Dandelion
Jerry
Doll and Tim Trower*
Family: Composite (Asteraceae)
Name: Taraxacum
officianle
Life Span: Perennial
Description:
Leaves are crowed in a basal
rosette, blades are simple and variously lobed. Blades may also
be lightly pubescent, especially on the lower surfaces and
mid-veins, and contains a milky substance. The most prominent
feature is the flower head, which upon first opening contains a
series of yellow ligulate flowers borne on a hollow pseudostem.
Reproduction:
Dandelion is generally an
apomictic plant and seed production normally occurs without
pollination. Seed production varies from 54 to 172 seeds per
head and a single plant can produce more than 2000 seeds. One
estimate is that more than 240,000,000 seeds/acre could be
produced annually by a dense stand of dandelions.
Flowering peaks in early summer
with a second flush of flowers from mid-September to early
October. Some plants may flower any time during the growing
season. Two patterns of flowering are found. In the early
spring, flower heads remain open from sunrise to dusk, but in
June to August, they close by noon. Unusual weather conditions,
such as a sudden drop in temperature or very cloudy conditions,
cause flower heads to remain closed. Flower heads open for 2 to
3 days in early spring and mid to late fall and for less than 2
days in the summer. The heads remain closed for 10 days in the
early spring and fall, 6 to 7 days in the summer and 20 days in
late fall before opening a second time to release seed.
Dandelion seeds are readily
disseminated by the wind. The pappus expands and forms a
parachute-like structure at right angles to the main axis of the
seed when the relative humidity is 77% or less. Wind velocities
of only 4 mph or more will keep seed air borne. Dandelion seeds
are non-dormant when produced.
Control Methods:
Dandelion is easily controlled by
a fall application of 2,4-D or dicamba at 1 pt/A applied alone
or as a tank mix prior to the first killing frost. Fall-applied
glyphosate can also give acceptable control. Do not make
glyphosate applications when the air temperature is below 50
degrees F or if the plant has ceased active growth.
Dandelion control in the spring
with glyphosate applied alone is often only fair and is seldom
acceptable. Broadcast applications of 2,4-D ester at 1 pt/A
provide fair to good dandelion control prior to corn emergence.
Broadcast application of a 2,4-D/glyphosate tank mix at 1.0/1.0
pt./A will usually provide increased dandelion control compared
to 2,4- D applied alone. Postemergence applications of growth
regulator herbicides usually provide acceptable dandelion
control in corn. Deep tillage such as moldboard or chisel
plowing will weaken the plant by disturbing the taproot and may
make chemical applications more effective.
2,4-D ester may be applied prior
to soybean planting if a seven-day interval is observed between
application and planting. There is a slight risk of soybean
injury from preplant 2,4- D applications if the soil remains wet
and cool during germination, with lighter soils at greater risk.
There are no good postemergence options for dandelion control in
soybeans at this time. If possible, control heavy infestations
of dandelions in the fall if the field is to be planted to
no-till soybeans.
SENCOR and VELPAR are both labeled
for dandelion control in established alfalfa. SENCOR must be
applied prior to alfalfa green-up and VELPAR must be applied
prior to two inches of new alfalfa growth or crop injury may
occur. Do not treat stands under stress or less than two years
old. SENCOR may cause injury to forage grasses. Do not apply to
a mixed legume/grass stand unless significant grass injury is
acceptable.
Other Information:
Dandelions
have minimal impact on quality forage and are readily consumed
by most livestock. However, they are wetter than alfalfa and can
delay the drying time of hay. The seeds and plant parts are a
food source for many types of wildlife. Dandelion seed was
available to pioneers as ornamental flowers and was occasionally
used as a planting for sod roofs.
Sources:
World Weeds: Natural Histories
and Distribution
Weeds of Nebraska And The Great Plains, Nebraska Department
of Agriculture
2000 Pest Management in Wisconsin Field Crops
Please read and follow the
manufacturer’s label.
* Senior Outreach Specialist |
