An expert will be along shortly, I'm sure, but I've noticed a few things raising them.

1) First year tubers bloom a little later.
2) That having been said, some dahlia are simply later than others--all my Sun Lady exploded early. All the Color Spectacle took their time. The Blue Boy and Sky Angel were in the middle.

Your care (off the cuff) sounds fine. Sunny, warm, well-drained soils with moderate feeding are perfect for dahlia. If the pots were large enough for them, that wasn't a problem. Plenty of people raise dahlia in pots all season long.

Transplanting into the garden might shock them a little bit, but I do that every year with my smaller, seed-grown dahla (Figaro and Harlequin). They barely seem to notice.

I have tried this method and I get very early blooms this year. Start the dahlias in pots in 1.5-2 gallons size. in late March/early April if your zone is colder than 6. In May after the danger of frost is past, plant them outside, but with the bud eyes close to the soil level. As they grow, pile soil on them to about 3-4 inches level, cover as much of the growing tuber. Basically you are making a slightly raised bed. With this method, I was able to get flowers as early as June and many start to bloom about July.

They are blooming pretty well now, but their leaves have gotten curled up and very dark, now. I am guessing this is due to the colder/rainy weather (50-60's) I will try Kousa's idea; I have heard of that before, and wanted to avoid planting them too shallow, just so they wouldn't topple over so easily. I will try it this year. Any other ideas - fertilizers, pinching, etc? Should I bother overwintering these tubers?

Over-winter if you can, the tubers perform better the second year if they got good care in your garden. Some people prefer to treat them as annuals and that's fine, too--first year tubers do quite well.

My oldest dahlia is about six or seven now. My newest was this year. Those and everything in the middle performed extremely well and I can't say I noticed any significant performance difference between them. The oldest tubers did tend to bloom a little earlier, but that's it.

My leaves have also darkened, and we had our first frost last night. I expect that either took them out or damaged them, so I may be digging tubers this weekend or early next week.

Some of my additions this year were very, very late (June 15th or so), and I shallow-planted the tubers to avoid waiting for sprout. Plus I wasn't sure how much energy they had left and didn't want to make them work for it!

Dahlia have pretty wide, shallow root systems that are capable of holding the plant up (wind may be a problem even with deeply planted tubers, however). All of mine, deep and shallow, featured strong, upright growth, strong stems, and good upright blooms. All survived multiple strong thunderstorms with no or extremely minimal damage.

One consideration would be winterizing in a marginal environment (which you probably don't have in Zone 6). There, deeply planted tubers are preferable. For those of us who lift (garden) or store (pot) dahlia, it doesn't seem to be that important.

I truly don't understand why you're saying that 'older' dahlia tubers do better then new ones, Morpheus. Do you keep the same mother tuber and replant from year to year? Most of them rot in the fall, or keep poorly overwinter, leaving crisp white new tubers for the next year's plants. What am I missing?

Most of them rot in the fall, or keep poorly overwinter, leaving crisp white new tubers for the next year's plants.

They rot if left in the ground in zones where it is too cold or winter soils too wet. And if dug and stored properly, they keep very well over winter. Like morpheus, I have planted the same tubers multiple years and they just keep getting bigger and better.

Nuclear, by all means, dig the tubers and keep them for next year. Unless infected by a virus, this years performance should not effect next year's plants.

You asked about topping techniques to get the plants to bloom earlier... That works to kickstart the plant to grow lateral branches quicker, but that actually delays the first flush of blooms by a couple weeks. But you will have a more constant supply of blooms when they DO start.

Kousa's method of piling soil on the sprouted tuber might indeed help stimulate growth earlier in the season, when soil temperatures under 60 degrees slows activity. Swan Island does exactly that, using a tractor to hill the tubers like potatoes. But SI also tops all their plants in July to keep them from growing high, as they don't use any supports. I bury my pre-started tubers with 12-18 inch growth about four inches down, and notice a stalling out of growth for 2-3 weeks.

It sounds like there is something else going on, if they are only blooming now...

I am wondering how many plants you are talking about, and how much you fertilized/watered them. Unless you were just growing 10 inch or larger varieties, you should have had blooms early August after putting out pre-started plants mid-may.

