Pelargonium x hortorum Geranium

Introduction

There are many varieties of geranium with flower colors of red, pink, white, orange, or combinations of these. 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.

General Information

Scientific name: Pelargonium x hortorum

Pronunciation: pell-lar-GO-nee-um hor-TOR-rum

Common name(s): geranium

Family: Geraniaceae

Plant type: annual

USDA hardiness zones: all zones (Figure 4)

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

Invasive potential: not known to be invasive

Uses: mass planting; hanging basket; border; attracts hummingbirds

Availability: generally available in many areas within its hardiness range

Description

Height: 1 to 2 feet

Spread: 1 to 2 feet

Plant habit: round; upright

Plant density: moderate

Growth rate: moderate

Texture: coarse

Foliage

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

Flower color: pink; white; red; orange

Flower characteristic: showy

Fruit

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

Culture

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

Other

Roots: not applicable

Winter interest: not applicable

Outstanding plant: not particularly outstanding

Pest resistance: long-term health usually not affected by pests

Use and Management

Planting in 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˚F–75˚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.