How did we make it to November already? Seems like yesterday when I was trying to figure out what to change in the garden for the spring. But to be honest, by this time of the year I am ready to put the gardening tools away for a while and retreat inside to catch up on my reading and writing.
Before I do, though, I must tend to my dahlias. Having come from Pennsylvania and a Zone 5 garden, I was new to the joys of dahlias. They are tender tubers and not up to the -20 degree temperatures that marked our winters. Most gardeners in my area didn’t bother with dahlias because they needed to be dug every fall and replanted in the spring. The growing season wasn’t as long, either, so many times dahlias wouldn’t be ready to bloom until it was too cold to do so.
But upon arriving in Oregon over twenty years ago, I was delighted to see so many lovely varieties to choose from for the garden. And now with Old House Dahlia Farm firmly entrenched south of Tillamook, we are treated to our very own growing fields to pick from. If you haven’t been there in late September or October, put it on your calendar for next year. The fields are a sight to behold. And you can shop having seen your choices in bloom.
Back to November. There are two schools of thought about local dahlia growing: lift the tubers in the fall, or let them stay in the ground until spring. I will explore both sides and let you decide which works best for you.
First, the benefits of lifting the tubers. Dahlias are not cold-hardy, so if your temperatures dip below say, 40 degrees on a regular basis in the winter, you will want to dig them up this fall. They also are prone to rotting if the winter is wet as well as cold. Digging can start about two weeks after a killing frost or by November 15, which ever comes first. You will know when the plants start to turn brown. Digging too soon will keep the tubers in a “green stage” and they will not be hardened off for winter storage.
Cut the stocks off the plants to about 6 inches and lift gently out of the ground with a pitchfork or spade. Be careful not to break off the tubers’ necks. After gently digging the tubers out of the ground, wash the soil from them and allow them to air-dry on layers of newspaper, protected from the weather, for about two days. Once they are dry, be sure and mark the tubers as to variety in such a way you will be able to tell what they are in the spring. Sharpies can work well, or use plant markers tucked in with the stored tubers.
They will then be ready for storage. I like to use a large, sturdy cardboard box or crate. (Don’t use closed plastic bags as the tubers will hold in moisture and more easily rot.) I layer dampened wood shavings (because I have access to them) or newspaper in the bottom of the box. You can then layer the tubers between moistened shavings, peatmoss, or pet bedding until the box or crate is full. Place them in a cool, dry spot where the temperatures are between 40 and 50 degrees. Any warmer and they may dehydrate or even start new growth. Any colder and you risk having them rot or freeze.
Dahlia tubers will need at least a three-month resting period between growing seasons. But you will also want to check on them about once a month. Look for dehydration or shriveling of the tubers so you can mist the storage medium with a little water. But also check for rotting, in which case you will need to dry out the storage medium and cut any rot from the tubers to keep the rot from spreading. By spring, you will notice little “eyes” starting to sprout. But that is a topic for a spring, 2022 column.
Now, if you live in an area where the ground never freezes deeper than four inches, you may want to leave the dahlias in the ground for the winter. This is, of course, a little easier unless you have extra-large dahlia beds. We return to the November 15 date for dealing with these dahlias, too. After a hard frost or the 15th, cut the stocks below ground level. Leaving any kind of neck will allow rain water to channel right down into the tuber and cause it to rot. After you have cut the stocks, cover the dahlia beds with plastic and then layers of straw, leaves, or sawdust that will serve as a “blanket” to keep the plants warmer during the winter months. The plastic will keep them dry.
In either case, you will want to divide your tubers about every two years to keep the plants healthy and productive. Another topic for that spring, 2022 column!