Taking Dahlia Cuttings

blown_dry I use a similar system. For some varieties I keep perpetual mother plants growing in my greenhouse and I also mark the best field plants to use as mother plants. About 90% of my field plants are from cuttings. I still assume most, if not all, of my stock has one or more viruses. I rogue any plants that are suspect but I am not concerned about virus when a plant shows no symptoms. If a plant has a virus but is asymptomatic I assume it has a weakened strain, has some resistance, or has aquired some cross protection. I don't sterilize my clippers when doing cuttings from my own mother plants. I do when taking cuttings from new stock I have purchased.

Bessie Dahlias root just fine WITHOUT rooting hormone

SteveM An important distinction not being addressed in the USU studies is that the DMV-D10 variant was determined to be an incomplete version of the DMV virus which has become integrated into the dahlia genome. Thus its transmission in the seeds. The paper was published in 2008 and is available at:
https://www.sciencedirect.com/science/article/pii/S0042682208001724

DMV-D10 is now referred to as an EPRV or EPRS (Endogenous Pararetrovirus or Endogenous Pararetroviral Sequence). DMV-Portland and DMV-Holland are now called DMV and DCMV (Dahlia Common Mosaic Virus) respectively. Since USU is using the outdated terminology and not distinguishing the integrated DMV-D10, and has not given the date of their study, their information here is of limited use. The virus team was contacted about this article in late 2021, and Dr Pappu wrote to USU then, explaining the need to update their information and testing, but the article has not been changed since. I wonder what they are using for testing.

PNWGal it's great to have someone likje you available with the latest information on dahlia virus research. I don't know why USU hasn't updated their web info but it probably has to do with the fact they had to stop both of their last two studies because of diseased stock. Hopefully they will get some results this year and update their web page.
Do you know if Dr. Pappu has any info on the mechanical transmision of the DMV variants?Especially as related to field cut-flower commercial operations. Maybe we should start a new dahlia virus thread, it would be nice to have virus info in one place

SteveM Steve, I'm watching a YouTube video Dr. Pappu created on Dahlia virus. I was just thinking there needs to be a Dahlia Diseases thread. Part of the video points out it may be difficult at times to distinguish between nutritional deficiencies and virus symptoms. Therefore, the discussion of virus and nutrition overlap. Some of the information is basic, but is a good starting point for those new to the topic.

Teddahlia I always have a problem with advice that is not backed up by actual research. In this case, they should use some contaminated tools and see if they can spread the virus that way.

I agree completely on the need to do actual research. The team asked Dr Pappu about doing some experiments like this on virus transfer. His response was that transfer via contaminated cutting tools was so well known that it was not worth while (for the WSU staff, anyway) to do another. Ron Miner (head of the ADS virus research team) did an experiment on his own. He had grown plants of an (unpromising) seedling in the middle of a patch of plants with virus, for four years, and none of those seedling plants ever tested positive for virus. Then he made multiple cuts on a plant which had tested positive for TSV earlier in the season, and then on one branch of one of the seedling plants. He cleaned his clippers, and then made a single cut on the infected plant, followed by two cuts, one on each side of a second seedling plant. A month later, both seedling plants tested positive for TSV. A small sample, but worth noting.

There's a new thread called "Virus and Nutritional problems" where I posted the link to Dr. Pappu's May 8, 2022 YouTube video.

Ted and Noni, was that the Portland DS meeting, or another one on Tues? I didn't get notified of that one, if it was. I love reading information on viruses....it's so interesting. If you're on FB, Darce is an admin on Friends Dahlia Clinic, with some pretty interesting threads and pictures.

PNWGal so is it possible that plants testing positive for DMV or DCMV could actually have EPRV/EPRS?

JessE Yes, I watched the PDS meeting by zoom that night since temps were falling to the low 20's and I did not want to deal with icy roads. HOwever, I had a lot of trouble hearing the talk...just not as well produced as most of the zoom meetings I have attended. I know the guy doing the demo (Name escapes my tired brain at the moment) is really experienced and I was sorry not to be able to follow it better. Every year he sells a lot of rooted cutting of really desirable plants at our meetings!.I have managed to be the top bidder on a few of them...He also propagated and and still does some of my early Salish Varieties so that I was able to get them back after my move. Ah yes, Mark...That is his name. His wife was also an excellent tour guide for the 2003 National SHow and I believe she is doing it again this time..
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Of the 43 cuttings I took on 2/6, 24 of them are showing roots. The interesting thing about this is that our day length is around 11 hours, 30 minutes (I’m in Hawaii). They were kept outside in an area that normally gets bright shade, though it has been quite overcast this week. Temperatures 65-80 or so and we have high humidity (70-80%) which works to my advantage, I think. If there are some that don’t root, I will put them under lights to see if they prefer that. I am curious to see if the ones that rooted under short days are less sensitive to photoperiod overall.

