Well it’s definitely that time of year- If you are digging your dahlias, it’s time to get them into storage. Here’s how we do it:
Each year in November, we spend most of the month digging dahlia clumps out of our field. Everything is hand dug, our field is not set up for mechanized digging. So it’s all shovels over here! Once the tubers come out of the ground they go into labeled bulb crates. Each crate gets two labels— one on the handle and one inside the crate. No mixing up crates on this farm! It happened once many years ago and I vowed never again!
This year we are washing tubers directly after digging. Then I am trimming the clumps up (removing any rotted tubers and the long stalks. After they have dried for a few hours, they spend the night in the flower cooler. Within a few days, I am putting them into storage in full clump form. I am putting the clumps into bins and then covering with vermiculite. Each bin is labeled and dated. We will return to these in January when we begin dividing.
In the past, we have allowed the tubers to dry for several hours after digging. We grow in heavy clay soil and sometimes the soil is damp while digging. I love when we have dry weather during digging but that’s never a guarantee. Then once the dirt had dried some, the clumps would go straight to the flower cooler. Sometimes I would wash immediately and then allow the clumps to dry. The flower cooler keeps them at the right temperature and humidity until we can get to dividing.
However, I found that this method worked for a lot of varieties but not all. Some would begin to shrivel before we could get to dividing. So I’m changing my process to get them into better storage conditions earlier. One of the biggest parts of storing tubers is evaluating and making changes until you get the method right.
Few washing tips:
1. Use a nozzle with a variable flow. This is important because sometimes you need a little more water pressure to bust the clay out of the center of the clump.
2. Wear water proof gear. We use a vinyl butchers apron. It has been a great addition to our set up- anybody can wear it b/c it’s one size fits all and it’s long enough to cover the majority of your body and thick enough the water doesn’t come through. Wellies are a good idea too.
3. Angle your table forward. I lift the back legs of my table up by about an inch or two so that the water rolls forward away from me.
We begin dividing the clumps in January. We do all our division before Spring because Spring is way too busy on a flower farm to be worrying about dividing dahlias. We also begin shipping our tubers in March. After division the tubers go back into the vermiculite for storage. They are graded into 2 grades: A or B. A’s get sold and B’s are kept for the farm planting. Each tuber is stamped with a 4 letter abbreviation of their name. I keep an excel spreadsheet with the key to these names. This also helps with ensuring varieties don’t get mixed up in storage.
We use vermiculite as our storage medium. I switched 2 years ago to this. We’d been using peat moss for 10+ years but I finally got tired of all the mess and dust. I like vermiculite so much better! No huge clouds of brown dust erupting every time we store a crate of tubers. We store in clear plastic bins- I prefer a shallow bin- one that’s about 10-12” tall. Deep bins are hard to check your tubers and it’s too easy for tubers to get moldy and then you don’t notice until spring. Your storage environment should be between 40-45 degrees and 85-90% humidity. I use a Govee device to monitor my storage conditions as it connects to my phone.
Once the tubers are in storage, then the checking process begins. I set a reminder on my phone to check every 2 weeks. I just go into the flower cooler and rummage around each bin a little bit. I’m checking to make sure they aren’t drying out or getting moldy. This process can save your tubers if you have a problem. If you store and forget about them until Spring, you’ll be one of the people emailing me with tails of woe- how all their tubers got moldy or shriveled! It only takes 5 minutes- so go set that reminder now!!
If you do run into a problem during storage, sometimes you can address it if you move quickly. If you begin to see mold on the crowns of your tubers, then your environment is probably too wet. So you need to lower the humidity or uncover your containers if they had lids on them. You can also take your tubers out and spray the mold with a 10% bleach solution, let them dry then return to storage. This will solve the problem if it hasn’t progressed to far.
If you have the opposite issue of shriveling, then you need to increase your humidity which may mean changing locations. Or you can also try potting the tuber up and taking a cutting off of it to save the variety. You can plump a tuber back up but sometimes there’s enough life left to get a cutting.
Storing in the Ground: If your climate allows, storing in the ground is often the best method. You must make sure your soil drains well. Rotting is a bigger issue than soil freezing in climates that allow this. Cut the stalks back in the fall (after frost). Cut flush with the ground. Cover with some mulch to keep the weeds down. Or some folks use a tarp if it’s a large area. We use landscape fabric on our rows that we leave in the ground. This keeps weeds away but also lets a bit of water through. I think this helps them to wake up on a more natural timing. Our rows are hilled pretty high so I don’t worry about them rotting.
Storing dahlias through winter can take a bit of finesse. But it’s not as hard as you may think. The main thing is to not forget about them over the winter. Check on them no matter how you store them. If you dig, set that reminder on your phone. If you leave in the ground, peak under that mulch or tarp. A lot of issues can be fixed if you are checking on them regularly.
