Environment

Revival of ‘railway’ hedges

A trial series of traditional ‘railway hedges’ are thriving at a North London station along one of Britain’s busiest main lines, following intervention by Network Rail and The Tree Council.

Train tracks

To demonstrate how the railway can contribute to UK’s biodiversity, a series of trial hedgerows were planted in 2018, which have now successfully grown to well over head height at Hadley Wood station on the border between Greater London and Hertfordshire.

Legally bound by the railway act of 1842, rail companies used railway hedges to ensure livestock were protected from wandering on to railway lines. Over the last century, many of these hedges have been replaced by wooden, wire or chainlink fences which have little to no value for wildlife. The 2018 experiment was therefore conducted to test how a new railway hedge could be established, estimated cost compared to metal fencing, and how fast different methods were at establishing a stock-proof boundary.

Railway hedges aren’t just an important feature of railway history but understandably they are invaluable 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. Considering the 20,000 miles of railway track running throughout the county, the opportunity is substantial.

The trial site consists of two long strips of ground about 2 metres wide and 180 metres long running roughly parallel to the Hadley Wood station platforms. Further divided into sections to trial various hedge creation techniques from planting whips, tree seed mixes and natural generation – left untouched.

Trial results showed:

  • Plots planted with whips were the most successful, having formed a dense hedgerow of average height of over 3.5m in just five years. Planting techniques resulted in variation in the tree survival rates from between 58% – 100%. Thereby, highlighting how good planting techniques are significant in the successful establishment of young trees.
  • After five years, the hedge whips had reached maturity, providing flowers and fruit for birds, mammals and insects.
  • Seed application showed some promise in parts of the trial site. The three different sowing techniques yielded different results.
    • Seeds sown 5cm below the surface fared best, producing a far greater density than a typical hedgerow, revealing that more than 50% of the seed germinated – 10 times more than predicted. Obervations are ongoing to see how these trees continue to grow with such high competition.
    • Where seeds were simply scatted on the surface, and raked in, only six plants per square metre germinated, mostly dogwood with a few hawthorns.
    • Where the seeds were scattered and not raked in, there were no young seedlings visible after five years – presumably eaten by birds or small mammals or become desiccated.
  • Overall, the hedges planted as seed took longer to start growing, with some seed not germinating for two years and the average height of the tallest stretch only reaching an average height of 1.3m over five years, compared to 3.5m tall in the planted section.
  • Natural regeneration did not result in hedgers formation, instead being dominated by bramble. Overall, only nine trees or shrubs became established in a 120 metres of trial plots, compared with the nine plants per metre in the planted areas.

Cost effectiveness

In all plots, the cost of creating these hedges was less per metre than the cost of security fencing, especially when taking into account the added value of greater biodiversity, visual appeal and the needs of local people. This raises the potential that the hedge could once again play a role along appropriate stretches of the railway’s boundary, although maintenance costs, species composition and effectiveness as a barrier would still need further investigation.

Growing a hedge from seed may be more than 50% cheaper than planting with whips (using contractors), but the method is currently more unreliable and would need further testing to ensure success.

The trials were conducted by Network Rail, The Tree Council along with volunteers and representatives from the Hadley Wood Rail User Group and Hadley Wood Association. Developments in the Hadley Wood Hedgerow Trials can be followed here.