Dahlias 101: A Beginner's Growing Guide
I don’t think I’m in the minority when I say that dahlias have to be among the most beautiful flowers that you can grow. I mean, just look at this gorgeous bouquet of dahlias:
I try not to play favorites in the garden, but it’s just so hard not to absolutely adore these gorgeous flowers that bloom in almost every color you can imagine. And, under the right conditions, they are not difficult at all to grow and care for (I promise!!). By following just a few basic tips, anyone can successfully add dahlias to a cutting garden.
To grow a healthy dahlia, it’s important to start with a tuber that has an “eye” (or growth bud) on the crown of the stem. A tuber without an eye won’t grow a plant, and tubers should be firm, with no signs of mold or rot. Dahlias are usually purchased as either single tubers with an eye, or as a clump of tubers around a stem. But, honestly, the size of the tuber (or clump) doesn’t really matter; a healthy plant will grow from any size tuber as long as it has at least one eye. I plant single tubers and clumps of tubers, and I’ve had equal success with each. Here’s what a single tuber looks like; notice the growth coming from the eyes:
And because it can’t be said enough, if the tuber doesn’t have an eye, it won’t grow. Sometimes it can be tough spotting the eye…if you’re having trouble finding it, simply put the tuber in a shallow container covered in slightly damp soil for a few days to encourage a sprout to appear.
It’s important to order tubers from a reputable dahlia grower so that you receive a healthy, disease-free product. Because I grow in large quantities (2,500+), I mainly order from a wholesaler, but for smaller quantities, Floret, Sunny Meadows, The Flower Hat, Swan Island, and Summer Dreams Farm all sell excellent quality tubers. If you’re looking for a specific or hard-to-find variety, Dahlia Addict has created a user-friendly, searchable database.
Because of the size of my order, my tubers come in crates (I use the empty crates later in the season to plant tulips for the following spring), and I always order my tubers from Gloeckner:
Smaller quantities of tubers are usually delivered in plastic or paper bags, and packed with a bit of shredded paper, peat moss, or cedar chips. When you receive your tubers (they usually ship out in March or April), take them out of the plastic and store in a cool, dry place (in the packing material) until you are ready to plant.
Popular varieties/colors sell out fast, so be sure to order early, in late fall or early winter. Tubers can be planted as soon as all danger of frost has passed and the soil has warmed up. In my zone, 7b, I usually start planting dahlias in late April/early May, but I’ve also done plantings as late as mid-June.
Find a sunny, well-draining spot in your garden, and place your tubers 5-6 inches in the ground, with the eye facing up, and space them apart about 12-18 inches or so. The tubers don’t like to get wet (or they will rot), so once planted, water very lightly until the soil is slightly damp, and then don’t worry about watering again until you see the plants emerging from the ground.
I’ve had issues with tubers rotting in the past, so my very sweet husband built raised garden beds for me. These beds have been AMAZING, and I highly recommend planting dahlias in raised beds if you can. They are fairly easy to build; just be sure to use cedar, which is rot and bug resistant. As a flower farmer, I have quite a few raised dahlia beds, but a home gardener can grow a beautiful showing of dahlias with just one or two boxes.
Now, technically, it’s best to water from the bottom of the plant, using drip irrigation. This gets the water closer to the roots, where the plant needs it the most. However, because of the way I set up my gardens, I overhead water from a sprinkler in the mornings or evenings. And although this isn’t ideal, the plants seem to do just fine! I’m just careful to water either very early in the morning or later in the evening when the sun won’t be able to evaporate the water too quickly. Also, when the dahlias are in active growth but still aren’t in bloom quite yet (June-August), I like to go through the beds once every other week or so and spray compost tea or fish emulsion on the plants.
The plants grow quickly in the summer, and once the dahlias are around 18” tall, I pinch them back by snipping the center stalk down several inches, just above a set of leaves. This is very beneficial to the plant, and encourages more branching, which then leads to more blooms later in the season. If you remember only one thing from this guide, remember to pinch your dahlia plants! Its makes SUCH a big difference later on.
Dahlias also need to to be staked to keep them from flopping over in storms and high winds. It’s fine to stake them individually, but if you’re growing a large number of dahlias, set out a t-post or bamboo pole every 8 feet or so and wind twine around everything so that the plants grow up and through the twine. Here’s a great visual guide to pinching and staking.
Once September hits, the dahlias are usually blooming so fast that it’s hard to keep up! When the blooms are fully open, cut them early in the morning or later in the evening, put in clean, warm water, and enjoy! I don’t use pesticides on the plants, but I do treat organically when necessary. Here’s a useful download of common dahlia pest problems and treatments.
Once the dahlias are harvested, we wrap ‘em up for our CSA customers or use them in our wedding arrangements.
Dahlias will bloom until the first frost, and once that first cold snap hits, they’ll turn black and that’s it! I cut them back at the end of November, lift them out of the ground, and store the tubers in crates in my basement (dirt and all). I check on them every few weeks and remove any rotted or moldy tubers. Once spring rolls around, I wash them off, divide, and plant as soon as I can. But this year, for the first time, I’m going to leave them in the ground and try to overwinter them in the raised beds. Fingers crossed that they survive!
For updates on this year’s crop of dahlias and all of our other flowers, including lots of gorgeous photos of our favorite varieties and additional growing tips, follow along on Instagram and join our newsletter. And click here to read our peony growing tips!