Geraniums

More than half of flower growers and retail nurseries in the United States grow or sell geraniums. This indicates their wide appeal and range of climatic adaptability. Geraniums are popular for their continuous flowering throughout the summer and early fall in most of continental United States and Canada.

Commercial producers together with public institutions, are actively breeding better geranium cultivars. They have compact growth, increased branching and flowering, longer lasting non-shattering flowers, earlier bloom, disease and insect resistance and a larger selection of different growth habits, foliage and flower color.

Traditionally geraniums are propagated exclusively by vegetative means. Commercial operators root cuttings from disease-free stock plants and sell them to local growers. Local growers use these cuttings as stock plants from which they propagate plants for sale. Geraniums take up considerable greenhouse time, space, heat and labor before reaching consumers, thus they are more expensive than many other bedding plants which require less time to produce. Recently, there is a trend toward growing geraniums from seeds. Seed propagate geraniums perform equally as well as vegetatively propagated material and produce smaller plants at less cost to the consumer. Seed propagated geraniums branch freely, are less leggy and seem to grow faster. Geraniums are at their peak of performance late winter through early summer in central and south Florida and early spring through early summer in north Florida. To ensure maximum performance, start with healthy, disease-free plants and follow proper cultural practices.

Geraniums grow best in full sun. They will tolerate partial shade but will usually grow tall, producing fewer lateral branches and consequently, fewer flowers. They should be spaced 18 inches apart in flowerbeds. To avoid disease problems and to give a well-groomed appearance, cut off all the old flower heads.

Geraniums grow best in soils that provide good drainage and aeration, and have good moisture and nutrient retention capacities. Florida's sandy soils should be amended with organic matter. Incorporation of two to three inches of organic matter into planting beds will increase both water and nutrient holding capacities. Organic materials such as leaf mold or peat moss should be thoroughly mixed in the soil.

Water geraniums during dry periods to prevent wilting and eventual yellowing and dropping of leaves. To determine the moisture content of the soil, pick up a handful of soil and press it in your palm. If it crumbles it needs watering. Soil should be kept moist but not too wet. Keeping the soil wet encourages snail and slug populations that chew on foliage and invites root-rotting organisms. Avoid overhead irrigation where possible, since wet flowers deteriorate very rapidly.

Garden soils, especially in new flower beds, are frequently low in fertility. Flower beds should be fertilized prior to planting or at planting time and then on a monthly basis. The rate of application should be based primarily on nitrogen content of the fertilizer. Use a complete fertilizer such as 6-6-6 or similar analysis fertilizer at the rate of 2 pounds per 100 square feet. Controlled-release fertilizers are ideal for Florida's sandy soils. These fertilizers help with maintenance, as applications are required less often than with rapid-release fertilizers. Controlled-release fertilizers can be incorporated uniformly throughout the soil before planting and applied on the soil surface of established plantings.

Mulching is a good practice to prevent weed growth and conserve moisture in the soil. In addition, mulching prevents rain and overhead irrigation water injury. Splashing water combined with loose particles of sand rasp leaves and causes injury. Wood chips, pine bark and composted yard waste can be used as mulches.

Occasionally cutworms or caterpillars will feed on geraniums. They can be readily detected by the cut edges of the leaves where they feed. If only a few are responsible for damage, they should be destroyed individually rather than spraying the entire bed.

The most common diseases that attack geraniums are non-specific in that they attack other plants as well. Black rot or Pythium blackleg, caused by the fungus Pythium, has been observed to attack geraniums for many years; and while losses to the disease mainly occur in the propagation stages, it can also be found on young plants. Plants infected with blackleg disease have a shiny, coal-black, slimy appearance. The rot progresses rapidly, often killing plants within a week. A commercial fungicide specific for Pythium can be used if the disease is in the initial stages.

Botrytis, caused by the common gray mold Botrytis cineris, produces spores which are airborne and germinate when they come in contact with wet foliage and flowers. To control Botrytis blight, avoid watering foliage and flowers, especially in the late evening and when the humidity is high. Also, since Botrytis starts most frequently on old decayed leaves and flowers, remove and destroy them.


Copyright by Dr. Bob's Gardening Tips