To establish vegetation on a bare soil site, most landscape architects
would develop an extensive planting plan complete with turf. One that would
have to be maintained that way through eternity. But what if you just allowed the
landscape to grow up on its own, to stop mowing and let the weeds fill in, what
would happen? To establish the Woodland Exhibits at The Crosby Arboretum in
Picayune, Mississippi; that’s exactly what was done—let the seeds of trees and
shrubs that were already in the soil, or from nearby plants, germinate and
grow. Because these were native plants with few exotic species, it developed
into a beautiful representative woodland on its own. All we had to do was to plant
in some of the missing species and use pruning to turn it into a woodland
garden. But would this work in someone’s backyard or on the newly graded soils
of a landfill? The answer is yes, it will. Of course it depends upon the
context, if you tried to do this in a front yard, I am certain the city (via
your neighbors) will knock upon your door with a request to mow your weeds. But
rather than highly visible areas, there are plenty of out of the way places that
are mown just for the sake of being mown, that could improve plant and animal
habitat by reducing lawn area.
In 2002, a study was published in Restoration Ecology
entitled Restoration of a Landfill Site
in Berlin, Germany by Spontaneous and Directed Succession, by Franz Rebele
and Cornelia Lehmann (vol. 10, No. 2). In it, they set up a series of plots and
let the vegetation grow. Five plots were mown twice a year and five plots were
left uncut. Then they just recorded what plant and animal species showed up
over the next few years. They found out that bare soil plots, even on poor soil
sites, develop into a woodland without planting any trees or any type of
management. They also found out, that if a diverse grassland is desired, that
mowing twice a year gives more plant and animal species diversity than by
leaving it alone. That’s because the aggressive species that move in, such as
goldenrod and some grasses (Calamagrostis), can grow so thickly and shade so
quickly that few other species can muscle in. Mowing a few times a year (or
prescribed burning), knocks back these plant thugs and allows other species to thrive.
The authors conclude that regeneration is a possible tool for restoration if
the right plants are around it.
