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Geraniums for Florida1
R. Schoellhorn2
Figure 1. Pink geraniums planted in a mixed container with white angelonia, pink sutera, and coleus. Geraniums are used as winter flowers in south and south central Florida, and as spring annuals in the northern parts of the state. General Information
More than half the flower growers and retail nurseries in the United States grow or sell geraniums, indicating their wide appeal and adaptability to a range of climates. Geraniums are popular for their continuous flowering throughout the summer and early fall in most of continental United States and Canada.Commercial producers and public institutions are actively breeding better geranium cultivars that have compact growth, increased branching and flowering, longer lasting, nonshattering flowers, earlier bloom, disease and insect resistance and a larger selection of different growth habits, foliage and flower color.
Geraniums are planted as soon as danger of frost is past in the spring in northern United States and Canada. Plants usually grow best at night temperatures of 60 to 65°F (16 to 18°C) and day temperatures of 70 to 85°F (21 to 29°C). In Florida the high summer temperatures retard their growth and flowering. Therefore in south Florida and the Keys geraniums should be planted in October or November. In central and north Florida where hard freezes occur during the winter, geraniums should be planted after the last frost in March.
For Floridians, geraniums pose some problems. They cannot tolerate a freeze, but they also do poorly in our summer heat and humidity. So, when is it best to grow them? For south Florida they become a winter flower, for central Florida they are best used in early spring, and for north Florida their season of interest is usually so short that they are not used heavily.
Some tips on getting the most from geraniums:
1. Avoid using geraniums where there is overhead watering or where they can get wet in our afternoon rains. A covered patio, or under the eave of a house is perfect; just make sure they get lots of sun.
2. Plant as early as possible; geraniums can take a light frost if they have had a chance to adjust to cool temperatures. Late plantings generally are short lived.
3. Keep geraniums in pots where they get better air circulation and you can keep them slightly drier than in the garden.
4. Always mulch any plantings of geraniums in the ground. Most of their disease problems originate in the soil, and when rain splashes dirt onto the leaves geraniums begin to decline quickly.
5. Look for plants better suited to Florida's climates, plants that require less care and chemicals to keep them looking their best. Try using pentas, coleus, and other heat-loving annuals that have a longer season and are more trouble free.
Culture
Geraniums grow best in full sun. They will tolerate partial shade, but usually will grow tall, producing few lateral branches and flowers. They should be spaced 18 inches apart in flower beds. To avoid disease problems and to give a well-groomed appearance, old flower heads should be removed.Soil. 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 2 to 3 inches of organic matter into planting beds will increase the water- and nutrient-holding capacities of the soil. Organic materials such as leaf mold or peat moss should be thoroughly mixed into the soil.
In areas where the soil is very poor, it is easier and less expensive to transplant small plants into inexpensive plastic 2- to 4-gallon (7.6 to 15.1 liters) pots filled with good organic soil and place the pots into flower beds in the yard. Sink the pots into the soil until the top surface of the pots is at soil level. Mulch with grass clippings, cypress bark or any other mulching material.
Fertilization. Garden soils, especially in new flower beds, are frequently infertile. Flower beds should be fertilized before planting or at planting time with complete soluble or partially soluble fertilizers. Use a complete fertilizer such as 6-6-6 or similar analysis fertilizer at the rate of 2 pounds (908 grams) per 100 square feet (9.3m2). The fertilizer can be incorporated when preparing the beds or it can be broadcast on top of the soil. Fertilizers should be applied early in the growing season and repeated monthly.
In recent years, controlled-release fertilizers have become available. These fertilizers release their nutrients slowly, thereby reducing frequency of application. Controlled release fertilizers can be incorporated uniformly throughout the soil on new geranium plantings. Surface applications are most effective on established plantings. (See Table 1 .)
Mulching. Mulching is a good practice to prevent weed growth and conserve soil moisture. In addition, mulching prevents injury from rain and overhead irrigation. Splashing water combined with loose particles of sand rasps leaves and causes injury. Grass clippings, straw, wood chips, sawdust and compost can be used as mulches.
Water. Water geraniums during dry periods to prevent wilting, eventual yellowing and dropping of leaves. The moisture content of the soil can be determined by picking up a handful of soil and pressing it in your palm. If it crumbles, the plants should be watered. Soil should be kept moist but not too wet. Keeping the soil wet encourages snail and slug populations that chew the foliage, and wet soil invites root-rotting organisms. Avoid overhead irrigation where possible, since wet flowers deteriorate very rapidly.
