Pot Roots

MissyWeitzel

I know we have discussed pot roots before but I couldn't find it and it didn't have its own thread so I'm starting one. I know I read about it in one of my ADS bulletins but I have been looking with no luck for the past hour. I haven't done this before and I have a few questions. I have a few hard to store, not good tuber makers I want to create back ups for.

Are 4" x 4" pots large enough?
Should I use potting soil or something else?
Do I essentially just take cuttings now, root them in their pots in the shade, then sink the pots out in the garden once rooted? Or do you start them inside under grow lights then harden off, then grow outside?
Do I do anything different with the plants themselves once growing outside? Cut buds off? Keep small?

Thank you for any advice you can give me.

Flowernut

MissyWeitzel I became a pot root grower one year when one of my sprouts broke off Lynn Slight (I love her, Steve) while planting. I threw it in a cup with water, placed under lights and waited for it to root. After rooting, I potted up in a 4" x 4" container and added a potting soil that is very light. After a couple of weeks and after hardening, I planted with all my other dahlias and it grew into a full sized plant with perfect flowers. I can't comment on pot tubers that you are growing just to save the cultivar due to poor keeping capabilities.

Teddahlia

Are 4" x 4" pots large enough? Yes an no. One size bigger is better but not necessary.
Should I use potting soil or something else? Good quality potting soil is what I have used for 30 years.
Do I essentially just take cuttings now, root them in their pots in the shade, then sink the pots out in the garden once rooted? Or do you start them inside under grow lights then harden off, then grow outside? No.
Do I do anything different with the plants themselves once growing outside? Cut buds off? Keep small? No

Do I essentially just take cuttings now, root them in their pots in the shade, then sink the pots out in the garden once rooted? Or do you start them inside under grow lights then harden off, then grow outside? I bet you did not like a one word answer. We root cuttings in very small pots and transplant the rooted cutting to the 4-5 inch pots using good potting soil. Then they can become either "sink pots" or "pot tubers" and there is big difference. Pot roots are grown on top of the soil or a bench and are kept small by "neglect". Their purpose is to provide cuttings for next year and they do not bloom. A sink pot is buried in the soil and it's purpose is to provide a full sized plant for your garden and then an easily dug pot in the Fall. They do not provide many tubers and the roots will be contorted in the pot that will be demolished.

MIDahlias

Teddahlia does the depth of the pot matter? I'm looking at purchasing one of the three highlighted in yellow. A couple of reviews on the pots claim the 4.25" pots crack easier than the smaller pots. The 4" pots are not as deep as the 3.5" pots. Which would you purchase?

MissyWeitzel

Very, very helpful. Thanks for taking time to answer my questions!

Teddahlia

ALL OUR 4 INCH POTS ARE RE-CYCLED FROM PURCHASES OR GARBAGE HEAPS. One brand that is 5% better(not much better ) HC. I saw McConkey on one pot and Gage on another. In my opinion they are all cheap flimsy pots good for one or two years and only one year if a dahlia plant is buried in the pot. Our pots are 4.25 x 3.6 x 3.4 approx.

A "7" inch pot by Gage called Durapot 500 is a very large super heavy duty pot that costs lot of money per pot. One geranium nursery where we buy geraniums uses them and I believe they cost $.35 each. They charge $7.00 for the geraniums but they are very large , well grown plants.

silvarerum

I am super into this pot roots thread. It's very annoying to search for "pot tubers" in Google bc you will get 8m posts about how to start your dahlias early in the spring in pots rather than the purposeful growing of pot tubers to be saved over winter. So thank you Missy for starting this thread. (I have, in the past, read all the posts I could find on cubits about this, thank you Ted and other growers for imparting all of your hard won wisdom. )

Groundhogs and maybe also chipmunks (??? think they got trained up on eating my tulip bulbs and are now numerous, monstrous eaters) ate ALL of my dahlia plants down to the nubs, repeatedly, mercilessly. Various rodent solutions would work for a bit, but when it rained would be washed away and next morning any growth eaten to nubs. They even dug tubers out of the ground?! It's been a battle. My surviving plants are 20" high max and NO FLOWERS.

It's quite sad, really, to have no dahlias this season.

The silver lining is (I hope!) that I never planted out my $$ mail order cuttings. I was too afraid to lose them to the rodents and left them in 4" pots on a table. I did have a grand plan to do a lot of pot tubers this year, purposefully, but these were inadvertent till in August I realized, "I accidentally have a table of pot tubers." I'd read in cubits that pot tubers thrive on neglect. So, check! It's super interesting to me that some are chock full of baby tubers and some have nothing but roots, even after the whole summer.

