Get back to basics with dahlias
The start of the growing season is a good time for a refresh on the dahlia-growing essentials
Dahlias have grown massively in popularity over the last few years. So there are a lot of you who’ve never grown them before or maybe you’ve been busy buying or collecting stock of tubers and plants. Whoever you are, read on for my top tips on dahlia-growing basics.
Planting
Whether planting green plants or growing tubers, I’d advise not to plant them until the end of May, even early June. This will vary depending on when you expect your last frost of the spring. If you’re planting dormant tubers this can be done earlier, as they’ll take a while to wake up and for the green shoots to be vulnerable. For a longer flowering period start them in a pot somewhere warm, such as a greenhouse or windowsill.
Plant your dahlias in an open, sunny position, with plenty of space for them to flourish.
They really don’t mind what sort of soil you have. If your ground is clay-based then the addition of organic matter and/or grit will help the drainage and give you better chances of overwintering your tubers in the ground.
When planting, dig an oversized hole and plant so that the plant is in a recess which can be filled as the season progresses. Initially this will direct your water to the roots then, as it backfills with regular hoeing or mulch, the ground will be more protected in the winter.
Growing
Although dahlias originate from the dry parts of Mexico, they do grow best if given regular water. Be careful not to over water in the early stages as the plants need to establish a root system first, but once they show signs of growing away, keep them moist.
Support the plant with either a single stake or a triangle of canes so that you can tie around with string as they grow. If you don’t want to see the supports then choose a size that’s not more than two thirds the advised height of the flowering plant and they’ll disappear.
If the ground has been well prepared with a good slow-release fertiliser, the plants shouldn’t need any additional feeds until the flower buds arrive. Once the buds start to form, a regular feed with a liquid tomato food will stiffen those stems and give you fuller, well-coloured flowers.
I’d always recommend removing the growing tip of the plant once only and when the initial shoot has four to five pairs of leaves. This will encourage the plant to develop from a low base and be much more stable. As the main bud forms in the growing tip, I really do advocate removing the wing buds on either side. This will mean that your flower opens unhindered and will keep the stem of the flower strong and straight. This also promotes the lower shoots to develop and means your next flowers won’t be far behind.
Remember to always remove any old flowers and if the plant becomes congested, then thin out any weak shoots and cut back any old ones. The energy will then go into the remaining stems and revitalise the plant.
Winter protection
I’d always mulch the planting area with either straw, garden compost or composted bark. A newer alternative is Strulch, which is a mineralised straw mulch that deters slugs. In autumn if you intend to leave your tubers in the ground you can gather this over the cut stems to protect the tubers from the worst of the cold. This would then be pulled back in the spring when the new shoots appear. Alternatively, they can be lifted and stored in a frost-free environment.