hmm....interesting. Hi David. I have been growing dahlia's in pots for the past 3-4 years in Emeryville. You are aware of so many things. What comes to mind is the amount of sun they are receiving. What does the flower look like; its shape/form and size?

For some reason the energy went into creating tubers and not stems/leaves/buds/flowers...I am really interested to hear what people offer up as possibilities.

It also sounds like the pot may need to be larger if you don't dig them up every couple of years. I found that the dahlias I grew last year didn't flower that much..what came to mind was that they probably needed greater access to prolonged water and also to be fertilized. I didn't fertilize last year. I may be having a similar experience.

Let's see what responses come forth...very best

My take is that it just needed to be divided. With a large tuber clump the plant feels like it is fat, happy, and lazy - no need to do any extra work like putting out flowers. Most experienced Dahlia growers plant only one tuber per year in order to get the best plants.
Gail

Gail is right- if you don't divide the clump at least every other year, the plant will become less & less vigorous. It has no reason to put out blooms to propagate itself so it relies on the huge tuber mass. To keep your dahlias producing nice plants & lots of blooms, divide every year & only plant one tuber or two attached together at the most. If you don't need to dig & store over the winter then you can just dig, divide & replant in the spring.

Many thanks to all.

I was already leaning toward the theory that all the energy was going BELOW ground instead of above ground I just didn't know if this was common or possible) so I am appreciative of your answers. I decided to run an experiment this year.

Firstly, I see several new shoots already in the tubers so I am going to divide into 2-3 plantable tubers. I am going to MOVE the pot to another location and plant a tuber in it (to see if it is the pot or not) but I am going to put the other tuber in the same location but in the dirt instead of in a pot. I am also feeding them this year with manure tea, so if all goes well and ALL bloom well, I won't really know what worked, but I'll have a slew of pretty dahlias!.

And I guess I better check the other dahlias too in casing they are heading to TUBERVILLE instead of heaven.

I'll keep you updated.

And just to annoy those who live where the ground still has snow, I actually have a new dahlia that I planted in January that has sent up a large stem already - in fact, it started poking up in late February. Even I am stunned at this development as most of my dahlias don't come up before April May and NEVER have I had one start before the first rose blooms (early April).

I wonder if I can credit this to global warming?

"heading to tuberville instead of heaven"...I love it! Thanks David.

Thanks Gail & Plantlady2008, the information you provided has solved an increasing issue for me...dahlias that are flowering less. I will now have more blooms again thanks to you sharing your know-how of growing dahlias.

I am glad you posted this David!

What a wonderful resource we all can be to each other. Thank you Gardenweb.com!

Very Best Dahlia Season to you all!

allie

New to dahlias, have a non-bloomer I got from a swap, so now I'm going to see if I have enough brains to divide it correctly. Thanks goodness for the internet!

Do you have an update on your experiment? I'd love to hear what happened!

It's funny you should ask. I was going to post an update after the season when I dug them up but I'll tell you what happened as far as the experiment went.

I never got around to planting any tubers in the ground but I did replant in the same clay pot as well as in 3 other plastic pots which were then located in other areas.

ALL (but one) came up, ALL gave me 3-4 blooms and then sat there for the rest of the summer like a doorknob - just like my original dilemma. It appeared that a couple of laterals were being produced but nothing ever happened. Of the locations I planted them in, one was in a bright sunny part, 2 were in the 'back' where they get filtered sun until 1pm but then sun all day. (The one that never bloomed at all was in this area.)

What this tells me is the advice I got about dividing the tubers every year was sound, simply because last year it never bloomed at all. But methinks I simply have a lousy dahlia. For 4 out of 5 to only give 4 blooms each tells me this dahlias was a sprinter and not a distance runner. I fully expect that I will have numerous tubers in each pot also, which will only confirm that I have a dahlia that likes growing DOWN and not up.

It's too bad too, because the blooms I got were very pretty. A yellow centered waterlily with burgundy purple edges. I took a pic of it but can't get it to load on this forum or I'd show it to you.

I'll update when I dig them up to confirm if I have a plethora of tubers again.

It has been a bad year for dahlias for many of us across the country. Here, it was just too dry and too hot. Since it's cooled down, many of mine are just starting their show and we'll get a killing frost sometime in the next month.

However, I've also run into a lousy dahlia, too.
Gail

I find that anything grown in a pot needs to have its soil replaced after a year. Even with supplemental feeding. At the least I would add some good compost and minerals.I have had this same experience with growing roses in big pots...first year, superior health and beauty, next year so so, and failing in the 3rd year. Perhaps in the spring you could lift your clump, divide and add fresh soil, then replant. ON the other hand, I planted some left over dahlias in a raised self contained bed with fresh potting soil added to top it up and had those dahlias grow way biggerr then the ones in my sunny garden! Even with less sun they are amazing! A good lesson I think. Probably the Miracle Grow in the bagged potting soil.... I use organic tomato fertilizer, compost, lime and alfalfa meal on my growing beds, no chemical fertilizers. The plants grow nicely, and flower well but I was amazed how much bigger the blooms were in the miracle grow potting soil. Maybe I will add one mid grow season feeding next year to the garden.

