Overwintering Begonias in the UK – Frost Free Guide

Although often sold as half-hardy annuals, most Begonia varieties are perennial. Here in the UK, they are not frost-hardy and will die during cold, damp weather. The following article will give you advice on overwintering Begonias. I will cover both bedding and tuberous varieties and how best to protect them.

How to Store Begonias Over Winter & Why

Both tuberous-rooted and rooted varieties can be overwintered in a cool, dark, and dry place. Doing so is especially favourable, as both mature Begonia corms and well-established rooted varieties produce bigger and stronger plants for next year. I like to leave my tuberous varieties in their pots or hanging baskets and place them in the garden shed during the winter months. Every year, I lose a couple of Begonia tubers. Tubers are prone to attack by vine weevil grubs during the growing season. This weakens or even hollows out the tubers, causing them to rot during the winter. Fibrous Begonias are best grown indoors on a bright, warm windowsill.

Fibrous Rooted Begonias

Fibrous-rooted Begonias such as ‘wax’, ‘Angel’ or ‘Dragon winged’ may be pruned into a manageable shape and taken into the house or conservatory during the winter. They make attractive pot plants. I normally re-pot my fibrous-rooted Begonias before bringing them in. I do this to avoid introducing stowaways such as slugs and grubs into my home. Avoid draughty areas of the house to get the most out of your bedding Begonias during the colder months of the year.

Overwintering begonias (Tuberous Rooted)

Although many have tuberous roots, the majority of Begonia varieties are very tender and incapable of surviving the UK winter. They will require a period of dormancy in a cool and dry place. If you prefer to overwinter your potted Begonias by keeping the rhizome (or corm) in the same pot, then ensure you replace most of the compost during early spring. Failure to do so will result in poor growth and fewer flowers. Begonias will also need feeding when they start to produce their first leaves. If you want to know more about how to store Begonias over winter in the UK, then read on.

Getting started with overwintering Begonias:

1. Before the hard frosts arrive, dig up the entire plant while the foliage is still attached. Take care not to damage the Begonia tuber during this process. Doing so may cause your Begonia tuber to rot and die. Shake any weevil grubs out.
2. Remove any diseased tuber parts with a sharp knife.
3. Allow it to dry for one week in a frost-free and sunny location.
4. By gently teasing the stems away from the tuber, you can remove the foliage. Again, take care not to damage the tuber. Begonia rhizomes are delicate and easily scratched.
5. With your fingertips, gently clean away any excess soil or compost.
6. To prevent rot, I recommend dusting your Begonia tuber with sulphur powder.
7. Tubers should be stored in a clean cardboard box. Space them evenly apart and place the box in a dry, frost-free, and dark cupboard until spring.

I recommend that you check on your overwintering Begonias regularly. This ensures that they remain dry and rot-free. To reduce the risk of infecting other tubers, remove any that have started to rot. If in doubt, set aside suspect tubers. Begonia tubers can appear dead at times, only to successfully re-sprout in the spring.

Note: If you live in a particularly mild area of the UK, you might want to try leaving your Begonia tubers in the ground over the winter. Cover them with straw, used compost, or leaves until the threat of frost has passed. In my coastal garden in Devon, I have several tuberous Begonias. They appear to thrive even when left in the ground during the winter. This approach, however, is not without risks. I am confident that a harsh winter will eventually kill them off. But my Begonias have been in the ground for 6 years and are doing well.

Begonias: when to plant

Protect your overwintering Begonias from very low temperatures and frost by adopting the following process:

1. Bring your Begonias out from their ‘overwintering’ during the month of April.
2. Place tubers hollow-side-up and individually in pots or rows in trays of fresh general-purpose compost.
3. Cover with 1 cm (1/4 inch) of compost.
4. Place your plants in a shady spot in a well-ventilated room, frost-free conservatory, or greenhouse. They will need plenty of light, but I’d recommend keeping them away from direct sunlight. I place my Begonias on a lower tray under the bench in my greenhouse. They get plenty of morning sun, but very little during the day.
5. Do not let the compost dry out. Spray or gently water. Ensure that the compost is well-drained.
6. Treat your Begonias with a high-potash feed as soon as flowering starts. Tomato feed such as Tomorite is ideal.
7. Remove dead flowers and foliage to encourage more growth and prevent rot and disease.
8. Don’t forget to enjoy your Begonia plants! They are very versatile, and most varieties can cope with some level of shade.

Begonia tubers: Dividing

• Plant the Begonia tubers in March or April. For the best results, grow at a temperature of about 18°C (64°F).
• Fill a tray or large pot with 3–4 inches of moist, gritty (or sandy), free-draining potting compost.
• Place each tuber on the surface of the compost. Ensure that the depressed side is facing up. Space them at half-inch intervals at a depth of 1 inch.
• Once growth begins, divide each tuber with a sharp, sterilized knife. Ensure that each section has at least a single bud and a root below it. Dividing each tuber into quarters is ideal.
• Before potting on, allow each sliced Begonia tuber to heal for a couple of hours.
• Place each segment into individual pots of firm compost. A good-quality, multipurpose compost will suffice. Ensure that the tops of the tubers are level with the top of the compost.
• Keep the compost moist, but do not overwater.

As well as overwintering Begonias, I also overwinter Dahlias. Please visit my guide to storing Dahlias over the colder months.

Frequently Asked Questions on Overwintering Begonias