Lifting and Storing Dahlia Tubers - Part One
If you ask 100 dahlia growers, you’ll get 100 thoughts on how to overwinter dahlia tubers. I’ve tried several methods and failed several times, but the info below is how I go about things now. Is that set in stone? Oh my, no. Every year I learn more and more about how to be a better gardener. My best advice for you is to read, read, read as many different articles, posts, etc. and see what works best for you. You may have some failures, but sometimes that’s the best way to learn what’s right for your unique situation.
Okay, get comfy…there’s a lot to read here (and this is just Step One of Four). Read this all the way through and then reread to see what you need to gather or purchase. Do you have something to tag your plant with (so you know which tuber clump you’re dividing in a week or two)? What planting medium are you going to use? Do you have storage bins? Do you have a space that will stay between 40-50 °F all winter? All Step Four. It’s a lot, but so worth it!
Planting Zones
In zones 8–11, dahlias are perennials, like leave them in the ground perennials (however, it is recommended in these zones to dig the tubers up every few years to divide). But in colder areas (zones 3 - 6 , Chewelah is zone 6a) tubers will not survive the freezing temperatures of winter. If left in the ground, the tubers will freeze, turn to mush and rot. While growing zone 7 is milder (sort of a shoulder zone), it is still recommended to lift and store.
Timing
Dahlias require exposure to a freeze to enter dormancy and allow their tubers to cure properly. When the first frost hits in the fall, it signals to the plant that it's time to rest for the winter. The stalks and foliage will blacken (this may not happen after a frost, but will after a hard freeze), while the tubers beneath the soil develop thicker skins in preparation for the colder months. The longer tubers remain in the ground to cure, the more fully developed they will become. If dug up too early, the tubers tend to have thinner skins and may have a harder time overwintering. Although they may initially appear healthy, they can be prone to shriveling, becoming unusable. Sad! So after that first freeze, you’ll want to wait 1-2 weeks before digging up your dahlias.
Tagging (!!) & Cutting the Stalks
Tools for lifting dahlia tubers
Here’s one of those “100 ways” mentioned above: Cutting the Stalks. Some say to avoid cutting down the stalks, as this opens the hollow stems, allowing water to collect, freeze, and potentially harm the tubers. But others mention that cutting the stalk back signals the tuber’s eyes to develop (so helpful when you go to divide your clumps) and the skins to thicken which helps them store better over the winter. If you anticipate rain before you lift the tubers, go ahead and cut the stalks and cover the top with aluminum foil or plastic and rubber bands. Win-win! A little more work, but worth the time to give your tubers their best chance of survival.
If you haven’t had a freeze by early/mid-November, you’re fine to lift.
Now hold on, put your pruners down. Seriously right now. Before you even think about cutting anything, grab a sharpie, flagging tape or something to wrap around the base of the plant, write down the name of the dahlia, and secure it to base. Do not skip this step. Do you know how many misidentified dahlia tubers I received this year? Heck, do you know how many of our plants have “?” as their name?? If you’re just growing for fun and really don’t care, the go for it, skip the tagging, but if you like to know what your growing or want to share your extra tubers with friends/family, take the time and add name tags. Once they go rogue, you won’t know the variety is until it blooms (and even then, it could be a guess!)
Okay, now go ahead and pick up your pruners. Cut your plants back to about 6”-12” from the ground. You want a good “handle” size stalk left so you have something to hold on to when you lift.
Lifting
Now that your plant is labeled and you’ve got breathing room to work, you’ll lift (aka dig it up) the tuber clump out of the ground. The best tool for this is a garden fork, but a pitchfork or shovel works just as well (but not a tiny trowel). Dig all around the base of the plant, about 12” from the stalk. Take your time, slow and steady wins the tuber-lifting race. You want to start away from the stalk to avoid piercing/slicing your tubers. But do not fret, few is the dahlia gardener that hasn’t done this, and will again. Just do your best to minimize this. Your goal is to loosen the soil around the clump and slowly start to work the clump free. Don’t think you can grab the stalk “handle” and pull. It doesn’t matter how loose the soil has become, please don’t do this. Continue to wiggle/loosen the soil until you can gently lift the clump out with your hands. This clump is so special! You have nurtured this plant all season and it has worked hard to produce these tubers for next season, so take the time. Trust me, it just takes one “Hey, I’m just gonna grab this stem and pull” and then feel/hear the ripping and tearing of tubers from the stalk to learn your lesson. Learn from my mistake. It’s not a happy feeling.
You’re going to bring these tuber clumps to your cleaning workstation/area, but feel free to have a paintbrush with you to wipe off some of the soil right there.
Chewy dahlia
Congrats! You’ve successfully labeled and lifted your dahlia’s tuber clump! I wish I could say “Hard part’s over”, but it isn’t. This is just step one of let’s say four.
Step One: Lifting
Step Two: Cleaning
Step Three: Dividing
Step Four: Storing
Uh, but now what? Step Two - Cleaning (yeesh!!)
