Planting Dahlias

Planting

If you’ve bought dahlia tubers and it’s not yet time to plant, keep them in a ziploc-style bag with the wood shavings they arrived in. Leave the bag open to allow airflow and control humidity. Store the tubers in a cool, dark spot indoors. If they appear wrinkled, don’t worry—they’ll still grow. A light misting can help if they seem too dry.

Dahlias grow best in a sunny, well-drained location. They prefer warm weather and can’t tolerate frost. Plant them outside after your area’s last frost date once the soil has warmed. You can also start them indoors to get a head start. Most dahlias bloom until the first frost.

When planting, dig a hole 6-12” deep and improve the soil with compost. If the soil drains poorly, mix in some fine gravel. Plant tubers 2-4” deep and space them 1-3’ apart, depending on the variety’s size. Water lightly after planting to avoid rotting. Growth typically begins within 14 to 20 days.

Growing

Tall dahlia varieties, like dinnerplate dahlias, may require support or staking to prevent the heavy blooms from toppling over. To encourage a bushier plant with more flowers, pinch off the top growth above the third set of leaves while the plants are still young.

Fertilize dahlias monthly with a water-soluble, organic fertilizer specifically for flowers. Avoid high-nitrogen fertilizers, which promote excessive green growth but fewer blooms. Mulching with straw or shredded bark helps reduce weeds and retain moisture. Regular watering is needed once dahlias begin growing.

Feel free to cut blossoms for indoor arrangements and remove old blooms to promote more branching and flowering.

Overwintering

To overwinter your dahlias, cut back the plants after the first frost and carefully dig up the tubers. Shake off the excess soil, but leave some on the tubers for protection. Let them dry for a few days in a cool, dry place before storing.

Store dahlia tubers in a cool, dark area like a basement or garage, ideally between 40-50°F (4-10°C). Pack them in peat moss, wood shavings, or vermiculite to prevent drying out. Check periodically through the winter to ensure they aren't rotting or drying too much.

In the spring, after the last frost, replant the tubers outdoors, following the same planting instructions as before. Dahlia tubers can be divided every few years to increase your stock or share with friends, ensuring healthier, more vigorous plants.