Monday, February 27, 2017

Advantage: Invasives

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.


  1. Our two problem ones are Garlic Mustard and Buckthorn.

    1. Hi, 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.