Hello! I planted 5 different varieties of dahlia this year but put them into the ground late and only 2 have bloomed. Should I overwinter even those that did not bloom this year? They have all become plants, just 3 did not produce flowers. Thank you!
Different varieties of Dahlia bloom at different times but your late start may be part of the reason for the non-blooming. Below, see some general guidelines that may help you determine your issue.
Blooms should start to appear approximately 8 weeks after planting most years, but this may vary depending on the amount of rainfall, sunlight and soil nutrients. Next year, you could get a head start by planting your dahlias indoors in pots and moving them outdoors in mid-May when the chance of a late frost has passed. You can use this method if you can provide a sunny indoor location or sufficient artificial light such as grow lights.
No fertilization is required at the time of planting outdoors but your dahlias will benefit from an application of liquid, organic fertilizer 30 days after planting and then monthly during the blooming season. Be sure to avoid a high nitrogen (N) fertilizer which will give you lots of leaves at the expense of fewer blooms, 10-20-20 would be ideal.
Dahlias should be treated as annuals here in Canada as they don’t tolerate our harsh winters. If you want to store your favorite dahlia tubers over the winter, wait till after the first good frost or when the plants have yellowed, then remove the tops to within 6 inches of the crown (where the stem joins the root) and carefully lift the tubers with a garden fork. This is an ideal time to divide the tubers should they have grown huge and tangled. Gently brush the soil off the tubers and lay them out or hang them upside-down to dry in a shady but airy location. After a few days, their skin will become wrinkled but they’ll remain firm to the touch and should be ready to be stored.
Before storing, remove any tubers that are infested, dead, withered or show signs of rot. Layer tubers in dry sand, vermiculite, perlite, peat or wood shavings/chips and store indoors in a cool dark spot. The layers should have 2 inches of the packing material between them and the tubers should not touch each other. The ideal storage environment is between 4.5 & 10 degrees C. Tubers should be checked on over the winter months and any that show signs of disease or decay should be discarded immediately.
I would suggest you dig up and store all your dahlia tubers this fall for re-planting in the late spring/early summer as some immature, small tubers need several growing seasons before being mature enough to bloom.
Hope this helps.