Begonias are tropical perennials usually grown as annuals in cold winter regions. Potted begonias cannot typically be left outside unless you live in a frost-free climate (USDA Hardiness Zones 9–11). These plants are exceptionally sensitive to cold temperatures, and a hard frost is fatal. Successfully preserving begonias over winter requires bringing them indoors, but the specific method depends entirely on the type of begonia.
The Critical Distinction Between Begonia Types
The strategy for winter preservation hinges on the plant’s root structure, separating species into two main groups: tuberous and fibrous-rooted. Tuberous begonias (Begonia x tuberhybrida) are recognized by their large, flamboyant blossoms. They grow from a fleshy, underground storage organ called a tuber, which naturally enters dormancy during colder months. Fibrous-rooted begonias, including wax begonia (Begonia semperflorens) and cane-like varieties, have a standard, fine root ball. Unlike tuberous types, these plants lack a storage organ and do not require dormancy, demanding active growth as a houseplant instead.
Preparing Tuberous Begonias for Dormancy
Tuberous begonias must be lifted and stored. Preparation begins when the foliage naturally yellows or after the first light frost causes the leaves to collapse. This dieback signals the plant is diverting energy reserves back into the tuber for winter survival. Once the top growth has softened, cut the stems back, leaving two to five inches attached to the soil line.
Bring the entire pot inside and allow it to dry out completely over the next one to three weeks in a cool, sheltered location. This curing period is crucial for the tuber to dry and for the outer skin to thicken, minimizing the risk of rot during storage. After curing, gently remove the tubers from the soil, brush away loose dirt, and discard any that appear soft, damaged, or diseased.
The cleaned tubers should be packed in a material that provides insulation and absorbs moisture, such as dry peat moss, vermiculite, or sawdust. Place the tubers in a cardboard box or paper bag, ensuring they do not touch each other, and cover them completely with the packing medium. Store the container in a dark, dry, and cool area, maintaining a consistent temperature between 40 and 50 degrees Fahrenheit. Check the tubers monthly throughout the winter to ensure they are not shriveling from dryness or developing mold.
Overwintering Fibrous and Wax Begonias Indoors
Fibrous-rooted begonias, such as wax and angel wing types, are maintained as active houseplants throughout the winter. This requires moving the potted plant indoors well before overnight temperatures dip below 45 degrees Fahrenheit. Before transitioning the plant inside, thoroughly inspect it for pests like mealybugs or spider mites to prevent infesting other indoor plants.
These varieties thrive best in a location receiving bright, indirect light for several hours daily, such as a south- or west-facing window, or under supplemental grow lights. While actively growing, they require a reduced but continuous watering schedule. Keep the soil lightly moist, allowing the top inch to dry out between waterings. Avoid the heavy watering required during summer, as this can lead to root rot in lower light conditions.
Maintaining a consistent indoor temperature, ideally between 60 and 73 degrees Fahrenheit, supports continuous growth. Indoor air often lacks the humidity these tropical plants prefer, so using a pebble tray or a small humidifier nearby prevents leaf edges from turning brown. Occasional light pruning of leggy stems helps the plant maintain a compact, attractive shape throughout the winter.