Dahlias require full sun (at least 6 hours daily) to thrive and bloom abundantly. Southern growers might need to provide plants with afternoon shade if summer temperatures are extreme. Dahlias are cold sensitive and should not be planted until the soil has warmed to above 60°F (15°C) and all danger of frost has passed. Check with your local county extension office to find out the date of your last spring frost.

Dahlias prefer soil that is well-drained and very rich. Select a sunny garden spot with freely draining soil and prepare it thoroughly before planting. It is recommended to amend beds with 2 to 3 in (5 to 10 cm) of high-quality compost or well-rotted manure, Mix all ingredients into the soil to distribute evenly.

To plant, dig a hole 4 to 6 in (10 to 15 cm) deep and place the tuber on its side, horizontally, with the growing eye facing up. Refill the hole with soil. Dahlias get quite large, so allow at least 12 in (30 cm) of space between plants.

o Water dahlias when they're first planted, then wait to water the tubers again until they sprout above the ground. Once they sprout, water regularly and deeply, being careful to let the soil dry out between waterings. Continuously wet soil causes tubers to rot, also avoid spraying the leaves with water, water the soil and not the plant, to help prevent diseases.

o For healthier plants and more blooms, fertilize dahlias once a month with an organic fertilizer that is high in potassium to promote flowering. Fertilizer with a nitrogen, phosphorus, and potassium (NPK) ratio of 5-10-10 or 10-20-20 is recommended.

In growing zones 7 and below Dahlias will not survive in the ground overwinter and need to be dug and stored inside. Wait for the first frost. Dahlia plants are very sensitive to frost. Wait until the foliage has turned yellow before digging up the tubers. This is important so that the plant can gather energy for the following year. Cut off the foliage and carefully dig out the tubers. Brush off excess dirt and let the tubers dry for a few hours.
Divide the tubers if necessary.
Store the tubers in a cool, dry place. Place the tubers in a box or paper bag filled with peat moss, vermiculite, or sawdust. Store the box in a cool, dry place, such as a basement or garage. The optimum storage temperature is between 40-45°F (4-7°C) with medium to high humidity. The goal is dormancy in a cool, dark place. Too warm or dry and they may wither or rot. If they freeze, they do not survive.

DAHLIAS 101