Dahlias are one of the easiest cut-flower crops you can grow. Follow the steps below to grow a bounty of your very own.
Select a location that receives full sun, has good drainage and shelter from wind.
On our farm, in Zone 5, we plant our tubers around the 15th of May, after all danger of frost has passed, and the soil has warmed to 15 degrees celsius.
Plant your tubers horizontally, 4-6 inches deep, with the eyes facing upward. Tubers should be spaced 1.5-2 feet apart within the row and 3 feet apart between rows. You may add a bit of bonemeal to each planting hole or prepare your entire bed with appropriate levels.
Do not water your tubers until greenery has emerged from the soil. This helps to prevent tubers from rotting. The tuber holds all the moisture it needs to produce the growing tip. Once greenery has appeared, water for 30 minutes 2-3 times a week.
Pinch the center of your plants by 3 to 4 inches when they reach 1 foot tall. This helps to ensure more usable side blooms that have longer and thinner stems, rather than a broomstick of a middle flower.
If you are not growing dwarf varieties, it is important to stake your plants before they get out of hand. Dahlias can easily as they can reach up to 5 feet tall.
Fertilize your dahlias with a low nitrogen fertilizer. On the farm we foliar feed with compost tea.
It is important not to fertilize too late into the season as it is not good for tuber storage.
If thrips, grasshoppers or other pests are found to be eating your dahlias, we highly recommend covering individual blooms with organza bags. This prevents any critters from munching on your flowers.
If cutting flowers for an arrangement, it is best to harvest in the cool of the early morning or evening. We harvest every two days to ensure that we are cutting dahlias in their prime. Ensure that blooms are fresh by looking at their backsides. Old blooms will have faded and browning petals. Remove any spent blooms from the plant often to encourage the formation of new buds.
In October you will likely experience a killing frost. We like to wait 2 weeks after the plants have been killed to allow the clumps to form eyes. This makes splitting an easy task that you can complete in the fall rather than waiting for spring eye formation.
Dividing tubers is a simple task once you learn that there will be some losses. Clumps come in all different sizes, some with evenly spaced tubers, some dense balls that you have to halve in order to see what you are doing. I recommend cutting down the middle and then identifying tubers that have an eye and a healthy neck. Trim scraggly tails and remove any broken tubers.
At the farm we store tubers at 5 degrees celcius, in a room with at least 80% humidity. All tubers are divided in the fall and then allowed to cure for one day before being packed into plastic tubs filled with wood shavings, and then sealed with a lid. We DO NOT recommend using cling wrap to individually wrap tubers. It is important t inspect your tubers at least once a month to ensure that there is no rot. If you find any rotting or mouldy tubers, remove at once and discard so that they will not damage your other tubers.