If you're lucky, you live in an area where you don't have to dig up your Dahlia tubers. For the rest of us we must dig, divide and conquer. This year I've updated a lot of the information on when to dig them up. It's breaking dahlia news.
The first year I grew dahlias I left the tubers in the ground to rot; I had no idea you could save them. The next year I knew more, so in the fall I dug the tubers up.
But I didn't know THAT much more because what I saved in the fall and planted in the spring were tuber clumps the size of a clown car. I had no idea you should divide the clumps into individual tubers.
I could write another 14 pages about all of my dahlia mistakes - enough that you would need to nap and snack throughout this post. So assume you'll make mistakes, assume you'll learn from them and assume I've made infinitely more mistakes than you, so there's no need to feel discouraged.
Table of Contents
Digging
*New Information 2024*
Thanks to my local (but Internationally known) Hamilton Dahlia Society's latest meeting I learned a little trick for making your dahlia's eyes easier to spot for when you dig them up.
Cut your dahlia stems to six inches about 2 weeks before you plan to dig them up. Doing this will alert the dahlia tuber that it's about to croak. This shocks it into starting to produce eyes.
When you dig them up 2 weeks later you'll have an easier time spotting the eyes for dividing them immediately.
Zone ⅞ or higher
Zone 6 or lower
- Consider your dahlias to be tender perennials and try your luck at leaving them in the ground.
- Zone 8 dahlias can be left in the ground as a perennial.
- If you live in Zone 6 or lower you have to dig up your dahlias or they will freeze and rot.
- Dig up when they're mature in the fall. You don't have to wait for frost to dig them.
WHEN
- Tubers are mature and can be dug up for storage once they've been in the ground for 5 months.
- Tubers begin to mature on the summer equinox, (when days begin to get shorter.) 90-100 days after the equinox, the tubers will be fully mature and are ready to dig up regardless of whether there has been frost or not.
Luckily you don't need a lot of dahlia tubers to produce a lot of flowers. You can see the mountain of Dahlias 10 or so tubers produced in this post.
And dahlias multiply QUICKLY.
In one season, a baby finger sized tuber will grow to the size of something you could base an entire horror movie around.
Tubers grow like hands with multiple fingers. Each finger can get separated, cut off and planted next year.
That one tuber you bought could end up being 10 tubers after just one season. And they KEEP doing it. Every year you plant a small tuber it grows huge, you split it and you've increased your stock yet again.
(it's about this point when you start to hope your tubers will just rot straight to hell so you don't have to deal with them anymore)
Digging Dahlia Tubers
Tubers are easily broken, so be careful when you're digging them up. You don't want to injure or lose any of the fingers.
Steps
- CUT any stalks back so there's only about 6" of them showing. This way you can still see where the plant is, but the stalks won't be getting in the way. It will also give you something to hold onto when pulling up the plant.
- DIG about 1' away from the centre of the plant loosening the soil. Use a shovel or fork to dig. Pull the plant straight up once you can feel that it's released from the soil.
- LABEL the tuber immediately. I have a bamboo stick pushed into the ground at the base of each dahlia plant. The top of it is split which holds a plastic tag and wire tightly throughout the season. When it's time to dig the tubers up, I have the wired tag right there to grab and put on the clump so I don't lose track of what kind it is.
- WASH the soil off with a garden hose and set it to dry. I use a rack made out of hardware cloth set onto a small adjustable workbench. I put the tuber on top and spray with the hose so all the water just falls below.
Set the cleaned tuber aside outside to dry until the next day.
How to Split Dahlia Tubers
For a dahlia tuber to be viable it has to have an eye. The eye is like a potato eye only much less visible. It's what the plant grows out of. If the tuber doesn't have an eye, it will not grow.
The eyes are found on the neck of the tuber.
One clump of tubers might have 9 fingers branching off of it and 5 eyes in total. Your job when dividing dahlias is to make sure you get all the tubers with eyes and throw away the ones without.
The process of splitting aka dividing is the same no matter when you do it; fall or spring.
STEPS
Move onto dividing the tubers once they've been dug up, cleaned and allowed to dry for a day.
1. If you have a large clump take your pruners and ruthlessly cut the whole clump in half. It'll make it easier to work with.
2. Remove the stringy, withered tubers that will never amount to anything.
See? That's not going to do anything for you.
3. Once you get all the extraneous stuff trimmed away you can better see what you're working with.
4. If there are any tubers growing off of other tubers, cut those off and throw them away. Those piggy back tubers will never produce Dahlias. The big main one will, just not its parasitic twin.
(see below for what I mean)
5. Dahlias sprout from eyes on the very top of the tuber necks. So start cutting off each tuber, making sure to include enough of the neck that you get some eyes.
