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Mandevillas don’t last too long in frigid temperatures, so it’s important to keep them warm during the winter. If you don’t have enough space in your home, you’ve likely considered bringing these plants into your garage during the colder months.
You can overwinter Mandevilla in a garage if your garage is warmer than 50°F(°C10). Keep the plant in a pot or a raised bed, then provide six hours of grow lamp light each day to ensure it gets enough nutrients. Also, water the soil enough to prevent the plant from drying out.
In this post, I’ll break down how to overwinter Mandevilla in a garage, when you can bring it back outside, and what you should know beforehand.
How To Overwinter Mandevilla in Your Garage
To overwinter Mandevilla in your garage, ensure the soil is slightly damp, keep it in a pot (if possible), and provide six to ten hours of artificial sunlight daily. Your Mandevilla will likely go dormant during the winter, which is good because you won’t have to worry about getting a bigger pot.
Here’s a detailed look at the way you should overwinter a Mandevilla in your garage:
- Wait until it gets around 50 to 55 degrees Fahrenheit (10-12 degrees Celsius) outside, then place the Mandevilla in a pot or a lightweight, portable raised bed. There’s no need to bring your Mandevilla inside before it starts going dormant. Natural sunlight and humidity are the best factors for optimal plant growth.
- NYBG suggests pruning the dead leaves and excess growth from your Mandevilla before bringing it into the garage (source). This process prevents the plant from requiring too much maintenance and crowding your garage. It also reserves the nutrients in the soil for the main vines and flowers on the Mandevilla.
- Keep the garage above 55 degrees Fahrenheit (12 degrees Celsius) throughout the winter. Overwintering your Mandevilla won’t do any good if the garage is just as cold as the air outside. Freezing temperatures can cause irreversible damage to the flowers, roots, and stems.
- Water the soil before it gets too dry, but avoid soaking the roots. Use a mister or a watering can instead of a pressurized garden hose. The soil should be slightly damp, about two inches below the surface. If it’s too wet, your Mandevilla will develop root rot. If it’s too dry, it’ll kill the roots and prevent them from recovering.
- Use extra heat lamps, heat mats, or burlap fabric to prevent the Mandevilla from freezing in the garage. These tools can help quite a bit if your garage doesn’t have good insulation or a thermostat. You can also use space heaters during the coldest parts of the day to maintain the garage’s temperature.
Overwintering Mandevilla in your garage is much safer than leaving it outside, especially if you live in an area prone to freezing temperatures. Mandevilla is extremely fragile and delicate when it comes to cold, harsh winters, so it’s important to know when it’s safe to bring it back outside.
When Can You Bring Your Mandevilla Back Outside?
You can bring your Mandevilla back outside when the last frost of spring is over, and the outside temperature stays above 50 degrees Fahrenheit (10 degrees Celsius).
Mandevilla shouldn’t be left outside when it’s too cold because it can die, get damaged, or go dormant for too long. Spring sunlight is perfect for bringing a Mandevilla out of your garage.
Garden Gate Magazine recommends tapering your mandevilla’s watering frequency once the temperature dips below 50 degrees Fahrenheit (10 degrees Celsius) at night. You’ll have to maintain this reduced watering level until spring (or whenever the temperature stays above 50 degrees during the coldest part of the night).
Once it starts getting sunnier outside (before you bring the Mandevilla back outdoors), you can bring it closer to a window to get better sunlight. This process allows the Mandevilla to get used to the external temperature to prevent transplant shock (yes, it can happen to the plant, even if you keep it in the same container).
See our guide on How To Get a Mandevilla Out of Dormancy.
Quick Tip: If you’re unsure whether it’s safe to bring your Mandevilla back outside after overwintering it in your garage, look for frost on the grass or trees. Once there’s no more frost, it’s safe to say that your Mandevilla will be safe to move outside. You can always move it back to the garage if it gets cold again.
What To Know Before Overwintering Mandevilla in a Garage
Before overwintering Mandevilla in a garage, you should know that it won’t do any good if your garage isn’t insulated or it’s too cold. While your garage can protect your flowering vines from wind, rain, and other weather conditions, cold temperatures are the most dangerous part of the winter for these plants.
Let’s take a look at everything you need to know before bringing your Mandevilla into your garage:
- Keep a thermostat and hygrometer in your garage around the clock. Keep the temperature above 50 degrees Fahrenheit (10 degrees Celsius) to prevent frost damage. The hygrometer should be around 45% to prevent the Mandevilla from drying out too quickly. Increasing the humidity can reduce the required watering frequency.
- Masterclass explains that your Mandevilla might not go dormant if it’s kept above 60 degrees Fahrenheit (15.5 degrees Celsius) in your garage (source). Be prepared to prune your Mandevilla regularly if you have a warm garage. Combining this temperature range with water and artificial sunlight is often enough to encourage flowering.
- Chemicals in your garage can cause all sorts of damage to your Mandevilla. Ensure every chemical is sealed and stored far from your overwintered Mandevilla; otherwise, you’ll risk damaging or killing the plants. Consider opening a few vents or windows to let more oxygen into the garage.
Overwintering a Mandevilla can be a lot of work until you settle into the routine. However, it’s more than worth it since it saves your plant from frost damage and potential long-term issues. If your Mandevilla stays outside during the winter, it could dry out and crack.