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MissyWeitzel Is it my light ratio while the cuttings are rooting?

Yes, your 12 hour nights are right on the edge of not forming roots. If you gave even longer nights your cuttings will only callus over and not form roots at all. For me, cuttings that have only roots are more desirable than cuttings with tubers. In addition to starting faster when planted out, the first blooms are fully double instead of open-centered. The long day length treatment is especially important if you grow seedlings and plant the seedlings out early in the spring. At my latitude, I will not get fully double blooms if I plant outside when the day length is less than 12.5 hours (April 1)

Any (most) commercial grower that ships cuttings will root the cuttings under long-day lighting . Some growers leave the lights on 24/7 to ensure vegetative growth and fast rooting. I keep my lights on for 16 hours and don't like to go much shorter than that. The mother plants also need to be kept on a long day schedule.

Maybe I am straying from the original question...

      MissyWeitzel The 12/12 ratio you are using might be the secret to growing early pot tubers and something I will consider if I ever decide to sell pot tubers. Too many experiments, not enough time!

        MissyWeitzel do the 12 on, 12 off cuttings adjust to longer days without any issue when you transition them outside in the spring?

            KitCMC Yes! Usually I harden them off pretty slowly so it isn't such a shock. Shade for a couple hours for a day, then 1 hour of sun and a few hours of shade, then 2 hours of sun, etc. over a week to 10 days.
            Last year I accidentally went too fast with sun exposure and I killed a bunch of them, but I won't make that mistake again! I will now set a timer on my phone so I remember to get them out of the sun at the appropriate times. When late April and early May weather cooperates, I actually have them all living outside in trays for several weeks before planting. They go in the garage at night if the temperature drops, but I always feel a lot better planting them out when they have been accustomed to the temperature fluctuations in addition to light differences for as long as possible!

                a month later

                I was looking over my cutting tray this evening and noticed that a potted tuber has some greenish mold on the crown area, around the sprouts. I separated it from the "herd" immediately. I've taken one cutting from this one, which luckily has already rooted. Pics of mold below.

                I will make sure to reduce the general moisture/humidity, but is there anything I can do to prevent mold from spreading through this area like wildfire? This one, and all the others, are potted in Pro-Mix BX.
                Does anyone have advice for how to help this particular tuber? Is it trash? I would love to get another cutting or to at least plant it. I think one/some of you have mentioned lysol . . .


                24 days later

                Since I'm only still experimenting with cuttings myself, I have a question about a cutting I received.
                The cutting
                Arrived in a clam shell
                Securely packaged
                The total length of the plant is 7.5"
                2" was the rooted area wrapped in a wet paper towel
                3 leaf sets were removed from the soil medium up 3"
                The top 3" had 3 small leaf sets

                The cutting is now dying and has severe powdery mildew.

                I potted it up on day two. I've had it 4 days and I have to throw it away. Edit: I'm going to cut it down and see if it regrows.

                I have successfully potted up 5 cuttings and taken getting ready to pot up a sixth I received from a society friend in a 2" pot last Tuesday. All six of these plants look great.

                Is the plant dying because so many leaf sets were removed? Is it more likely to get powdery mildew because it's trying to recover from the leafs being removed?

                  I just got off the phone with club member who has powdery mildew on a cutting plant he got from a friend. Comment: If it ain't fungus gnats it's powdery mildew. 😳
                  The least "chemical " solution is hydrogen peroxide. 3 to 1 as a spray on the leaves, once per week. More powerful chemicals are out there but if this works, hydrogen peroxide is very safe.
                  Tubers die generally because thy have rot and it is generally incurable., although surgery may save it. The powdery mildew you get from "friends" may be a version that is hard to control.

                  MIDahlias Is the plant dying because so many leaf sets were removed? Is it more likely to get powdery mildew because it's trying to recover from the leafs being removed?

                  I'm guessing the vendor removed the lower leaves before shipping because they were mildewed. I would notify the vendor and let them know of the mildew. A good vendor will want to know and will probably offer you a refund or replacement.

                  If you try to save it I would do as Ted recommends. And keep it away from your healthy plants.

                    Well I made the mistake of taking my time with digging up my tubers and should've just left them in the ground as the sprouts are quite big. They're already withering today and I'm not sure if that's gonna ruin the eye for good if it continues. Should I just slice off the sprouts for now and take what I can for cuttings to save the eyes on the tubers?

                      edewitt In the past I have dug clumps with 6-8" sprouts and chopped the clump in half (with a shovel) and immediately replanted with 2-3 sprouts/clump. They looked pretty sad for a few days but eventually took off. I don't know how it would damage the eyes unless the sprout rotted back to the crown. I would probably water them in well and give them some shade, if possible. Your air is less humid than mine but I would give them a few more days to see if they recover.

