can you cut back cranesbill geraniums

Both Ruffin and this can lead to a second flush of flowers if you're lucky !

You can also divide them too to make more plants.

Yes you can be quite ruthlless and pull out all the dieback and you should get another set of blooms

If you look at the centre of the plant, you can usually see new, shorter growth coming through during late June, July or August. Once that appears, you can then cut back all the rest of the longer growths to the base.