That's interesting, I wouldn't expect such rooting success with under 12 hours of day length. But, I don't know exactly what intensity of natural light is needed to interrupt the dark period. Is the "Day Length"" oosted on weather sites the same "length of day" a dahlia needs for vegetative growth or does it correspond more closely to "Civil Twilight" or "Length of Visible Light ".

I would have bet money that Honolulu HI was north of San Diego and I would have lost big time. Are you able to grow fully double dahlias year-round (without lights) at your latitude?

I leave my florescent lights on for 24 hours a day. As they get old they put out less light. I put some really bright LED bulbs(cheap ones ,color unknown) on one shelf and there was probably about 40-50% more light than the old florescent shelf. The cuttings rooted faster in the increased light but only by a couple of days and in the big picture that is not enough to change out everything to LED until more of the the florescents wear out. But I was impressed that the LEDS caused green growth and the leaves were bigger and the plants grew taller. More light is a good thing.

I'm still experimenting with the optimal light time parameters. Since I live in a cabin with a loft, leaving lights on 24/7 isn't really an option unless I don't want to sleep too. So, I have my new cuttings in the kitchen and my office area where they have 15 hours of light. Then, after about 2 months of that, I move them upstairs into the loft where they have 12 1/2. Since my goal is to get the ones I grow over the Winter to produce tubers, I've tried going below 12 1/2 (to 11 or 11 1/2) but haven't found that to have any real difference. I know the standard is "above 12 hours they grow feeder roots, below 12 they grow tubers) but if they were outside, they'd still be getting more than 12 hours of light a day in late July/August/early September when they're building tubers so I don't think that's a hard & fast rule.

PNWGal
I agree. Every virus has different properties and modes of transmission. Some viruses are more environmentally stable like TMV, others won't even survive a few minutes of air or sunlight - with or without plant juice. So unfortunately, every discussion about virus transmission has to be specific to a particular virus or virus family.

I wouldn't be worried about spreading viruses between cuttings through the shared water in a tray. The stems of the cuttings would have to be actively infected and release large amounts of virus particles into the water or the soil (unlikely). The water/virus concerns apply primarily to hydroponics or large scale growers who recycle their water multiple times (as in greenhouses).
To avoid spreading absolutely anything between cuttings, one would have to disinfect the plant material and all tools using protocols for tissue culture (orchids for example) plus grow the cuttings under sterile conditions in special containers and growth chambers.
I saw some dahlia growers are planning to do that. I expect they will charge $40+ for each precious virus-free dahlia cutting - which of course will get rapidly infected as soon as it's planted outside....

Virus resistant or at least virus tolerant varieties will really be a better way.

SteveM I was pleasantly surprised, this is the earliest I have taken cuttings. We do have high light intensity at 22 degrees North latitude. However, cuttings I have taken in the fall under similar day length failed to root, I will try again this year. Perhaps they can sense lengthening vs shortening days.

Without supplemental lighting, dahlias do not grow well year round here. Around late September/October, bloom quality declines. I stop watering and they go dormant. The ones I have left growing over winter kind of just stop growing, they keep their leaves but not really growing. An odd flower here or there but with weak stems and poor centers. One of my goals is to add lighting and try growing year round, but I’m not there yet.

HiDahlia Perhaps they can sense lengthening vs shortening days

To me that sounds entirely possible. I am at 33 degrees north and with most varieties the flower quality declines to the semi-double state the third week in October and they quit blooming soon after. Most varieties I grow don't vary from that time by more than a few weeks. With 2 hours of supplemental lighting I can grow through December (after then the soil temp here is too cold to grow dahlias). Without supplemental lighting my plants follow the exact same pattern of decline as you describe and I am not able to root cuttings taken from these very late Fall plants.

It will be interesting to follow your lighting experiments.

I have a question.
I sourced tubers of the same variety from 2 different people this fall and I have them both in my cuttings tray to propagate more. The sprouts on one tuber start out very purple/maroon and stay that way until they get larger, while the other are quite green from the start. Neither are large enough for me to compare full leaves, however it brought a question to mind.
Is it possible for the same variety to produce different colored sprouts? Would it perhaps have to do with where those tubers were initially grown (in this case 1 was nearby and the other from halfway across the country). Or would another factor change the color of the sprout? Or should I assume that one (or both) are mislabeled?
I can't remember ever seeing this but I've only ever sprouted tubers of the same variety that all came from one place or were from my own stock.

"Is it possible for the same variety to produce different colored sprouts?" Yes.