AGRICULTURAL EXTENSION SERVICE
By JOHN V. WATKINS
Associate Professor of Horticulture, University of Florida
Attractive small-flowered chrysanthemums like these are easily grown in
Florida when given proper care. (Photo by D. G. A. Kelbert.)
Chrysanthemums, popular wherever gardens are grown, are
to be found in all sections of Florida. These hardy perennials
will bloom dependably if they are given good conditions and if
certain precautions are observed.
Because of the rapid strides that are being made by the
hybridizers, and current selection for resistance to the virulent
stunt disease, the lists are constantly changing and beautiful
new varieties of striking color and form are being introduced
each year. The nursery from which you order will furnish a
list of the best varieties for Florida.
Many gardens are adorned by the small-flowered chrysan-
themums, but the huge mums that are seen at football games
are so seldom in evidence in Florida gardens that people often
ask if they can be grown here. The answer must certainly
be made in the affirmative. This gardener has grown large-
flowered mums of excellent quality, and some specialists are
producing them here commercially. The great amount of hand
work required for tying and disbudding during the warm days
of July and August and the frequency with which spraying is
needed to keep the plants free of insects and diseases are dis-
The genus Chrysanthemum is a large and variable one.
Some of its species are unadapted to our gardens while others
are very much at home here. Among our good species is that
great favorite, the Shasta daisy. Giant forms in single fringed,
double and anemone flowered are grown by commercial growers
and amateur gardeners. The Shastas can be lifted, divided and
reset during the autumn and winter, pointing toward spring
bloom which reaches its height in late spring. Soil-borne dis-
eases may reduce plantings, but generally Shastas may be
grown as perennials in the northern part of the state. In
southern Florida it may be necessary to renew the Shasta beds
with fresh plants each autumn.
Frequently we are asked about growing the widely exploited
azaleamums that have become so popular in the North. While
the plants grow well here, the blossoms, produced very early
in the autumn (August-September), are sometimes badly
browned by the feeding of flower thrips and mirids. The tradi-
tional propagation of azaleamums by division encourages the
spread of leaf spot and it is strongly recommended that all of the
precautions noted below be observed. Much-branched, low-
headed, stubby growing, azaleamums do not need staking and
The annual chrysanthemums, not to be confused with the
perennial forms, are summer composites that are sown after
danger of frost has passed. Needing much room because they
are rampant flounderers, the seedlings can be taken from the
seed flats and set about 24 inches apart in the row. In Florida
the widest use of the annual chrysanthemum is in adding a bit
of variety to the ubiquitous marigolds and zinnias of early
summer. Annual chrysanthemums are gross feeders, so plant
the seedlings in fertile beds and furnish supplementary feedings
about once every two weeks as suggested for the perennial
Planting and Culture of the Perennial Garden Type
Although perennial chrysanthemums will carry over for sev-
eral years, and can be divided for increase plantings when
growth starts in the spring, it is usually more satisfactory to
destroy the old plants and start new, disease-free plants each
year. The best time to plant is May or very early June.
Planting distances will vary with the type and fertility of
the soil, the method of support and other factors. When chry-
santhemums are grown on fertile soil and staked individually,
18 inches apart in 24-inch rows is a satisfactory distance. If
plants grow in rows to be supported by double horizontal wires,
shorten the interval to 12 inches and allow the branches to
intertwine for additional support.
Drive a square wooden stake close by each plant, and tie
the growing plant with soft cotton cord every 8 or 10 inches.
Wire stakes are likely to whip in the wind and bend under
the weight of water-filled blossoms, when used for out-door
plantings. Wires are used in greenhouses.
After the plants are growing well, apply a mulch of oak
leaves, pine straw or cow manure and start bi-weekly feedings
of a balanced fertilizer. This material may be applied dry
and watered in or, better still, in water solution from a sprinkling
can. Caution-do not allow the nutrient solution to fall upon
the leaves. If this is unavoidable, sprinkle the foliage carefully
after you have finished putting out the fertilizer.
Pinch small-flowered chrysanthemums to induce branching.
Remove the terminal bud when there are four to six leaves.
Repeat as necessary, but don't pinch after July. Handle large-
flowered varieties so that the single terminal bud of each shoot
forms the flower; remove all axillary buds at the leaf bases
as soon as they can be grasped by the thumb and forefinger.