Liza

I was thinking the exact same thing. I have about 30 dahlias - half in pots and half in the ground. By far the ones in the ground do better and that goes for my 30+ roses as well.

I had not thought of changing the soil but that makes perfect sense and I'll try it this year.

What I don't get is your success with Miracle Gro. According to almost ALL the dahlia experts I have read, they say the use of nitrogen (after sprouting) RETARDS dahlia growth and blooms. So this year I only used MG on all my other plants and 0-10-10 type fertilizer on my dahlias. The result was underwhelming.

My overall crop (of dahlias) this year was down. Many only gave me limited blooms. I initially blamed this on the fog - you may have heard this was the coldest (meaning foggiest of course) summer in SF in 11 years and that was BEFORE Sept was 95% foggy and here we are in October and it is still foggy!- but I wonder now if they NEEDED MG instead. My neighbor works for Monsanto and is a chemical agronomist and is very pro natural fertilizers etc. When I asked him about MG once and how I had stopped using it, he asked why? He said it has everything a plant requires so go ahead and use it along with my manure teas and mulching. I ignored that advice and look where it got me - a lousy crop!

I'm going to re-think this MG thing next year.

While Plantlady and Gail were right on (tubers needing dividing), doing so did not solve the problem.

As stated earlier, I divided them onto 5 different plantings, of which all sprouted, though only 4 bloomed and only 4 blooms per pot.

So I dug up the first two pots and here we go again with the tubers! 14 in each pot. I don't need to dig up the others to know what to expect.

So the bottom line is that I just have a dahlia that loves MAKING kids (additional tubers ) but has no desire to actually raise them (to blooms). At least dividing them DID give me a few blooms (versus last year when I got zilch) but it is time to shovel prune the bunch into the green cart and let them make hay in a dump site somewhere.

And on a global warming alarmist front, get this: I have a ranuncula blooming now! For those not familiar with ranunculas, they are a spring and early summer blooming tuber. I have no idea if it is blooming 5 months too LATE (for 2010) or is 4 months too EARLY (Spring 2011).

Go figure.

David, I just don't know about the miracle gro in the bagged potting soil. The plants in it in the planter boxes did put out a lot of green growth but they also bloomed really better then I thought they would, considering that it was into July when we got them out of their gallon sized starting pots and into the soil. I think it gave them a boost to get up and going fast just at the warmest time of year, then they probably used it all up. I think the potting soil only has enough to get things off to a good start. I add my organic fertilizers when I plant them out. MY climate has been a lot like yours this summer...grey and fog with a few gorgeous days thrown in but not nearly enough!

I wouldn't pitch the tubers. Try them in the ground, or give them to someone else who has room to try them in the ground. I've never been able to get anything to bloom in a pot, but the same ones have happily bloomed in the ground.

I believe that your dahlia plants are suffering from virus and will never grow properly.
(1) Throw all stock away and start over
(2) Order new stock from a reputable nursery or get stock from the San Francisco Dahlia Society.
(3) Grow them in the ground if possible
(4) In the pots use Miracle grow but each month give them some weak epsom salts, so that the plants can take up the iron. Miracle grow has too much phosphorus and the magnesium will displace the phosporus and in turn the iron will be made available for the plants.
(5) In the ground, make sure they get lots of sun and fertilize with a fertilizer that has plenty of nitrogen. There is myth out there that dahlias need less nitrogen. It has been proven wrong over and over by reputable growers.

Many thanks Ted(dahlia)

I agree - they may have gotten a virus (which is an answer I was looking for originally). So I have already accomplished 1 and 2.

3 is a problem - I have limited ground space available in my yard which is why I have twice as many container dahlias (and roses) as ground dwellers.

4 is a great point. I use Epson Salts for my roses (growers and old time gardeners say it makes the colors more vivid) so I will try it this year on the dahlias. Never heard that iron angle before so that is interesting.

5 is a BIG problem. Can't control how sunny it will be this or any year in SF so I can only do my best and hope for the best. (I realize that is NOT what you meant but believe me,I have a dahlia in every area of my yard). What gets me is a blooming dahlia in the sunniest spot can be next to another dahlia that MAY or MAY NOT bloom well. That is the maddening aspect that I suspect we all share.

I was one of those that heard nitrogen was bad for dahlias because of advice like this from a well known grower: "Dahlias require a low nitrogen fertilizer, such as used for vegetables". Somewhere else I read you shouldn't use (high? a lot?) of nitrogen either and I always thought it was the nitro that made Miracle Gro such a miracle! As I wrote elsewhere in the forum yesterday, I am going to go back to MG this year though, in part because of advice like yours.

The saddest part is I rent an in-law and in Sept. the owner moved back in (above) and informed me that he wants to build a deck from their unit (I have the only access to the yard) so he and his sons can plant vegetables! (Now that I made his weed patch into a Butchart Gardens.) Building a deck will put about 30% of my BEST sunniest growing space in shade and I will obviously lose more space to beans and peas apparently.

It only figures that by the time I get this growing thing down right, I'll lose half my dahlias/roses/yard. :>(