Trialling the reintroduction of “railway hedges” five years on

The original way to keep livestock off the line…

The volunteer planted plot of whips reached 3.5metres after five years of growth

The railway act of 1842 made rail companies legally bound to protect their lines from wandering livestock – and the “railway hedge” was born.

As the decades passed, many of these hedges were replaced with fencing so, working with Network Rail and community groups, The Tree Council carried out a series of trials at Hadley Wood station in North London with the aim of bringing the railway hedge back to our lineside.

Railway hedges aren’t just an important feature of railway history; they are fantastic for wildlife – acting as green corridors, providing flowers that attract pollinators, capturing and storing carbon, and reducing soil erosion and flood impact, as well as delivering visual and noise screening.

To determine the best approach, The Tree Council established a series of trial plots on the embankment area at Hadley Wood – a busy commuter station.

The site at Hadley Wood Station in North London, following ground preparation and planting five years ago

The first plot used the traditional railway technique of planting two-year-old whips of traditional hedgerow species – hawthorn, field maple, dog rose, dogwood and wayfaring tree – at a density of six plants per metre squared.

In trial plot two, a tree seed mix was sown using three different methods: seeds scattered over the surface; seeds scattered and then raked over; and finally, a five-centimetre trench was dug, seeds were scattered in and soil was raked over. All the sites were watered.

Trial plot three was left to natural regeneration, with no human intervention and vegetation colonising either through existing seed on the ground, or dispersal by wind or birds.

The plot to the left was left to natural regeneration, while that on the right was planted with seeds dug into a 5cm trench, raked over and watered

In collaboration with nearby community groups, The Tree Council and Network Rail then made twice yearly visits to collect data and make observations – and, five years on, the results are in!

The whips were the most successful, forming a dense hedgerow reaching 3.5 metres in height, with flowers and fruit production in evidence. At seven years old (two in a nursery, five in the ground), the hedges are already providing an additional important benefit for birds, mammals and insects.

In the seed plots, results were mixed. The most successful was the section where seeds were sewn 5cm below the surface. High density hawthorn and dogwood seedlings developed to deliver 65 plants per square metre – revealing 50% germination, ten times higher than predicted. The field maple, dog rose and wayfaring tree seed did not germinate.

Where the seeds were scattered and raked, only around six plants per square metre germinated with the dogwood the most successful, followed by a few scattered hawthorn.

For those seeds scattered and not raked, no young seedlings were visible after five years, suggesting they may have been consumed by small birds and mammals, or become desiccated.

Overall, the hedges planted as seed took longer to start growing, with some not germinating for two years, and the average height of the tallest stretch reached 1.3m, compared to 3.5m for the whips. But, as the whips were two years old when planted, the seeded plot after five years is approaching where the planted plot was after two years.

The Tree Council is now incorporating seed sowing into other hedgerow establishment trials to broaden the evidence base.

The plot that saw seed scattered over the surface and raked over - here dogwood is above the bramble, reaching a height of around one metre.

Unfortunately, natural regeneration was not successful at this site, with only nine trees or shrubs established in the 120m of trial plot made available to test this method. But we should bear in mind that five years is a very short period of time in the context of natural regeneration, and that the nearest trees to the plot location at Hadley Wood are around 30 metres away.

There are important cost differentials to consider. If we take contractor planting as 100% cost, including the price of materials, trees, seeds, and labour, we are able to compare it with alternative methods

·        Whip planting by contractors: 100%.

·        Whip planting by volunteers: 34%

·        Direct seeding into 5cm trench by contractors: 42%

·        Direct seeding to surface (including raking) by contractors: 39%

·        Natural regeneration: 20% (as a proportion of overall site preparation costs).

While there are many variables to consider at this site, from different soil types to variations in elevation along the embankment, the trial has certainly yielded useful insights and prompted further questions and research. All the data gathered will be fed into a larger dataset for further analysis and to inform future research.

Interestingly, the trial does provide valuable support for the effectiveness and accessibility of nature-based solutions. In all plots, the cost of creating the railway hedges was less per metre than the cost of security fencing, and that’s without taking into account the added value of greater biodiversity, visual appeal, and the needs of local people.

Find out more about The Tree Council and Network Rail’s Hedgerow Trials at Hadley Wood by visiting: www.treecouncil.org.uk/science-and-research/hedgerows/hadley-wood/

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