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Planting Dahlia Tubers Directly Into The Garden: (By Murray Thompson) Now that you have selected your location which has adequate sunshine, and you have completed whatever upgrades to the soil and your garden is properly cultivated, and you are past 'Last-Frost' date, you are now ready to plant. If you look on the internet or in your library, you will find many diverse (and sometimes strongly held) views on how planting should be done. While each view has its merits and sometimes downside, the fundamental truth is that a sprouting tuber, however planted, tends to grow! We'll give you the basics here. Then consider coming to our meetings to get discussion on the finer points of cultivation. Some Basics To Consider: Timing: If you wish to get a jump on the season, the best way is to start them indoors. It is possible to plant the tubers directly in the ground about a week before the last frost date, since the plant is totally below the ground, but the tuber growth may be stopped a bit by the cold soil. If you preplant this way, be sure it is in a micro-climate, such as southern exposure, brick or concrete wall behind, protected from the prevailing winds, or sloping ground to the south for better catching the sun's rays. However, better to let plants get their indoor or greenhouse start, then plant the tuber (with lots of green leaves) after the last-frost date. Support: All but the smallest Dahlia plants need solid support, such as metal rebar, hardwood stakes 1" square, or 2"x2" spruce stakes. Best to avoid the smaller bamboo or plastic types. Stakes which look OK on sunny days may bend or break on days of rain accompanied with wind. The ideal height of this stake will typically be between 3' and 6', depending on the expected height of your plant and how deep is needed for support. Light sandy soil types will need the stake deeper for support than will heavy clay soils. Rebar will also need to be a little deeper than wooden stakes as well. We will get into various ways of securing the plant to the standards later. At this point, support means placing the stake of your choice, and then planting with adequate depth, which typically is 6-8" deep. Too shallow means less anchoring, too deep means harder to dig up in the fall. The sequence for this planting is: Dig the hole, mix fertilizer, if used, in the bottom of the hole, drive your support stake at the edge of the hole, then plant your tuber. Hole Location & Spacing: It is helpful to know what size of plant you can expect from your tuber, for at least two main reasons. If you have a small plant, you may be able to space your plants at 18" intervals or less. For the larger plants, you will need 24" (or more) between plants so you can maintain a bit of air circulation. Good prevention for mould. You may also wish to taper your garden for best visual effect, by placing the shortest plants closest to the front of your viewing field, and the tallest toward the back. You may also wish to stagger the plants, so that the final bed looks 'more filled in' . To do this, plant your back row. Then plant the next closer row, with the holes at the midpoint of the row behind. Be sure to maintain the 24" or so of spacing between the two rows. The third row, if needed, will be the same as the first row. Fertilizer: Mix your choice of fertilizer with earth in the bottom of the hole. The tuber goes on top of this. Which Plant Goes Where? If all your tubers are of similar varieties, meaning same height, same width, then perhaps the decision is whether to group your colours or plant at random. Again, shortest plants at the front, tallest at the back. Sprouts Up or Down? The first point here, is that either way, the tuber grows. You may wish to experiment. If you plant with the shoots up, the plant will break through the surface sooner, but may have less support. This might not be a concern if you are careful to secure it to the stake when the plant has sufficient height. If you plant with the shoots down, the plant will take longer to appear, yet will possibly have better support, since there is more stem in the ground.. but it may be marginally more difficult to split in the fall, depending on the variety. How much earth is required over the tuber? Best to use only about 2" of earth to cover the tuber for two main reasons. First, the warming effect of the sun is easier to get to the tuber through minimal cover. Secondly, water is easier to put and keep in the right spot if there is a depression in the ground to hold it. The hole can be filled as the dahlia grows, and the earth can even be hilled-up around the stalk of the dahlia as it becomes a mature plant.
Some Visual Help for Planting:
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Send mail to
mg.thompson@sympatico.ca with
questions or comments
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