Although often sold as half-hardy annuals, most Begonias varieties are actually perennials. However, they are not at all frost hardy. The following article will give you advice on bedding begonias over-winter within the UK.
Tuberous rooted (and rhizomatous) varieties can be overwintered in a cool, dark and dry place. This is especially useful to the flower gardener, as mature rhizomes (or begonia corms) produce bigger and stronger Begonias plants. I like to leave mine in old hanging baskets in my garden shed. However, be prepared to lose a couple. Tuberous rooted begonias are prone to attack by Vine Weevil grub during the Summer. This will weaken, or even hollow out the tubers – the main cause of tuber death during the Winter.
Fibrous rooted Begonias such as ‘wax’ and ‘Angel’ or ‘Dragon winged’ varieties may be pruned into a manageable shape and taken into the house during Winter. They will also make for an attractive pot plant. Avoid draughty areas of the house to get the most out of your bedding begonias during the colder months of the year.
Although many Begonias have tuberous roots, the majority of varieties are very tender and incapable of surviving the UK winter. They will require a period of dormancy in a cool, 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 in during early Spring. Failure to do so will result in poor growth and few flowers. They will also need feeding when they start to produce leaves.
Protecting Begonia Tubers
Overwintering Begonias is easy:
- Dig up the entire plant with foliage still attached before the hard frosts set in. Ensure that the tuber is not damaged in the process. Damage will often lead to rot and the death of your Begonia. Shake out any Weevil grubs
- With a sharp knife, cut away any diseased parts of the tuber
- Leave it to dry in a frost-free and sunny place for 1 week
- Remove the foliage by gently teasing the stems from the tuber. Again, avoid damaging the tuber. Begonia rhizomes tend to be very delicate and easily scratched
- Gently clean away excess soil or compost with your finger tips
- I would recommend dusting your Begonia tuber with sulphur powder to guard against rot
- Store tubers in a clean cardboard box. Space them evenly apart and place the box in a dry, frost-free and dark cupboard until Spring
I’d recommend that you occasionally check your overwintering Begonias. This will ensure that they are still dry and rot-free. I prefer to remove any tubers that have gone bad to prevent the risk of infecting other tubers. If in doubt, keep them. Sometimes, Begonia tubers look totally dead, but re-sprout in Spring.
Note: If you live is a very mild part of the UK, you might want to try leavings your Begonia tubers in the ground overwinter. Cover them will straw or leaves until the risk of frost has passed. I have a number of tuberous Begonias in my garden in Dawlish, Devon. They seem to thrive, even when left in the ground during Winter. This can be risky. I am sure a harsh Winter will eventually come and finish them. But they have been in the ground now for the past 6 years!
Begonias: when to plant
At all times throughout the following processes, ensure that your plants are protected from very low temperatures and frost.
- Bring your begonias out from overwintering during the month of April
- Place tubers hollow-side-up individually in pots or in rows in trays of fresh general purpose compost
- Cover with 1 cm (1/4 in) of compost
- Place your plants in a shadier 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 mine on a lower tray under the bench in my greenhouse. They get plenty of morning sun, but very little during mid-day
- Do not let the compost dry out. Spray or gently water. Ensure that the compost is well drained
- As soon as flowering starts, feed your Begonias with a high potash feed. Tomato feed such as Tomorite it ideal
- Remove dead flowers and foliage to encourage more growth and prevent rot and disease
- 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 during March or April. For best results, grow at a temperature of about 18°C (64°F)
- Fill a tray or large pot with 3 – 4 inches of moist and gritty (or sandy), free draining potting compost
- Place each tuber on to 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, sterilised knife. Ensure that each section has at least a single bud on it and root below it. Dividing each tuber into quarters is ideal
- Allow each sliced begonia tuber to heal for a couple of hours
- Place each segment into individual pots of firm compost. A good quality, multi-purpose 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 over water
As well as overwintering begonias, I also overwinter Dahlias. Please visit my guide to storing Dahlias over the colder months.