You can save my mandevilla for next year with a simple process that starts in early fall. The whole thing comes down to good timing and picking the right storage method for your home. Whether you have a bright window or a cool dark garage, your vine can make it through winter. I've saved the same plant for five years running with this approach.
Start watching your forecast when fall arrives. Begin your prep once nighttime temps drop to 55°F (12.8°C) on a regular basis. You want to have the plant inside well before the first frost hits your area. A single cold night below freezing can kill the vine if you wait too long. Mark your average first frost date on your calendar and aim to finish the move at least two weeks before that.
Here are the key mandevilla overwintering steps you need to follow for a smooth transition. First, cut the vine back by about one-third per Clemson Extension. This makes the plant easier to handle and move inside. Next, inspect every leaf and stem for pests. Look for whiteflies, spider mites, and mealybugs under the leaves. Spray the whole plant down with a hard stream of water from your hose. Treat any bugs you find with insecticidal soap before bringing the pot indoors.
You have two options for storing mandevilla winter months. The active method keeps your vine growing as a houseplant near a bright south-facing window. Give it at least four hours of direct sunlight each day. Water when the top inch of soil feels dry. The plant will grow slower and may drop some leaves but it stays green and active through the cold months.
The dormant method works best if you lack bright window space. Put the pot in a cool garage, basement, or closet that stays above 50°F (10°C). You don't need much light for this approach. Water once every two to three weeks and stop all fertilizer. The vine will drop most of its leaves and look bare by midwinter. This is normal and not a sign that the plant is dying on you.
I use the dormant method in my garage with a small grow light on a timer for six hours a day. The first year I tried it, the vine looked dead by February. I almost gave up on the whole thing. Then in March, tiny green buds popped out along the stems. By May the plant had full leaves and was ready for the porch. Now I trust the process and don't worry about the bare winter look anymore.
Reduce your watering right away once the plant moves inside. Too much water kills more saved mandevilla than cold temps ever do. The roots sit in wet soil with no summer heat to dry things out. Root rot can set in within a few weeks if you keep up your summer watering schedule. Let the soil go dry between drinks and your roots will stay healthy all winter long.
Come spring, wake your vine up by moving it to a brighter spot and watering more often. Start feeding again with a 10-20-10 fertilizer once you see new growth appear. Wait until nighttime temps stay above 55°F (12.8°C) before putting the plant back outside. Move it out over seven to ten days, starting in shade and working up to full sun. Your saved mandevilla will reward you with even more blooms than it gave you the year before.
Read the full article: Mandevilla Plant Care and Growing Guide
