Digging and Storing Dahlias
- I am in zone 6B, southern PA. My experience is based on this environment.
- Label your dahlias prior to frost. There are many methods to do this, but I use plastic tree tags and a zip-tie.
- Frost occurs around mid October. Once a killing frost hits, I try to wait until at least two weeks before digging. This allows time for the plant to send all its nutrients down to the tubers for winter storage. If you do not get a killing frost, it is okay to dig, but be careful to not dig too early. Dahlias tubers need to be mature for better chances at storage.
- Cut the plant stalks down to the ground and remove the plant material.
- There are a few tools that are needed to dig. A potato fork : I like this compact straight tine fork because it allows for control. I know exactly where the tines go. Water pressure and a nice nozzle (preferably one you do not have to squeeze): I spray all the dirt off the clumps prior to taking them out of the field. Be careful to not use too much pressure to strip the skins off the tubers. I like to wash the clumps immediately after dig for a few reasons. 1. to leave the top soil in the field. 2. to get a better eye on the clumps - looking for leafy or crown gall 3. clean clumps = easier to see the eyes & easier to divide.
- Take the fork and make sure its at least the width of the forks away from the stalk of the plant. If you dig too close to the stalk you run the risk of damaging the tubers. Stick you fork in all the way to the top of the tines and gently pry all the way round the plant, then on your last stick - lift the clump. You are loosening the soil around the clump first, heavy soils will break tubers if you rush the clump from the ground.
- The tubers are fragile and brittle. They need time to toughen up, this is called curing. In a perfect world it would be great to put them upside down to drain any moisture from stalks, and let them dry fully for a few days. I would not leave them in direct sun for this time, it may start to dry them down. I do not have a perfect world situation, nor a place to store them safely to cure, so the clumps are loaded into crates and stacked in a block cellar. I do try to space them out as best as I can and will run box fans to move air for drying.
- I try to manage the block cellars environment the best I can to assure the clumps do not freeze, do not get to warm or too dry. I have multiple humidistats to get an accurate picture of the environment and make adjustments accordingly. Too hot? - this usually is not my problem, they're underground. Too cold? It can still freeze because the cellar is drafty. So I use foam boards to make an 'insulated room' and put in heat lamps or a small electric heater to keep the temps above freezing. To humid? That's not a problem as long as the clumps can breath. Not enough humidity? Add water to the environment - run a humidifier, dump water on the floor, etc.
- In my experience dahlias store best at 40-43* F and 90%+ humidity. They do need stored in material that will help wick away moisture so it does not settle on their skins. Some farmers use vermiculite, I use shavings purchased from Tractor Supply. It is best if the environment stays stable and does not swing. Meaning, it does not go from 40* to 60* to 34*, etc.
- I divide in the fall. This task takes time and my end storage area (cooler or root cellar) is not large enough to store all the clumps I grow. I need to condense the clumps as quickly as I can.
- Once I divide a variety, it is put into its own mesh bag and packed into a black bulb crate lined with paper and cushioned with shavings. Then those crates are stacked into my cooler area (most insulated room I have).
So what if I don't have the perfect conditions for storing?
You need to figure out the limiting factor of your storage situation. Buy humidistats to help you accurately see the environment. Is it : Too hot? Too cold? Too dry? Then manipulate the environment to make it the best it can be. Try storing a bag of potatoes in the designated area and see what happens. Use the plastic wrap method. Buy a insulated cooler or an old refrigerator to store them in. Leave the dirt on the clumps. Run a humidifier. Get a heat lamp or a milk house heater that kicks on at a certain temp. Find someone with a root cellar or a dirt floor basement. There are also climate controlled storage units that can be rented. Just get creative.
The possibilities are endless but you won't know what works or doesn't until you try. And if it makes you feel better, the first year I tried to store dahlias, I didn't wash them. I left the dirt on, let it dry out as much as I could and wrapped a grocery store plastic bag around each clump. They were put in a true root cellar - which holds 40-42* and 99% humidity. Needless to say those tuber clumps rotted because the soil sucked up the water and the plastic bag kept it in. Lesson learned and I'm all the wiser for it.
The possibilities are endless but you won't know what works or doesn't until you try. And if it makes you feel better, the first year I tried to store dahlias, I didn't wash them. I left the dirt on, let it dry out as much as I could and wrapped a grocery store plastic bag around each clump. They were put in a true root cellar - which holds 40-42* and 99% humidity. Needless to say those tuber clumps rotted because the soil sucked up the water and the plastic bag kept it in. Lesson learned and I'm all the wiser for it.