Pelargonium x hortorum Geranium1
There are many varieties of geranium with flower colors of red, pink, white, orange, or combinations of these (Fig. 1). Red geraniums attract butterflies and hummingbirds to the garden. They make good potted plants, but the lower leaves will turn yellow and fall if allowed to get too dry. Dead blossoms should be removed regularly to promote continued flowering. Geraniums can be used nearly year round in warm climates. They do best in cool weather in most parts of central and southern Florida.
Scientific name: Pelargonium x hortorum
Pronunciation: pell-lar-GO-nee-um hor-TOR-rum
Common name(s): geranium
Plant type: annual
USDA hardiness zones: all zones (Fig. 2)
Planting month for zone 7: May
Planting month for zone 8: Apr
Planting month for zone 9: Feb; Oct; Nov; Dec
Planting month for zone 10 and 11: Feb; Nov; Dec
Origin: not native to North America
Uses: mass planting; hanging basket; border; attracts hummingbirds
Availability: generally available in many areas within its hardiness range
Height: 1 to 2 feet
Spread: 1 to 2 feet
Plant habit: round; upright
Plant density: moderate
Growth rate: moderate
Leaf arrangement: opposite/subopposite
Leaf type: simple
Leaf margin: serrate
Leaf shape: reniform
Leaf venation: palmate
Leaf type and persistence: not applicable
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: not applicable
Fall characteristic: not applicable
Flower color: pink; white; red; orange
Flower characteristic: showy
Fruit shape: no fruit
Fruit length: no fruit
Fruit cover: no fruit
Fruit color: not applicable
Fruit characteristic: inconspicuous and not showy
Trunk and Branches
Trunk/bark/branches: not applicable
Current year stem/twig color: green
Current year stem/twig thickness: very thick
Light requirement: plant grows in part shade/part sun
Soil tolerances: clay; sand; acidic; loam
Soil salt tolerances: unknown
Plant spacing: 18 to 24 inches
Roots: not applicable
Winter interest: not applicable
Outstanding plant: not particularly outstanding
Invasive potential: not known to be invasive
Pest resistance: long-term health usually not affected by pests
Use and Management
Planting into a full to partial sun location in the landscape can be done from October to about March in south and central Florida. Plant in the spring after danger of frost in the north and western part of Florida. If plants can be brought indoors on cold nights, geraniums perform nicely most of the winter in north Florida in a full sun location. Come summer time, if plants receive no more than about 3 hours of sun, flowers may continue to form for most of the summer. Flowering fades by mid to late summer. Cut plants back in north Florida in early fall and fertilize to stimulate new growth and improve appearance. Plants should begin to grow and do nicely again in the fall and winter.
Geraniums grow best in full to partial sun in loamy, well-drained soil. Plants may become established more quickly if flower buds are removed at planting time, but setting the plants too deeply could cause stem rot. Geraniums grow best when fertilized at regular intervals. Yellow leaves could be a sign you waited too long to fertilize.
Geraniums used as bedding plants can be spaced 12 to 24 inches apart to form a solid, colorful ground cover. Provide good drainage by planting in a slightly raised bed.
Geraniums are propagated by seed or cuttings. Cuttings need at least three nodes and are usually taken in late summer. Remove the lower leaves, leaving only the tuft of leaves at the top of the cutting. Geranium cuttings root well in vermiculite. The seed germinates in one to three weeks at temperatures between 70 and 75-degrees F. Cover the seed with about an eighth-inch of soil. Do not allow the soil to dry out excessively.
There are numerous cultivars and series available for flower color and plant size.
Pests and Diseases
Aphids suck plant juices and heavy infestations cause distorted growth.
Four-lined plant bug causes small, round, sunken, brown spots to form on the leaves.
Greenhouse whitefly and sweet potato whitefly can rapidly build up on geraniums. Early detection and control is necessary.
Bacterial leaf spot causes spots on the leaves of garden plants, particularly if they are overcrowded. The spotting will be worse on the lower leaves. The spots are small, circular or irregular, and brown and sunken. When the spots run together, a portion of the leaf is killed. The entire leaf may turn yellow, then brown, then drop off. Use proper spacing and pick off and destroy infected leaves.
Blossom blight or gray mold causes flower petal discoloration and flower drop. A gray mold may be seen on the leaves.
Cuttings may be attacked by stem rot or blackleg. The stems of cuttings turn black with rot. Use healthy cuttings and sterile rooting media.
Bacterial fasciation causes formation of masses of short, thick and aborted stems with misshapen leaves near the soil line at the bottom two nodes. The plants are not killed but will be dwarfed.