6. If there are no eyes throw it away. If you aren't sure, keep it and see if it starts to sprout in the spring.
7. Immediately label the tuber by writing the variety on it with a Sharpie. You can also tag it by tying it with flagging tape.
8. Let the cut dahlias dry for a day before storing them.
Parasitic tubers like this can be cut off.
The eyes are much easier to see for dividing in the fall when they've just been dug up.
TIP: I'm performing rudimentary dahlia surgery here, but a competitive dahlia grower will also do things like use 2 pairs of pruners, which they sterilize between cuts to ensure no crossing of disease. They'll also
If you chose to divide them in the spring, if you're lucky, your Dahlia will have already started to sprout which makes spotting the eyes easy. They'll have a stem coming out of them. Or they'll be swollen enough that you can spot them like in the photo below.
I'm not an expert - I'm just a girl with a pair of clippers whose made enough mistakes to know a few things.
These ones above are spring divided tubers. You can tell because they have sprouts emerging from their eyes. Leaving tubers to divide in the spring means they'll be very easy to see where to split them.
Once you've decimated the horror show of tubers, you'll have several individual, viable tubers for planting or giving away the next year. This compounds year after year until eventually you have enough Dahlias to start your own free love hippie compound.
A DAHLIA TUBER'S EYES ARE VISIBLE FOR ONE HOUR AFTER FIRST DIGGING THEM UP.
The eyes on a fall tuber are almost impossible to see.
The one time this isn't true is within 1 hour of digging them up. The change in temperature and conditions from being in the ground to being out of the ground makes the eyes swell up. Once the tuber has adjusted to its new surroundings (in about an hour) the eyes disappear again.
Storing Dahlia Tubers
If you've split the tubers and let them heal and dry for a day you can go ahead and store them.
Methods
I tested a new method in the winter of 2023 for storing my tubers. Playground sand.
SAND
- Pour sand into the bottom of a plastic bin.
- Add a layer of tubers making sure they don't touch.
- Cover with sand.
- Continue for another layer.
- Put a lid on the bin, but don't close it tight.
The lid helps trap the moisture in the damp sand* but not closing it tight allows excess moisture to escape.
*You don't have to wet the sand, when you open the bag of playsand it will already be damp.
The tubers stored perfectly, most of them looking even better than when they went in. By the time I decided to wake the tubers up in late winter they had already started to develop eyes and tiny roots.
BAGGING
- Put them into either plastic bags or boxes with vermiculite. You don't need to fill the bag or box. Just enough to give the tuber a good blanket of vermiculite to help keep it from drying out or rotting.
You can add more than one tuber to a bag as long as they're not touching and are separated by a layer of vermiculite. - Leave the bag slightly open so the tubers don't rot OR seal the bag closed and poke 2 holes in it for gases and moisture to escape.
- Store tubers somewhere that's 10 degrees celsius (50 degrees F) or below.
- Check on your tubers once a month or so. If they are starting to shrivel give 1 or 2 sprays of water into the bag. If they are rotting remove them and then make sure each bag or box is getting proper ventilation. You don't want the bags or boxes sealed completely.
Remember : Tubers must be completely dry before storing them or they'll rot.
WRAPPING IN PLASTIC
Last year I tried storing each of my tubers by wrapping them in cling film aka plastic wrap. This method worked surprisingly well. Most of the tubers were perfect with only 2 or 3 that rotted.
- Pull out a swath of plastic wrap and lay it on the counter.
- Place one dahlia tuber on it then roll so the whole tuber is encased in plastic wrap.
- Place another tuber onto the plastic and roll again. Continue doing this until you have a group of 4 or 5 tubers wrapped in the swath of plastic. Doing it this way keeps the tubers from touching each other (they always have plastic between them) so it prevents any rot from migrating from one tuber to another.
- Don't forget to make sure each tuber is labelled with a Sharpie. I label my bundles as well.
Best Storage Temperature
Store tubers somewhere that's 10 degrees celsius (50 degrees F) or below. If you don't have those conditions, put them somewhere that's as close to that as possible. Inside a kitchen cupboard on an outside wall is a good place to try.
How to Divide & Store Dahlia Tubers.
How to divide and store dahlia tubers for the winter in colder climates.
Materials
- dahlia tubers
- coarse vermiculite*
- tags
- sharpie marker
- tape
- pruners
Instructions
- Dig up Dahlia tubers 1 week after they have been killed by frost. On that same day wash and label all of the tubers. LABEL AS YOU GO OR YOU'LL GET THEM MIXED UP.
- As you dig up the tubers, wash all the dirt on them away with a hose. It's a cold November job.
- Allow the clumps to dry for a day before dividing them.
