Growing Dahlias in Shropshire: What We've Learned Over Seven Seasons
We've been growing dahlias on the plot for seven seasons now. Some of what we know came from books, some from other growers, and a fair amount from getting it wrong and trying again. Here's what's actually worked for us in the UK Midlands climate.
Storing tubers over winter
Dahlias are not frost-hardy. In Shropshire, the first hard frost usually arrives sometime in October or November, and when it does, any tubers left in the ground will rot. We lift ours after the first frost blackens the foliage, cut the stems back to about 10 cm, and store the tubers in wooden crates filled with barely damp coir.
The crates go into the studio's cold room, which stays at around 5-8°C through winter. A garage or cool shed works just as well, as long as it doesn't freeze. We check the tubers every few weeks and remove any that are showing signs of rot before they spread to the rest.
Planting out in the Midlands
We start tubers off in pots in the studio in late April, then plant out after the last frost risk has passed. Usually mid-May in Shropshire, though we've had late frosts as late as the first week of June in a bad year. Planting too early is the most common mistake; a frosted dahlia tuber is a lost tuber.
We plant at about 10 cm depth, in a spot that gets at least six hours of sun. Dahlias are hungry plants and we work in a good amount of well-rotted compost at planting time. Staking goes in at planting too. It's much easier than trying to stake a plant that's already 60 cm tall and leaning.
Pinching and cutting
Pinching. Removing the growing tip when the plant is about 30 cm tall. Produces a bushier plant with more stems. We pinch every plant, every year. The first year we didn't, we got tall plants with a few large flowers. After pinching, we get shorter plants with many more stems, which is what you want for cutting.
For cutting flowers, take stems when the flower is about three-quarters open. Fully open dahlias don't travel or last as well. Cut in the morning when the stems are full of water, put them straight into a bucket, and get them into a cool place as quickly as you can.
Dahlias reward patience and a bit of attention. Seven seasons in, we're still learning which varieties suit our particular patch of Shropshire clay.