What gardeners commonly call Geraniums are Pelargonium species and hybrids, not to be confused with some native wildflowers and herbaceous perennials that are truly of the genus Geranium. All are within the Storkbill family (Geraniaceae), along with their cousins, Filaree. Geraniums are one of the most reliable herbs and bushes grown in the home garden and add color from spring through late fall. Grown both indoors or outdoors as perennials in Davis, geraniums (Pelargoniums) should receive six- to eight-hours of full sun to produce abundant blooms and are frost intolerant. Scented type geraniums in particular should receive full sun to develop the fragrant volatile leaf oils. Scented geraniums are somewhat more frost-tender than those types grown for their flowers; planting these in a south- or east-facing exposure can provide added winter warmth. Soil should be reasonably well draining, although they are not fussy so long as you don't water too often. Mulching helps reduce high summer soil temperatures and plants should be watered weekly at ground level. Remove the flowers as they fade to encourage bloom production.
Most geraniums root easily from stem cuttings, and many cultivars must be propagated this way to maintain desired flower and/or leaf color, shape and scent. Propagate in the fall, allowing for 3 to 4 weeks of warm weather for rooting to take place. While relatively pest- & disease-free, some of the problems affecting geraniums include botrytis or mildew, rust, blight and black leg; in addition to these bacterial/fungal diseases, geraniums can be attacked by invertebrates such as slugs, aphids and caterpillars of the geranium budworm. Organic control measures exist for all these pests.
True Geraniums are easy-to-grow herbaceous perennials for sun or partial shade. Most bloom in spring and early summer; some varieties continue to bloom through the summer and into fall. They are propagated by division in fall or spring.
Martha Washington Geraniums (Pelargonium x domesticum) are typically sold as a flowering indoor plant. Because it is not heat tolerant, it may not perform as well outdoors as zonal geraniums.
Ivy-Leaved Geraniums (Pelargonium peltatum) have a vinelike habit with smooth, leathery leaves and flowers with narrower petals and less dense flower heads.
Scented Geraniums have a wide range of foliage types and habits, make excellent houseplants, and often have soft, finely textured foliage, and small, demur flowers.
For a listing of other plants found growing in Davis, visit our Town Flora.