How to Plant Dahlia Tubers
From our field to your garden, with love from Dynomite Farm
We’re thrilled you’ve chosen our dahlia tubers. Dahlias range from 1.5 to 6 feet tall, with blooms from petite “golf balls” to impressive “dinner plates,” and the American Dahlia Society recognizes 20 distinct flower forms. Here is how to plant dahlia tubers so they reward you with blooms all season.
Blooms from our field, with a few of our fair ribbons behind.
When your tubers arrive
Open the box and check your tubers, then keep them in their packing somewhere cool, dark and dry, like a closet or garage, until planting time.
How to plant dahlia tubers, step by step
Pick a sunny spot
Dahlias want well-drained soil and about 8 hours of direct sun a day. Some afternoon shade is fine.
Prepare the soil
Two weeks before planting, work compost into the bed along with bone meal and a balanced fertilizer such as 5-5-5 or composted manure.
Give them a head start
Optional: set tubers in a tray under lightly dampened vermiculite in a warm spot. A seedling heat mat is ideal, and the top of a refrigerator works too.
Plant after your last frost
Once the soil has warmed, lay each tuber on its side about 6 inches deep, with the eye facing up. Depth and spacing details.
Hold the water
Skip watering at planting, because wet soil can rot a tuber before it sprouts. Start watering once sprouts appear.
Feed lightly
Too much nitrogen gives weak stems and small blooms. A lower-nitrogen fertilizer keeps the plant strong all season.
Planting depth, spacing and stakes
Dig a hole about 8 inches deep. Mix a tablespoon of bone meal into the bottom and cover it with 2 inches of soil, so the tuber sits about 6 inches deep. If your variety needs a stake, set it now so you don’t spear the tuber later. Lay the tuber on its side with the eye or sprout facing up, and fill the hole.
Space tubers 20 to 24 inches apart. In our raised beds we plant closer, 12 to 14 inches apart. If you gave them a head start, some varieties sprout within a week while others take longer.
Watering and feeding
Watering
Once sprouts appear, water deeply once or twice a week, especially in warm, dry spells. Water at the base of the plant to keep the leaves dry and reduce the risk of disease.
Feeding
Use a lower-nitrogen fertilizer such as 5-10-10 about 30 days after planting and again six weeks later. If you use a slow-release fertilizer, apply it after planting instead. Stop feeding by mid-September so the plant can prepare for dormancy.
Dahlia tuber questions we get asked
When should I plant dahlia tubers?
After your last frost, once the soil has warmed. Cold, wet soil can rot a tuber before it ever sprouts, so a little patience in spring pays off all summer.
Do I water dahlia tubers right after planting?
No. The tuber carries enough moisture to get started. Wait until sprouts appear above the ground, then water deeply once or twice a week.
What happens to the tubers in winter?
Here in Santa Cruz we dig our tubers each fall, rinse them, and store them in peat moss until spring planting. In colder areas, dig them before the ground freezes and store them somewhere cool and frost-free.
When your dahlias bloom, our guide on how to care for cut dahlias keeps your harvest fresh for a week or more.
Questions about how to plant dahlia tubers?
Email us at support@dynomitefarm.com or text 831.281.8363. We’re happy to help you grow.