Dahlia Growing Guide

Planting

When soil has warmed to at least 60℉, select a sunny location that receives full sunlight. If the forecast predicts wet weather, hold off on planting until after the rain. If your dahlia tuber sprout is over 3 inches long, cut it back to 1”.

Staking

Dahlias require adequate staking throughout the growing season. It is best to put your stake in at planting time so you don’t disturb the roots or tuber later on. Any staking product will work (bamboo stakes, tomato cages, etc.).

Watering

Watering is the #1 problem when dahlias are not growing and blooming properly. They need lots of deep (8-10") watering to reach the roots once they sprout above ground level. Once the dahlias are above the ground and established they will require deep watering 3-4x per week. Watering deeply 3x a week is better than watering lightly 7x a week.

Fertilizing

Dahlias will need 1-2” of well-aged compost mixed in the soil at the time of planting. Avoid using commercial fertilizers, as dahlias have a strong preference for native soil. We also add a handful of a high phosphorus bone meal in the hole before planting, which promotes flower and tuber development throughout the season. Once the plants are established, we use Neptune’s Harvest Fish Fertilizer 2-4-1 and apply biweekly foliar applications according to the directions on the label.

Pinching

Pinching is highly encouraged to promote shorter, bushier plants with better stem length for cutting. Pinch or cut the center shoot just above the third set of leaves or when the plant height is about 18-20" tall. This is just a one-time pinch. Lots of tutorials online if you need more info!

Cut Flowers

You can expect flowers to bloom ~90 days after planting, usually late August or September in Zone 5. Removing dead blooms and cutting your dahlias will help promote more blooms and stronger plants. Cut when flowers are ⅔ to almost fully open and place directly in water. Change water every 1-2 days for the longest vase life.

Digging

After a killing frost in the fall, cut dahlia foliage back to about 6-12” above ground level. After 2 weeks, carefully dig your dahlia tubers out of the ground. This 2 week wait period will allow the skins on your tubers to cure, leading to better winter storage. Use a pitch fork to dig carefully around the dahlia, starting about 12” away from the base. You will need to dig 2-3 times around each plant to lift the tuber clump out intact.

Dividing & Storing

There are many great resources online for dividing tubers that are much more effective and thorough than we can explain in writing, so we recommend starting there. You will need a sharp pair of scissors and some sort of storage material (peat moss, wood shavings, etc.).

Wash the soil off of your dahlias if you plan on dividing them right away so you can identify the eyes more easily.   Ideal winter storage conditions for dahlia tubers is a cool, dark, humid place (45-50 degrees and 80-90% humidity). Do not let your tubers freeze. How you store your dahlias will depend on your storage conditions, but here we use a root cellar in our basement, and pack peat moss around tubers in plastic boxes to maintain moisture. Your conditions may be drier (tubers will shrivel), or wetter (tubers will mold), so finding the right balance for your environment is key. Check on your tubers frequently throughout the winter so you can adjust the storage conditions as needed. Some loss is inevitable. We lose about 10-15% of our tubers each year due to shrivel or mold.