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This is nearly the time to start your tubers or pot tubers to take cuttings. There are so many different methods involved in this process that it would be a good thread for Cubits.
I generally am using pot tubers to provide my cutting material but do sprout lots of individual tubers also. I want to say that Dick Parshall and I both leave the tuber/pot tuber in the pot for the sprouting process. Others (Kristine Albrecht for example) place tubers in bins of damp potting soil.
Many people use Oasis cubes for rooting cuttings and are very enthusiastic about them. Dick Parshall uses them. I dislike them and do not use them. I may be in the minority but that does not bother me. Teresa Bergman of Cowlitz River Dahlias commented that she uses Oasis only because she roots and ships her cuttings and they are ideal for shipping.
So this thread is started and please comment or ask questions.
We like to place a sign on our porch that says: We are in the garden. Really, we are always in the garden.
Many people use Oasis cubes for rooting cuttings and are very enthusiastic about them. Dick Parshall uses them. I dislike them and do not use them. I may be in the minority but that does not bother me.
What medium do you use Ted? Last year I used Root Riot cubes and liked them. For me, my cuttings did better than ones I received which were is oasis foam, but I’m not sure if that was really a difference in medium or simply a matter of the cuttings not having to go through the shock of the shipping process.
For both mediums, I found that there was an annoying amount left at the end of the growing season. It was difficult to clean off the tubers.
Last year was my most successful year of taking cuttings. I'll usually take the cutting and put it in a little peat pot with some potting soil, soak it, then put it in a plastic bag in a warm place (usually with some sunlight), and they usually take root within a couple of weeks. I've never tried it with rooting hormone because dealing with that stuff weirds me out. Currently experimenting with 10 plants (grown from cuttings) in 1 gallon pots I've managed to keep alive this winter to get some pot tubers for more cuttings. I'd definitely be interested in trying out leaf node cuttings this year too.
For 25 years or so we have used germination mix, a peat moss based light potting soil that is basically sterile as far as any pathogens. The list of items that have been used by dahlia fanatics for rooting cuttings is probably over 50 items long and varies from a glass of water, to sterilized river sand, to vermiculite, perlite, rock wool( marijuana growers love rock wool), my germination mix and the now popular Oasis products. that are expensive but very popular with dahlia celebrities. Many more that I have forgotten.
I watched Kristine Albrecht on Instagram today but quit watching before she placed the cuttings into whatever medium she uses.
We like to place a sign on our porch that says: We are in the garden. Really, we are always in the garden.
I have tried many mediums, but ultimately landed on using ProMix germination blend potting soil. Use a new bag every year. The one year I used up the previous years bag I had molds growing (thankfully didn't harm the seedlings).
Using a thermostat controlled heat mat in my basement with the potting soil in my "incubator" (10x20 celled tray under a high dome) and keeping the mix wet is the perfect formula for my space. Everything stacks neatly on a 5 tier shelving unit.
Pro mix is not a brand that is prevalent here in the PNW. They do sell it at Concentrates(an organic and and everything garden store here in Portland) but they seem to sell everything from bat guano to azomite. We have Sunshine mix products. Our club is buying custom blend from a local company call OBC. They have it made by a local soil mix company.
We use about 30 cubic feet of it every year.
We like to place a sign on our porch that says: We are in the garden. Really, we are always in the garden.
I have given Root Riot cubes and Oasis cubes a go. Both are quite forgiving of overwatering and indulge impatience (constant inspection for roots).
However I agree wholeheartedly with Juliarugula that the rooting cubes don’t break down during the growing season. The same foam that holds the cubes together annoyingly masks eyes when dividing clumps. It will not be hosed away. Last spring I had leftover cubes to use and found myself picking away excess bits of foam, especially around the root nodes. After that experience, I am ready to join team germination mix.
Name: Steve San Diego Commercial cut flower grower
I use the 1" sheets of Oasis Rootcubes mainly because I can get 450+ cuttings on my 2' X 4' heating mat. These work well for varieties that I do 50+ cuttings one variety of at a time but do not work well for small quantities of cuttings because they are too difficult to keep labels secured. For small batches of a variety I use 50/50 perlite/Sunshine #3 in small pots. Also, as Janell mentioned, the oasis cubes annoyingly hide the eyes so if I am trying for tubers I break off the oasis before I transplant. With a little practice this is not too time consuming.
Here, the humidity is high enough that I never have to use any dome or plastic to enclose the cuttings while rooting. I water overhead once a day.
