Pelargonium is a genus of flowering plants that includes about 280 species of perennials, succulents, and shrubs, commonly called geraniums, pelargoniums, or storksbills. Geranium is also the botanical name and common name of a separate genus of related plants, also known as cranesbills. These plants are typically herbaceous perennials and can grow to a mature size of 1 to 3 feet tall and wide.
Out of the 280 species, relatively few of these species are commonly cultivated, many varieties of certain species are commercially produced. Breeding efforts in the past few decades have resulted in the introduction of many new and superior varieties.
Geraniums originated in Africa, according to the Old Farmer’s Almanac. Dutch traders brought them to Europe, where they were named geraniums because of their similarity to a hardy, wild geranium (Geranium) native to Europe. Botanists mistakenly included them in the geranium classification. They were later classified as Pelargonium, which means stork’s bill, referring to the shape of the seedpod.
Geranium leaves can be rounded, lobed, or deeply dissected and may have a smooth or hairy texture. The flowers are five-petaled and are borne in clusters or umbels. They can be in shades of red, pink, purple, white or salmon. Its growing habit include trailing (ivy-leaved geraniums), upright (zonal geraniums), and bushy or spreading forms.
These flowers are an excellent addition to the summer annual garden. They are hardy in U.S. Department of Agriculture hardiness zones 10 and 11 and usually flowers as annuals or perennials. Geraniums can be propagated from seeds, cuttings, or division.
Geraniums are drought and heat tolerant but can tolerate only minor frosts. Some species are extremely popular garden plants, grown as houseplants and bedding plants in temperate regions. They usually have a long flowering period. They work well when planted on their own or combined with other plants such as lavender and nemesia. Some types of geranium are perfect for growing in hanging baskets.
Common pests that may affect geraniums include aphids, spider mites, whiteflies, and caterpillars. Diseases such as powdery mildew, botrytis blight, and bacterial leaf spot can also occur, especially in humid conditions.
List of Geraniums
- Pelargonium × hortorum (Zonal geranium)
- Pelargonium x domesticum (Martha Washington or Lady Washington geraniums)
- Pelargonium peltatum (Ivy-leaved geranium)
- Pelargonium grandiflorum (Large-flowered geranium)
- Pelargonium odoratissimum (Apple-scented geranium)
- Pelargonium graveolens (Rose-scented geranium)
- Pelargonium citrosum (Citronella geranium)
- Pelargonium tomentosum (Peppermint-scented geranium)
- Pelargonium crispum (Lemon-scented geranium)
- Pelargonium sidoides (African geranium)
- Pelargonium cucullatum (Hooded-leaf geranium)
- Pelargonium capitatum (Rose-scented geranium)
- Pelargonium radens (Lemon-scented geranium)
- Pelargonium gibbosum (Nutmeg geranium)
- Pelargonium echinatum (Spiny-leaved geranium)
- Pelargonium fulgidum (Bright red geranium)
- Pelargonium reniforme (Kidney-leaved geranium)
- Pelargonium caffrum (Cape geranium)
- Pelargonium triste (Sad geranium)
- Pelargonium zonale (Horseshoe geranium)
- Pelargonium quercifolium (Oak-leaved geranium)
- Pelargonium fragrans (Apple geranium)
- Pelargonium denticulatum (Pine geranium)
Description
Pelargonium × hortorum (Zonal geranium)
Zonal geraniums are complex hybrids which have P. zonale and P. inquinans as dominant parents. These plants are characterized by leaves marked with a brown annular zone and inflorescence in the form of large balls of tight flowers, usually in shades of red, pink, or white. They are among the most common geraniums found in garden centers and florists, available in pots for windowsills, balconies, or planted in flowerbeds.
Hybrids are available in both F1 seed varieties (single flower types that flower the first year from seed and come true from seed) and vegetative varieties (semi-double to double types that are propagated by cuttings).
