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This one didn't get answered while the forum was sick but I know nothing about dahlias
This is an interesting question. I think they all do form tubers after a season's growth but, although I grow several dahlias, I do not know for sure. Every dahlia for me has formed tubers.
Dahlias are tender perennials .. Or, ..are some simply annuals?
I have been told by a supplier some done by cuttings in the spring may not develop tubers and have been bred to concentrate growth more into flowering. Not sure if this is correct though? I wonder whether the use of growth retardant could affect tubeer production? The ones we had to try have produced tubers though
If I was to guess, I would say they form roots and then, when ready, form tubers. The natural habit of dahlias...as with some tender salvias....is to, eventually, form tubers.
What about Begonias?
Do these form Corms too from those bedding plants that you buy? ( I bought the Illumination variety)
If no-one knows I guess I'll find out come November :P
Illumination begonias are tuberous, they will die down to a large corm, which can be saved in a frostfree place and then regrown next year.
There are fibrous rooted(semperflorens) begonias used in bedding displays (small flowers), which will not form a tuber or corm.
This will save me some money for next year
I don't like those bedding begonias anyway!
Dahlias grown from seed or cuttings do eventually grow tubers.
Think we are agreed......dahlias do all form tubers eventually
Have you kept them well watered?
While everyone is on the subject of Dahlias - I have 2 large clumps which appeared from nowhere (we have only lived here for a year so were obviously planted by the previous owner) and must have overwintered ok despite the snow. Dahlias aren't my first love, and I certainly don't want to keep them where they are. Do I just dig the tubers up and bung them somewhere else, or should I store them over winter? Also can I split them? All the blooms were on top of each other, and they just looked 'plonked' in a border.
Yes,,you can dig them up, split them, move them, etc.
Just make sure each clump of tubers has a piece of STEM. won't grow otherwise.
Strictly you wait until frosts blacken the foliage then you bring indoors to,overwinter. However you can do it now. I would put half approx back into the ground...new area you want it....and pot up the rest. I would divide these clumps again to,overwinter if you have enough
Thank you Verdun - it would have been on my list of things to do today, were we not getting the startling downpour which we are! Very good tip about the stem - it would never have occured to me.
Tubers are basically swollen roots which act as a food store, so the unswollen ends of the roots look just like normal plant roots. I grow all my dahlias from seed each year and they all produce tubers, but late-sown ones may not have time to produce large enough tubers to survive the Winter by the time the frosts come. Regular dead-heading will encourage tuber formation as if seeds are allowed to form the plant may decide to put all of its energy into those instead - plants do whatever is most efficient in order to reproduce or survive.
I asked about water as tubers are 95% water, hence they are not frost hardy. I have grown similar small Dahlia (Bishop of Llandaff) from seed and they had small thich roots rather than tubers in their first year - they were difficult to overwinter and restart. I did notice that the seedlings with most water had the thickest roots/tubers.
I leave my dahlias in the ground in winter and most survive. Arabian nights, Park Princess, Bishop's Children (that I grew from seed) and some others even survived the year it was -17°! Pooh and the others I planted last year (forgotten names) all survived -10°. I live in Dordogne, winters are usually colder than in UK, last winter and spring were very wet, but years of manure and limestone rock under the earth mean my beds are well drained, although it was clay to start with.