In my experience, the size of the container will slow down the growth once roots don't have room to expand and food is depleted. Watering will become difficult, as the roots will suck up the water as quick as you can deliver it, slowing growth as well.

I have been an idiot and started dahlias ten weeks before being able to plant out... There was no benefit to those plants compared to ones started 4-6 weeks prior to planting out. In fact, I believe the later-started plants were stronger and took off quicker then the earlier-started plants, but I did no record keeping to prove or disprove that claim.

With this said, I have buried four inch pots with cuttings into the ground, and have had full-sized plants with lots of blooms and miniature roots, but that is with foliar feed, consistent slow-leak watering and full sun.

I suggest pinching out the center after 5-7 leaf sets, and later bury the plant exposing only 3-4 of those leafsets. This will provide more tubers in the fall, and avoid the plant from getting too lanky.

Cheers!

CiCi

Thanks for the reply! To be safe, I went out and purchased 2 eight-inch wide pots to transplant the 2 Kelvin Floodlight plants. The larger pots are taking space away from for me to start other dahlia pots.

Each plant only has one sprout. Is this normal ? They are very stocky under the T5 grow lights.

Stocky is good! Excellent, in fact!

One's average for the biggies. If you accidentally knock the sprout off or take it for a cutting, the KF tuber will probably produce two more in its place. Smaller sized varieties might shoot up four more in its place, or start out with two in the beginning. Normally only one or two sprouts becomes dominant to make the main plant, unless you have a clump of tubers that were never divided.

Thanks again for the reply Cici. Can they be too stocky ? There is less than 1/2 inch of vertical stem between each set of leaves. The first set of leaves is already 8 inches across in diameter.

Kelvin Floodlight tends to be a very late bloomer, and there is a correlation to number of leaf sets and when a variety will bloom. Bottom line: if your plant is staying stocky with multiple leaf sets, BRAVO!

When the stem is skinny and long with stretched out leaf sets, it can cause problems for the plant once it's put into the ground. Sometimes, the plant will die back to the tuber and a new, healthier sprout will take its place.

Here is a picture of one of the very stocky Kelvin Floodlight plants. Should it be pinched soon ?

Nice!

I'd be tempted to let it get to a foot or so before pinching out the center. Might be interesting for you to do an experiment, stopping the KF plants at different points and observe the results.

Good suggestion ! I was first thinking about pinching the side flower buds off to compare final bloom sizes in the summer.

I do that on a regular basis for good stem length. It definitely helps if you can roll off the side buds before they are pea sized, as the stem gets thicker and sometimes lopsided if they are allowed to develop. It helps force the energy of the plant into the remaining bud, too. Not so sure you will see a remarkable size difference with simple debudding, though I believe the form is better on the remaining flower.

If you are going for the largest size, you'd only allow 4-5 branches total per plant, with only one bud on each branch. You'd take out the one branch on each side so only one bud is maturing at one time. It's pretty hard for a new grower to strip a dahlia plant back as much as it needs to be for the largest possible blooms.

I'm getting better at it, but it's still psychologically heart-wrenching to snip off all those potential flowers. Folks that grow primarily for show do it all the time for the perfect blooms. The amount of laterals (branches) you leave on depends on the typical bloom size of the variety: the rule of thumb is the bigger the bloom, the fewer laterals left on the plant.

Okay, none of my dahlias are looking like that. My tropical stem is thin. I think the leaf sets look good. It is just over a month old and is only working on its 3rd set of leaves.

On my pom pons, they are thick stocks. There seems to be a bit of a distance from the leaf sets. The leaf stems are really long, too. Should I be worried?

As long as the watering is maintained with adequate light, you are fine. Varieties look different at different stages. I have stopped growing a couple varieties that always had spindly stems every year, and was a flopper in the garden even with careful staking.

Thank you!

Ha, now another question....

My Tropical formed another sprout. I wanted to try to propagate it. I dug a little to see if I can find where the new shoot is attached to the tuber to get a slice of the tuber. As I was carefully trying to dig, I broke off a tuber :(.

I didn't go any further. I don't have any rooting medium so is it okay to try to root the new shoot under a light in the house? Also, with the broken piece, did I just sentence my mother plant to death? It wasn't a huge clump to begin with.

Sounds like you have pot tubers from Holland, sold by general catalog plant companies and big box stores ... A confusing mess with what looks like a stalk with lots of tubers (often broken) hanging off it? Sound familiar?

The great thing about these things is that there are normally many potential eyes ready to sprout up if the main sprouts are broken off. The not-so-great thing about holland' pot tubers is that they are very difficult for the new grower to divide or take cuttings from, as the clump is often a mess. It might be advisable to rein back on your learning curve, and save cuttings for next year's project. But if your spirit moves you to be adventuresome, go for it! Just be prepared for failures while learning... All part of the learning curve.

"Get a slice of the tuber."

Not sure why you'd want to do that. If you cut a sprout out of the tuber, you have effectively ended the sprouting capability in that area. If you cut under a leaf set and above the tuber by an eighth of an inch, three or four new sprouts will develop around the sprout stub within the week. You can pot up the 2-5 inch cutting, water well and cover tightly with a Baggie... The sprout should root well in a couple weeks and begin top growth.

Lol! Yes. BBS tubers. Messy clumps. Cheap. Hopefully good for a newbie....I do plan on adding some upgrades next year. I still have not decided if I will overwinter the ones I have or not.

"Get a slice of the tuber."

I read, in my research, that if I can get a slice of the tuber it helps the cutting to root better.

I decided to be adventurous. I pinched the new sprout yesterday, put it in a jiffy pod under a heat light and am patiently waiting to see what happens. He drooped a little yesterday but is standing straight today with much bouncier leaves. :)

This is what my 5 week old Tropical looks like. From what I read, she will not be as big as I thought. Maybe 24" or so, with 4" to 5" blooms.

Does she look okay at this stage. Her stems are still red, but I am beginning to think this may be characteristic. My pon poms greened up when they got bigger. She has opened 3 leaf sets and is working on her fourth, which seem short to me. I do see the beginning of some laterals too. She seems to be lagging behind the pon poms who took off like rockets....

Sorry, I didn't mean to take over the tread....

Plant looks good, no worries about red stalk. Will probably green up when the plant is mature, but some always stay darker.

I wouldn't pinch off a sprout you want to root. That limits the amount of moisture the sprout can take in while it's trying to root. Much better to cut it off cleanly. You need to be sure a leaf junction is under the soil, as that is normally where the roots will emerge. I would suggest covering the cutting with a Baggie, trying to avoid direct contact with plastic and plant material. Hmm... Or is that the same as a 'jiffy pod?' That's a new one for me!

Jiffy pods are little pods of soil, they expand when you add water. They have a greenhouse type of lid to them. I put the the baby in that and have kept her indoors and under a warm bulb 24 hours a day for the last week. She is holding her own right now. When I compare the pictures for last week, it looks like the too leaves have greened and are trying to open.