Once your hardy garden geraniums have finished flowering, you are left with a mass of dead flowers, and untidy foliage spilling out over the path, flopping down over everything else, and generally looking messy.
What's the best thing to do? Simple answer - cut them right back.
It's harsh, but if you do it now, as soon as they have finished flowering, there will be time for the plant to grow a new mop of foliage, and you might even get a second flush of flowers!
The pictures show a clump of hardy Geranium which are clearly over - the flowers are gone, and the foliage is flopping limply to one side. There are hardly any new leaves in sight, the brown rhizomes are clearly visible, and frankly the whole thing looks pretty unpromising.
But if you are brave, this is all you have to do: cut off all those limp leaves, cut them off really low to the rhizomes, as low as you can. All that is left is the brown lumpy base, but be patient and lo! and behold, in no time at all - well, two weeks or so - new leaves will appear.
Picture number one shows the limp, bedraggled leaves. Picture number two shows the bare rhizomes (no doubt shouting “Don't look! We're naked!”). Picture number three, taken just 12 days later with dramatic early morning sunshine, shows the perky new growth, already looking fresh and lovely. In another couple of weeks, there will be a dense dome of foliage, and this plant will once again be contributing to the border.
I have just given the same treatment to all the G. phaeum (Mourning Widow) in my various gardens: the flowers have finished and the foliage is floppy, so by being harsh now, they will have bounced back in time to fill in the gaps, later in the year. It always looks horrifying at first, but it's good to get rid of all the floppy stuff: it gives you a chance to weed around each plant, and it removes what is more or less a buffet for slugs and snails, not to mention giving them nice safe hiding places.
To speed up the process, you can water the newly-cropped plant, which will encourage it to get on with the production of new leaves.
There is always a temptation to just snip out the flowered stems, leaving the best of the newer leaves behind: but frankly, it takes ages to do, and by the time the new flush of leaves appear, the ones you painstakingly left behind will be looking quite tired, and you will have to repeat the process in order to remove those ones. So it's best all round to be firm, be brave, chop the lot, water well, and try to avert your eyes for a week or so!