Oasis has it's uses that are mainly commercial. But it is personal preference what you use. I do it my way because I do not have to transplant the rooted cuttings to pots as they are already in a pot. Rooting is only part of the process and the whole process involves having a plant ready to go into the ground. The methods that people use in the cutting process seem to vary more than just about any part of growing dahlias.
There needs to be more discussion about going to LEDs although florescent still works for me but I am switching to LEDS as my florescent fixtures fail. Lots of people believe the kelvin is important but I am not much of a believer. The 3 weeks under the lights is just to get roots on the plants, not to grow 6 inch flowers on them.
We like to place a sign on our porch that says: We are in the garden. Really, we are always in the garden.
Name: Steve San Diego Commercial cut flower grower
As long as they are on for 16+ hours/day I have never noticed any difference between incandescent, fluorescent or LED. I used to think they had to be warm color until I accidentally bought cool bulbs and they seemed to work the same. But I have never done a serious comparison. I am now using a combination of fluorescent and LED.
Another discussion might be the importance of keeping the stock (mother) tubers under the same long day lighting while growing for cuttings. Should they be grown under the same long day lighting as the cuttings are when rooting?
Most of my lights are LED. I use 4’ shop lights, 2 fixtures (4 bulbs) per shelf on 18”x48”x72” five tier wire shelving units. Each unit accommodates 16 1020 flats and requires 8 shop lights. I am partial to Sunco shop lights as they have linkable fixtures, where like Christmas lights, I can plug one into the next, for up to 4 fixtures.
My old fluorescent lights had a low tolerance for stray water drops reaching them. I haven’t lost any LEDs yet. This part of my basement is 65 degrees and ~45% RH, so humidity domes are a must. When my heating pad was unplugged for a spell, I didn’t notice. The lights throw off a bit of heat.
I keep mothers and cuttings on the same timer with 16 hour light periods.
".....annoying amount left at the end of the growing season." Not just annoying as the stuff holds moisture and I lost a $30- pot tuber to rot as it had the stuff still around it and when you water it holds water close to the tuber. All things we use have positives and negatives. Oasis is expensive too but the frugals use very small amounts and just root the plant. When you devise a procedure that works well for you, there may be no good reason to switch as with any new procedure there will losses as you learn how to to use the new procedure.
HH Sweet 16 and it is a first or second year seedling in this old shot.
We like to place a sign on our porch that says: We are in the garden. Really, we are always in the garden.
The one thing that I’ve found to be inconsistent is the rule that 16-17 hrs of light = feeder roots and less than 12 = tuber and flower production. I’ve had cuttings that were still in the 16-17 hr spot starting tubers. Wondering if others have had the same experience? Also, how long do folks usually keep the cuttings under longer day lengths before moving to shorter? (If growing year round.)
Name: Steve San Diego Commercial cut flower grower
Erika, plants grown under long days will eventually develop tubers, just not as fast, or as many, as plants grown under short days. The length of time it takes to develop tubers varies with the cultivar and other variables. (plant stress, root confinement, low fertilizer).
Technically, Dahlia is a short day (long night) plant which means flowering and tuber formation is initiated under periods of long dark periods. However, the best blooms are formed under long days (short nights). There is also the caveat that if the days are too short the plants will not bloom and will go dormant.
Anecdotally, I have noticed cuttings taken from field plants grown under short fall days, and that have quit blooming, will not root. Instead, they form calluses (small tubers) where the roots should be. This will happen even if the cuttings are under long days. This is equivalent to trying to root cuttings under short days.
I have also had cuttings form tubers under long days if I leave them in the oasis for too many weeks before transplanting (stresslng the plant).
My father, and many excellent growers, leave cuttings under lights 24/7 until rooted. I'm guessing these cuttings would root even faster than the 16 hour light period I use.
It will be very interesting to see how your dahlias perform when buds are set under your super-long days of summer.
Thanks Steve. I think I need to be better about documenting which cultivars do what under what conditions. I should know that by now - I do it enough with my rhubarb research. Would give me some data to help inform my cuttings approach when growing over the Winter in my cabin.
You guys want a good laugh?!? These are currently sitting in a very chilly bay window and are last years cuttings that never made it to their ‘pot up’ let alone outside. I have no idea what will happen now, but I suppose I’ll pot up these poor little survivors and see what happens. They deserve a chance now
I have no idea what will happen now, but I suppose I’ll pot up these poor little survivors and see what happens. They deserve a chance now 
