Get in the zone with zonal geraniums. A true garden favorite, zonal geraniums are one of the most easily recognized annuals on the market—although most gardeners just call them geraniums. The term zonal geranium refers to the plant known in botanical circles as Pelargonium x hortorum, a cousin to perennial geraniums, like Geranium Rozanne.
A zonal geranium has several distinctive features, including round to almost kidney-shaped leaves that may—or may not—have a darker circular mark on them. The mark may be dark green or perhaps shades of burgundy. It’s this mark or zone that birthed the common name zonal geranium.
Flowers on zonal geraniums resemble spheres that stand atop sturdy stems. Colors encompass nearly the entire rainbow, except true blue. Today’s modern hybrids offer blooms in shades of pink, lavender, yellow, orange, rose and the classic red. Flower hues also include bicolor blends and petals with contrasting whiskers or spots. Some blooms have double petal counts, while others have pointed or ruffled petals. Variety is the consistent factor among zonal geraniums.
Plant breeders have created many types of zonal geraniums. Some hybrids grow from seed. These plants are typically smaller overall, opening single blooms and reaching smaller mature heights. The price point for seed geraniums is usually lower. Vegetatively propagated zonal geraniums are grown from cuttings. These plants are beefier in every way—plant size, flower size and price. Zonal geraniums grown from cuttings have semi-double and double blooms.
Growing zonal geraniums is a snap. These blooming beauties thrive in full sun, except in the hottest parts of the country, where the plants benefit from a little shade during the afternoon. In planting beds, tuck zonal geraniums into well-drained soil that’s been amended with plenty of organic matter. A slow-release bloom booster fertilizer helps keep the flower show going strong.
When planting in containers, including hay racks, hanging baskets, pots and window boxes, use a commercial soil-less mix developed specifically for use in pots. These mixes often include slow-release fertilizer. This gets zonal geraniums off to a solid start, but it’s a good idea to give plants a water-soluble bloom booster fertilizer starting about four weeks after planting. Feed zonal geraniums with bloom booster every two weeks throughout summer.
As flowers fade, snap their stems as close to the main plant as possible. During periods of prolonged rain, if flowers start to develop mold, remove them, even if all the individual blossoms aren’t open. Once botrytis mold attacks a zonal geranium, it’s tough to get rid of, especially if rainy, wet conditions persist. Removing any leaves or flowers showing signs of mold helps keep the disease from spreading.