Spontaneous vegetation succession

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.