Mowing and the invasive plants conundrum

We're all too familiar with the pale billows of wild chervil flowering profusely along our roads in May and early June, and later in July its yellowing foliage, brown stems and copious bunches of flat seed capsules.

It used to be, maybe fifteen or more years ago, that wild chervil could be found mostly along Route 5. Then a few clumps began appearing along Rt 113, on the south side of Thetford Hill Then some more appeared at the top of Thetford Hill. Now this invasive weed lines the road all the way to Thetford Center and beyond, as well as spreading onto Tucker Hill Road.

But why care about invasive roadside plants? 

In general invasive plants damage the VT rural economy by infesting fields where they compete with and reduce the diversity of livestock forage plants. They can also out-compete crops for resources and alter soil composition, further damaging crop vitality. They suppress native plants, like New England's wildflowers, by shading them out and taking water and nutrients from them. As native plant species disappear, so does biodiversity. Invasive plants cannot substitute for natives in the food chain or the  life cycles of native insects and animals. In fact many invasive plants offer little or no nutrition to native wildlife. Roads act as a conduit for invasive plants to move into new areas, where they soon spread away from roads and into once pristine environments. Dense stands of invasives alter the physical structure of habitats and can make them unsuitable for some wildlife. Thickets of honeysuckle and barberry are also found to increase populations of disease-bearing ticks because deer, the tick's host, are attracted to this shrubby, dense type of cover.

Mowing, roadside maintenance, and construction are all great at spreading seeds of invasive plants like wild chervil, not only to un-infested sections of road, but also to private property. A lesser role is played by vehicle tires and even the feet of pedestrians. The transport of soil - aka fill - from one place to another can also bring in roots and offshoots of nasty plants like goutweed, knotweed, and phragmites.

The State is aware of the problem, and through efforts of the Department of Forests, Parks & Recreation, and the UVM Extension published "Resilient Right-of-Ways" a guide to stewardship of VT backroads.

Invasive plants get their own chapter in this guide. 

Invasive plants are favored by soil and vegetation disturbance, so the frequent disturbance of road edges by mowing, ditching and even snow plowing work to their advantage. Unfortunately people do not feel responsible for what is growing on the side of the road, as opposed to in their yard or garden, places where they would much rather put their energy. The roadside is viewed as a public space, but also somewhat of a no-mans' land. The Thetford Conservation Commission made a determined effort some years ago to raise awareness and recruit volunteers to pull invasive roadside plants, but the momentum did not persist enough to have a lasting impact. 

The guide to backroad stewardship recommends that someone (the Town presumably) identify the location and species of roadside invasive plants so the Town can implement "specific treatment practices" and also "exercise extreme caution" when excavating, ditching or mowing, to avoid spreading the seeds, roots or even stem fragments of invasive plants. It also advises that the road crew learn how to identify new infestations that can be more easily treated. In addition it recommends that landowners become educated about how invasive plants spread.

Indeed, the Thetford road crew, to their credit, did take a class on invasive plant identification. In a perfect world we would now be following the recommendations to "mow first in areas without invasive species, then mow areas with known infestations (but do not mow knotweed or purple loosestrife)" and to "not mow invasive plants after seeds have set."  Can we (or in reality the road crew) make the determined effort to really do that, especially when different species set seed at different times? And at the beginning and end of the day, will the road crew thoroughly clean mowing equipment so it is not a vector of seeds?

As always, time is money, and the Town has only so many hours of employee time and so many dollars in its highway budget. Thetford maintains 49.3 miles of gravel roads and 14.2 miles of paved roads - that's a lot of man-hours and diesel fuel to pay for, even for one mowing. Not included are state roads Rt 113, Rt 244 and Rt 5 that are mowed by the state. Indeed, not to point fingers but the state is doing its part to spread invasive plants too and appears oblivious to its own recommendations. The main concerns of roadside mowing appear to be with safety - maintaining a line of sight for motorists and keeping shoulders open in case a vehicle has to pull over. 

 The Town manager agrees that more can be done, and that the budgetary constraints may not be as limiting as imagined. And so the conversation continues.