Some of are really outgrowing the little 4" pots so I moved into slightly larger pots. But I am wondering if it makes sense to pot up the chonkier plants, or leave them confined especially now as we are getting to shorter days. Is it the confining that does the magic? Do I want the little pots as dense with roots as possible? And will the pot tubers that are just masses of roots make it over the winter?

Finally, does it make sense to keep these guys going as long as possible in a protected environment? (Temp steady basement under lights, for ex.) Reading about insects in overwintered outdoor plants has me a little bit concerned. Do I want to swap out the soil? I often overwinter whole clumps of plants in pots and haven't had problems but thinking about some of these delicate rootballs.

Thanks! Meghan

Teddahlia

"And will the pot tubers that are just masses of roots make it over the winter?" Think about that statement in relation to the same variety planted in the garden and having a propensity to make only hair roots. Keeping over the garden grown plant results in nothing but a dried up or rotten mess that does not grow. The pot tuber, however has a chance to grow and send up some cuttings because you have not disturbed it and the soil from the pot surrounds it and protects it. I will not say that all or maybe even a majority of the pot tubers will succeed but there is a lot more hope for them than the plants grown in the ground. And, if you remember these varieties in pot root pots may benefit from a balanced fertilizer(still in minute amounts). I say balanced because all three, elements, NPK are needed to make tubers.
Pot roots take less time to make enough roots and unless you created them very late in the season, they will have enough roots without further growing inside.
I will say that the ultimate best way to keep over a very poor tuber maker and Mi Wong would be an example, is to grow the plant in a large pot, and perhaps for Mi Wong that would be a 4 gallon or 5 gallon pot. Mike Riordan grew his Mi Wong for 4 or 5 years in that same pot and had nice sprouts for cutting. He never disturbed the root ball in the pot.
Note: Mike Riordan and I are the same age but he began growing dahlias when he was 16 years old and is still growing them some 61 years later.
Mi Wong; some say the very best show pom.

Teddahlia

Pot tubers that succeed: Most of my pot tubers store very well. Poor tuber maker varieties have a lesser success rate and I remember a quote from a commercial grower where he said a 75% success rate was good for poor keepers and his worst was about 50%. The success rate for average or good tuber makers is probably well over 90%. So, for poor tuber makers, you need to do several pot tubers to be sure you keep it. That is not a very hard thing to do as they need so little care. Pot tubers are the best thing since sliced bread. That is a stupid old quote. Years ago, I had an occasion to talk to an emergency room doctor. I asked what kinds of cases showed up in the emergency room. At that time bagels had become very popular. He said one of the most common things was people trying to slice a bagel with a knife and cutting themselves. Perhaps sliced bread was a big deal.

Krista

Will micro tubers (smaller than an AA battery) be suitable to grow as pot tubers (above ground in 4” pots) vs cuttings? I think I’ve read folks have done this with their smaller, extra tubers but wanted to head off any issues I may be missing.

Bessie

Krista Hi Krista! I made some cuttings of my seedlings in August of last year, at the time when the gophers were attacking while I was on vacation. On a sunny day in January I decided to dig the "cuttings" up that were in the growing bed in regular soil. The tubers were attached to the "cutting" and were no larger than small to medium size grapes, with one or two of the cuttings forming a small tuber cluster. I placed them in small baggies in storage and maybe a month later I potted them up in small yogurt cups. I watered them very carefully. When they sprouted, I placed them in a cool area under LED lights. When they were well rooted, and seemed well on their way to growing, I potted them up into deep 4" pots. At that point they went under warm lights. They've been outside for several weeks(zone 9b) and are doing great. I hope they continue to do well, since a few are the only genetic material I have of some of the most promising 2024 seedlings.
I can understand how a professional grower would not have time to deal with tiny tubers! However, when it's your only source of the genetic material it is worth the effort. I'll post some pictures.

The middle one didn't survive/sprout, but the others did fantastic.

SteveM

Krista Will micro tubers (smaller than an AA battery) be suitable to grow as pot tubers (above ground in 4” pots) vs cuttings?

if the micro tubers sprout they will do as well in 4" pots as the cuttings and probably produce a nicer formed (is that a term?) clump of tubers than the cuttings. I haven't tried it but I would bet that, if I planted a 6" tall plant grown from a micro tuber, a regular tuber, and a cutting, into the field that I wouldn't be able to tell the plants apart in August. I often keep (and grow) thumbnail size tubers that were grown from cuttings in a 72 cell tray.

