be eradicated but
requires special attention to its manner of growth and reproduction. Although it
is native, sumac is highly invasive. Allowed to proceed unchecked, it is able
to take over a prairie or savanna natural area. The shade under a sumac patch
can be enough to suppress virtually all native vegetation.
If the character of a natural area is to be maintained,
control of sumac is essential.
|A large sumac clone that has established itself in what was once a large prairie|
|The shade from this dense sumac clone has suppressed all native species|
The techniques described here are based on studies and observations done
over the past five years on both large and small sumac clones.
Sumac is a woody
plant that has the potential for forming large clones (thickets). It spreads
rapidly and is the single most-important woody invasive plant at many sites. It
spreads by rhizomes which form complex underground root systems. In addition to
their role in increasing the size of the clone, sumac rhizomes are capable of
sending up myriads of new shoots, called “root suckers
Sumac is very sensitive to herbicides such as triclopyr (Garlon 3A and 4),
so that existing stems can be killed by cutting and treating, or by basal bark
treatment. However, although herbicide treatment will kill above-ground stems,
rhizomes and the buds that turn into root suckers usually escape treatment. If
sumac is to be eradicated, these below-ground parts of the clone must be dealt
with. A principal part of the present post focuses on how root suckers can be
Sumac is sensitive to a variety of herbicides that are active against
broad-leaved plants. One of the best is triclopyr (Garlon).There are two chemical
forms: Garlon 3A is the water-soluble form and is recommended for foliar spraying
(used at 3% concentration) whereas Garlon 4 Ultra is the oil-soluble form and
is recommended for cut stem and basal bark treatments (used at 20% in bark oil). (There are
“generic” versions of triclopyr that are less expensive and but are equally effective.)
|Mowing a large sumac clone that had invaded a prairie remnant|
Mowing is often recommended as a
means of controlling sumac. What happens when sumac stems are cut?
the length of each sumac stem are buds that remain dormant as long as the top
part of the stem is alive. However, if the stem is cut, one or more of these
dormant buds are released and grow. The photo to left shows the response of a sumac stem to cutting. Thus, it is not possible to eradicate a sumac clone by mowing, although mowing can work well as part of an integrated management system.
Fire is often recommended as a way of
controlling sumac. What happens when sumac stems are burned?
growing shoot and all the buds along the sumac stem are generally top-killed by fire. However, each sumac stem has one or more dormant buds present at
its base. Since these buds are below the soil surface, they are not harmed
by fire. Therefore, when a stem is top-killed by fire, a dormant bud of that stem becomes activated
and sends up a new shoot. Thus, the sumac plant resprouts vigorously when killed by
burning. The photo to the right shows a new shoot just starting from the base of a stem that had been top-killed by fire.
What happens when sumac stems are
treated with herbicide?
|A prescribed burn will generally top-kill all stems of a sumac clone|
When a sumac stem is treated with triclopyr, either
with a foliar spray of Garlon 3A, or a cut stem or basal bark application with
Garlon 4 in oil, the stem and all its above-ground and below-ground buds are
|The stems of this small sumac clone were treated with Garlon 4 by basal bark. Within a few days the leaves exhibited damage by turning red and within several weeks the whole plant was dead. |
Root suckering, an important property
|Herbicide-treated sumac plants in a short-grass prairie|
Although herbicide will kill the sumac stem, the network of rhizomes associated
with this stem are not affected. Dormant buds will be released and
send up vigorous new shoots. These new shoots are called root suckers.
clonal plant species produce root suckers.)
Thus, although the above-ground sumac plant can be killed by either fire or herbicide treatment, root
suckers are formed from buds within the extensive rhizome complex. In fact, more root suckers may
be formed than there were in the existing above-ground stems. Therefore, killing
of root suckers is essential if the clone is to be eradicated.
How are root suckers eradicated?
|Typical root sucker, arising from the hidden underground rhizome system.||Note that there is no sumac stem nearby.|
a sumac clone is treated in such a manner that its above-ground parts are
killed, it must be monitored for the formation
of root suckers and when they are found they must be killed with foliar
Garlon (3% aqueous Garlon 3A). Each root sucker must be sought out and
destroyed. Not all the root suckers appear at the same
time. The timing of this search-and-destroy operation will depend on the growing
conditions at the site, and must be done for at least three years.
Locating sumac clones
clones are easy to locate. Smaller clones are harder to find but should be given high
priority since they have the potential of making larger clones. Since sumac
leaves develop intense red color in the fall of the year, this red color can be used to look for sumac clones.
Mark each clone,
either with GPS or with a permanent marker (wooden stake, rebar, or other
suitable marker). Each clone should be given an control number.
Any single sumac plants will not have formed a rhizome system yet. They should be herbicided immediately, using the basal bark technique. (The basal bark technique is effective twelve months of the year and can be used any time a sumac plant is found.)
Eradicating a large sumac clone: an example.
|Canvassing a short-grass prairie for isolated sumac plants|
Here is an example for southern Wisconsin (probably applicable to other nearby states). This work was done in a high-quality remnant prairie where sumac had become established. On August 1, 2009 the sumac stems of a clone were mowed with
a Stihl brush cutter and all the cut material was hauled away. There were 202
cut stems, each of which was treated with 20% Garlon 4 diluted in bark oil.
Treatment was a combined cut stem and basal bark.
Seven weeks after cutting and treating the results were monitored. The Garlon 4 treatment
of the cut stems was completely effective. Because it was late in the season, no root suckers formed, but they were anticipated for the following year.
In 2010, the next growing season, the plot was monitored
frequently. Root suckers appeared throughout the season and by late summer 183 root suckers had been formed. Note that none of these root suckers
arose from the original cut stems. As the tally was being carried out, each root
sucker was sprayed with aqueous 3% Garlon 3A. This herbicide treatment was
very effective and all root suckers were killed.
The following year (2011), the plot was monitored again and 25
new root suckers were present. These new
stems were treated with Garlon 3A.
In 2012, three years after the original procedure, no new
root suckers were present. A summary of the results is shown in the graph.
Thus, in this study it was possible in three years to eradicate the sumac clone by cutting and treating
followed by treatment each year of all new root suckers.
During the three years that this study was underway, the
area of this sumac clone was not barren. Many good species moved in. A survey
done at the end of the study revealed the following species: flowering spurge,
showy sunflower, rosin weed, compass plant, spiderwort, prairie thimbleweed,
bergamot, butterfly milkweed, rough blazing star, false boneset, lead plant,
evening primrose, Indian grass, little bluestem, and solomon’s seal. Thus, the
dense sumac monoculture was converted into a highly diverse prairie!
Follow this link for extended information on sumac ecology