Brian Whyer brian.whyer@btinternet.com
Thu, 10 Mar 2011 11:23:20 PST
< Are you talking about cuttings from the stem ? Because when you say "cuttings from the < previous year's tubers" that confuses me, since you say the plant doesn't "need to form a < new tuber system" ? 
You can carefully divide the tuber "cluster" vertically down through the stem, taking care to keep a portion of the main stem with each tuber, preferably after the plant starts shooting so you get 1 or more new shoots on each division. Or you can slice off the shoots close to the stem and root them in the usual gritty rooting compost, and establish a new plant first from each cutting. They should root in 2-3 weeks; as long as you cut close to the tuber. Leave a couple of shoots on the old tuber and you will have a number of new plants from the one original tuber clump.
Brian Whyer, Buckinghamshire, England, zone ~8

-----Original Message-----
From: Brian Whyer brian.whyer@btinternet.com

Dahlia nurseries will grow named forms year after year taking cuttings from 

their previous years tubers, with the same quality each year. If you are 

planting or splitting tubers and restrict the shoots to just 2 or 3 then they 

should be little different from the previous year. If you grow from tubers they 

will flower slightly earlier than from rooted cuttings, presumably because the 

plant does not have to form a new tuber system first. Usefull for the large 

flowered monsters which tend to flower late. Disbudding side shoots will give 

you larger flowers.

I think named form Dahlias are only cheap in countries where they don't have to 

be lifted and stored each year, or if you grow seed strains.

Brian Whyer, Buckinghamshire, England, zone ~8

There are no hardy ones that I am aware of. I can winter them over, keep dry in 

paper bags, but the second year's display is never the same as the first, from 

freshly bought tubers. For me, anyway. 

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