Very interesting, gardengal. Thank you.

My experience is very different then yours. There are few acceptably firm mother tubers in any of my clumps when I dig. Most are hollowed out or soft, some rock hard and very dark.

I was taught by my mentors to toss them immediately, or if you must keep them, separate from the other tubers to keep rot from spreading to the rest of the stock.

Wow! I have never heard of that. And most dahlia resources never mention discarding the mother tuber unless it is somehow damaged or diseased. When I used to dig up my tubers, they were fat and happy at the end of the growing season.....never any reason to discard the older portions. In fact, I never considered dividing them until I took them out of winter storage in spring to give them a little light to encourage some eye development and then only if they were huge or a lot of finger tubers developing from the mother tuber. And I never had issues with rotting during the overwintering process. The tubers were washed of all soil after digging and then wrapped in newspaper while still slightly damp and layered into some old apple crates I had. Sawdust, sand or peat moss works equally well although I prefer all of these to be slightly moistened so as not to desiccate the tubers during their winter rest.

Since our soils warm up quite late in spring, I now grow all my dahlias in containers, which I store intact (minus the top growth, which I remove after frost) for winter and bring out again in early April to set out on concrete to warm up fast. Warmer soil prompts earlier growth and IME, early growth translates to earlier blooming. About every 2-3 years, I unpot the tubers, divide and repot with fresh soil.

Ah! Okay, so you are keeping the clump intact, then, and only cut the clump into pieces every few years... I would imagine it hard to separate the individual tubers if I did that multiple years in my beds, as my clumps often are massive with just one growing season, but I have never tried growing clumps from spring.

I've heard that growth from clumps are quite vigorous, and folks in the
UK make all their cuttings in spring from last year's clump, throwing out the 'mother' clump after it is spent or they don't have need of more plants.

If that is what Morpheus was referring to, that makes more sense.

For an active trader/seller like me, I wouldn't dream of 'wasting' tubers by throwing them all in the ground for just one plant. However, that is exactly what I was suggesting to some older folk I was just helping earlier today. They only want one plant of each variety, and don't have the dexterity required to splice out a dozen individual tubers from each clump they have. I was showing them how to cut down the clump of any extra broken tubers and squishy mother tuber, so it would store better and they would be assured of spring growth.

>>I've heard that growth from clumps are quite vigorous, and folks in the
UK make all their cuttings in spring from last year's clump, throwing out the 'mother' clump after it is spent or they don't have need of more plants.

>>If that is what Morpheus was referring to, that makes more sense.

Pretty much. I remove the mother tuber(s) from the clump at the end of the season. They're clearly spent and not in great condition, but...well...

OK, I'll admit it. With 2,000 square feet of garden, I'm too lazy to split everything that gets lifted every year. My Sky Angel had seven or eight mothers, and I don't have room for another seven or eight Sky Angel dahlia. They're nice, truly gorgeous, but would take space from the zinnia and salvia and marigold and Easter eggplant and...

So instead I have two absolutely enormous, jungle-like clumps of those, plus (at this point) eleven other enormous, jungle-like clumps of other dahlias.

When I do split, I immediately start looking for people to adopt them, but I rarely do more than divide the clump in two.

Again, time. My dexterity and vision are up to the task, the amount of time I have during the window of frost to freeze is not up to the task.

Older clumps sprout earlier (of course, some of those eyes are more active than others and sprout first), produce huge "bushes" of greenery, and bloom profusely on many branches at once...so of course some blooms appear earlier.

Care of larger clumps differs, including keeping a close eye out for fungus, and they do seem to like a heavier feeding than a smaller single-tuber dahlia would. That's fortunate as I don't isolate them from the rest of the (demanding) garden.

Large clump dahlia perform well--I've included a link to my garden images, which get updated about once a month or so at worst.

I like to use them as central showpiece items with smaller plants around them for accent and color contrast. We should point out that I never met a saturated flower color I don't like, nor do I approve of blank space in a garden!

Here is a link that might be useful: Garden and Lawn Photos