Growing Geraniums in Containers
Geraniums will grow well in pots and planters. Pots and planters should have drain holes to allow outflow of excess water. Pot and planter geraniums grow best in well-aerated soil mixes such as 1/3 native soil, 1/3 peat and 1/3 sand by volume. Incorporate 1/3 cup (3 ounces or 85 grams) of superphosphate, 1/3 cup (4 ounces or 113 grams) of dolomite and 1/5 cup (2 ounces or 85 grams) of a minor element mix into each cubic foot of soil mix. An easier way is to purchase sterilized ready-made soil mixes from garden stores.Overwintering
Geraniums will grow as a perennial in areas where frost is seldom experienced, such as Key West and Dade County, and protected areas in central Florida. This practice is discouraged since plants will grow out of bounds and become unsightly. Plants overwintered in the garage or indoors will not do well. Best results will be realized when new, good quality plants are used at each planting.Selection
Finding the best geraniums for Florida is difficult as the cultivars for sale in nurseries change year to year. The following tables are meant only to give you an idea of where to look, but the types of geraniums listed in the tables may or may not be available at your local nursery. In general, your best bet is to follow the culture guidelines in this article and the tips listed on the front page. Properly grown, almost all geraniums do well in their season.Traditionally, geraniums were propagated exclusively by vegetative means with commercial operators rooting cuttings from disease-free stock plants and selling them to local growers. Local growers used these rooted cuttings as stock plants from which they vegetatively propagated plants for sale. Important vegetatively propagated geranium cultivars as measured by their sales nationwide are presented in Table 2 .
Recently, there has been a trend toward growing geraniums from seeds. Seed-propagated geraniums perform as well as vegetatively propagated material and produce smaller plants at less cost to the consumer. Seed-propagated geraniums branch freely, are more compact and grow faster than vegetatively propagated plants. Seed geranium cultivars that are available and have shown outstanding performance in home gardens across the nation are presented in Table 3 .
There are also a group of geraniums called the ivy geraniums that are used in hanging baskets and mixed containers. This type of geranium is even more sensitive to heat and humidity, so for best results with ivy-type geraniums, keep them out of the rain and provide some protection from midday sun and heat. See Table 4 .
Pests
Occasionally cutworms and caterpillars will feed on geraniums. These insects can be readily detected by the chewed edges of leaves where they feed. If only a few are responsible for damage, they should be destroyed individually rather than by spraying the entire bed. Through periodic close examinations, insects can be detected and control measures taken before the entire flower bed is infested.For information on pesticides effective against various insects, contact your local county extension office. Follow label recommendations when spraying and thoroughly cover underside of leaves where many insects feed.
Diseases
Pythium blackleg. Black rot or pythium blackleg, caused by the fungus pythium, has been observed for many years to attack geraniums. Losses from pythium infestation occur mainly in propagation, but the disease also can be found on young plants.Pythium blackleg shows up first as a brown water soaking of the stem bases or at wounds on young plants. The rotted areas enlarge rapidly and turn coal black, progressing 3 or 4 inches up the stem from the base of the plant. Leaves wilt when the rot girdles the stem and death of the entire plant soon follows.
Blackleg may sometimes be confused with bacterial stem rot and in some cases both diseases may be found in the same group of plants. Plants affected with blackleg disease have a shiny, coal black, slimy, wet appearance and the rot progresses rapidly, often killing plants within a week or so. Plants affected with the bacterial stem rot have a dull-brown appearance and plants may not die for several weeks.
Pythium blackleg is spread primarily by infested soil in the flower bed area or potting media. The fungus also may enter plants' roots by way of holes in the bottoms of pots if they are placed on infested gravel, cinders or soil. There is some chance of spread through the use of propagation material from diseased plants. The best control is to pull out diseased plants and destroy them. A commercial fungicide specific for pythium can be used if the disease is in the initial stages.
Bacterial stem rot. Bacterial stem rot is caused by bacteria, which can be transmitted from infected soil by splashing water. The disease causes basal rot or die back on the growing points of older plants. This disease can be controlled by destroying infected plants.
Botrytis blight. Botrytis blight is probably the most common disease of geraniums. It is caused by Botrytis cinerea, a fungus that primarily lives on aging and dead tissue such as flowers, leaves, broken stems and cutting stubs. Under the right conditions it can attack and cause severe damage to leaves, stems and flowers of healthy plants, especially if they are soft and succulent.
The disease shows up on the blossoms as premature fading and drying of petals. The central florets are often the first to be affected. During periods of high moisture, affected blossoms may be covered with grayish brown masses of spores and the florets may be matted together.
