Dahlias

Question from Randy:

Randy in SB here again. I know that you are supposed to leave dahlias in the ground until the foliage dies down but was wondering if I get sick of looking at them and want to make room for my winter plants—what would happen if I pulled them early. Would they not bloom as well next season? Thanks,

Answer from Pat:

I don’t blame you for wanting to cover over the mess of dying dahlia foliage, but you are correct in thinking that it’s best to wait until foliage dies down or turns yellow before cutting the stems back and digging up the roots. Cutting back too early will weaken the roots and flowers will gradually deteriorate. Here is a calendar of care for dahlias growing in the Bay Area of California. http://sfdahlias.org/how.to.grow/calendar/calendar.htm The schedule is much the same for Southern California. About 20 years ago I often drove past a field of dahlias grown professionally near my home. I always noticed the field lying dormant with foliage dying down in November with no irrigation and then I would see workers digging up the roots in December. Though this grower could have planted and grown a cover crop, such as fava beans, to improve the ground instead of letting it lie fallow in winter, in actual practice he dedicated space year-round to this one flower crop.

If this situation drives you batty, I can suggest two other alternatives. One is to grow dahlias in drifts to the back or center of a mixed perennial border while making sure to plant something such as chrysanthemums in front of the dahlias so they will take the stage as soon as the dahlias have faded. Many English gardeners grow tall varieties of dahlia at the back of beds or in shrubberies, where they are seldom noticed while they are dying down. Perhaps one could even stick spray-painted leafy branches in the bed to hide the stems until the dahlia leaves die and then can be safely cut back. Maybe that’s a bit silly but perhaps you can think of something clever to use as camouflage. Another way is to treat dahlias as an annual and simply dig up the bed as soon as the plants fade, throwing away the old roots and purchasing new ones every spring. Meanwhile, in winter you could grow a cool-season flower in the bed in the space where you plant dahlias every spring to bloom in summer.