One of the joys of planning a spring and summer landscape is choosing different types of flowering plants that add bright spots of color to beds and borders or produce a sweep of color when used in massed plantings. Plants commonly called geraniums (Pelargonium sp.) are one of the best choices and, if you live in a frost-free area, they can grow year-round in your garden. Knowing when and how to prune these versatile plants keeps them attractive and well formed.
Young geraniums commonly found at garden centers in spring usually have one or two main stems, generally with a few side shoots and flower buds. Proper pruning of these young plants in the spring encourages them to become bushy and many stemmed, a form that promotes abundant blossoms. A week or two after planting, when the plants are established, prune the main stems by about one-third to encourage additional new stems to form. Several leaves should remain on each stem after pruning. As the plant grows, pinch back new branch tips to encourage bushiness, avoiding areas with flower buds to preserve blossoms.
Geraniums develop complex flower heads made up of many small flowers that open in sequence. When the last blossoms on a flower head have faded, remove the flower stem at its base, a process called deadheading that encourages new flower buds to form. If plants begin to look leggy later in the summer, prune back some of the side stems to encourage new branching and keep the plant from becoming thin and tall.
Geraniums are generally winter hardy in U.S. Department of Agriculture plant hardiness zones 10 and 11. In these warm-winter areas, they can be left in the ground during fall and winter. In early spring, before new growth starts, the plants benefit from a hard pruning, leaving just a few inches of last year's growth above the soil line. New growth generally appears when the weather warms. In colder areas, you might dig up and pot geraniums to overwinter indoors, placing them in a sunny but cool spot. Deadhead an overwintered plant by cutting it back by about one-third and reducing water to keep it healthy until spring, when you can move it outdoors for another season.
Although most common geraniums have a naturally compact growth habit, scented and trailing geraniums need some special care. Scented geraniums, which come in dozens of different-scented varieties, are fast-growers that tend to be large, naturally leggy plants. They need aggressive pruning twice yearly, taking each stem back to about three leaves, with the first pruning in late summer and the second in late fall. Avoid winter pruning of these types since they set flowers when evening temperatures fall. Trailing geraniums, sometimes called ivy-leaved geraniums, have a vining habit and are excellent in hanging baskets or on trellises. This type needs little pruning of its long stems but benefits from deadheading to encourage season-long flowering.
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