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The thing to remember about Mandevilla is that it is a tropical plant. It’s not meant to suffer through freezing winters. Cold temperatures can cause long-term damage that’s often irreversible.
A mandevilla will often come back after a freeze if the inner stem is green and hydrated. However, a black, dried stem often shows there’s too much frost damage to recover the plant. You can use heat lamps and heat mats to keep your indoor mandevillas warm during the winter.
My neighbor planted his Mandevilla under a pergula. He was able to wrap plastic over the top of the pergula before a freeze which kept the inner stems from dying. This was a short freeze, however. They likely would not survive a prolonged one.
How To Bring a Mandevilla Back After It Freezes
To bring a mandevilla back after it freezes, check the inner stem for damage, then bring the plant indoors if possible. Use heat lamps or heat mats to warm the soil and roots. You can use burlap fabric to heat the soil of mandevillas that are planted in the ground.
Here’s a guide on mending a frost-damaged mandevilla:
- Use your fingernail to remove a thin layer of the stem to expose the inner greenery. If the portion under the upper layer looks green and watery, then your mandevilla is dormant and not damaged. If the layer looks black, brown, dry, or cracked, it’s likely too late to save the plant.
- Keep the mandevilla watered, and make sure the soil is never dry. Too much water can freeze the mandevilla’s soil and roots. Mandevillas are prone to freezing during the winter, especially if rainwater or snow freezes the roots. Place your finger a couple of inches below the soil, ensuring this depth is always slightly moist.
- Heat the mandevilla vines and roots if possible. If you can bring the plant indoors, use heat lamps and heat mats to encourage root growth and rejuvenation. If the plant is vining and growing from the ground, lay thin sheets of burlap around the soil to heat the roots and retain warmth.
- Bring small mandevillas inside. You’ll have much better control over the plant’s temperature when it’s in your home. This is your best option, but it’s not always available if your mandevillas aren’t in pots or planter boxes. Besides, vines growing around the outside of your home usually insulate themselves or go dormant.
- Add new topsoil around the base of the plant. Soil often stays much warmer than the air above it. If you add more topsoil, there’s more room for the base of the mandevilla to stay warm. Furthermore, a new layer of topsoil will heat the soil under it, providing oxygen to the roots to encourage growth.
According to NYBG, mandevilla flowering vines typically go dormant and stop growing around 60°F (15.5°C) (source). However, that doesn’t mean they’re damaged or they won’t grow anymore once they get warm enough. For this reason, most mandevillas don’t grow too much during the winter months.
See our guide on How To Get a Mandevilla Out of Dormancy.
Can I Leave Mandevilla Outside in the Winter?
You can’t leave a mandevilla outside in the winter if it gets below 55°F (12°C) because it could damage the plant. Once the roots get too cold, they won’t be able to absorb moisture, nutrients, or sunlight through the leaves.
Keep these factors in mind when growing a mandevilla during the winter:
- HGTV claims mandevillas need at least 6 hours of sunlight daily, so you might need to supplement them with artificial sunlight (source).
- It’s much easier to maintain potted mandevillas during the winter months because you can bring them inside, especially when it’s below the aforementioned 55-degree threshold.
- Row cover and garden fleece can be used to heat the soil if you have mandevillas plants in your garden that you can’t bring inside.
- I suggest checking your mandevillas once a week during the winter (or every time it dips below 45°F or 7°C) to ensure that they’re not damaged by the cold temperatures.
- Mandevillas are much better off in a house, shed, garage, or greenhouse during the winter than exposing them to the elements (hail, snow, cold temperatures, and heavy windstorms can damage these delicate vines and flowers).
Those living in tropical climates or places with semi-warm or mild winters shouldn’t worry too much about winterizing their mandevillas. They’ll likely go dormant, but they’ll come back after the winter because there’s not enough cold weather to freeze them.
LoveForPlants has an excellent guide to preparing Mandevilla’s for winter:
Also be sure to read our guidance on Overwintering Mandevilla in a Garage.
What Is the Lowest Temperature a Mandevilla Can Tolerate?
The lowest temperature a mandevilla can tolerate is 45°F (7°C), but they start experiencing frost damage around 55°F (12°C). You can use burlap sheets to keep the roots warm, or consider bringing your mandevilla indoors when it’s too cold outside.
Mandeville can get as cold as 45°F (7°C) before permanent frost damage takes place (source). However, it’s not worth risking it for younger, smaller plants. Once the roots and vines are settled and have grown for several years, they’ll be much more resilient to cold weather.
It’s best to start the new Mandeville in the spring once the outside temperature is steadily above 50 to 55°F (10 to 12°C). This range ensures that they won’t freeze or crumble apart. If you plant them later in the summer, keep them indoors in a pot until the following spring.
Note: If your mandevilla plants are growing vines all over the outside of your home, trees, sheds, and other tall, bulky structures, they tend to maintain their health during mild winters. However, these plants aren’t native to freezing temperatures that you’ll find in the midwest or in most high-elevation mountainous regions.
While Mandeville plants don’t last long in cold temperatures, there are a few ways you can inspect them and try to bring them back to life. As long as the stems are in good shape, you should be able to restore the plant. Providing adequate water and warmth will help Mandeville come back after a freeze.
Additionally, remember to keep your plants away from temperatures below 55°F (12°C). It’s ideal to bring them indoors during autumn and winter.