Breaking tuber dormancy

SteveM · 2025-04-18T01:51:09+00:00

Even with ideal temperature and moisture, the ability of a tuber to break dormancy depends (at least in part) upon the conversion of starch into sugar duri...

Teddahlia

I am not big believer in waking up tubers. I see an eye on the tuber and I plant it. It is an extra step that is not needed. At Swan Island Dahlias where they plant 450,000 tubers, it is not part of their planting process. Yes, if you are not experienced in finding the eyes, maybe.

Dahlia53

I'm not a pro but have grown dahlias for over 30 yrs and have never seen anything like this - 2/3 of my stock not waking up or showing eyes by now. This is new. . Oh well. Few more days to see if the light will do something. If not, I wonder what could have caused this big of a crop failure. It wasn't the cold. We had a mild winter and no northeasters. Maybe they were stored too warm (someone's basement) before any sugars could develop since I had to dig in early Sept. due to wet conditions that rot my tubers. Oh well. One of those unsolved mysteries! They were stored in small cardboard boxes in bigger cardboard boxes, saran wrapped because I have to divide immediately or rot gets from the stem to the tuber clump. There were ones in the boxes that had no trouble sprouting, so I'm mystified.

SteveM

Dahlia53 Few more days to see if the light will do something.

Tubers don't need light to eye out, they need moist and warm.
I pre-sprout my tubers by lining a 1020 flat with about 1/2" of potting mix, lay the tubers flat with eyes up, and then cover all the tubers and crowns with about 1/2" of soil. (the total depth of everything is less than 2") I then place the flat in partial shade (or sun, depending on temp) and keep moist. I can get about 30 tubers in a 1020 flat. If I were to do this with saran-wapped tubers I would remove the saran wrap, follow the above procedure, and give them at least a month of warmth and moist before I gave up on them. I have received a few saran-wrapped tubers from vendors that have taken a month to eye out. I think it must be a very good way to keep tubers dormant.

Dahlia53

SteveM Thank you - so... light alone isn't going to help. Hmmmm... Yes, Saran wrap apparently keeps them dormant longer - and saves me from needing a lot of room and having foot long white sprouts in Feb. or March. But this year I really screwed up, and have too much else going on.

The tubers I was trying to eye up and sprout were extras that I was going to give to friends and sell some locally to help pay for my tuber-buying addiction - which as usual, got out of control. Oh well!

Thanks to you all - Steve, Ted, Missy, and Barry O for all the good information and tips. Will try to figure out what went wrong and do something different if I go on with all this next year. I'll file all this information away for if I do the saran wrap method of storage again. I need to get them out of the saran wrap much sooner than i did, and do the soil/tray method so they're ready for mid-April/ May. For now, I hope the humble pie I need to eat is Pumpkin, or Chocolate mousse! 😄

blown_dry

Dahlia53 It could be if you tossed them in a big container with potting soil (or @SteveM flat method) and kept them at room temperatures they would sprout eventually. One thing I do sometimes is nick the crown with my fingernail. If it's green/pink and alive under the skin, there is still hope. If it's dry like cork or black or slimy, then not so much, unless that's a very localized problem.

Dahlia53

blown_dry thanks for the tip! By crown, do you mean where the sprouts or eyes would be, or anywhere on the tuber? I noticed a few varieties are dark under the top layer of skin (did the scratch test under and the tubers are fine, just discoloration I guess). or Most feel firm; a few are suspect like Bloomquist Jean. Feels not firm enough, suspect rot. 🙁

I guess i am resigned to finding some flats that can hold moist soil and hoping all the tubers will fit on the table I have. I will pick the best looking and start with those; it'll still be tight. I would just toss them but I need the money this year due to extra unforeseen expenses. Thanks! they've been inside for some days now, but it's nowhere near 70 degrees in here. More like low 60s.

Teddahlia

Crown is a very old term for the area where a tuber was attached to the stalk. The tuber is removed with some crown material as that is where the eyes are located. It has been said it is impossible for an eye to form on the body of the tuber. I remember a commercial grower exclaim that in all the years of examining many thousands tubers, he finally found one tuber with an eye halfway down the tuber. I bet you will say he told me that he saved that tuber and used it for breeding or that he told me the name of the variety. This story goes nowhere.

Dahlia53

Teddahlia that dahlia you are picturing sure goes somewhere! Is this one of yours? I love the wine color toward the centers and on the petal edges. so pretty - looks like the reverse on the petals is that color too.

Teddahlia

We are 4 years behind Noni in breeding some in the color scheme of Salish Twilight Girl.

calico20hill

Teddahlia And to think, I got it on my first seedling! Actually, I am reselecting STG with the ones with the darkest backs. I see too many on the market where it is a light red violet and while pretty enough it lacks the drama it started out with. The only thing I accomplished between rain showers today was to plant out 20 started plants or seedlings from parents that showed the very dark back. That is a lot of space to dedicate to one variety out of my 6 raised beds for dahlias!

BarryO

Dahlia53

BarryO

I also saran wrap my tubers for the winter. As earlier stated, I have much success then removing them from the saran wrap and placing them in zip lock plastic bags with ever-so-slightly-moistened potting soil. They are kept at room temperature but NOT in the sun. Most then eye up and develop hair roots within 2 weeks.