Leaf-spotting of chrysanthemums, the result of infection
by several different fungi, is particularly serious in Florida,
and in certain years clean foliage is restricted to small rosettes
just below the blossoms. A suitable fungicide, such as cuprous
oxide, Flordo or the new Fermate spray, should be used fre-
quently during the growing season to keep these insidious dis-
eases from becoming established on new foliage. The old
brown leaves carry the disease over from one season to the
next, and for this reason the ground under the plants must
be drenched with the fungicide.
Because the foliage diseases are carried over so readily, the
old practice of increasing chrysanthemums by division is dis-
couraged. This easy method of propagation is almost certain
to transmit leaf-spot to new plantings. The preferred method
is to buy new, clean, rooted cuttings in June from a specialist,
pot these in fresh soil, and then set the plants in a fertile bed
which has not had chrysanthemums in it recently. Rooted
cuttings may be set direct in fertile beds if they are carefully
shaded and faithfully watered.
Chrysanthemum stunt is a virus disease which became wide-
spread in the nineteen forties. Plants infected with this virus
remain dwarfed and flower-less. Northern chrysanthemum spe-
cialists take great pains to grow stunt-free planting stock. Upon
inquiry these firms will submit lists of their stunt-free varieties.
If it is not feasible to purchase fresh plants, take leafy
tips from vigorous new shoots and dip these slips in a solution
made by mixing 1 ounce of Fermate in 3 gallons of water.
Set these leafy cuttings in fresh sand in a propagating box
made from new boards.
While the application of the fungicidal spray at frequent
intervals is the first line of defense, it is considered that a
mulch of leaves or straw may be of some help by decreasing
the splattering of spores by rain from infected soil under the
plants onto the leaves. The mulch increases the vigor of the
plants by conserving moisture and lowering soil temperatures.
As a further precaution against the leaf-spotting diseases,
it is suggested that rotation between several plots be practiced.
Two or three well drained, sunny areas can be used in alter-
nating years, and these may be planted to annuals or bulbs in
It has been noted that some varieties show marked suscep-
tibility to leaf-spotting fungi, while others are less severely
attacked. This varietal difference is noted with regard to the
stunt disease as well.
Probably the most troublesome insect pests are the flower
thrips and plant bugs belonging to the family Miridae. Both
are usually present in large numbers during the warm, dry
weather of autumn. Control by spraying with 15 percent wetta-
ble parathion used at the rate of a level tablespoon in a gallon
of water. Repeat every 7 to 10 days after color shows. This
chemical is a deadly poison and so the operator should wear
a gas mask, waterproof gloves and heavy duty clothing.
If a rigorous program of spraying is not feasible, back-
yard gardeners should do well to select varieties that flower
during November and December. At that time of the year
lower temperatures usually aid in reducing infestation by flower
thrips and mirids and blossoms should be of good quality.
The mealybug is another insect that was of importance in
the past, but this pest will not appear if parathion is applied
regularly on schedule.
Aphids are easily controlled by nicotine sulphate, rotenone
or pyrethrum sprays.
Only recently has the foliar nematode been recognized as
a pest in Florida, yet it has long been rated as one of the prin-
cipal pests of chrysanthemums in the North. Tiny eelworms
work inside the leaf, where sprays or dusts cannot reach
them. Injury by foliar nematodes is sharply defined by leaf
veins where the brown area stops, while the leaf-spotting dis-
ease involves rounded areas without being delimited by leaf
veins. This leaf-infesting worm crawls up the moisture-coated
stems to invade fresh foliage which soon turns brown. During
periods of rainfall this pest may spread rapidly to involve the
total leaf surface and cause much damage.
The immediate destruction of all infested plants, minimum
wetting of the stems and foliage when watering and frequent
applications of bordeaux mixture are thought to be helpful.
(In this case the bordeaux is a repellent.) Some gardeners
in the North report that a mulch of tobacco stems is definitely
worth while. As the eelworm is carried over in stolons and
bits of plants as well as in dried, fallen leaves, the destruction
of old plants and rotation of plots as recommended has added
In parts of Florida where frosts are expected in late autumn
it will be necessary to protect chrysanthemum blossoms that
come in November and December. Several methods of frost
protection are used by commercial growers and fanciers.
1. A muslin cover can be tacked to wooden supports over
the plant when color shows in the buds.
2. The plants can be potted about the middle of November
so that they can be moved indoors on cold nights.
3. The plants can be dug with balls of earth and trans-
planted to a greenhouse, sash-house or other protected place.
With good care, the plants will scarcely wilt and the blossoms
will be of excellent quality.
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of Mayn 8 and June 30, 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLORIDA
FLORIDA STATE UNIVERSITY
AND UNITED STATES DEPARTMENT OF AGRICULTURE
H. G. CLAYTON, Director