Do NOT water Dahlias for at
least TWO weeks after planting!!
WHEN TO PLANT DAHLIA TUBERS
The dahlia tuber is unlike many other bulbs in that it wants to be planted in warm soil compared to say, tulips. A rule of thumb for planting time is: I used to recommend planting dahlia tubers on Mother's Day weekend. Now, I recommend you plant them when your lilacs are bursting into bloom. In other words, spring should be well on its way with the longer and warmer days. When it is regularly 50 degrees is best.
PLANNING A DAHLIA GARDEN
Now that the area for planting your dahlia tubers is well prepared and your stock of tubers is in hand, it is time to prepare a garden layout plan. Because certain varieties grow considerably taller than others, you should plot where you want tall plants and where the shorter than average should go. Also, if color mass is important, then get these details laid out before you actually begin to plant. Many commercial dahlia suppliers indicate the approximate height of the plants in their catalogs. Using this information can be a help in formulating your layout plans. The layout plan will also need to take into account the number of varieties that you plan to plant. The average planting space between plants is 18 to 24 inches, especially for the large flowering varieties. The shorter varieties can be planted closer together, but remember, when you dig those clumps in the autumn, you definitely don’t want them intertwined with their neighbour. Plan for the rows to be three to five feet apart, depending on the size of the plant. When the rows are two to three feet apart, the plants will generally grow taller as they ‘reach’ for light and your access up and down the rows becomes more difficult. Close planting also shuts down air circulation to the lower leaves, encouraging powdery mildew. If you plan to use a hand tiller between the rows, then plan your rows according to its width and be sure to leave extra width so as not to till too close to the plants and damage those new tubers.