How to grow dahlias in your garden
You can get a jumpstart on your gardening season by presprouting your tubers and planting out dahlia plants instead of dormant tubers. Remember though, dahlias are very sensitive to frost, so you’ll want to wait until all danger of frost has passed to plant them outside. As a general rule, you can put your dahlia plants in the garden when it’s safe to plant tomatoes.
How to Plant
Dahlias come in all sizes, but the ones we grow for cut flowers tend to be tall. They need support. A stake or tomato cage will do the job, and it’s best to install your support at the same time you plant. Be careful not to damage the tuber or root system when you add the stake or tomato cage.
Choose a well-drained spot in full sun (direct sunlight for at least 6 hours each day). Dig a hole as big around as the pot and up to 4” deeper.
Gently remove the dahlia plant from the pot. Try not to disturb the roots.
Place the root ball in the hole and backfill with the soil you removed.
Tamp down the soil around the tuber and stem. You want good soil contact with the roots.
Add your stake or tomato cage.
If using a stake, you’ll use garden twine to tie your plant to the stake as it grows. If using a tomato cage, consider adding a stake to help secure the tomato cage. Plants get heavy in the summer, and they can topple unsecured tomato cages.
Water well after planting, and water twice a week all summer as if it doesn’t rain at least 1”.
Pinching for More Flowers
When your dahlia has three sets of leaves, pinch off the growing tip of the stem. This will encourage the plant to branch out, producing a bushier plant with more flowers and stems that are easier to cut.
Cutting Flowers
Many dahlias produce three flower buds per stem. When the center bud is about 75% open, it’s time to cut the flower! Make a deep cut, 12-18” below the flower and above a Y branch. This will encourage the plant to grow more long, strong stems for the next flowers.