Teddahlia

I do not waste a 4 inch pot full of expensive potting soil and my good space under the lights trying to grow those miniature tubers that have a checkered success rate(most grow but some do not).

However, I start them in a very small 2.5 inch pot and if and when they are a nice plant, transfer them to the 4 inch pot. Some varieties make lots of them and the most prolific miniature tuber maker for me is Scott's Snowcap. You can get lots of "quails egg" tubers from it and they store well too. Remember too that very small tubers have very small sprouts and take a long time to get to a full sized plant. I sometimes plant them in the garden but put two in the same hole.
This picture has absolutely nothing to do with this post. New variety of orange I bought at the Fred Meyer store., Flesh is also darker and taste is darker too(less sweet but tasty).

Krista

Teddahlia miniature tubers that have a checkered success rate

This is really good to find out, Thank You! The mantras I have heard over and over seem to be iterations of “no matter the tuber size, the plant will grow the same.” Great to find out that the minis may not be worth the time or space.

KitCMC

Teddahlia is that a “blood orange?”

Krista

Bessie SteveM
Thank You! This is definitely more like what I’ve heard about small tubers. I quite a few minis that are the only genetic material I have of some varieties, since last year was such a bomb of a grow season for me.

Thanks for sharing your experiences with these little guys, I am encouraged and will take the time and space to pot them up after all! 🌱

Teddahlia

KitCMC We tossed the bag but I believe it is a type of blood orange. Probably a sport that has more "blood."

KitCMC

Teddahlia bloodiest orange 😂

Dahlia53

Please forgive my ignorance about pot tubers... I thought that they were grown from a small tuber in a 4" pot, but in reading this I see I might have had it wrong all this time. They're grown from cuttings? I ask because I want to keep some varieties, yet not put them in the ground. I have some small tubers that would easily fit into a 4" pot, Dick Parshall style, but I think it's far too late for cuttings and I don't have lights or a grow setup, I'm a long time hobbyist. Maybe I should just let the varieties I'm on the fence about, go. I only have energy and time this year for about 50 varieties and I have 70 and like or love them all so I thought pot tubers might help me to dither about them for one more year.

I just pulled the saran wrapped tubers out of storage and they look good, no sprouts on most yet, or sprouts just beginning.. I love the saran wrap for that.

I have another question about how to tell good stock from bad, and if open centers the first year you grow a variety means that variety is bad stock and will always have open centers - but maybe that is for another thread.

Thanks as always, Ted and other pros who patiently help answer our questions.

Teddahlia

A pot root is most often created from a rooted cutting but small tuber pot roots are just fine, if you know the stock is good. A rooted cutting already has leaves and diseased plants are culled but a tuber is a "pig in a poke " Many people do "big tuber" pot roots too but the tuber needs to be reduced in size to fit the pot in many cases. I have found that the big tuber pot roots rot more often as the tuber is getting old and subject to rot as compared to a rooted cutting that has all new roots.
I knew a person who knew he was moving and he potted up 200 gallon pots with his favorite varieties and had a 98% success rate when he planted them at his new house the next year.
One of the advantages of pot roots is that they take almost no space in the garden. In the UK I found out that "dahlia variety collectors" would save most of their varieties only as pot roots for several years at a time as they had very small gardens but wanted to keep over their favorites for a later year. I have saved one for 6 years and then grew it and it was perfectly healthy.

Open centers issues demands a long post but we cull them if we have other
good stock. Why chance it?

Dahlia53

Teddahlia Thanks so much for this detailed answer to my questions. I will cull the open centered ones and focus on small tuber pot roots and ask any questions at the next dahlia talk - or if you know of some good articles on pot tubers, I am interested in growing about 30+ varieties and keeping them in the 4" pots if there's a way not to plant those in the ground. (and how to keep them alive in such tiny pots.) I wonder if growing the small tubers point-down is advisable. I tried some of this in the garden last year a la Dick Parshall but didn't take good enough notes on which ones were planted that way. I think everything made tubers, though.

I may be losing this garden space of 14 years (not my land) so I probably should try to make pot tubers of all my favorites, but I'm in a 3 month intensive course and had to go back to gardening work to pay for it in my 70s, so I'm not really functioning that well in the garden! 😄