                        edewitt I'm never sure what to do with those either. That said, I don't think you have to worry about damage to the eyes. My limited experience is that if you divide conventionally, the big sprouts are often a loss and you may as well cut them off, but the tuber will perform fine, ultimately. The only loss is some growing time and maybe not much of that.

                          7 days later

                          I'm sorry - it's late and i don't have time to look back through almost 500 posts in this thread. I have a dilemma. My friend dug her Taratahi Ruby (which I had given her many years back). It seems to be weak and dying out. She gave me one tuber which had winter rot and didn't make it through storage. She gave me another; this one has a long sprout about a foot long and it was a double tuber start, but one was completely rotten and the rot looks to be in the remaining tuber when I went to cut off the rotted tuber, so I want to try to use this long cutting which is beginning to color up; it's not white anymore - because I think the tuber won't make it. Her double tuber seems OK - I left her the good one but I suspect the whole plant got rot in all its tubers and hers might die too.

                          If it could be rooted, how would I cut it down? close to the tuber or leave some sprout, even with no leaves? It is so long and spindly and I don't even think it has made two sets of leaves yet but everything is up near the sprout end. Has anyone tried this to save one of their dahlia varieties - and would it even work? Day lengths are rapidly increasing; maybe 15 hrs now. I've wanted Taratahi Ruby back for many years and have never had luck obtaining one in the dahlia sales. I don't even know if I have any rooting hormone but i can get some in the morning. would I need to make a little 'mini' greenhouse to hold in moisture while it roots?
                          I am going to try to find an article on this. If I need to buy rooting hormone, what should i buy? I remember someone talking about mycorrhizal rooting hormone and that they like it better - if i can get anything like that on an island with few choices.

                          What medium should I use and how deep to bury the end, if there are no obvious leaf nodes?How would the roots form if I didn't have at least one leaf node buried?

                          I also have a few 1" or shorter sprouts that have broken off. It's late but I thought to try cuttings on those, just as an experiment. Would any of these have the chance of making any tubers? I'm sorry if this is elementary and redundant or in the wrong thread. Any references, even to a post in this thread by its number, would be appreciated. If i am wasting my time and energy for no return, just tell me to forget it since I still have over too many tubers to plant in an overgrown, weedy garden so things are taking way longer than anticipated.

                            I have taken so many cuttings over the years that it is difficult to give advice to someone who has not done so. We stopped using rooting hormones about 25 years ago. Dahlias root fine without them and they may help some and with the recent advances in chemistry that I see , you may be able to get a picture of dahlia to root. We chose not to expose ourselves to concentrated, modified plant hormones when it is not necessary as cancer could be the outcome. When rooting disasters like yours, my key takeaway is to get the sprout off of the rotten tuber right away. Then cut off any rot and hope the remaining tuber piece sends up another sprout. I would cut up a long sprout into pieces each with two internodes, one for roots and one for stalk and leaves. The one for roots goes under the rooting medium(we use a peat moss based germination mix) and then water it and place it under some indoor light source and it may or may not root. Please get opinions form others as explaining something so simple to me is impossible.

                            Thanks - you did fine explaining something so simple to you - I understood your instructions very well. I have nothing to lose. Plus you saved me money on rooting hormone! 🙂

                            Nothing tried, nothing gained. Will do as advised and see what happens. So far, there is no rot at all on the sprout. I see a lot of dark at the eye end of the tuber so am not holding out much hope for it since I think the rot is throughout and came in through the stalk. which is how it usually gets in to my tubers.

                            Dahlia53 In addition to what Ted said:

                            • If you are taken cuttings inside it is probably pretty dry air so most growers will place the cutting inside a plastic bag (or similar) which is closed at the top. This is to keep the humidity high until rooted. I do my cuttings outsider and the humidity here is high enough that I don't need an enclosure to raise humidity. Also, if doing inside, keep the lights on for 16+ hours/day to encourage roots.

                            • Keep the temperature at 70-75F. High temps + high humidity will rot the cuttings.

                                I was successful with a couple of trays of cuttings this year. I'm now trying to up pot them from 1" trays and I only have 32 oz deli cups. I wish I would have invested in 4x4 pots. One of the dahlia societies orders in bulk and they were 10cents each (i think) back in January.

                                  MIDahlias I like the square pots and trays from Greenhouse Megastore. Not 10 cents each, but they were reasonably priced and sturdy enough to run through the dishwasher at the end of the season. The 4.5”x4.5” are nice to give early cuttings lots of room.

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