My newsfeed is full of lots of different ideas and methods for saving dahlia tubers through the winter for planting out in the spring after the last frost. I think that it is important to carefully consider your own storage area, climate control situation, and pest pressure before applying others’ methods to your own home or farm. Take what makes sense, and leave the rest, I guess! And, if you’re unsure - don’t put all your eggs in one basket. Try a few different techniques and see which ones work best for you.
There are so many different ways to accomplish the task. Some of the methods I’ve seen for saving tubers simply won’t work for us. We have a cool fieldstone basement for storage. The temperature is about 50 degrees. 40 degrees is preferable for dahlia storage. It can be very dry in the depths of winter, and damp in late fall and spring. The field mice sneak in from time to time. But I make it work. Here is how I save our tubers.
Toward the end of dahlia season, I label my plants with flagging tape at the base of the stem while they are blooming. I mark the tape with a black oil-based pencil (Sharpie, Peel Off China Marker). It doesn’t fade or wash off. I find this pencil to be better than any kind of “permanent” marker, which tend to fade. I dig the dahlia plants up in the fall after they have experienced several frosts.
Because our winters are harsh and because I have no indoor space to clean tubers and because the snow persists until its summer outside—- I clean all the tuber clumps with a garden hose in the fall, let them dry, and divide them right away, or as I have time in the winter. My goal: get the messy cleaning work done before the hoses freeze!
Individual tubers or tuber clumps (note: you can plant whole clumps back out in the spring if you don’t want to divide them) are then packed by variety in labeled re-useable plastic mesh onion sacks with a mix of half peat moss and half pine pet shavings. You can buy these bags from Uline here. The peat moss keeps the tubers from drying out too much and has some acidity to ward off mold. The pet shavings prevent tubers from getting too damp. I put several onion bags in a cardboard box with dryer sheets (to prevent the field mice form taking interest) or into a clear plastic storage bin with a few air holes drilled in it. The boxes and bins are stacked on shelves in the basement. I keep a spreadsheet with the varieties and quantities of tubers I’ve saved.
I check the dahlia tubers every week or every other week in the winter for signs of condensation or shriveling. If things seem damp, I’ll open lids for a day. If they seem too dry, I add a little more peat moss and pull out some pet shavings. If I find a dahlia with signs of rot or mold, it is removed and thrown away immediately to prevent contaminating the others. The key is to be vigilant. One bad tuber spoils the rest of a bag or bin.
I keep an inexpensive, but large and easy to view thermometer on one of the shelves so that I can take a quick peak at the temps whenever I like. Because our basement starts to warm up to the high 50s and low 60s in late spring, it isn’t surprising to find growth at the eyes of many of the tubers when we start to narrow in on planting time. I love it. That growth says, “We made it!” “We’re alive!”
I scrape off the shoots when I plant the tubers out so that several more stronger shoots will grow in place of the “basement shoots” in the natural light outside.
This process works for us and for our scale right now. We don’t have a large cold barn to keep tubers in. I don’t have a tractor or fork lift. Everything is moved by hand down the bulk head stairs. This is what works for us right now. I hope some of it might be helpful to you.