has half the flowers about 30cm about the top buds and flowers. T

==.. i presume a typo. and you mean above..

excessive green growth is a sign of excessive fertilization.. usually too much nitro..

how do you fert .. explain in detail ...

i dont see how you will change too much fert.. if that is the issue.. except to not fert anymore this season...

thinning is probably the way to go.. many flower peeps thin out plants.. and flowers.. to grow bigger single flowers for show.. so there would be no reason for you to not do it...

ken

@ken_adrian Adrian MI cold Z5 - thanks for the advice. I only use tomato feed to feed my flowering plants. I don’t follow a specific schedule in terms of when I water them and when I add this liquid tomato feed into the watering can. I will only do the tomato feed if it is budding or flowering. Tomato feed isn't that high in nitrogen is it?

How often would you advise watering a dahlia that is flowering like this one and how often would you do a liquid feed? I probably water them every other day so 3-4 times a week and I would say 2-3 of these have tomato feed added. So maybe 75% of the watering has tomato feed added - is that too much? It’s regularly mid twenties here (degrees celsius) with little rain so it definitely needs to be watered at least 3 times a week.

It may also be temperature fluctuation. The same is happening to a couple of my dahlias and I chalk it up to rapid high and low temperature days messing with the plant's growth besides any untimely fertilizing. Growth is more compact in cool weather and if it goes back and forth between hot and cool, the buds formed during cool weather are buried by the newer faster growth before that bloom is done.