Geraniums are versatile perennials that can fill annual beds, be brought indoors or, in warm zones, be grown outdoors all year. However they are used, forms like wild cranesbill, bedding pelargoniums, variegated zonals and species scented geraniums should be cut back to keep a compact shape. They can also be kept over the winter in cooler zones if cut back and given a sunny window. As a bonus, new plants can be grown from cuttings. All you need is a sharp knife and a plant in need of pruning or propagation.
Train geraniums to tree shapes by cutting side branches. Cut just alongside the node where branches leave the main shoot--never into the main shoot itself. Brush the wound on the main shoot (leader) with fungicide and reserve healthy cuttings to propagate new geraniums. When the desired height is reached, cut the leader just above a nodule to encourage branching.
Remove young shoots to keep geraniums shrubby. Slice across green shoots above a nodule (growth nodes look like knuckles--they have tiny leave-like growths around them) to make "softwood cuttings." Take as much as you need from a branch to keep an even shape.
Cut branches that "bolt"--suddenly much grow longer than other shoots. Slice or clip the new growth where it leaves the general outline of the plant, above a node if possible. Dust the cuts on the plant with fungicide.
Prune geraniums back sharply when over-wintering; leave a well-shaped set of three or four main branches about 6 inches long. Cut across branches above nodules. New branches will grow along the old ones.
Lay trimmings on a piece of wax paper and cut across the shoots below nodules to make 3 to 4 inch softwood cuttings. Brush the ends of these cuttings with rooting hormone and put them in light, sterile potting soil or sharp sand to root.