To my mind, one of the greatest strengths of dahlias, is that they can go on flowering from mid-summer right until the first frosts.
Depending on where you live, that could mean that you can have dahlias in bloom for three, four or even five months.
However, the most important word in that first sentence was can.
Once you know how to grow dahlias, they can flower for extended periods but only if you, the gardener, help them do so.
Taking care of dahlias involves the usual necessities of feeding, watering and mulching. But to get prolonged flowing, you need to dead head.
And it can be a little bit harder to dead head dahlias than it is for most flowers, unless you are aware of one important fact – how to identify the spent flower head.
(I have to say, I can never think of dead heading, without thinking of the Grateful Dead. But maybe that’s just me.)
The two step tip for dead heading dahlias
In case you don’t know, dead heading is simply a matter of removing spent flower heads.
This prompts the plant to produce more flowers, because removing the spent flowers deprives the plant of the potential seeds that evolution is driving it to produce.
Step 1 – Identify the spent flower
This is what makes dead heading dahlias a little bit tricky.
The problem is that once all the petals have fallen from a spent dahlia, the hard green part at the base of the flower (the calyx) closes over and what is left looks very much like like a bud.
So unless you know how to tell the difference between the buds and the remains of the spent flowers, you can end up removing the very buds that you are trying to induce into flower.
Fortunately, it is pretty easy to tell which is which when you know how. So here’s the trick:
The buds are rounded and the dead heads are cone shaped.
Take a look at the picture below.
This is a bud.
It is rounded, a kind of flattened sphere of compressed petals, with the calyx (the hard green outer ring of sepals) fanned out below the bud.
In contrast, what you see below is the spent flower.
Notice how the overall shape is pointed rather than flattened, a cone instead of a sphere. In addition the sepals of the calyx have folded up to enclose and protect the reproductive parts of the plant.
These are what you need to remove.
Step 2 – Cut right back
This is the easy part.
When you remove the dahlia’s dead head, don’t just cut it off below the flower. If you do, you’ll leave a flowerless stem that will just look ugly.
Instead, cut back, with sharp secateurs, to just above the point where the flower stem joins a main stem.
As you do so, you’ll probably notice a couple of tiny buds nestling there. With the removal of the spent flowers, those will sparked into life and they will bloom in a week or two.
If you are attentive in taking care of your dahlias and keep up your dead heading regime all summer, you’ll have blooms until the plant is knocked over by the first frost.
What you might need
If you’re just deadheading your dahlias, you can just as easily use kitchen scissors. But if you’re anything like me, then you’ll be scanning the garden for anything that needs a prune or a bit of cutting back while you’re there.
I pretty much never step into the garden without my classic Felco Classic number 2 secateurs. These are the best secateurs or pruners I’ve ever found – and, believe me, I’ve tried plenty.
For a great selection of dahlias, check out what is on offer at DirectGardening.com – you’ll find quality plants at great prices.
Just to be clear, the product links above are affiliate links (see the affiliate disclosure page for a full explanation)
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