Community ClicksOh, the beautiful dahlia! With plants that range from container-sized to 8-feet tall and flowers of every imaginable color, dahlias are a welcomed addition to any landscape.
On the North Olympic Peninsula, plant dahlias in the springtime when all danger of frost is past. Do not plant dahlias in the fall when you plant spring-flowering bulbs. Plant dahlias in full sun in well-draining soil for best results.
Dig a hole, 1 foot deep by 1 foot wide, and mix in organic matter and a handful of 5-10-10 fertilizer. Set tubers five to 8 inches deep, placing larger tubers deeper.
If the plant is expected to be more than four feet tall, place support stakes as you plant; if placed later,
you might damage the tuber. Position the tuber horizontally with the growth bud pointing upward and about two inches from the stake. Cover the tuber with three inches of soil, adding more soil as the plant grows. Plant tall dahlias three feet apart and smaller ones 18 to 24 inches apart.
Dahlias require regular water and will stop flowering if they dry out. Use ground level irrigation to avoid powdery mildew.
Water your dahlias into the fall for continued blooms. If you have good soil you may not need to fertilize your dahlias again but some sources recommend that you fertilize them lightly every month or apply a fertilizer high in phosphorus (second number in the fertilizer analysis) when plants are ready to bloom.
To encourage bushier plants with more blossoms, nip out the growing tip of tall dahlias when they have three pairs of true leaves. To increase the bloom size on large-flowered dahlias, remove the lateral (side) buds, leaving only the terminal (center) bud. Dahlias bloom from mid-summer through the first frost.
Cutting dahlias for bouquets and deadheading promote more blooms. To prolong the life of cut dahlias, place the stems in two to three inches of very hot water (160 degrees) and allow the water to cool for several hours before arranging them. When the foliage dies back after the first frost cut your dahlia down to the ground. If winter temperatures do not go below 20 degrees where you live, you can leave the tubers in the ground, covering them with four to six inches of mulch such as straw. In the spring, remove the mulch when danger of frost is past.
Most dahlia tubers, if planted at the recommended depth, will weather local winter conditions (USDA climate zones 7 and 8); however, the occasional severe winter can kill them. If you live at higher elevations or if your dahlias are planted in pots or raised beds, consider digging and storing them for the winter. To lift dahlia tubers from the ground, gently dig around the plant with a garden fork. The tubers multiply and grow in size, so dig about a foot away from the stalk.
Leave the stalk intact with the clump and remove as much dirt as possible. Let the tubers dry in the sun for several days.
Store them in dry sand or barely damp sawdust in a dark, dry place at 40 to 45 degrees. Replant the tubers in the spring as directed above (dividing the clump first, if necessary) and enjoy gorgeous blooms again next summer!
Betty Ashland and Janet Oja are certified WSU Clallam County Master Gardeners.
For more gardening information, attend the Class Act educational series at the Master Gardener Demonstration Garden, 2711 Woodcock Road. These free educational events are held at 10 a.m. on the first and third Saturdays of each month. On Saturday, Sept. 3, veteran Master Gardeners Janet Oja and Florence Larsen will provide more tips about growing dahlias on the North Olympic Peninsula.
