Dahlia
Overview
| Plant Type | Perennial Bulb |
| Hardiness Zone | n/a - the bulbs are removed at the end of the season. |
Dahlias bloom July thru October or November.
Dahlias have either an open center or a closed center. The open center allows more exposure to the pollen.
Petunias are good companion plants for dahlias.
Dahlia Classification Guide
| Bloom Size | Form | Color |
| AA Giant (over 10") | AN Anemone | BI Bicolor |
| A Large (8-10") | BA Ball (over 3.5") | BR Bronze |
| B Medium (6-8") | C Cactus | DB Dark Blend |
| BB Small (4-6") | CO Collarette | DP Dark Pink |
| M Miniature (up to 4") | FD Formal Decorative | DR Dark Red |
| MC Micro (up to 2") | IC Incurved Cactus | FL Flame Blend |
| ID Informal Decorative | L Lavendar | |
| LC Laciniated | LB Light Blend | |
| MB Miniature Ball | OR Orange | |
| MS Mignon Single | PK Pink | |
| NO Novelty Open Center | PR Purple | |
| NX Novelty Double Center | R Red | |
| O Orchid | V Variegated | |
| OT Orchette | W White | |
| P Pompon (up to 2") | Y Yellow | |
| PE Peony | ||
| S Single | ||
| SC Semi-cactus | ||
| ST Stellar | ||
| WL Water Lilly |
Ongoing Management
Planting
Start tubers indoors during first two weeks of April. Harden off and plant outside after danger of frost is gone.
Tubers may be planted outside in early May, planting them ~5" deep, but they will take longer to produce blooms.
Most dahlias need support. When planting, set a stake at the same time. A 5-7' stake is recommended. This prevents potential damage to the tuber when adding one later. A good stake is 1/2" conduit, painted green. Other options are to use garden decorations such as bird houses.
Dig "happy" hole and plant with 2" of stem below the surface. Tie off to the stake, and continue to tie as the plant grows.
If planting in containers, large containers (3'+ in diameter) are recommended. Use MiracleGro potting soil with moisture retention. The American Dahlia Society's online information, Growing Dahlias in Containers is quite useful.
Insect & Disease Control |
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Fungus and bacterial disease is usually not a major problem. Powdery mildew can be an issue in cool, wet weather. Treat with the same material as for roses. Viruses can cause dwarfing, wrinkling, and twisting of plant foliage. There is no control; it is necessary to recognize symptoms and destroy plants.
Generally use the same materials (insecticides) as on roses. Sevin and Merit usually control most insects; It is a good practice to alternate between the two.
Spider mites are controlled with Avid, Floramite, and Forbid.
Fertilization |
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Work in balanced fertilizer at time of tiling soil. Add a balanced mix (12-12-12, 16-11-13, etc.) or Miracle-Gro monthly through August.
Watering |
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Must keep an adequate supply of moisture; water 1-2" at a rate of 2-3 times per week. Mulch will help significantly. Watering at base of plant is best.
Pruning / Cutting Back |
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Topping
After 2-3 sets of leaves emerge, can break or cut off top. This will increase branching and result in a denser, more compact plant.
Do this in the morning.
Disbudding
Remove side buds to improve the size of the blooms. This will reduce the number of blooms but increase their size. If desired, disbud from 2-4 sets of leaves down from the desired terminal bloom. The larger the variety, the greater the disbudding.
Deadheading
Remove spent blooms regularly to promote continued blooming and prevent the plant from expending energy to seed production.
Harvesting |
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Best to cut early in the morning and place immediately into a bucket of warm water with flower preservative.
Site Selection & Preparation |
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Ideal is full sun, 6-8 hours of sunlight, lasting until 1500-1600 daily. Shade in late afternoon will help preserve color and prevent wilting. Sun in the morning will help dry foliage and reduce disease. Dahlias should have at least 1/2 day of sun. Plant far enough from trees and shrubs to prevent competition from roots. Some slope is desirable to aid drainage.
Soil Considerations
Good organic content which is rich. Modify with peat, compost, or manure and work in well. Soil should be well-drained and not retain moisture. Ideal pH should be 6.5-6.8.
Tuber Recovery & Propagation |
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Tubers need to be removed from the ground after the first frost in the Fall.
- Cut the plant back, leaving 4-6" above the ground to use as a handle for the clump of tubers.
- Dig the tuber clump up with a fork, staying ~1' out from the plant.
- Wash off the tubers
- Allow the tubers to dry in a shaded area
- The mother tuber will have writing on it. It is spent and should be discarded.
- Cut the other tubers from the part dug up, ensuring each tuber has a crown.
- Write the plant's name on each tuber you keep using a Sharpie.
- Always sterilize cutting tools after dividing each clump.
- A good resource for doing this is How to over-winter your dahlias from Linda & Jeff Laine.
- Another good resource for doing this is the American Dahlia Society's online information, Digging, Dividing, and Storing Tubers.
- Individual tubers with the attached crown need to be stored in bags with pine shavings.
- Label each bag with the plant's name.
- Don't close up the bag as that will cause the tuber to rot.
- Store the bags in a box.
- Store the harvested tubers in a space kept around 40° - 50° F.
- Too hot and the tubers may start growing prematurely
- Too cold and the tubers will probably die (or at least be damaged).
Inspect stored tubers monthly during the winter. Discard any tubers which show signs of rotting. By checking frequently, one can throw away rotting tubers before the rot spreads to otherwise healthy tubers. Some growers say that if one stores tubers so that they do not touch (as one could in a wood container but not in plastic bags), then rot will not spread. A rotting tuber releases a gas that hastens the developing of eyes and sprouts. A rotted tuber can therefore be useful for tubers that are very late to develop. Anyone who uses a rotted tuber for this purpose should check the bag frequently to ensure that the rot does not spread to the healthy, late tubers.
More Information
Web Sites
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eMail comments to me at GardeningBoK @ Gmail.com. |