So many of you wonderful flower followers have asked for help with overwintering your own dahlias. A workshop is a bit tricky because Dahlia digging, dividing, and storing is a multistep process, which takes a bit of time because you must wait a bit in between each step. Basically, you can break down the process as I just described, into digging, dividing and storing PLUS PREP WORK, DESCRIBED BELOW.
This is the first of 4 blog posts to help you through the process. Check back for 3 more blog posts in the near future to read about STEPS 2 through 4.
PREP WORK STEPS – 1 - wait for frost. For most of you this might have already happened. Here, at Butternut Gardens, the night of October 18/morning of October 19 was our first frost date. By later in the day on the 19th, many of the dahlia leaves had turned black. While some of the flowers still looked pretty “normal” (and many definitely looked bad) the season was done. A few days later, we had another frost, leaving all visible parts of the plants definitely looking like their season was over. If you have not yet had this happen to your plants, i.e. you have not yet had frost, be patient, as it will happen sooner than later.
2 – Make a note of this frost date. Once you have frost and your plants look as described above, you may cut back the stems to about a 6” height, but leave the underground tubers alone.
3 – Wait about 2 weeks and do nothing more to the plants. For me, for 2018, this means waiting until November 1st. During this waiting period, get together some supplies. For dividing your tubers you will need hand held pruning shears at a minimum. Other tools that have been employed in dahlia dividing operations range from pvc pipe cutters to hack saws to butcher knives and the likes. Tubers can be clumped together and very thick, making it difficult to cut through the individual tubers. I have used many cutting tools, but usually go back to my trusty Felco brand pruners, which I use for all manner of operations related to flower farming. I don’t need every single viable tuber, so some, admittedly, are sacrificed in my less than perfect dividing method. Aside from a cutting tool or tools you will need supplies for storing your dahlias. You have several choices. I have stored dahlias in moist peat moss or moist pet shavings. I use the clear shavings not the cedar shavings. An alternative to these items is clear cling wrap from your kitchen. I have used this storage material with equally good results as the moist shavings or peat moss. I have not used vermiculite, but I know others have successfully stored dahlias in it as well. You will also need to label your dahlias. You can either do this by writing on your saved tubers with permanent marker or permanent wetable pencil. I no longer label every saved tuber. I do, however, make sure to label groups of like tubers in one way or another. Permanent marker on blue painter’s tape works well. If I am wrapping in clear cling wrap, I put additional wrap around a group of individually wrapped tubers, and then put the tape on this package and write the dahlia name on the tape. If I am using peat moss or pet shavings, I often package them in packing paper (newsprint paper without ink on it), wrap the blue painter’s tape around the package and, again, use the permanent marker to label the tuber package. So, now is the time to determine which method or methods you want to use, and gather cling wrap, peat moss, and/or pet shavings, painter’s tape and permanent markers. In addition, you will need to put your tuber packages into a container of some sort. I use cardboard boxes. I want the tubers to be in box so they do not receive any light during this storage period. I use cardboard so there is some airflow. Having said this, I know some people annually store their dahlias in black plastic garbage bags with no problems at all.
4 – Consider where you will store your dahlias. Your ideal storage location will remain at a temperature between 40 and 50 degrees until you are ready to plant out next spring. A basement often works, but not a finished basement, which is heated. The space under a Bilco doorway works for some, but for others this space becomes too cold. Garages can be good, but not if the temperature goes below freezing. Some people combat freezing temperatures by surrounding their tuber packages with vermiculite or other material, which can act to insulate against the cold. Newspaper can insulate to a certain extent as well. How do you know if your garage freezes? Leave some water in a container. Keep it closed or covered so a small animal cannot get stuck in it. If the water freezes even a little bit, it is too cold for your tubers. Dahlia tubers are not able to withstand freezing temperatures.
So, that’s it for now. Cut your plants back. Gather your supplies. Wait.
The second set of dahlia tips will be coming in the next few days, so check back here soon.
Thanks for growing these beauties!