Tuberous and wax begonias grace summer gardens as some of the most popular spring bedding and container plants available. If you grow a special begonia in your garden, you can keep it going for ten years or even longer with good care and overwintering.
Gardeners in hardiness zones 8 and higher with warm winters and stable climates may be able to grow begonias year-round or prune them back in autumn to regrow when the weather warms in spring.
If you live in zones 7 and lower here is how to keep your begonias alive during winter.
How to Overwinter Begonias
How to overwinter begonias depends on both the type and cultivar, so it’s important to find out the growing requirements for your specific plant. Some are more heat or cold-tolerant but all begonias grow best with steady temperatures and are vulnerable to wide fluctuations. Here are some general rules for overwintering plants.
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Tuberous Begonias
Tuberous begonias are sensitive to hard frost and don’t tolerate temperatures below 45°F. Freezing kills the entire plant so you need to dig, cure, and store the tubers overwinter.
The first light frost causes leaves to die back. If you haven’t already done so now is the time to dig plants and place them in a warm dry location to cure for several days. Bring them indoors if overnight temperatures drop to 32°F. When tubers are dry, stems fall off or are easily removed. Shake off excess soil and discard any damaged tubers.
Store them snugly in a box separating each tuber with dry material like peat moss, coco coir, or sawdust. Treating with anti-fungal powder is an option. Keep the container in a cool—not cold—dark, dry location until outdoor temperatures remain above 50°F.
Wax Begonias
Wax begonia cultivars are slightly more tolerant of frost but won’t survive freezing. The exception is Rex varieties which should be reacclimated to indoor climates before temperatures drop below 50°F.
You can overwinter other wax begonias by digging and potting them up and bringing potted plants indoors for winter. Remove spent flowers and foliage and trim back leggy growth.
If you’re transplanting into a container, fill it with good quality potting soil, separate plants into small clumps, and place them at the same level as in the ground.
Place pots in a location that receives bright indirect light. If your potting mix includes fertilizer, do not feed the plants. They may not require any fertilizer during winter months, but if leaves turn yellow, feed them with a balanced NPK 10-10-10 fertilizer applied at half strength. Continue to deadhead spent flowers and foliage.
When to Overwinter Begonias
The key to successful overwintering is knowing the low temperature your particular type and cultivar can survive. If foliage starts to turn brown and dry, it’s time to winterize plants. If plants remain green as temperatures begin to fall, here are general rules to go by.
Before temperatures drop below 45°F, dig tuberous begonias, dry, and store the tubers.
When temperatures approach freezing, dig up and prune wax begonia plants. Transplant them into pots or bring potted plants indoors.
If your Rex begonia has summered outdoors, reacclimate the plant to indoor conditions well before temperatures drop to 50°F.
How to Care For Begonias in Winter
Stored tubers need to be kept dry throughout winter. Check them occasionally to remove and discard any with insect damage or rot.
For potted wax begonias, choose an indoor location with bright, indirect light away from drafts and heating vents. Try to keep temperatures consistent between 60°F and 73°F and a little cooler at night.
Continue to water when the top inch of soil gets dry. Mist plants if indoor air is particularly dry or place a small humidifier nearby. Fertilize no more than once a month and only if leaves start to yellow.
Revive Begonias For Spring
When soil and air temperatures stay above 50°F, remove begonia tubers from storage and plant them in pots or in the ground. Dig small holes about 1 inch deep and cover tubers lightly. If growing in containers use a well-draining, quality potting mix.
You can also give tubers a head start by planting indoors six to eight weeks before the final frost. Place them 1-inch deep in a shallow, soil-filled container. Water lightly to keep the soil moist until new sprouts appear. Once tubers grow roots and true leaves transplant them into the garden or containers and resume a regular watering and fertilizing schedule.
Slowly reacclimate potted begonias overwintered indoors to outside weather conditions. After the final frost, start by keeping pots in a shady spot protected from wind, rain, and fluctuating temperatures. After several weeks, it’s safe to move pots to their permanent summer locations.
FAQ
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In northern zones where the ground freezes, tubers need to be dug, dried, and stored over winter. Container-grown wax begonias can be treated as houseplants or moved into an unheated garage where temperatures remain above 32°F. In warmer, frost-free climates, lay potted tuberous begonias on their sides and protect them from rain and excess moisture.
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Prune begonias in autumn prior to overwintering. Cut main stems back to 3 to 4 inches tall with two or three sets of leaves. Wax begonias treated as houseplants can be trimmed back as needed to curtail leggy growth.