Geraniums love to be pot bound, frequent transplanting tends to produce dwarf plants.
Geraniums purchased in three-inch pots will be ready for an immediate transplant to five-inch pots. Start with clean pots, wash old pots in a solution of a combination insecticide and fungicide that disinfects and cleans away algae, hot soapy water works.
Soak new clay pots in water over night before using, other wise they will pull the moisture out of the soil and away from the roots of your geranium.
If your soil mix contains a large proportion of sand, insert sphagnum moss in the drainage hole to keep soil from washing out. Cover the drainage hole in the bottom of pot with a piece of broken clay pot, rounded side up. Add a half inch of clay pot chips to a five-inch pot and you are ready to pot new plants or transplant old ones.
Too Transplant Geraniums:
To transplant your geranium, hold the lower part of the plant with one hand, and using the other hand give the plant base a sharp whack against a table to dislodge the geraniums roots. If geraniums are really root bound break the pot to free the geraniums root ball. Too, prevent the stunting that results from spiraling root growth, make three one-quarter inch vertical slashes on the side of the root base. Holding the plant over the new pot with one hand and adding soil with the other hand. Lower the geranium into the fresh soil and continue to add soil until the geranium is in the center and approx. one-inch of space is visible between the top surfaces of the soil and the pot rim. Do not pack tightly, as subsequent watering still do the job for you. Do pack a peat moss mixture tightly; water will still pass through it freely.
When geraniums grow too tall, cut off the top growth, to he desired height. New leaves will appear below the cut area. Stop cutting back or pinching at least three months before you want your geranium to bloom. For mid spring blooms on your geranium, pinch tips until February, for fall and winter blooms on your geranium pinch or cut back plants in August and September.
If you have tall leggy plants, cut them down to two or three nodes or joints with a sharp knife. New growth will spring from the remaining plant, cut back to last pair of leaves, as new growth emerges in lower areas continue to cut the plant back to the desired height.
Geraniums growing in the open garden or large pots often develop tremendous root systems. When you lack space to accommodate such large plants or pots, you want to keep all or part of them, trim the tops as suggested above then prune the roots to separate them by pulling, or chop them apart with a sharp knife. Repot in fresh soil and give them plenty of light. Within two months, they will be strong, bushy geraniums.