of Rhode Island GreenShare Factsheets
are popular shrubs and ornamentals in the southern part of the United
States where severe cold won't damage the plants. Plants always
seem to have more blooms at the time you receive them than any other
time in their life due to less than favorable growing conditions
in most homes.
thrive on 68-74 degrees F temperatures in the day, and 60 degrees
F evening temperatures. Plants prefer full sun indoors; if grown
outdoors for the spring, summer and early fall, keep plants in partial
shade. An east or covered west porch will be satisfactory.
humidity is essential to gardenia care. Avoid misting the foliage,
though, as leaf spot fungal problems will develop. The soil
be kept uniformly moist, but dont overwater. A loose, well-drained
organic soil is recommended.
monthly between April and November with an acid fertilizer.
regularly for insects and other pests such as aphids,
mealybugs, spider mites, thrips and scales.
Follow recommended control practices if pest problems occur.
most irritating problem encountered with gardenias is "bud
drop,"when flower buds abort just before blooming. Common
causes include low humidity, over-watering, under-watering, insufficient
light high temperatures, rapid temperature fluctuations, cold drafts
or change in plant locations. In other words, gardenias are temperamental!
Plants that do not set flower buds may be experiencing too much
One of the most common gardenia diseases, canker is identifiable
by a main stem swollen near or below the soil line. The bark also
becomes corky and contains numerous longitudinal cracks in the
cankered area. The stem above the canker is bright yellow in contrast
to normal greenish white. If the humidity is high, a yellowish
substance may be seen on the surface. Affected plants are stunted
and die slowly. Destroy all diseased plants to prevent spread
of the disease. Place new plants in a different location. Disease
is easily spread on propagating knives.
Leaf Spot (bacteria--Pseudomonas gardeniae, Xanthomonas
campestris cv. Maculifolium-gardeniae)
Small, round ovoid spots on young, tender leaves are the first
sign of bacterial leaf spot. As the spots enlarge, the center
is at first pale yellow and later becomes reddish-brown surrounded
by a yellow halo. Margins of the lesions are thickened and water-soaked
in appearance. Spots may coalesce to form large, irregularly shaped
spots. Severe infection may cause defoliation. Avoid overhead
watering. The disease is spread by taking cuttings from infected
plants. Use sterilized soil and pots.
Leaf Spot (fungus--Rhizoctonia spp.)
Leaves infected with this fungal leaf spot disease have tan to
brown spots up to 1/4 inch in diameter. Spots are circular and
zoned. The disease begins on the older leaves and spreads upward
when the plants are watered excessively or when air circulates
poorly because of overcrowding. Diseased leaves should be destroyed
and sterilized soil should be used. Disease-free plants should
be used for propagation. Avoid wetting foliage when watering.
Spot (fungi--Cercospora spp., Phyllosticta spp.)
These fungi cause spots of various sizes on leaves throughout
the year. Spots may be small, dark-brown necrotic areas surrounded
by a yellow halo. In severe cases, premature leaf drop may occur.
Control is obtained by spraying with a folia fungicide at regular
Sooty mold causes black, thin layers of the fungus to form over
the upper surface of the leaves. Sooty mold is caused by a fungus
that grows on sugary exudates from white flies. Control white
Bud drop, the abnormal dropping of buds, occurs during periods
of high night temperatures or during periods of low light intensity.
Some bud drop is a natural condition. Every effort should be made
to keep the soil uniformly moist, but not wet, during flowering.
Powdery mildew is characterized by white, powdery spots on leaves.
Use preventive fungicide.
Root Knot Nematode, Cotton Root Rot, Crown Gall and Mushroom Root
from the University of Illinois, 2001
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program