Not a tuber to be found

bloomhjelm · 2024-10-18T20:36:25+00:00

I've seen an increase in photos from many growers of KA's dahlias which haven't produced any tubers in 120+ days. Obviously these plants have to produce so...

Bessie

I came across this Dahlia Photoperiod 10 minute video that talks about tuber formation and day length. I found the video/speaker a bit hard to understand, but the content speaks directly to tuber formation and cuttings(aka "liners"). His research indicates as soon as a Dahlia hits a certain day length it will start forming tubers.
1) Dahlia liners should be rooted with a 14 hour day length to promote vegetative growth and flowering
2) In some cultivars as little as 2 days of short day length will trigger tuber formation
3) There is varietal variation in the response to day length
My conclusion is you'll need a short day length to promote tuber formation. One of the concerns that I thought of is the darkness exposure when cuttings are shipped to a customer, which in theory might promote or initiate tuber formation and in turn stunt vegetative growth. He gives an email for questions at the end of the video.
Dahlia Photoperiod

SteveM

Bessie you'll need a short day length to promote tuber formation

Short day length (it is actually the long nights) will promote tuber formation but there are other stress factors that can promote tuber formation. Anecdotally, I have seen tuber formation promoted with extreme crowding of cuttings, even when grown under long days. I suspect other stresses such as (severe) under-fertilizing or under-watering will promote tubers. According to the research you linked to a few posts back, it seems cold temps might also promote tubers.

Bessie the concerns that I thought of is the darkness exposure when cuttings are shipped to a customer, which in theory might promote or initiate tuber formation and in turn stunt vegetative growth.

I turn my lights off when it rains, sometimes for several days, but I have never noticed any increase in tuber formation or a decrease in vegetative/root development. I don't think the time in darkness during shipping would have any effect if the cuttings were placed back on long days when they were received. Also, contrary to what the video says, I have found the effect to be reversible (takes about 6 weeks of long days) and does not interfere with normal plant growth later on. Again, there is a lot of room for controlled experiments in this area.

Bessie

SteveM your experience and knowledge is incredible! Thank you for taking the time to educate us. Have you considered writing a book on dahlias?

SteveM

Bessie Have you considered writing a book on dahlias?

Ha! I prefer to not have all of my lies published in one place. But thanks for the thought.🙂

Teddahlia

Steve M.:
Have you considered writing a book on dahlias?
😳 Does she know?

bloomhjelm

I polled the Dahlia Cuttings group on Facebook on the hours of light they use for new cuttings.

The majority of respondents give 14-16 hours of light daily, but the next most popular response was 24 hours. A few commented: 24 hours while rooting, 16 hours after rooted.

Also many, many new growers have asked on Facebook if they should dig tubers before or after frost, and I'm surprised in the replies no one has mentioned potential tuber growth as a factor in when to dig (other than: wait about 120 days).

Teddahlia

Tuber growth in cool weather is probably minimal. If you grow plants from cuttings in your garden and you want tubers, plant the rooted cuttings in the ground in 4 inch pots buried up to the rim and they will at the very least be nice pot tubers and at best and more typical, will give you the equivalent of 3 or 4 tubers. The plants will be full size and I will say that again they will be full sized, and you will also be able harvest quickly and store them in the pots and no need to divide until spring. All this talk about no tuber production from cuttings is solved using this method.

Caveat: I have never grow Stone House cuttings and it is possible that even this method may not work well. I doubt it.

NCDahlia

Plant out mothers day, dig them up halloween. Usually that's enough time. Bury the entire pot. Take a cutting of a cutting. All the FB groups crying about no tubers I bet less than 5% who paid $40 for a cutting take their own cuttings from the plant after it is out in the field.

As mentioned above the nice thing about pot tubers is you do not have to divide them in the fall (good for lazy ppl like me busy with work) you just store the whole thing with the dirt I have 2 4X8 foot hardware cloth tables I made that I store all my pot tubers on stacked high. My garage does not freeze on interior wall.

As for 2025 I did order 3 cuttings of the 2023 hollyhill waterlilies so i'll be taking cuttings of them once they are growing. And that's the only order I've placed for next year.

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