How to Grow Dahlias
Artist Frances Palmer, famous for her vases and pottery, is also a passionate dahlia gardener. May is a great time to plant dahlia tubers and Palmer gives step-by-step instructions, along with photos of her beautiful dahlia garden in bloom and her beautiful vases.
Frances Palmer is a well-known potter, a passionate gardener, and a lover of dahlias. She's also a member of GARDEN DESIGN's design board and when she offered to write about how to grow dahlias, we were so excited to be able to feature her garden and advice. I had a chance to see Palmer speak at a Wave Hill talk, "My Life in a Conneticut Garden," earlier this year, and I was absolutely charmed by Palmer's knowledge and enthusiasm for dahlias.
In this slide show, Palmer shows how to plant dahlias (May is a good time to plant these tubers), her own magnificent dahlia garden in bloom, as well as a few of her own vases with dahlias cut from her gardens. She also suggests her favorite mail-order sources for dahlias. Palmer is happy to answer any questions about growing dahlias, so please feel free to leave your questions in the comments.—Claire Lui
What a dahlia tuber looks like
The tuber on the left is a new plant from a supplier and it should have a small bud already starting.
The bunch of tubers on the right is an older dahlia that was stored over the winter. This should have a quite a number of small buds sprouting and can be divided before planting to provide several different plants. I usually break a large group apart with my hands, but quartering with a long knife works equally well. Before placing them in the ground, I tag each tuber or bunch with a Tyvec label that shows the name of the that particular flower.
Setting up cages and stakes for the dahlias
Select a spot in your garden with well-balanced and composted soil that receives full sun throughout the day. In my garden, I use tomato cages and wooden stakes to hold the dahlias as they grow. I purchase these at Home Depot, but most garden stores will have them as well.
Place the cage in the ground first and then drive in two or three stakes per plant/cage.
Planting the tubers:
For new tubers, I dig a fairly shallow hole, about three inches deep, and place the tuber with the new bud facing up into the hole. Gently cover the tuber with dirt and do not water.
For a larger group, a deeper hole is needed to keep the tubers about three inches below the surface. A handful of bone meal may be thrown over the top of the soil, however, at this point, it is not necessary.
Once the tuber is placed in the ground, I tie the label onto the tomato cage for identification. Do not water as there is plenty of moisture in the soil at this time of year. Over watering will cause the tubers to rot in the ground.
Taking care of young dahlias
The first leaves of the plant should poke through in a week or two. When the first set of leaves is about eight inches to a foot high, I pinch out the center bud to encourage the plant to form multiple stems. This will produce a greater quantity of flowers per plant. I find that dahlias planted mid-May in Connecticut will begin to bloom by the third week of July.
For fertilizer, I use only bone meal or two parts bone meal to one part sulfate of potash. These two ingredients encourage the flowers to bloom, instead of promoting the leaves. I throw this down around the plants two or three times between June and October. Some years though, when I have been too busy, I have not fertilized at all. If your soil is healthy, they do not need too much fussing. If the plants attract beetles, I buy Safer insect spray and this eliminates them quickly.
Supporting the dahlias:
Here is what the plants look like in early July. As the dahlia grows, I encourage the stems, as carefully as possible, to keep inside the cage. This will give the most support as the season progresses and the plants get really tall. If a plant begins to spread anyway, I tie garden twine around the outside for additional support.
Planting around the dahlias
I fill the rest of the garden around the dahlias with vegetables, annuals, and flowers that will self-sow from year to year, such as calendula, echinacea, sunflowers, nigella, Verbena bonariensis, and poppies.
Dahlias in full bloom
By September, the dahlias will be in their full glory. If the flowers are cut for vases after they open, the plants will continue to bloom until the first frost.
A view of the cutting garden
My cutting garden is adjacent to my studio and this allows me to keep seeing the flowers as I work.
When new pots are finished, I go out and cut dahlias for photography. Every year I try different varieties, but I keep a classic group that gets planted each season. I never cease to be amazed by the perfection, symmetry, and colors of dahlias. They are enormously fun to grow and once you get the hang of it, really quite easy to do.
Most of my pots are thrown on the wheel and I primarily use white earthenware, terra cotta and high fire porcelain. These different clays have their own personalities and technical demands, yet are wonderful to work with. I want the ceramics to be functional, yet have a sense of humor and a rapport with the garden.
Here, one dahlia bloom is placecd in a black Etruscan vase.
See dahlias being used in late summer flower arrangements.