I don't know of home gardeners who grow other "bulb" plants from seed. But there are lots of tubers/bulbs that you can buy, and then lift in the fall for storage, though if you can grow a coconut palm, most of them - including dahlias, you probably don't have to lift, unless you are going to divide them. Many people in zone 8 in the US only dig their Dahlias every couple of years to divide the tubers. There is a Bulb forum on GW - I would ask this question there if you really want to start from seed.

FWIW, I cannot speak to your environment. However, now that you've explained it the way you have, I think I understand what's happening. When I was first introduced to Dahlias, a friend had a "bush" that they divided because it was too big. I got not a clump from a single plant, but a clump from a divided bush tuber. I could be wrong, but I think most here grown single tubers (or cuttings as I did this year) and don't run into this (or at least if they do, its not talked about often.) My friend thought to curtail her Dahlia by dividing it, the way I'd divide a hosta. She simply cut the "root ball" in half. For that variety of Dahlia, it worked. When I got it, however, I didn't simply plant the clump. My research said to break it apart into individual tubers and plant each alone. They grew too. So perhaps, and this is just wild speculation, you have varieties that cannot survive this way. I can see how a single plant would produce enough tubers that, if left undivided, could actually collapse in on themselves. Too many plants growing from a clump can, often, produce no plants. My recent research on "pot tubers" tells me you take the pot tuber clump and let one stem grown (ultimately.) To let too many grown would mean that none would grow really well (again, depending on the variety.) Conversely, we know that we only need a single tuber to produce a great new plant. Ergo, its not rocket science to take your experience and say, if you don't divide, you're going to have (or may well have) problems. Now this is my first your growing pot tubers. My plan is to have a clump of tubers in a small pot at the end of the year. When I grow these on, I will let a single stem grow up. Anything outside of the 4" pot I will cut away. So I will neither have excess tubers (which if they rotted could very well spread to all of the tubers) nor too many stems (which if they all grew could mean none are getting enough to propagate new tubers.) My suggestion would be to follow our (colder clime) procedure. When you cut the stalk back, let them stay in the ground for a week or two. The tubers should "eye up", or start to form new sprouts. Take the clump out and find one or two tubers that have the most eyes. Cut away everything else, and put them back into their same spot (discarding the excess, or planting it far enough away from the original so there's no chance of them intertwining.) Dahlias were originally cultivated as a replacement for potatoes. If you don't "cull" them, perhaps you leave them without soil nutrients (because they'll be surrounded in tubers.) So "pare" them down. But given that every tuber can make you 10+ plants, give yourself the most prolific tubers when paring. Of course the other thing to think of is soil composition. Given how they may produce a lot of tubers, they may well be taking way whatever nutrients they need to produce more (which could explain why they only last a couple of seasons.) I lived in Liberia, and there, they used to burn the rainforest to get enough nutrients in the soil to grown rice (hopefully you can see that that would only last a couple of seasons.) Test, and amend. But reduce your growing mass (e.g. take away tubers) so it can be sustained. Anyway, enough speculation...;-] Perhaps something in this will ring true. Again, I've no experience to help you with other than what we do in colder climes, but its what I would imagine will happen...;-] Good luck, and I miss being in such climes...;-] Cheers, Russ

These are the Manila mango fruits from June of 2006,and just starting to going through it's first flushes after the winter of 06. These might be the worst photos I took!..but with thousands of images..These are the ones I memorized where and in what file. The others if I run across are of flowering,pea sized fruit and ripe cut open fruit of a 9',then 5 year old potted tree. Potted up by me after a few years in an extra SANDY soil like it came in. I curse the winter of 2007. btw, A second Manila was thriving and growing fast in a pot...did well for a short time in ground,went through a winter fine...then in late spring of 08..died Just shriveled up. Could have been root virus or Gophers.

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.