- On tuber dividing day remove the stringy, withered tubers that will never amount to anything.
- If there are any tubers growing off of other tubers, cut those off and throw them away. Those piggy back tubers will never produce Dahlias. The big main one will, just not its parasitic twin.
- Once you get all the extraneous stuff trimmed away you can better see what you’re working with.
- If it's a very big tuber with lots of fingers, it's usually easiest to cut the entire huge tuber in half so you're working with a smaller bunch. It's O.K. if you have to sacrifice a few eyes to do this.
- Dahlias sprout from eyes on the very top of the tuber necks. If you split your tubers a day after digging them up the eyes will be more prominent. Waiting even a few days will result in the eyes shrinking, making them hard to see.
- Start dividing and cutting off each tuber, making sure to include enough of the neck that you get some eyes.
- Write the name of the variety on the tuber with a Sharpie as soon as you cut it off of the mother plant.
- Let the tubers dry another day to allow the cut wounds to heal and dry then store them in either an open plastic bag filled with vermiculite (label the bag as well) or in a plastic bin with vermiculite.
Notes
*coarse vermiculite is larger than regular vermiculite and helps prevent moisture build up around the tuber.
For individual tubers, sandwich bags are perfect because you can write the name of the variety on the bag and use them over and over every year
You can pot them up under grow lights a couple of months before you plan to plant them out so they get a good head start.
Some years I kind of hope the tubers will just up and die on me to relieve me of the stress of digging, dividing and storing them. And sometimes they do up and die on me.
A few years ago, despite all of my efforts, I could not kill my dahlia tubers over the winter. I stored them improperly, ignored them and silently cursed them.
I'd have given them the evil eye if I believed in that sort of thing but I don't, so I stuck with a garden variety exorcism.
No luck.
At the beginning of April I excitedly opened up my plastic bags of Dahlia tubers expecting to find a wrinkled or rotted mass of nothing and found perfectly fine tubers.
This goes to show you that dahlias have a mind of their own. You can store them improperly and have them either rot into a putrid mess or shrivel up into a fossilized version of a tuber. Or. They'll turn out just fine.
Dahlias can seem overwhelming because they do need a bit of work - what with having to dig them up, curse them, and replant them every season. They demand attention, you can't just plant them and forget them. Don't let their bossiness stop you from growing them though. Divide ... and conquer your Dahlias.
Annie Young
Hello Karen. I so appreciate this very detailed instructional article. It is an addendum to the very sparse details from my just-turned-100 year old Polish neighbour who shared some tubers with me last year. I did as she instructed and they were all fungusy and moldy this spring. So she gave me some that were perfect from her batch. And I don’t want to mess this one up because it was and still is just so beautiful. No name though. One question… you say make sure you label the tubers with a sharpie. When do you do this? Before you wrap them in plastic? Thanks again.
Karen
Hi Annie! Yes, once the tuber is dry, write the name on it with a Sharpie (but if you only have one variety and you don't know the name, so you won't have to do this). Then store it however you choose to. I recommend labelling the tubers right away because if you're working with multiple varieties it's REALLY easy to lose track of what's what. ~ karen!
Randy P
I remain in silent awe of all those who find joy in gardening, edible or decorative. It is an obvious labor of love.
Dani
I was just looking at tutorials last night and your post came through this morning. Perfect timing. This is my first year growing dahlias and I got all my tubers at Walmart or some inexpensive online wholesaler. They. Were Amazing.
I said I’d never grow anything that had to be dug up every year but here I am. Thank you for the updated article!
Karen
I know, I have the same struggle every year. But every year I dig them up, store them, and plant them again. They're just too magnificent. ~ karen!
Chris W.
I think that dahlias are THE most beautiful flower - so the entire process would be a labor of love. My father used to grow like a gazillion of them every year but I never knew all the work that went into keeping them. I don't have any but may reconsider after reading this post. I so appreciate the way you explain things - the clarity, directness, and of course the humor is very enlightening. Thank you from those of us who aren't quite as "green thumbed".
Kat - the other 1
Recently read that dahlia petals are edible.
Is this why you keep vases and vases of them all over your house, snacks? Lol 😆😉
Elena
Hey Karen, I've been following you for years, now. I've learned so much (also, your Christmas calendar is an absolute Life Saver!!) But I have a question for you about dahlias - I may or may not have planted mine a weeeeee but late. I don't know if they're going to flower here in zone 4 before frost finds us. Any idea if these tubers will come back next year - do they need to flower to be able to return (provided I dig them up, obvs)?
Many thanks!
Karen
Hi Elena! As long as your dahlia has grown some stems and leaves they should also be producing tubers under the soil. Even if they don't have a chance to flower! They won't be as big as fully developed ones, but as long as the plant is alive and growing you should find something in the fall to save and replant next year. :) ~ karen!
