How to overwinter dahlias in the UK
Dahlias are one of our top late-summer flowers. They often flower from August until the first frost. However, don't let these perennials fool you; they are not frost-hardy. So, if you're struggling to know what to do with dahlias in winter, read our handy guide, which will give you all the options.
British winters can be unpredictable; some plants need lifting or mulching to survive. Dahlias fall into this category of plants that need "overwintering".
You have two options for helping dahlias survive the winter: leaving tubers in the ground or lifting and storing them.
Can you leave dahlias in the ground over winter?
Whether you can leave your dahlias in the ground over winter depends on your garden and soil type. The more significant concern about leaving them is not the cold but rotting from sitting in wet soil too long.
The best type of soil to leave tubers in is free-draining soil. This way, they're likely to avoid rot. If you live in an area with clay soil or wet conditions in winter, lift the tubers. Once you lift them, store them indoors during the winter months.
Another factor is the cold. You can likely leave them in the ground if you live in a milder part of the UK, like the south. Make sure the temperature does not drop below 10°C for a prolonged period.
However, we always recommend covering them with a good layer of mulch or strulch to keep them warm. Cover well with at least 10- 15 cm of good-quality mulch.
Can you leave dahlias in pots over winter?
Storing dahlias in pots is easier than storing them in the ground. You can easily control the drainage and temperature of the soil in the pots. To keep the pots frost-free, move them to a sheltered area or wrap them with wool or something similar.
If you notice the pots getting waterlogged, move them to a covered area, where they will stay dry.
How to lift and overwinter dahlias tubers
If you live in an area that gets waterlogged, has clay soil, or gets cold in the winter, we recommend lifting your dahlia tubers.
When to lift your dahlias
Some people wait until the first frost when the leaves have blackened and begun to die back. You can do it earlier than this, from November onwards; however, you might miss out on the final flowers of the season.
How to dig up dahlias
Carefully dig around your dahlia tuber using a garden fork. Give it enough space around the base to avoid slicing the tuber. Gently lift the tubers by tugging on the stem at the base while leveraging with your fork.
Tip: Your dahlia tuber has probably grown bigger since you planted it in spring. Dig about one foot away from the stem.
Preparing them for storage
Once you've dug up your tubers, cut the stem and compost the rest of the plant, leaving a stem around 5-10 cm long.
Knock off most of the soil, leaving a little attached. Next, place the tubers upside down to allow any sap to drain out of the stem. Leave in a cool and dry place for about a week until the tubers are dry.
How to store dahlia tubers
The best type of box for storing tubers is a cardboard box. You can easily get these from a local supermarket or grocery.
Cover them with shavings or straw and leave them somewhere dry but with good air circulation. Don't store the boxes on the ground; they may get damp and rot the tubers.
Avoid plastic bags or containers, as these will create a warm and damp environment, which will cause the tubers to rot.
Store throughout the winter until spring, when you'll start potting them up again. Check on them regularly to make sure they have stayed dry.
Our top dahlias
If you're new to dahlias and haven't grown them yet, we've chosen some of our favourites. These are great for new dahlia growers.
1. Dahlia 'Totally Tangerine' is a classic for a reason. This hard-working dahlia will continue to flower for months and months, putting on bigger and larger displays every year.
2. For a large dinner plate variety, try Dahlia Café au Lait. The large flower heads are around 25cm across and come in gorgeous cream and peach tones.
3. Dahlia 'Misses Miley' is a fantastic dark-coloured dahlia. The warm red and plum tones will flower in abundance for months.
4. Dahlia 'Penhill Watermelon' is a recent introduction but a show-stopper. It varies in colour from soft reds to light pinks with hints of soft yellow. Large blooms will cover the stems.
5. Dahlia 'Crème de Cassis' is a perfect addition to any border scheme. The good-sized flower heads will fill your garden with light pink and purple flowers.