Dahlia53

BarryO Thanks, Barry. I have never had to do the baggie step; they always showed signs even in April but I had the little boxes outside so that must have been too cold for them. since I put them inside in open beverage trays, have them inside, a handful are eyeing. Yesterday I put about 2/3 in moistened potting soil and lined the cardboard trays with plastic.l but i ran out of plastic, so have to find more to do the rest. I didn't have any plastic trays recommended to me. Thanks! I'm glad I asked for help with this. Even though light is not a factor, it did seem to help to get them out of the dark and put the tubers inside in bright indirect light. When I didn't wrap them before, they would have broken dormancy far too soon. Since I can't plant til June anyway, my tubers are about 2 wks behind everyone else's to bloom. But other people have better conditions than I do and want their tubers sooner.

I think next year i will be more ruthless and only keep several of each of the best looking tubers and nothing too small (like little finger size). I used to have better drainage on another garden plot, and my tubers were much nicer looking without even any fertilizer.

Teddahlia

"...and develop hair roots within 2 weeks." Hair roots are the main source of water and nutrients for the dahlia plant. You need to carefully preserve them from damage when you transplant the "woke up" tubers. Those hair roots are what give you a head start on the growing season. A tuber with only a sprout and no hair roots has to form hair roots to grow properly. A tuber with just a swollen eye grows hair roots and the sprout at the same time. They are "matched set" . If you plant a tuber with a long sprout and no hair roots, the hair roots need to form before the sprout will grow very much. The sprout will be skinny too. I suppose this is why the late Phil Mingus cut back the sprout to less than an inch or if there was another sprout, removed it entirely. He wanted a very fat sprout to emerge from the soil. Having learned all this from Phil Mingus who grew dahlias for 70 years, I am a bad student as I leave some long sprouts on and have them poke out above the soil. For some reason it makes me feel better when I see that sprout above the soil. All these "best ways" to do something are really just suggestions and you can just plant the tubers "willy nilly" as they say and they generally grow very well no matter how you do it. I always remember the Swan Island method where tubers are tossed into a hole on the platform behind the tractor and they land in the furrow and are covered by the tractor as it goes along planting in 600 foot long rows on the way to planting 450, 000- tubers. 😳

Dahlia53

calico20hill I know this is changing the subject from my original thread topic and it probably belongs in another topic, but what causes stock to fade or morph or change color? And if we have stock that is sold as one thing and doesn't match what we thought we ought to be getting in the picture, does this mean it has sported or is bad stock and should we start over buying it again? Thanks!

Aha = I read on and I think Ted just answered my question. Find stock as I remember that it should look. All the more reason to take cuttings if one has good stock - and spread it around to the serious dahlia addicts who will keep it going! Some dahlias are notoriously hard to grow. Or genetic decline. Or virus. Or a host of other unknowns. The lesson is, learn to do cuttings of good stock and share with people who take cuttings and dig their clumps. 😁

bloomhjelm

Is there a word or term for that, re-hybridizing? 🙂 to restore a dahlia's gene expressions to its intended ones?

Teddahlia

One of the oldest "tricks of the trade" for growing dahlia is the careful selection of your planting stock to be sure it is healthy and retains the characteristics it is supposed to have. Do we do enough of it here? HH Pink Tigress we grow has much less pink but grows healthy. Missed that selection. When the majority of the stock has "declined" commercial growers cruise the gardens for good examples and take cuttings to "re-vitalize" the stock. Why do they decline? The old funny reply from the 1960s was: "Why is there air?" I never got the meaning of that saying but I think it means in this case, that some stock is prone to a virus(and probably a virus not tested for) or is prone to genetic decline.
The why is less important than the cure of saving only good stock. Or, if all your stock goes bad , get new stock.
We still grow some of this never released 2020 seedling. Why? We like it but not enough to name and sell.

Teddahlia

HH Snowfire was a tricolor variegated but the breeders liked a sported version that was a red and white bicolor with out the pizzazz of the variegation or the extra yellow color. The breeders like the bicolor better but should probably try to get some of the tricolor version back.

bloomhjelm

It's unfortunate that the 800k sellers of dahlia tubers online give you only single photos to judge the soundness of their stock, but I don't know how you would remedy that. Take videos of every variety? Give every variety a grade? We spend so much time giving caveats on the size/firmness of tubers (if we think the buyer is going to be dissatisfied) but almost never tell each other when we suspect the stock has lost petal count, color, vigor, or developed any unsavory characteristics. (Well, hopefully we're not selling stock with blown centers but I wouldn't put it past a new seller.)

Bessie

bloomhjelm I very much appreciate when a seller has multiple photos of a variety. It helps me decide if the purchase is something I'll be satisfied with. When a website is exceptional, with several photos and relevant information, I always reach out to let them know how much I appreciate the information provided.

The American Rose Society publishes a booklet ( 2025 Handbook for Selecting Roses )with an overall grade for each rose variety based on multiple criteria. I used this booklet many years ago when I grew roses specifically to dry in silica gel.

@blown_dry it would a really cool ( also perhaps challenging to implement?) feature for the Dahlia Addict website to allow users and growers to "grade" varieties. What grade is assigned for varieties as a cut flower? What varieties do home growers like for a border, or for cut flowers? or for wedding work? How is the tuber production? How is the vigor? How is the disease resistance? On second thought, this may be it's own website 😃. Also, allow vetted users to upload photos of varieties, and those photos would by agreement be considered open source.

blown_dry

Bessie

Bessie it would a really cool ( also perhaps challenging to implement?) feature for the Dahlia Addict website to allow users and growers to "grade" varieties.

I would like to try to address this with a tagging system, so people could tag a variety as "tall" or "prolific" or "wedding." It's on my wish list!

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