Pelargonium x domesticum (Martha Washington or Lady Washington geraniums)
Pelargonium x domesticum, commonly known as Martha Washington or Lady Washington geraniums, regal or royal pelargoniums. These plants were named after the wife of the first president of the United States, George Washington, and are native to North Africa. They feature large, flowers in shades of pink, purple, red, white, and yellow, with contrasting markings in the center of the flower. They are usually identified from their ruffled petals and bright green, serrated leaves.
Pelargonium peltatum (Ivy-leaved geranium)
Pelargonium peltatum, commonly known as Ivy-leaved geranium or ivy geranium, is trailing or cascading in nature with succulent, ivy-shaped leaves. They produce round clusters of single or double flowers in shades of pink, mauve, lilac, and white. The upper two petals of the flowers may have dark markings and curve back almost 90° degrees. They bloom throughout the warmer months from spring through fall.
Pelargonium grandiflorum (Large-flowered geranium)
Pelargonium grandiflorum, commonly known as the Large-flowered geranium feature large flowers and attractive foliage. Foliage is deeply lobed, with serrated edges. This geranium has an upright growth form, with stems that may become somewhat woody with age. The blooms are single or semi-double and can be in shades of pink, red, purple, white, and salmon. The petals may have some markings. They bloom throughout the warmer months, from spring through fall.
Pelargonium odoratissimum (Apple-scented geranium)
Pelargonium odoratissimum ( Apple-scented geranium) feature velvety and deeply lobed foliage with a scalloped edge. It is a small, spreading species that only grows up to 30 cm high and 60 cm wide. The leaves emit a strong, sweet fragrance reminiscent of ripe apples. This geranium produces small flowers in clusters above the foliage. The blooms are white or pale pink in color. It forms a dense mound of foliage, with stems that may become slightly woody with age.
Pelargonium graveolens (Rose-scented geranium)
Pelargonium graveolens (Rose-scented geranium) or Sweet-scented geranium, Old fashion rose geranium, has deeply lobed and serrated leaves with a fuzzy texture. The leaves too have a rose-like scent, when touched or lightly bruised which is why it is commonly known as the Rose-scented geranium. The blooms are pink or lavender in color. The flowers are not as showy as some other pelargonium species. In frost-free regions, Pelargonium graveolens usually develop into a large shrub.
Pelargonium citrosum (Citronella geranium)
Pelargonium citrosum, commonly known as the Citronella geranium or Mosquito plant has bright green leaves that emit a strong lemon-like fragrance when crushed. It has a bushy growth habit and its good for container gardening or as a bedding plant in garden borders. The blooms are usually pale pink or white in color. It is generally grown as an annual or brought indoors during the winter in colder climates.
Pelargonium tomentosum (Peppermint-scented geranium)
Pelargonium tomentosum, the Peppermint-scented geranium is an aromatic, low-growing, sprawling subshrub, with branches spreading in all directions. The stems are herbaceous and brittle, becoming somewhat woody with age. The leaves are grayish-green in color with fine hairs covering the surface. The leaves emit a strong, refreshing peppermint scent when crushed, similar to spearmint or peppermint candy. The leaves can be used to flavor tea, jellies, and pastries, and they are also included in pot-pourris. The blooms are white or pale pink in color.
Pelargonium crispum (Lemon-scented geranium)
Growing Geraniums
Though common geraniums tolerate partial sun, they flower best with at least four to six hours of direct sun each day. Water the geraniums thoroughly, but allow the soil to dry out between watering sessions. Spent flowers need to be removed to encourage the plant to produce more blooms. Pinch off stem tips to promote the development of more branches, which creates a bushy plant. Half-strength fertilizer applications help the geranium grow if applied every two months during active growth. You can propagate common geraniums through stem cuttings. They do not need rooting hormone to grow roots, so just slide the stems into dry soil and allow them to root.
Common geraniums are not usually bothered by insects or diseases. Whiteflies and aphids can infest the plants, using their leaves as hiding places, but a strong stream of water from a hose will get rid of these small pests. The main problem for these flowers is watering. Both under-and over-watering will cause the leaves to turn yellow. Over-watering causes stem and root rot. Always check the soil before watering and, if in doubt, wait another day before watering.