0 °C and 5 °C, the roots awaken from their winter dormancy. This ability of the roots to absorb water even in winter is essential to prevent the leaves from drying out.
It is particularly important to protect the roots well from frost. A thick blanket of snow can insulate the soil and protect roots from frost. Late snowfall, when the ground is already frozen, can have the opposite effect. Repeated freezing and thawing of the soil can damage the delicate roots responsible for absorbing water and nutrients. That is why it is so important to mulch the soil well and protect it from strong temperature fluctuations.
Which rhododendrons need special winter protection?
Young plants
Newly planted or young rhododendrons have not yet developed a deep root system and are therefore more sensitive. They should be protected with jute bags or special anti-freeze covers until they acclimate. You can find a recommended optionhere on Amazon. However, be sure to choose the right size of covers so that they do not restrict the plant.
Sensitive varieties
Some species of rhododendrons are more susceptible to cold, especially those that come from warmer regions. Hybrids likeRhododendron ‘Catawbiense’orRhododendron 'Nova Zembla'need additional protection in particularly cold winters.
Budding and flowering varieties
Rhododendrons with delicate flower buds, such as some deciduous azaleas, require additional protection to protect the flower buds from frost damage. These plants should be protected, especially in areas with strong temperature fluctuations in winter.
However, there are also varieties that are known for their cold resistance. Rhododendron 'PJM' is a particularly hardy variety, but others such as Olga Mezitt and Spring Parade have also proven resilient in harsh winters.
Mulch protects the roots
Rhododendrons have a very shallow root system. That's why it's particularly important to cover the ground around the plant with a thick layer of mulch. To do this, use about 10 cm of organic mulch, such as bark mulch or pine needles. This protects the roots from cold and reduces the evaporation of water from the soil.
Water correctly
Before the first frost sets in, it is important to water your rhododendrons thoroughly to keep them well hydrated. But you should also keep an eye on the plants during the winter. It is important not to water too frequently.
Instead of small amounts of water every day, it is recommended to water vigorously every three to four weeks? and only in dry and clear weather. This is particularly crucial for freshly planted rhododendrons, as their roots do not yet reach deep enough. If the subfloor is frozen, be sure to lightly moisten only the top layerTo avoid waterlogging.
Create wind protection
Cold winds are one of the main causes of cold damage. A windbreak made of fleece (like this one on Amazon) can slow the winds and reduce leaf evaporation. Are you careful not to cover the plant completely? The American Rhododendron Society recommends never covering the top of the plant to ensure adequate air circulation.
So you can cut open the winter protection bag at the bottom and use plant support rods to create a suitable structure that offers the plant additional support without affecting air circulation.
Protection in heavy snowfall
If you live in a mild region that occasionally experiences heavy snowfall, you may want to provide your rhododendron with some protection to prevent branches from breaking. In areas where it snows regularly, this is usually not necessary.
With regular snowfall, the snow can gradually accumulate on the plants, allowing the branches to slowly adjust to the extra weight. Occasional heavy snowfalls, on the other hand, force the branches to suddenly bend sharply, often leading to breakage. To prevent this, during heavy snowfall, you can place a blanket, jute bag or tarp over the plant to give the branches additional stability.
A few long sticks inserted into the plant can give the cover additional support. A simple trick is to stick a shovel into the ground to stabilize the tarp. However, remove the cover as soon as the weather improves.
For particularly ambitious gardeners, there is also the option of building mini greenhouses around the rhododendron to provide even better protection.
What to do if there is frost damage?
If, despite all caution, your rhododendrons have suffered frost damage,cut the affected leavesand shoots in spring. This allows the plants to recover quickly and sprout vigorously.
Those:
American Rhododendron Society: Caring for Rhododendrons in Winter by Steve Henning
