Planting different types of dahlia tubers will guarantee a summer rainbow of blossoms for years to come.
By Kim Haworth
Late summer brings up some of my favorite flowers. The first growing dahlia I ever met was in a hillside house I rented in Mill Valley. We had moved in during the winter months and were enchanted by the multiple surprises the garden revealed as winter turned to spring, then summer. One of the lovely things about moving into an older home is the opportunity to see the garden unfold, it’s rather like a surprise package.
The dahlias in Mill Valley were bright yellow and the tubers must have been in the ground for many years, because the flowers were the size of a dinner plate. They were the spidery shaped blooms, called ‘cactus form’ that looked like sunbursts. Magnificent! When we moved, I tried to take the tubers with me, but I’m afraid I did the plant a disservice. It never regained it’s former glory after the transplant.
Since that time, I have learned more about dahlias and still rejoice in their profuse display of blooms. ‘Candy Cane’, a red and white formal decorative dahlia, has long been one of my favorites. Dahlias grow from tubers that are usually planted in the early spring. They can also be started from seed, although you won’t achieve the same spectacular results in the first year. They are native to Mexico and Guatemala meaning they require some heat and regular water. I always try to mimic the native environment as much as possible. They need well drained soil that is rich in organic matter. Dahlias are greedy for rich soil and can never have enough compost. The flower colors in all colors except blue and there are miniature dahlias, tree dahlias and everything in between.
At planting time, select a spot in full sun, then incorporate some slow release, low nitrogen, fertilizer into the planting hole. Bury the tubers at least 3 inches beneath the surface. Sometimes it’s difficult to tell which end is up, but if you look carefully, you will see last year’s stem end with a few leaf scars. Dahlias like plenty of room to grow. Smaller varieties should be planted at 1-2 foot intervals, larger types 4-5 feet apart.
Once the plants emerge from the soil in early summer begin watering regularly so that the soil is damp to a depth of 1 foot. Continue watering throughout the active growth period.
Some thinning and pinching is necessary to produce bushy, branching plants. If you have tall growing dahlias, remove all but the strongest 4 – 6 stems when the plants are about 6 inches high. When the remaining stems have three sets of leaves, pinch the top so that the stems form branches. Branches mean flowers, and that’s the desired result of all this cultivation. Smaller types of dahlias need only tip pruning once during the season.
It is not necessary to lift and store dahlias during the winter here in Northern California providing that your soil is well drained. As a matter of fact, digging them from the soil each year may actually be harmful to the tubers if you nick them with the shovel or spading fork.
One of the best things about dahlias to my way of thinking is that they make wonderful cut flowers. The variety of colors and shapes are a flower arrangers dream. Cut almost mature blooms in the early morning or late afternoon hours, never mid day. The stems should be plunged immediately into hot, but not boiling, water and allowed to rest for several hours or overnight before arranging in a vase.