Over time, hedgerows evolved to suit multiple functions. Looking across the contemporary landscape, the variety of forms speaks to these variations in natural materials, intention, and the variety of human intervention styles over time. These are not landscapes instigated and then observed. The bocage landscape is a landscape of constant, albeit episodic, agency, the results of a long term dialogue that has influenced the evolution of both flora and fauna, the creation of social and cultural systems, human population densities, and even the weather. With a basic understanding of the origins and functions of the hedgerow networks, I offer a series of brief considerations as to how hedgerow dynamics might be able to impact contemporary, highly manipulated landscapes.


Windshadows

Woodland

Hedgerow

Beetles over winter in the bank. The soil under the shelter of the hedge and the insulation of the leaves is the last to freeze, making this zone a popular feeding spot for ground birds.


The term hedgerow traditionally refers to a complex unit, not just the plants. Often used along property boundaries, the ditch beside the hedge, and not the hedge itself, is the delimiter of that edge. The ditch was dug in order to pile up the dirt just inside the property line and create a bank. Banks are ecologically valuable not just for their protection of the root zone, but also for the herbaceous layer they acquire, and for the species that can harbor within the soil. Varying by species, climate, use, and other related factors, a hedgerow must be laid every 6 to 20 years. This involves cutting the thick stems (pleachers) nearly through, leaving a narrow band of bark, cambium, and sapwood. The pleacher is then bent at an angle and woven between 4’ rods driven into the ground. Pleachers are held in place by a weaving of vines or other narrow wood in a manner similar to the tops of many woven baskets.

In fact, the bank is sometimes the hedge. One or two stone walls with dirt behind (one) or between (two) and turf on top is what constitutes a hedgerow in some stonier areas. In the 1800’s in Devon the banks were larger, commonly six feet high and five feet wide on top. The walls are built somewhat concave, anticipating that they will settle out to be flat. If the wall remains concave, it scoops the wind, protecting the far side of the wall more intensely.



The ability of a hedgerow to buffer the wind on a site is related to its density. In general, wind is diminished on the leeward side for a length equal to 10-15 times the height of the hedgerow, and a short distance on the windward side as well. Too dense of hedge, such as juniper, will cause an air pressure vacuum on its leeward side, sucking some of the wind down sooner and creating turbulence.

Hedgerows placed perpendicular to a slope will impact the natural daily air movements up and down the hill. In cold areas, the “U” shape shown to the right is ideal for diverting frosts as they sink down a hillside. As the cold air sinks, the warmer air from below is displaced and moves up. The hedgerow here catches that warmer air and creates a nice microclimate pocket downslope. Note that even though most of the frost will be diverted, some will pool just above the hedge, creating a colder microclimate than there would have been without a hedge there.