The answer is to apply the Chelsea Chop!
So, what do we do?
Simply take your secateurs, grab your courage with both hands, and cut out a small section in the very centre of the clump, as short as you can reach.
There you go, that's all you have to do.
Sharp-eyed reader will spot that this really is the same clump, you can see the small light green plant to the right - it's a rogue Tanacetum (Tansy) which will be weeded out eventually, but I'm quite soft-hearted about them, because they smell so great! Luckily, once you have one Tanacetum in your garden, you will have millions of them for ever more......
That's it - you have removed a small handful from the very centre, and that allows them enough room to grow without being so crowded that they flop open.
Within a few days, you won't even see the hole, the other stems will have leaned inwards to fill it.
But this summer, the clump will be much less likely to flop open.
And as proof, if proof were required, here are a series of photos of these Sedums (see, I can do it now!) from last year:
This was taken in 2018, in mid August, and as you can see, they are flopping all over the place.
"They always do that," complained the garden owner: "is there anything you can do?"
So last year I did the chelsea chop on all of them.
One week later, you can barely see the holes - as promised!
Here we are in early August, and they are all standing up very well - such a difference from the first picture!
Note how they start off quite white, before slowly turning pink.
And finally, here we are in September, all gone pink, and virtually all standing up.
Quite a difference from the floppy ones of the year before.
So there you have it: the Chelsea Chop - how to do, when to do it (ie when they are just starting to form nice rounded clumps), and why to do it.
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