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not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
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Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
R.J. Black and B. Tjia
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences
University of Florida, John T. Woeste, Dean
GERANIUMS FOR FLORIDA
Robert J. Black and Benny Tjia
Department of Ornamental Horticulture
University of Florida
Gainesville, Florida 32611
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 (Figure 1).
Figure 1. New geranium cultivars are such prolific bloomers that the foliage is
often hidden under a canopy of flowers.
Geraniums are planted as soon as danger of frost is past in the spring in north-
ern United States and Canada. Plants usually grow best at night temperatures of 60
to 650F (16 to 180C) and day temperatures of 70 to 850F (21 to 290C). 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.
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 well groomed
appearance, old flower heads should be removed (Figure 2).
Figure 2. After geranium flowers shatter, the unsightly flower stalks should be re-
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 water and nutrient holding capacities of the soil. Organic
materials such as leaf mold or peat moss should be thoroughly mixed in 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 infer-
tile. Flower beds should be fertilized prior to planting or at planting time with
completely 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 g) per 100 square
feet (9.3 m2). 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 on a monthly basis.
In recent years controlled release fertilizers have become available. These
fertilizers release their nutrients at a slow rate, thereby reducing frequency of appli-
cation. Controlled release fertilizers can be incorporated uniformly throughout the
soil on new geranium plantings (Table 1). Surface applications are most effective on
Table 1. Suggested application rates of controlled release fertilizers for geraniums
grown in flower beds or containers.*
Osmocote Nursery Mix + iron
2-3 months 4-5 months
100 sq/ft (9.3 m2)
of bed incorporated
4" (10 cm) deep
100 sq/ft (9.3 m2)
of bed surface
1 gallon (3.8
2 gallon (7.5
3 gallon (11.4
4 to 5 Ibs
(1.8 to 2.3 kg)
5 to 7 Ibs
(2.3 to 3.2 kg)
1 heaping tsp.
(approx. 6 cm3)
2 heaping tsps.
(approx. 12 cm3)
3 level tbsps.
3 to 4 Ibs
(1.4 to 1.8 kg)
4 to 5 Ibs
(1.8 to 2.3 kg)
1 level tsp.
2 level tsps.
3 heaping tsps.
(approx. 18 cm3)
2 to 3 Ibs
(0.8 to 1.4 kg)
7 to 8 Ibs
(3.2 to 3.7 kg)
1 level tsp.
2 level tsps.
3 heaping tsps.
(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 as a result of infrequent or light irriga-
tion, poor drainage, high salinity levels in irrigation water, when pot plants are growing in
shaded or low light locations and/or when plants have been previously supplied with water
The use of trade names in this publication is solely for the purpose of providing specific infor-
mation. It is not a guarantee, warranty, or endorsement of the products named and does not
signify that they are approved to the exclusion of others.
Mulching. Mulching is a good practice to prevent weed growth and conserve
soil moisture. In addition, mulching prevents injury from rain and overhead irriga-
tion. Splashing water combined with loose particles of sand rasp leaves and cause
injury. Grass clippings, straw, wood chips, sawdust and compost can be used as
Water. Water geraniums during dry periods to prevent wilting, eventual yellow-
ing and dropping of leaves. Moisture content of the soil can be determined by pick-
ing 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 encour-
ages snail and slug populations that chew the foliage and invites root rotting organ-
isms. Avoid overhead irrigation where possible, since wet flowers deteriorate very
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.
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.
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.
Table 2. Vegetatively propagated geranium cultivars.
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, self
branching and has 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.
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 sim-
ilar to Sincerity, somewhat shorter.
Attractive salmon pink similar to Didden's Improved
Picardy. Little shattering, but susceptible to botrytis
under wet and humid conditions.
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 sensi-
tive to botrytis of the Irene Series.
Salmon pink. Early prolific bloomer with excellent
flower form. Compact growth habit. Large flowers, near-
ly shatter proof. Fine spring performance but susceptible
to botrytis and develops foliar problems under high
Dark salmon, bright color, most prolific blooming variety
in the Irene family. Compact, self branching habit.
Flowers shatter and do not tolerate summer heat. Sus-
ceptible to botrytis in wet outdoor conditions.
Light salmon pink. The leading light pink. Rated highly
for its compact growth habit, attractive color, prolific
flowering, and speed. Major objection is its extreme
sensitivity to bacterial wilt.
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.
A white Irene similar in growth characteristics to Irene.
Large semidouble flowers, partially shatter proof and
flower form resembles Irene. More spreading than Snow-
Rose purple flowers.
*Cultivars that perform well under Florida's growing conditions.
Recently, there has been a trend toward growing geraniums from seeds. Seed
propagated geraniums perform as well as vegetatively propagated material and pro-
duce 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.
Table 3. Seed Geranium Cultivars
Carefree Bright Rose
Carefree Bright Pink
Carefree Deep Salmon
Carefree Fickle Rose
Carefree Fickle Scarlet
Carefree Light Pink
Carefree Light Salmon
Bright red, single florets borne in large compact trusses.
Bright rose, compact habit and early bloom. Deep green
Intense crimson, deeper in color than carefree scarlet.
Well defined zonal markings on leaves.
Early bloom. Leaves lightly zoned.
Rich rose florets with white centers.
Soft delicate pink.
Soft, luminous salmon.
White with pink edge.
A deep salmon red.
Sprinter Deep Red
Glowing coral salmon with leaves deeply zoned.
Salmon scarlet. Dwarf habit.
Pure white under most growing conditions.
Bright vermillion scarlet.
Sooner Deep Salmon
*Cultivars that perform well under Florida's growing conditions.
Occasionally cutworms or caterpillars will feed on geraniums. They 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 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.
Pythium Blackleg. Black Rot or Pythium Blackleg caused by the fungus pythi-
um has been observed for many years to attack geraniums. Losses from pythium
infestation occur mainly in propagation, but it also can be found on young plants.
The disease 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 black-
leg 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 bot-
tom 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. 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 gerani-
ums. It is caused by Botrytis cinerea, a fungus which 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 which 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 which 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.
iThis publication was printed at a cost of $1092.00, or 7 cents per copy, to
provide information about growing geraniums in Florida. 3 15M 80
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLOR-
IDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,
K. R. Tefertlller, director, In cooperation with the United States
Department of Agriculture, publishes this Information to further the
purpose of the May 8 and June 30, 1914 Acts of Congress; and is
authorized to provide research, educational information and other
services only to individuals and Institutions that function without regard to race, color,
sex or national origin. Single copies of Extension publications (excluding 4-H and Youth
publications) are available free to Florida residents from County Extension Offices.
Information on bulk rates or copies for out-of-state purchasers is available from C. M.
Hinton, Publications Distribution Center, IFAS Building 664, University of Florida,
Galnesvllle, Florida 32611. Before publicizing this publication, editors should contact
this address to determine availability.