It may be feeling distinctly autumnal right now, but if you’ve planted dahlias the good news is they will keep on flowering right through to the first frosts.
There’s just one catch: to prolong flowering you will need to keep deadheading them, thereby encouraging the plant to produce new buds.
The only problem is it’s not always easy to distinguish a spent dahlia head from a new dahlia bud. And you don’t want to be snipping new buds off!
Identifying spent dahlia heads
If you spot an ageing flower early when there are still a few wilted petals visible, then there’s no problem. Snip it off. The difficulty arises when the old dahlia flower has lost all of its petals. The hard bulbous part at the base of the flower (the calyx) then closes over to form what looks remarkably like a bud.
However, you can tell the difference between a spent dahlia head and a new dahlia bud by the shape. A spent dahlia head is slightly conical, almost pointed (as in the example above), whereas a new bud is a more compact rounded shape (as in the example below).
If you give a new dahlia bud a squeeze it will feel firm and you may be able to see the compressed petals within waiting to explode out into a fully formed flower. If you squeeze a spent dahlia head, it will feel squishy.
Where to cut
Once you’ve identified the right heads to remove, make sure you trace down the old flower stem and cut it off where the stem intersects with a leaf.
If you cut it off directly under the dead flower head you will be left with an unsightly flowerless stem. Multiply this by several flowerless stems and your plant will start to look quite ugly. Keep it trimmed down and you will have a neat bushy plant.
Keep deadheading
It’s amazing how quickly new buds form, flower and die, so deadhead your plant as often as you can. Your dahlia will reward you with a stunning supply of colourful blooms late into autumn or even into early winter. And if you have chosen a bee-friendly variety it will be a source of much-needed nectar late into the year.
Happy snipping!
I’m new to Dhalias, thank you for the advice, just starting to dead head.
Do you ever cut the whole bush down before winter ?
Yes, when first frosts blacken the leaves, cut the stems down to 4–6 inches from the ground, then either lift them and store the tubers over winter, or give them a good mulch and hope they survive the winter (it will depend on your climate). As mine are in pots on the patio, I lift and store them over winter and replant the pots with spring bulbs.
Thank you, the most easily understandable explanation. I shouldn’t have been surprised that my dahlias have three stems, haha but I felt I’d just read a master class and was able to put into practise what I’d learnt.
That’s so nice to hear. I’m glad it helped!
Very helpful advice on how to tell the difference between buds and seedheads, thanks
I’m glad it was helpful.
I’m confused some dahlia have flowered and dieing off and I’m not sure when to cut these off as I still want dahlia to bloom but would like seeds from the flowers that’s gone over.
Please can you tell me if I leave them to seed.
Or cut them and put the little bit of stem in water
I’m confused.
Thank you
You could leave a couple of spent heads on, which should provide you with plenty of seed, but I would keep deadheading the rest to keep the plant flowering.
You could leave a couple of spent heads on the plant, which should provide you with plenty of seed. I would keep deadheading the rest though, to prolong flowering.
Thank you, that is so helpful and easy to understand for a novice gardener.
I’m so pleased you found it helpful. Thank you.