Invasive shrubs manage to overwhelm many ecosystems by more
effectively exploiting the resources available in their environment. They are currently busy demonstrating one of
the characteristics that allows them to claim such a dominant role in any
ecosystem they occupy. Plants use
sunlight captured by green leaf area to fuel the photosynthetic process that
supplies the energy needed for plant growth and reproduction. Invasive shrubs, like the Bush Honeysuckle
shown above, produce leaves quite early in the year and hold those leaves into
late fall.
Our native plant species have evolved a sequence growth that
allows each species to capture the sunlight necessary to its survival. Spring wildflowers generally complete their
growth early in the year and by the time the trees have developed their leaves,
the early plants have stored the energy they need to produce seed and carry on
to the next year. At Blue Jay Barrens, the
leaves of invasive shrubs develop in advance of most of the early wildflowers and
deprive the native species of their needed sunlight. Eventually, the invasives form a solid thicket
and the natives disappear.
The vining Japanese Honeysuckle does the bush type one
better. In some years, the previous
year’s leaves remain green through the winter.
The leaves to the upper left are from last growing season and the rest
are new to this month. As long as the
leaves are green, photosynthesis can occur.
While native plants are in their winter dormancy, Japanese Honeysuckle
grows continually stronger and more able to compete for a place in the
landscape.
Autumn Olive is quick to take advantage on the slightest
winter thaw. The long leaf season of
these invasives allows them to put on some tremendous growth. This four foot tall specimen represents only
two years of growth. In that short time
it went from a seedling, barely reaching above the leaf litter, to a major
producer of shade.
These leaves are the result of about two weeks growth. The growth will soon begin to elongate into
the production of new stems. The shrub
could easily double its height and quadruple its width before the end of this
growing season. That is, it could have
if I had not cut it down and sprayed the stump with herbicide.
Seedlings may take a couple of years to develop a root
system capable of sustaining rapid top growth.
This seedling managed to hold onto one of its leaves for the entire
winter. The benefits from this one leaf
have probably greatly increased its competitive edge. If I hadn’t cut and sprayed this little guy,
it could have reached over two feet tall by the end of summer.
Multiflora Rose is another that is quick to put its leaves
into play. Frosts and freezes may cause
some leaf damage to these shrubs, but the damage is generally restricted to
shrubs growing in the open. Shrubs
growing beneath the canopy of taller plants are often protected from frost
damage. If some leaves are killed, they
are quickly replaced. All of these
species are highly susceptible to a cut stump application of glyphosate during
this early growth season. I usually
carry my pruners and spray bottle with me everywhere I go during this time of
year. Fortunately, I am now only dealing
with newly arrived invasives, so a pair of hand pruners is all I need for the
job.
Our two problem ones are Garlic Mustard and Buckthorn.
ReplyDeleteHi, Stew. I used to have some Garlic Mustard, but after a couple of years of pulling the plants in the spring, it disappeared and hasn't been seen for over 20 years. I have two species of native Buckthorn, but the invasive species hasn't reached here yet.
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