The leaf spot phase of botrytis blight often appears when petals from affected blooms fall on the leaves and the pathogen attacks healthy leaf tissue. The leaf spot usually assumes the outline of the infected flower part that falls upon the leaf. However, when leaves are wet or the humidity is high, spots enlarge and become irregular, brown and water-soaked. If the high humidity continues, the spots become covered with grayish brown masses of spores. These spores are light and are carried by air currents or by splashing water to flowers, to stubs where parts of plants have been removed, or to healthy tissue if sufficient moisture is present.
Botrytis is a fungus that primarily lives on dead and aging plant tissues such as flowers, leaves and broken stems; thus, the probability of its spores being present in large numbers is in direct proportion to sanitation practices of the gardener. The more dead leaves and old flowers on the plants, the larger the number of potential disease-causing spores and the greater the chance of occurrence of the disease.
To control botrytis blight, avoid watering the foliage, especially in the evening and whenever humidity is high. Also, remove and destroy old, decayed leaves and flowers. Spraying with an appropriate fungicide should control the fungus.
Viruses. Several virus strains are known to affect geraniums. Crinkle or leaf curl virus causes wrinkled, deformed, young leaves, with colorless spots that are slightly thickened. The spots expand and turn yellow and finally develop into necrotic areas. This disease can be prevented by using virus-free plants. Diseased plants should be rogued out as soon as they are noticed. Yellow net vein virus causes yellow coloration of leaf veins. Control is the same as for other virus diseases: sanitation and control of insect vectors.
Tables
Table 1. Suggested application rates of controlled release fertilizers for geraniums grown in flower beds or containers.*
Osmocote® 14-14-14 lasts 2-3 months
Sierrablen® Nursery mix + iron19-6-10 lasts 4-5 months
Osmocote® 18-6-12 lasts 4-5 months
New Plantings
100 sq/ft (9.3 m2) of bed incorporated 4" (10 cm) deep
4 to 5 lbs (1.8 to 2.3 kg)
3 to 4 lbs (1.4 to 1.8 kg)
2 to 3 lbs (0.8 to 1.4 kg)
Established Plantings
100 sq/ft (9.3 m2) of bed surface applied
5 to 7 lbs (2.3 to 3.2 kg)
4 to 5 lbs (1.8 to 2.3 kg)
7 to 8 lbs (3.2 to 3.7 kg)
1 gallon (3.8 liters) container 1 heaping tsp. (approx. 6 cm3)
1 level tsp. (5 cm3)
1 level tsp. (5 cm3)
2 gallon (7.5 liters) container 2 heaping tsp. (approx. 12 cm3)
2 level tsps. (10 cm3)
2 level tsps. (10 cm3)
3 gallon (11.4 liters) container 3 level tsps. (15 cm3)
3 heaping tsp. (approx. 18 cm3)
3 heaping tsp. (approx. 18 cm3)
*The above rates are maximums. Do not exceed these recommendations. The above rates should be reduced when a build up of salinity occurs (for instance, as a result of infrequent or light irrigation, poor drainage, or high salinity levels in irrigation water), when potted plants are growing in shaded or low-light locations and/or when plants have been previously supplied with water-soluble fertilizers.
Table 2. Vegetatively propagated geranium cultivars.
Cultivars
Description
Red
Red Perfection Intense orange red. Similar in performance to 'Sincerity,' with large, brilliant, prolific flowers.
Improved Richard Orange red. Fine outdoor durability and somewhat non-shattering flowers. Shorter growth habit, slower and less prolific than 'Irene.'
Irene Rose red. Early and prolific flowering. Flowers shatter badly and are susceptible to botrytis. Sincerity* Brighter, more intense color than 'Irene' and 'Improved Richard.' Larger and more showy flowers than 'Irene.' Does not shatter as much and is botrytis resistant and self branching with stocky growth.
Cardinal Scarlet red. Intermediate color between 'Irene' and 'Dark Red Irene.' Strong growth habit and more vigorous than 'Dark Red Irene.' Strong flower stems.
Dark Red Irene Dark red. Similar to 'Irene' but a deeper color.
Yours Truly A sport from 'Sincerity' that blooms earlier and has more flowers and shorter growth habit. Other characteristics are identical to 'Sincerity.'
Pink
Skylark Large medium pink, profuse flowering and semidouble. Plant is erect, vigorous, bushy and compact. Genie Irene Rose pink. Self branching and compact. Prolific bloomer, sensitive to shattering and susceptible to botrytis. Penny Irene Dark salmon. Earlier flowering than the other Irenes. Large flowers with moderate shattering. Susceptible to botrytis in prolonged wet conditions. Quest Bright rose pink, large flowers. Other growth habit similar to 'Sincerity,' somewhat shorter.
