Very decorative for the greenhouse is a pair of tree or standard geraniums, especially well-trained double-flowered zonals. The glowing salmon 'Mrs. E. G. Hill', pink-and-white 'Apple Blossom Rosebud', pale pink 'Princess Fiat', or strong 'Olympic Red' make handsome standards in only a little over a year's time.
Select straight healthy cuttings that have been rooted in February in sand, and plant each in a 2 1/2-inch pot. Fertilize and train to a single stem by pinching off all side shoots. But don't pinch out the top for this causes branching that you do not want yet. Shift to larger pots as necessary until your plants are big enough for a final 8-inch pan. This could well be mid-September if you promote growth by regular fertilizing, say every other week.
When plants are 8 to 10 inches high, support them with 15-inch bamboo stakes. Fasten stems to stakes with plant ties. As stems reach 30 to 36 inches, pinch tops to induce branching and the formation of a flowering head.
Blooming starts in March or April.