Table of Contents
- Growth Characteristics
Coltsfoot (Tussilago farfara) is a perennial weed native to Europe,
North Africa and parts of Asia. It was introduced to Canada in the
1920's, and can now be found in most provinces. It has been positively
identified through the Weed Alert Program in 27 counties in Southern
Ontario. While widespread in Southern Ontario, coltsfoot is still
found on only a relatively few farms. For example, up to 1986, it
has been reported on only 10 farms in Middlesex County. The most
common location for coltsfoot is on roadsides, both township roads
and highways. From this foothold, it can spread by seed or rhizomes
to adjacent fields. While this weed has not spread rapidly, it is
of concern because there are very few herbicides that will control
it adequately, and it thrives in several crops.
Figure 1. Coltsfoot patches in winter wheat, late flower
stage in early May.
Figure 2. Coltsfoot patch in flower, late April. Note absence
Figure 3. Coltsfoot, flowers and unopened seed heads.
Figure 4. Fully developed coltsfoot leaves in July.
Figure 5. Rhizomes and emerged flower heads.
Figure 6. Coltsfoot patch in corn in June. Leaves only partially
Figure 7. Coltsfoot patches in seed on roadsides.
Coltsfoot is a low growing perennial plant. It has large, deep
green leaves, somewhat similar in size and shape when fully grown
to those of velvetleaf or cocklebur. The plant has no main stem,
however. The leaf petiole holds the leaves 10 to 20 cm above the
soil, often forming a complete canopy covering the soil. The top
leaf surface has a smooth, almost waxy appearance, while the underside
of the leaf is covered with white wool-like hairs. Usually leaf
stems and larger leaf veins are distinctly purple in color.
Coltsfoot spreads by underground rhizomes, which develop mainly
in the plow layer (5 to 20 cm deep). These rhizomes produce quite
dense stands of above-ground foliage. It is common to find only
2 or 3 patches of coltsfoot in a field, with patches gradually expanding
outward due to rhizome growth. These patches usually range from
3 to 6 metres in diameter. Coltsfoot has a very unique flowering
characteristic. The bright yellow flowers, similar to dandelions
but slightly smaller, appear early in the spring, before any leaves
emerge. In Southern Ontario, coltsfoot flowers in April, often before
the last of the snowbanks have melted. Flower heads have even been
known to push through snow. The white, fluffy seed heads also resemble
those of dandelions. However, coltsfoot seed will mature by the
time the very first dandelions are coming into bloom. Coltsfoot
is not a prolific seed producer compared to many annual weeds, with
each plant reported to produce about 3500 seeds.
As seed on earlier flowers ripens, the coltsfoot leaves finally
begin to emerge above ground. Leaves will continue to grow in number
and size for several weeks, so that the canopy does not reach full
density until late June to mid-July. During the summer, food is
stored in the rhizomes for the following year's early spring growth.
Coltsfoot has the ability to thrive on gravelly soils, and is a
common weed in gravel pits. When gravel from infested pits is used
in roadbed maintenance, some rhizomes survive, and start up new
coltsfoot patches. Coltsfoot seems to compete strongly with the
roadside grasses, and is not controlled by commonly used roadside
herbicides. Eventually the patch may expand to creep under the fence
and into an adjoining cultivated field. Tillage operations can then
spread the weed throughout the field. Seed blown by the wind may
also start new patches, depending on the herbicide program being
used on the field where the seed germinates.
In field crops, coltsfoot has been reported in corn, soybeans,
winter wheat, spring grain and alfalfa stands. Once well established,
coltsfoot appears to hold its own against competition from these
crops. Field observations indicate that tillage equipment, particularly
chisel plows and cultivators, will carry rhizomes from a main patch,
and drop them elsewhere in the field, giving rise to new patches.
The spread of coltsfoot by this method is much slower in a field
than is the spread of quackgrass. However, if not controlled, coltsfoot
can in time take over a field.
While no doubt seed is a method of reproduction, it is much less
significant than for the common annual weeds. Seed production is
relatively low, and seed of coltsfoot will completely lose its viability
one year after production.
Field observations and research trials indicate no control of established
coltsfoot by the herbicides 2,4-D, MCPA, 2-4DB, Kil-Mor®, Banvel®
or Basagran®. Rates of atrazine up to 2 kg/ha active have not
given control in corn. The ppi and pre herbicides registered in
soybeans have not given control.
Roundup® has been used for the non-selective control of coltsfoot
and has often given good control. Poor control has usually been
due to herbicide application too early in the season. Coltsfoot
foliage is slow to develop in the spring, particularly if the field
has been worked and planted to a crop. Leaves may not be fully developed
until late June or mid-July. Application of Roundup at an earlier
stage will kill all foliage, but not eradicate the rhizomes.
When coltsfoot is detected while it is still present in only a
few patches, the application of a 2% solution of Roundup in water,
applied to runoff on fully developed coltsfoot leaves, has given
good control. A knapsack sprayer works well for such an application.
If applied in corn or soybeans, apply before corn starts to silk
or soybeans begin to pod. The crop will be killed in the sprayed
Control in an alfalfa stand is often not practical. There may not
be sufficient foliage development in coltsfoot prior to each alfalfa
harvest. Since Roundup will also kill the crop in the sprayed area,
the sprayed spots soon become infested with other weeds such as
dandelions. Any affected forage in the treated spots cannot be harvested
until treated plants turn brown.
To date, most coltsfoot occurs in only a few patches in a field.
If the weed has been well distributed in a field by tillage operations,
it may be necessary to apply an overall spray in a non-crop situation.
Additional information on use and precautions when using this herbicide
is available in the Ontario Ministry of Agriculture, Food and Rural
Affairs publication 75, Guide to Chemical Weed Control.
The best approach to coltsfoot control is to stop its spread when
only a few patches are present and before it becomes a serious problem
throughout the field or farm.