How to plant dahlia tubers

Plant your dahlias 12" - 24” apart in full sun if possible, after the last frost date for your region. Closer spacing helps suppress weeds and allows plants to support each other better, but farther spacing gives each plant more airflow and more access to nutrients in the ground. Keep your tubers in a dark, humid storage environment until you're ready to put them in the ground.

Place the tuber 2-6” below ground in soft, worked soil, either on its side with at least one of the growth points (called "eyes") facing the sky, or vertically, with the crown facing up. Deeper planting allows the soil to help support the base of the plant as it grows, but it means you'll have to work a little harder to dig them up in the fall.

Some varieties of dahlias grow very spindly necks or small crowns. Be careful not to damage the neck or crown while planting - a broken neck severs the connection between the body and the crown. The body provides nutrients and water, and the crown is the only place eyes occur on a dahlia tuber.

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But what do you do if your tuber already has sprouts by planting time?

Dahlia sprouts start out hard and white, but once exposed to light, they soften, leaf out, and turn green. Once those hard white "dirt drills" are gone, a sprout will have a very hard time breaking the surface!

Both "dirt drill" and leafy sprouts that grow on tubers in storage before planting time are often leggy or twisted and will need more support as the plant grows. So we recommend snipping the sprout off just above the crown. It won't hurt the tuber any, and the tuber will grow two, three or even four sprouts back! Just be careful not to remove the actual growth point.

If you'd like to keep the sprout, plant the tuber no deeper than 6", leaving just the top set of leaves above ground. The extra soil depth will help support a leggy sprout.

Make sure the soil over the tubers is nice and soft for the sprout to push through. Dahlias like PH similar to tomatoes, but with more drainage. Consider adding natural material or even sand if you have very high clay content in your soil. Bonemeal is a great all around natural fertilizer for dahlias that promotes healthier tubers and plant growth. If you like, you can mix a teaspoon of bonemeal into the soil at each planting site.

Grass or leaf mulch in dahlia beds is fine for weed control, but avoid heavy wood mulch until the plant is established above ground, and don't use fresh mulch, because it can burn plants as it decomposes.

Keep the soil only very lightly damp. Dahlias do not like wet feet! Overwatering is one of the most common ways beginner growers lose dahlias, since tubers sitting in damp soil are more prone to rot and bug infestations, even if they were planted with a healthy eye or sprout.

For more information on the rest of the dahlia life cycle, check out our dahlia faq!