PLANTING DAHLIA TUBERS

Below are the materials I share with customers for planting tubers in the Spring.

While there are countless online tutorials on growing dahlias, below are the steps I follow here in Zone 6a. Whether you’re a beginner or a seasoned gardener, I hope you find these helpful.

Before Planting

Tubers are sensitive. Until you’re ready to plant them, keep them where they won’t be jostled and where the temperature will remain consistent at around 50-60° F.

Find the sunniest spot in your garden. Dahlias need 6 hours or more of sun daily.

Bring your soil to “Goldilocks” condition—not too moist, not too dry, just right. Dahlias need drainage, so experiment with potting mix, sand, and compost until you have a rich, porous soil that turns easily in your hands. (Avoid chicken compost if you can. It’s high in nitrogen, and too much of it may produce weak stems.)

Supplies. It’s wise to gather everything before the last frost, so you’re ready to plant. Below is a list of supplies I use.

  • Garden gloves.

  • Compost, sand, and potting mix.

  • A garden fork to turn the soil and mix everything.

  • A small bag of bone meal or wood ash and a small bag of Epsom salt.

  • Six-foot garden stakes, one for each tuber. (I like bamboo.)

If you fertilize, do so every 3 weeks. I like Dr. Earth’s Flower Girl, but you can use a mix of what’s called “10-10-10.” You’ll also need water—I use rain barrels, hoses, watering cans, etc. because I lack running water at the farm.

Looking ahead, you’ll eventually need twine and pruning snips. You’ll also need a bucket in which to gather your blooms. Vases can be found at your local charity shop if, like me, you enjoy being part of the reduce-reuse-recycle economy, or if you want to give bouquets to friends and neighbors.

Planting

Plant your tubers after the last frost. Many gardeners know their USDA “Zone.” From there, you can learn when your last frost usually is. A good rule of thumb for most of my clients in Zone 6a will be to plant after the last full moon in May.

Check the forecast for rain. Tubers may rot if planted in wet soil, or if rain drenches them before they can send up shoots.

Dig a shallow, wide hole about 5 inches deep. I place a spoonful of Epsom salt and a spoonful of bone meal at the bottom of the hole. I find that if I mix them into the dirt by hand, critters are less likely to be curious about the bone meal.

Lay your tuber horizontally in the soil, sprout facing up.

Gently cover your tuber with dirt. Avoid pressing down so as not to crush the eye.

Plant tubers roughly 12-18 inches apart. Many grow to 5 feet tall and several feet in diameter, so be sure to leave room to prune foliage and cut blooms.

Stake and tag your dahlias. You’re done! Good job!

After Planting

Watering. Make sure that once shoots appear above ground, you water your dahlia plants weekly.

Staking. You’ll want to tie your plants to the stakes with twine when they’re about 18” and 3’ tall. Otherwise, a downpour or windstorm may topple them.

Pruning. I remove the bottom 12” of foliage on each plant once they’re established. The air circulation and reduced contact with the ground support their overall health by keeping pests, mold, and general ickiness at bay.

A Word About Mistakes

They’re inevitable. I can’t tell you how many times I’ve thought “Oops!” because I forgot to spoon in bone meal or I didn’t have time to tie up my dahlias before a storm. The good news is, these tubers want to grow! They’ll figure it out, even if you missed a step.

Mistakes are part of what make growing a garden meaningful for many. We’re never done learning, and we all need do-overs. Focus on what you got right, and enjoy their beauty.

There’s always next season.