Salmon Supreme Attractive salmon pink similar to 'Didden's Improved Picardy.' Little shattering, but susceptible to botrytis under wet and humid conditions.
Springtime Irene Salmon pink. Similar in color to 'Salmon Supreme' and 'Didden's Improved Picardy.' Most compact grower in the 'Irene' family. Its early and free flowering characteristics make it very attractive. Less shattering, but most sensitive to botrytis of the 'Irene' series.
Didden's
Improved Picardy Salmon pink. Early prolific bloomer with excellent flower form. Compact growth habit. Large flowers, nearly shatter proof. Fine spring performance but susceptible to botrytis and develops foliar problems under high temperature conditions. Salmon Irene* Dark salmon, bright color, most prolific blooming variety in the 'Irene' family. Compact, self-branching habit. Flowers shatter and do not tolerate summer heat. Susceptible to botrytis in wet outdoor conditions.
Enchantress Fiat Light salmon pink. The leading light pink. Rated highly for its compact growth habit, attractive color, prolific flowering, and speed. Major objection is extreme sensitivity to bacterial wilt. White
Snowmass Produces more flowers in the garden than any other white geranium. Upright growth habit, but not leggy. Flowers are shatter resistant and less sensitive to botrytis.
Snowman* White flowers. Modesty A white Irene similar in growth characteristics to 'Irene.'
Summer Cloud Large semidouble flowers, partially shatter proof and flower form resembles 'Irene.' More spreading than 'Snowmass.'
Purple
Springfield Violet* Rose purple flowers.
*Cultivars that perform well under Florida's growing conditions. Table 3. Seed geranium cultivars.
Cultivars
Description
Nittany Lion (Inbred cultivar)
Bright red, single florets borne in large compact trusses. Variegated leaves. Red Express* Red. Ringo Rose* Rose. Showdon* White. Carefree Series
Carefree Bright Rose
Bright rose, compact habit and early bloom. Deep green foliage.
Carefree Bright Pink
Bright pink, compact habit and early bloom. Deep green foliage.
Carefree Crimson* Intense crimson, deeper in color than 'Carefree Scarlet.' Well-defined zonal markings on leaves. Carefree Deep Salmon Early bloom. Leaves lightly zoned. Carefree Fickle Rose Rich rose florets with white centers. Carefree Fickle Scarlet White throat. Carefree Light Pink Soft delicate pink. Carefree Light Salmon Soft, luminous salmon. Carefree Picotee White with pink edge. Carefree Red A deep salmon red. Carefree Scarlet Scarlet blooms, compact habit and early bloom. Deep green foliage.
Carefree White White flowers, compact habit and early bloom. Green foliage.
Carefree Coral Glowing coral salmon with leaves deeply zoned. Sprinter series
Sprinter Scarlet Salmon scarlet. Dwarf habit. Sprinter Deep Red Vermillion red. Sprinter Salmon Medium salmon. Sprinter White Pure white under most growing conditions. Flash series
Fire Flash* Vermillion red. Salmon Flash Deep salmon. Scarlet Flash Scarlet. Sooner series
Sooner Red Bright vermillion scarlet. Sooner Deep Salmon Bright coral-salmon flowers, long bloom season. Green foliage.
*Cultivars that perform well under Florida's growing conditions. Table 4. Ivy geraniums for Florida.
Stardom Series Many colors available, heat tolerant and vigorous. Global Red Peppermint Burgundy and white flowers, heat tolerant. FloraStar winner Global Neon Cherry Hot pink ivy geranium has semi-double florets with a medium green foliage, heat tolerant. FloraStar winner.
Cascade and Blizzard Series Many colors in the series. Also known for strong performance and heat tolerance. Table 5. Websites of the major breeders of geraniums in the United States and Europe.
Fischer Geraniums http://www.fischerusa.com
Oglevee Geraniums http://www.oglevee.com
Proven Winners http://www.provenwinners.com
Ball Corporation http://www.ballfloraplant.com
FIDES North America http://www.fidesnorthamerica.com
The Flower Fields http://www.ecke.com
Footnotes
1. This document is Circular 472, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: June 1990. Reviewed: March 1991. Reviewed and revised October 2003.2. Rick Shoellhorn, associate professor, commercial floriculure specialist, Environmental Horticulture Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
Copyright Information
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