Petunias are popular and reliable flowering ornamental plants. Versatile
annuals, petunias can be used in flower beds, hanging baskets, window
boxes and other types of containers. They also can be used as cut
flowers. The blossoms of petunias come in many colors with petal
edges that are straight or ruffled.
general classes of petunias are Grandiflora and Multiflora. Grandiflora
petunias are characterized by having fewer, but larger, showy flowers.
A number of Grandifloras are cascade selections, well suited to
growing in hanging baskets, window boxes and other types of planters.
Multiflora petunias have a more compact growth habit and have smaller
but more numerous blossoms. Multifloras generally withstand wind
and hard rains better than the Grandifloras.
Grandiflora and Multiflora types may have single flowers, with one
set of petals on each flower, or double flowers with multiple sets
of petals on each flower.
There are hundreds of petunia varieties available in the nursery
industry. Local landscape nurseries and other retail stores usually
handle those varieties that are best suited to local environmental
are normally propagated from seed. Petunia seed is best sown indoors
four to six weeks prior to planting outdoors. Sow the seed in a
moist, well drained, pasteurized medium. Commercially prepared mixes
work best to germinate seed. Do not cover the seed when sowing.
with a fine mist from above or sub-irrigate from below by setting
the germination container in a shallow container of water. Excessive
water should be allowed to drain. The germinating medium can be
kept from drying out by covering the container with a pane of glass
or with a plastic bag. Keep the container in a location with bright
light, but not in direct sunlight, until germination begins. Maintain
a minimum soil temperature of 70 degrees F and maximum of 80 degrees
F. Seedlings can emerge in three to four days under optimum conditions.
During germination, try to avoid conditions (seedlings being too
thick, excessive soil moisture and cool soil temperatures) that
favor damping-off disease.
the seedlings have emerged, remove the covering and allow the growing
medium to become slightly dry between waterings, but do not allow
the seedlings to wilt. Watering is critical at this small seedling
stage! Fertilize the young seedlings with a diluted formulation
of starter fertilizer.
Transplant the seedlings to trays or individual containers at the
two leaf stage, or in about 14 to 21 days. Use disease free containers
and sterile growing medium. Carefully lift the young seedlings from
the germinating medium using a knife or flat stick. Lift only a
few at a time to prevent excessive root drying. When transplanting,
hold the young leaves of the seedlings, not the stems. Maintain
the plants at about 65 degrees F, if possible. Fertilize every two
weeks with one ounce of 20-20-20 fertilizer in three gallons of
water. When well-rooted, these plants can be moved outdoors on warm
days. Like purchased transplants, they should be acclimated slowly
to the outdoors. Protect the seedlings to prevent sunscald, wind
damage or wilting.
plants, whether purchased or grown at home, should be carefully
transplanted when set outdoors. Plant after all danger of frost
is past and when the soil temperature has reached at least 60 degrees
F. Avoid excessive root and soil disruption around the transplant.
Plant the young transplants at the same depth they were growing
in the containers. Water thoroughly after transplanting to avoid
excessive wilting. A soil ridge around the plant will help hold
water in the vicinity of the plant. Young plants may need protection
for a few days following transplanting during hot, windy weather.
Plant on a cloudy day if possible. Plants can be spaced about 12
inches apart in the garden.
do best in full sun, although they will tolerate several hours of
light shade a day. Two pounds of 5-10-5 fertilizer or one pound
of 10-10-10 dry fertilizer per 100 square feet can be incorporated
into the soil at planting. A half rate application can be spread
around the plants in July if needed. Too much fertilizer can cause
excessive vegetative growth and sparse flowers. In high pH soils
(alkaline soils) additional iron or iron sulfate may be beneficial
to reduce chlorosis (yellowing) of the foliage.
to a depth of six to eight inches when the soil becomes dry. The
frequency of watering will depend on the type of soil, weather conditions
and the amount of mulch. A mulch will not only reduce soil water
evaporation but will also reduce splashing of water onto the lower
leaves, moderate soil temperatures and reduce weed competition.
Do not allow the soil around the plants to remain excessively wet
for several days, as this can lead to stunted, chlorotic growth
or disease. Remove weeds from the plantings that compete with the
petunias for moisture, nutrients and light.
the plants can be used to increase the number of flowering stems
and discourage excessive vegetative growth. Remove old flowers (dead
heads) when they start to fade to encourage repeat blooming.
Petunias are relatively free of disease and insect pests. Damping-off
can be a serious disease problem, however, rotting the seeds during
germination or killing the seedlings after emergence. Good sanitation
practices and maintenance of proper moisture and temperature levels
can minimize damping-off disease.
Petunias with virus diseases can have foliage that is stunted and
deformed, often with light-green streaks, and discolored and deformed
flowers. The best control is to remove and destroy diseased plants
and keep aphids and other insects which transmit the virus under
control. Alternaria blight, crown rot, fusarium wilt, botrytis and
fasciation are other diseases of petunias. Insects are generally
not a problem on petunias. However, isolated cases of aphid
and cutworm infestations do occur. Remember
that healthy, vigorous plants are less susceptible to pest damage
than unhealthy plants.
foliage on petunias may also be caused by nitrogen or iron deficiency
within the plant. Both can be corrected with the proper supplemental
from Dale T. Lindgren, Nebraska Extension, 2000