October 2023 • Nebraskaland 51
wetlands or other sites that often dry up over the summer,
those practices are much easier. Other wetlands hold water
through most summers, making it much more diffi cult to
attack cattails at that time of year.
If plants can be weakened during the previous summer, it
becomes more feasible to drown them the following spring.
While it seems illogical that a plant growing in water can
drown, cattails need access to oxygen in the air to survive.
In the spring, cattails can grow for a little while without
oxygen, but need to extend their leaves above the water
as soon as possible. The speed and amount of growth they
can manage without oxygen is tied to their carbohydrate
reserves. If the plants start the season underwater with low
reserves of carbohydrates, they may not be able to grow fast
or tall enough to break the water's surface before they drown.
In addition to the energy they get from stored
carbohydrates, cattails have one other hack for growing
underwater. If the previous year's dead stems are present,
those porous stalks have air trapped within them. Cattails
can draw oxygen from those stalks to make more effi cient use
of their carbohydrates and grow quickly. If those old stalks
have been removed, however, cattails that start their year
underwater are at a big disadvantage.
The reliance of cattails on last year's stalks provides an
important opportunity for land managers. In addition to
reducing stored carbohydrate levels, managers can also burn
or mow any stalks left after the end of one growing season
so they won't be there at the beginning of the next. If cattail
plants are low on energy reserves and don't have their backup
option for accessing oxygen, it might only take a few inches
of water above the base of the plants to drown them.
One of the more active and experimental fi ghts against
large scale cattail invasions in the Sandhills is taking place
at the Valentine National Wildlife Refuge. Staff there have
been employing a variety of strategies to reduce the size,
density and impact of cattail patches to improve habitat and
provide better food resources for migratory birds. Treatments
include grazing, mowing, prescribed fi re and herbicides, and
combinations of those treatments seem to show the most
promise. The results so far have ranged from disappointing
to spectacular, but it's still too early to know why some
treatments seem to be eff ective in one place but not another.
Natural resource professionals look at the results of various cattail suppression strategies at Valentine National
Wildlife Refuge.
