29 December 1995

Thumbs-up for black plastic

FENCING to protect young hedges is an expensive luxury, according to trials at Morley Research Centre. Only under extreme rabbit pressure might it be worthwhile, the work suggests.

In general the more is spent in the early stages of establishing a hedge the less the outlay later on, says researcher Mike May. Three years work assessing a variety of approaches highlights the "very superior growth" that can be achieved by fencing out deer and hares. But the extra cost cannot be justified, he maintains. "Its just too expensive compared with the alternatives."

The experiments, begun in winter 1991/2, examined three planting densities and a range of weed control and pest prevention techniques on plots 23m (75ft) long.

"Out of all the systems weve tried the use of black polythene is the easiest and gets round the problem of weed control," says Mr May. The same strategy, with a slightly modified planting density and spiral rabbit guards where necessary, has since been adopted on about 1000m (0.6 miles) of farm hedge planted at Morley with advice from local FWAG adviser Richard MacMullen and grant from Norfolk County Council.

The scheme, based on a four plants a metre double-row of mixed species to provide a stronger, less permeable hedge, was easily installed, says farm manager Andrew Thurston. "We put in 6in whips, ploughed small furrows away from the plants and laid the polythene over the top of them." Slots were cut to allow them to poke through, and the soil was replaced by hand to hold down the 1m (3ft)-wide plastic, he explains.

"Theyve taken very well and weed control hasnt been too much of a problem." A summer spray of glyphosate 0.4m (16in) either side of the 0.75m (30in) of exposed plastic is all that has been required, he says.

The use of a double row lessens the impact of "misses" or dead plants, adds Mr May.


Hedge establishment and management comparisons at Morley. Planting costs, mean heights and "misses" in three autumns

CostHeight (cm)Dead plants/plot

£929394929394

No protection:

Hawthorn 6 plants/m, double-staggered row555786113000

Mixed species 2 plants/m, single row20638589111

Mixed species 4 plants/m, single row407088106010

Rabbit fencing + black plastic:

Hawthorn 6 plants/m, double staggered row213*92123147000

Mixed species, 2 plants/m, single row177*93107136000

Mixed species, 4 plants/m, single row198*103125144011

Tubes & spirals:

Mixed species 2 plants/m, in tubes, single row74899994000

Mixed species 4 plants/m, in tubes, single row1487999116001

Mixed species 4 plants/m, in spiral guards, single row148133129133767

Tubes & black plastic:

Mixed species 2 plants/m, single row657510196115

Mixed species 4 plants/m, single row11684116118012

*Not including labour for fencing.