This "how to..." article deals with topping your dahlias. This technique, sometimes called pinching or stopping, should be done for two reasons. First, to encourage lateral branches to start development so that you will have plenty of blooms in time for show season and second, to produce a bushier, sturdier and more compact dahlia plant. This will make your plants less susceptible to high winds and inclement weather. An additional benefit is that because you are actually forcing earlier blooms you will naturally have more blooms during a growing season. (Itís true that letting the terminal bud bloom would give you a single early bloom, but then a longer interval would occur before your laterals begin to develop)
There seems to be a natural reluctance for most novice dahlia growers to perform this necessary task. Donít think of it as a beheading but rather as grooming. Along with disbudding and disbranching, which will be discussed in our next article, topping should be considered more like a haircut for your dahlias. Remember that more new growth will replace what you have removed and it will replace it faster.
The technique itself is quite simple. Gently grasp the central growing tip on your dahlia plant and bend it until it snaps off. Be careful not to damage the two emerging lateral branches that will just be beginning to form on each side of the plant tip right at the base of each leaf. This task should be performed early in the morning or in the evening when your plants are crisp with moisture. It may be a little more difficult in the afternoon when they are all rubbery from the sun and heat. Now all of your plantís energy is directed into the growth of the lateral branches rather than the plantís terminal bud.
Now that you know how and why to top, you need to learn when to top. This is where things get more complicated. It takes approximately 50 to 70 days for a lateral branch to develop into a full bloom. Small varieties usually develop faster than large varieties. Since most shows are in August and September, most dahlia growers will top their plants during the middle of June so that they will have plenty of blooms for the shows. Furthermore, depending upon the size of a plantís bloom, experienced growers will usually leave a specific number of lateral branches on each plant. This is done by topping and then removing one or more sets of leaves beginning at the bottom of the plant and moving up. * The removal of the bottom one or two sets of leaves gives the added benefit of getting the plant up off the ground so that air can circulate around the plant which helps prevent the development of powdery mildew. The following guidelines will help:
A(Large) or AA(Giant) - 2 or 3 sets of leaves (4 or 6 lateral branches)
B(Medium) - 3 or 4 sets of leaves (6 or 8 branches)
Varieties under 6 inches - 5 or 6 sets of leaves (10 or 12 lateral branches)
As the branches grow, some can be removed to allow only a specific number of flowers to develop, especially for the larger varieties. Only allow 3 to 5 blooms to mature on large and giant varieties and 5 to 8 on mediums. Smaller varieties will usually not require disbranching.
Rough Time Table for Topping (Days before Show)
A or AA size - About 70 days before show
B size - About 65 days before show
BB and Ball size - About 60 days before show
Smaller blooms - 55 days or less
Plant growth and bloom time is very dependent on weather conditions, soil type, fertilizing programs and watering schedules. These conditions may vary from year to year and individual varieties may also differ from the norm, so please use the above information as a general guide in helping you grow bigger and more beautiful dahlias.
*Authorís Note: Some people believe that the bottom laterals develop into the largest and nicest blooms on a plant, they, therefore do not remove the first true leaves from the bottom. These dahlia growers will count up from the bottom to get the required number of leaf pairs and then top their plants.