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Dahlia Care
Each dahlia variety is unique, but generally require similar conditions to produce lovely, full plants with abundant blooms.
Starting Inside
Potting Up
After bringing your tuber home, plan to pot it up into a larger container. Choose a container with plenty of drainage holes, deep enough to be able to plant the entire tuber just below the top of the surface.
Location
Give your dahlias in plenty of light. A south-facing window or under grow lights is great!
Water
Water your tuber lightly after potting, then only again once the soil has dried out. Dahlia tubers are prone to rotting if overwatered, so be sure to provide good drainage and avoid excess moisture.
Pinching
Pinch/cut 3-4" off the main stem when they reach 12" tall with at least 3 sets of leaves. This will push back blooms by about 2 weeks, but give you a much bushier plant with plentiful blooms.
Planting Outside
Transplanting
Plant your dahlias outside after the last spring frost (early June for us in Thunder Bay). Loosen the soil and add compost or fertilizer, then plant the tuber about 2" below the soil surface with the sprouts upright. Press the soil firmly around the tuber and water. Dahlias do best planted directly in the ground or raised beds, but do not thrive in a pot!
Sun Requirements
The more sun, the more dahlias bloom. They can manage in part shade but may get a bit more leggy and need extra support.
Water Requirements
Water when the top 2" of soil is dry to the touch (just use your finger to check). Once planted outside, dahlia tubers are less likely to rot as the plant is using more water to grow, however overwatering is not recommended.​
Plant Spacing
12 - 18" is recommended between dahlias, although we have successfully planted them a bit tighter and still had large, full plants.
Maintenance
Deadhead (remove wilted blooms) regularly to encourage blooming all season long.
Support
There is a wide range of plant heights, but almost all dahlias benefit from some type of support. Some of our favourite dahlias can get up to 6 feet tall! We support all of our dahlias to protect them from bending during heavy rains or when flowers become abundant. Some easy support options are staking or corralling, but tomato cages work great too! Hot tip... It's easiest to install your support when the plants are still small.
Harvesting
Cut dahlias when they are 3/4 of the way open, but not completely open to the center. Dahlias don't unfurl much once cut, so catching them at the right time is important. Cut the flowers just above a leaf, as deep (low) into the plant as you dare (18" is great) so you have nice, long stems for arranging. Cutting deep also encourages the plant to grow blooms with longer stems for the rest of the season!
Vase Life
Each variety is different, but expect blooms to last 3-7 days. We've done some experimenting with adding a dash of vinegar and pinch of sugar with some success.