Genus: Geranium

Pelargonium

Photo/Illustration: 
Jennifer Brown
Geranium (Pelargonium)
pel-ar-GO-nee-um
Geraniaceae
This genus of mostly evergreen perennials, shrubs, and succulents comes mainly from South Africa. The innumerable cultivars are divided into 6 groups, and they originate from roughly 20 species. They are a staple for hanging baskets, summer bedding, and greenhouse displays. They have terminal clusters of flowers with 5 petals, which may be shaped like saucers, stars, butterflies, trumpets, or funnels. Most bloom in spring or summer, but some may flower in winter if temperatures are kept around 45° to 50°F. Many have foliage with attractive markings and a distinct, rich aroma.
Noteworthy characteristics:  This plentiful and charming genus offers plants with an abundance of flower colors and decorative leaf forms for both indoors and outdoors.
Care:  Deadhead spent flowers consistently. Outdoors: grow in neutral to alkaline, well-drained soil and preferably full sun (regals prefer partial shade and zonals tolerate some shade). In hot climates, provide mid-day shade; in cold climates, overwinter indoors and trim back by one-third and repot when grown resumes. Indoors: provide with light soil mix, good light and ventilation, and mid-day shade. Fertilize every two weeks during growth and water sparingly in winter.
Propagation: 

Root softwood cuttings in spring, late summer or early fall. Sow seed from late winter to early spring at 70°F.

Problems: 

Spider mites, thrips, mealybugs, caterpillars, mildew, gray mold, black leg, flower break virus, Xanthomonas blight, edema.

Species, varieties and clutivars for genus Pelargonium

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Pelargonium 'Crystal Palace Gem'
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Geranium
Pelargonium crispum
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Geranium
Pelargonium crispum ‘Variegatum’
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Kalwerbossie geranium
Pelargonium sidoides
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Mint-scented geranium
Pelargonium tomentosum
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Geranium
Pelargonium ‘Attar of Roses’
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Geranium
Pelargonium ‘Lady Scarborough’
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Geranium
Pelargonium ‘Pungent Peppermint’
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Geranium
Pelargonium ‘Roger’s Delight’