Dahlia Planting and Care Guide

Preparation: Dahlias are cold sensitive and should not be planted until soil temperatures are consistently above 60F. Before planting, they can be stored for up to three weeks in a cool, dark, ventilated place 45-50F. Alternatively, they can be started indoors up to 6 weeks before outdoor planting. Large tubers can be divided in spring by cutting the segments apart with a sharp knife, making sure each segment has at least one visible eye (bud). Tubers can then be planted.

Container Started Dahlias: Select a container large enough for the roots to fit comfortably. They can be ready for outdoor planting as soon as 6 weeks, but may require 7-8 weeks if planted in a larger container. Bury the tuber in potting soil with the eye facing upwards, 1-2” below the soil surface. Water sparingly as the tubers rot easily. Place under grow lights for 12-16 hours a day. A light fertilizer can be used after 4 weeks.

Garden Grown Dahlias: Select a location with at least 8 hours of direct sunlight, and well draining soil. Add fertilizer if your soil test recommends. Incorporate needed amendments 8-12” deep into the soil. In hot regions, afternoon shade may be needed to provide cooler temperatures. Dig a hole 6-8” deep, backfilling until you reach a 4-6” depth and place the tuber with the eye facing upwards. Backfill with soil and space plants 12-18” apart.

Care: Tubers rot easily before plants have sprouted. Water only if your soil is dry to the touch several inches down. Once sprouted, water regularly around the base according to your soil, climate, and 

time of year. If soil has been amended then no additional fertilizer may be necessary for 2-3 months. If not then fertilize once plants have sprouted at 3 week intervals until early fall. Pinching may increase the number of stems and flowers overall. Pinch off the top 2-3” of stem when plants reach a height of 10-12”. Dahlia stems can become heavy in late-summer, and break easily from the weight and windy conditions. Trellising or a stake is recommended to keep stems growing upright. Removing spent blooms encourages the production of more flowers. Flowers can be harvested when petals are almost completely open. Floral preservative is essential in lengthening the vase life of dahlia.

Diseases and Pests: Dahlias are prone to damage from snails, slugs, grasshoppers, and earwigs. Insect bait will minimize damage caused by these insects and mesh bags can be placed over developing flower buds and stems if you are planning to use stems for floral arrangements.

Dividing Tubers: Tubers can be divided in spring by cutting the segments apart with a sharp knife, making sure each has at least one visible eye (bud). Tubers can then be planted.

Storing Tubers: After frost has turned the top growth brown, cut the stem back a few inches above the soil. Then carefully dig carefully around the roots and rinse off excess dirt from and remove any tubers that may be rotting or damaged. Allow tubers to dry for several weeks allowing the roots to develop a slight wrinkled appearance before placing them in storage following the same storage procedures as above.