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By Tom Stanley Extension Agent
There has been increased interest in the flora and fauna that can inhabit open fields in the Mid Atlantic. From the time of European settlement up until the mid-20th century, there were many pastures that were not mowed annually and an ecosystem of birds and plants compatible with grazing livestock was established. Cedar was the pioneer tree species that might begin to sneak into these open fields but its relatively slow rate of growth gave farmers a 24-month window to easily remove them and keep the fields open. As rapidly growing invasive species like multiflora rose, autumn olive, and ailanthus trees became more prevalent through the last decades of the 20th century, annual mowing became a necessity to keep fields open unless herbicides were used regularly to keep woody invasive plants at bay.
Naturalists and wildlife advocates recognize the loss of “Eastern Grassland” habitat and a pilot program to restore this habitat is being tried in the Virginia’s Northern Piedmont and some of the northern counties of the Shenandoah Valley. Wildlife biologists tell us that it takes a large contiguous tract (70-acres or more) in order to attract the full range of nesting birds that prefer this habitat. The field should have minimal disturbance between April 15 and July 15. By late July, the nesting season has passed and the pasture can be intensively grazed or harvested for hay. However, there are some landowners with unfenced tracts that are not readily utilized for grazing or hay.
For fields that are not needed for grazing or hay, the question is when is the best time to mow the field to suppress the pesky woody invasives yet optimize the habitat for wildlife. Do we mow in late summer, wait until fall, or wait until winter dormancy? Dr. Jim Parkhurst, VA Tech Extension Wildlife Specialist, says most biologists likely would come down favoring the late winter/early spring mowing.
Dr. Parkhurst goes on to say the difficulty with fall mowing is that you never know if environmental conditions will be conducive to good regrowth (i.e., too wet or too droughty from year to year) which is important for providing cover for some wildlife. With declining day length during the fall, the ability of many plants to muster strong regrowth is challenged and the later into the season you push the mowing, the greater the likelihood of not getting a decent cover back on the site. That stated, the primary wildlife benefit of an unmown grassland is realized by late July and late summer mowing does not destroy the wildlife benefit.
Dr. Parkhurst adds that in the best of all worlds, he likes the spring prescribed burns (where feasible) as the method of choice to ensure vigorous growth, nutritious output, and better overall cover and diversity; second best would be early spring mowing, followed then by the less preferred fall mowing (with preference for doing so as early in the fall as possible). Prescribed burning of fields takes comprehensive planning, coordination, and people power and not all fields are located in a place conducive to prescribed burning. Watch for this column to explore this topic further in the coming weeks.
