Tree planting vs natural tree colonisation – busting the binary thinking

Since 2017 I have been involved with helping Moor Trees a Devon-based native woodland and tree planting charity ( to run volunteer days to survey sites using ‘citizen science’ ten years post-planting, collecting data on tree survival, tree biomass, and natural tree colonisation. I want to briefly discuss the results on tree survival  and natural tree colonisation to show how the often binary argument between tree planting vs natural tree colonisation is miss placed. 

As well as being a great experience (Devon in a young woodland is idyllic) – establishing woodlands are beautiful, and offer a reminder of just how quickly you can make positive change. Tree planting however is winter work, often conducted in muddy fields in the pouring rain, so to return and find trees in some areas starting to form a canopy and develop a woodland ecosystem is very heartwarming.  The aim of these volunteer ‘citizen science’ surveys was to find out a bit more about what is happening following tree planting and provide volunteers with a worthwhile experience. We collected data of tree success and establishment, ground flora and local contextual site details such as slope angle, slope aspect and soils.

After three years of surveys (2017 – 2019 – two sites each year) across ten-year-old sites, the collected data was analysed and showed planted trees had very high survival rates at sites, with 97.7% of trees surveyed alive and in leaf. Alder (Alnus glutinosa) were found to be the most successful and consistent species across sites. Results contrast widely with the image often and increasingly assigned to tree planting either of low mono-cultural stands of spruce planted inappropriately on deep peat or of trees dying of thirst in plastic tree tubes associated with large infrastructure projects. Our results highlight that there are many forms of tree planting and that if done well tree planting and assisted regeneration is highly effective.

Methods matter – Moor Trees plant on average at least 10 native species per site and plant in clusters so there is a large variation in conditions across each site, providing more room/ opportunities for natural tree establishment. Indeed, perhaps the most interesting of results was that an average of approximately 30% of trees across surveyed sites had naturally colonised. The most common of these were Blackthorn (Prunus spinosa), Ash (Fraxinus excelsior), and Hazel (Corylus avellana). This large input of natural colonisation into tree planting schemes runs counter to the narrative increasingly adopted by some in conservation that tree planting creates sterile woodlands with little dynamism and low opportunity for natural processes.

In some sites these natural processes need a helping hand – and survey results find native tree planting schemes added significantly to tree diversity, notably so where natural tree colonisation was poor, such as in UK upland sites. Indeed, on average planting schemes added on average five tree species to sites additional to those colonising naturally – this number was as high as nine additional tree species where natural establishment was low. Diversity is important both for ecosystem functioning but also in ensuring future woodlands are resilient to climate changes. It seems clear  if we are to meet climate change commitments (Committee on Climate Change, 2019) and make sure future woodlands are diverse at a timescales that are meaningful for the biodiversity and climate crisis, then strategic tree planting will be needed.

This is only a small selection of the results but findings highlight the tree planting vs natural colonisation debate is often far too binary to be useful. In order to make sensible decisions needed to maximise the potential benefits offered by woodland expansion, there needs to be a much clearer definition of the merits of different woodland expansion methods and of when and when not to plant.


Murphy T.R. (2020) ‘Moor Trees’ tree planting schemes ten years post establishment – assessed via citizen science.

Committee on Climate Change (2019) Net Zero: The UK’s contribution to stopping global warming. London.