Tawnya Walsh
Brilliant! Plastic wrap? Come on...!?! Well now I have to try it. I suppose I must've cursed my dahlia tubers this past winter as I lost every*single*one. Mold. Ugh. Even those from my son's wedding. Sigh. Bright side is I get to design an entirely new dahlia garden this year and I'm psyched! Love your tips & humor - thanks!
Karen
Hi Tawnya! I just took mine out from cold storage and I'd say 80% of them were good. I did get a few that rotted. But the rest are good and some are sprouting already. It really does work! But most of the people in my dahlia society use open plastic bags filled with medium coarse perlite. It really takes a few years to figure out how to store them. Once you find a way that works for you stick to it! ~ karen
Celia
Thank you for this ,I live in Scotland so have to dig them up, This will be my third year of Dalias and I've just found out you separate them, oops but never mind better late than never, so when I take them out later in the year I will know what to do x
Karen
I didn't know the first go round either, lol. ~ karen!
Darlene
Love your take and humor on dahlias. We don't want to see them die and rot but when you start digging them up...oh my goodness...thanks for the info. My husband says it is against my religion, the gardener's/plant lover's religion, to let any cutting, bulb or whatever be put into compost!
Millie
Can I leave them in the ground and divide in the spring, hoping for a frost free winter?
Karen
Hi Millie. It very much depends on where you live. What is your gardening zone? Or city? ~ karen!
Millie
I am in WA State, near Seattle. The flowers were cut back so the building can be painted. :(. Can I remove now or leave them in until Spring and dig them out then? They have been left in the ground for years. I want to move them to my house.
Karen
I see. Your best chance is to leave them until they're dormant. So either in a few weeks or in the spring as soon as you can dig them out (but before they start to actively grow). ~ karen!
Karen
Thanks for this! Someone gave me some bulbs last year! They did great but I was worried about the fall process! Wish me luck!
Karen
Hey Karen! If you have any questions let me know! ~ karen!
Randy P
Crikey - you have given me fresh insight into the cosmos of life within a garden. Calling it the trite "labour of love" as I have in the past seems more like a gross understatement of the reality than I ever dreamt. You and all those with the passion of the green thumb have my deepest respect and admiration. Good onya!
Nan Dolphin
Can I store the dahlias in my garage over the winter? It gets cold - below freezing.
Karen
Hi Nan! I'm afraid that's too cold. The tubers will likely freeze and rot. If I were you, I'd store them inside in the coolest place in your house. You can also store a few of them in the garage over the winter just to test it. If they make it through the winter without freezing then you'll know. ~ karen!
Karen Purpero
When you wrap in cling wrap do you still put them in vermiculite?
Karen
Hi Karen! If you wrap them in cling wrap you just need to keep them in a cool room. No vermiculite or baggies needed. ~ karen!
Elaine
I did the divide and wrap in Saran last Fall and ended up with over 100 viable tubers this Spring. Only lost a dozen or so. Potted up and planted out they have been gorgeous this year. Worth all the effort
Karen
I found the same thing. It's a good method! ~ karen
Leah Bonebrake
Dahlias are SO worth the trouble!
Shauna Solomon
I didn't divide my dahlias in the fall. This spring I planted all the attached tubers in pots inside my home. There are now multiple growths and lots of leaves (really, I thought they all died but everything is growing). Is it possible to separate them at this point?
Ellen
I have stored some tubers (as per this post) and I haven't dared look to see how they've fared, but when I do, I am wondering when they can be planted back in the garden? I live in Toronto, Ontario.
Karen
Hi Ellen! Not until it's very warm out. Probably the end of May. :) ~ karen!
Ellen
Thanks for that!
Petra
Yup, today is Tuber Dividing Day. I don't meticulously divide down to singles but make sure I separate the clumps enough so that air can circulate and dry them enough. This means prying them apart with two garden forks, making sure there's no damp dirt hiding in between. These are huge galaxy clumps. I totally agree with removing withered, mushy or otherwise pocksey lookin stuff. The idea is to keep your dahlias healthy and though they are really tough, in some soils and climates they can get diseased. It might not kill them but can weaken them so the flowers they produce become smaller, less colourful, etc. My tubers overwinter in covered tubs of dry peat. I think they are totally worth the fuss.
Jane
Karen,
Something totally different - just came across this and want to point it out to you and your readers in case you don't already know: crochet chicken sweaters
https://www.etsy.com/shop/AnimalFunandFashion?ref=simple-shop-header-name&listing_id=603942691§ion_id=23427856
Vikki
Those are so cute! and funny! Thanks for cluing us in on this.