On our theme this year of all things green and sustainable, Michele Lavelle of 4D Landscape Design followed up a fascinating chat we had with her over the sourcing, journey and lifespan of trees transplanted ‘to order’. Her thoughts about the sustainability and longevity of imported species yet the vulnerability of some own-grown native trees (in response to changing Brexit trading patterns) illuminate just how complex and fragile the whole industry is. We hope you are equally intrigued….

I had a lovely catch up over coffee with Jules and Lyn several weeks ago. We don’t meet often but as usual we chatted about 101 things at breakneck speed and long enough to order another coffee.

We met just before the first heatwave this year and now, just after the second (coupled with government chaos) aspects of our conversation seem very relevant.

Jules mentioned the successful progress of the Jubilee Pool and how important it is for everyone’s health and what a pleasure it is to be able to swim locally. I totally agreed and the only way that I survived the heatwaves was by walking back with wet hair after my daily swim. It always takes me a while to acclimatise from cool summer temperatures to suddenly hot.

Lyn had just been to Glastonbury and was still buzzing from the experience (and so was everyone else that I know who went there this year). Lyn told us about the almost overwhelming numbers of people and sheer scale, how well organised it was, the safety of her children and the enjoyment of it all.

What an incredible phenomenon Glastonbury is. People from all over descend on a few fields in an English rolling landscape which for 5 days turns into a pop up city of 200,000+ with all its infrastructure and functionality. Most people are happy and when they’ve all gone it’s tidied up and left to rest before the next one.

I would love to have experienced this magical event but have never dared to go because my eldest son said that it’s ok if it rains you can choose to get wet or shelter in your tent, if it’s sunny then you have no choice of shade or anywhere to cool down.

So… the conversation meandered onto the need for shade in cities, the urban heat island effect and the race across the country to plant hundreds of thousands of trees to increase canopy cover for the future.

Jules asked me a seemingly simple question…

“Where are they going to get all these trees from?”

It sparked a great outpouring from me about stuff that I’d mostly forgotten I know!!

In the first instance the simple answer is pips, acorns, conkers, chestnuts, cuttings, catkins, seeds – sycamore seeds for example have their own propellers so they can helicopter further afield.

However, the nursery growers will be the primary suppliers of our future canopy cover. The nursery trade is quite complex, fascinating and highly skilled. They really understand plants which most of us don’t even though there’s a new wave of general public interest adorning everyone’s homes, leisure, retail and office space with greenery (sadly some of it fake) together with annoying terms such as re-wilding and miyawaki method becoming part of the dialogue.

I’ve always inspected plant material before it’s delivered to site and have therefore had many conversations with nursery growers. Particularly so when we had 1,000 trees contract grown by Wyevale for a large PFI hospital in Bromley. The contractor agreed to this so that they could be assured that what was submitted for planning would be delivered regardless of whether they paid us to inspect and monitor the works on site. To further save on long term maintenance costs we asked for the crowns to be lifted from the British Standard of 1.8M to 2.5 or 3.5 metres at the nursery, which was carried out at no extra cost and nursery supply prices were reduced by some 30% because they weren’t growing at risk. Win win win all round.

From many discussions with the nursery I learned that not only are plant names an international language but also they are easily traded across borders between the UK, Netherlands, France, Italy and Germany. At the time (about 15-20 years ago) the Dutch were great propagators of tree species and so transplants were mostly imported from the Netherlands to the UK and elsewhere. These were then grown on for supply as whips, standards (Std) and advance nursery stock (ANS) to be supplied on projects across the UK. Also at that time, Wyevale were exporting many of their Std and ANS to Germany to be grown on and sold as semi-mature trees, often back to the UK.

Because of the Continental Climate in Germany trees grow taller and stronger. They have a deeper and longer rest in the cold winter months and more warmth to grow during the summer. For this reason they are major suppliers of semi-mature trees in Europe.

I have always wondered if my fellow landscape professionals know how well travelled their trees are when specifying semi-mature stock. The scenario being as follows:

  • Starting life as a transplant or root stock in the Netherlands.
  • Imported to the Uk to grow on as whips, Std, ANS stock for local supply and export.
  • Std and ANS stock exported to Germany to grow on as semi-matures.
  • Semi-matures imported from Germany for projects back in the UK to create an instant impression for the handover photoshoot.
  • Whips and Std Trees establish quickly and grow whilst semi-matures suffer shock and take a while, which might be many years, before they settle in and have the energy to grow again, if not then they start to die back and stag head.

Apart from the travelling of a semi-mature tree there is also the question of how many trees can be transported on a lorry-load and how sustainable that is. Having researched the question the detail needs to be given serious thought:

  • Only 1 large semi-mature at 65cm+ girth per lorry travelling all the way from Germany to a site in the UK.
  • 3 to 10 semi-matures at 35cm girth upwards per lorry load.
  • Compared with 500-1,000 whips per pallet or 150 std trees.

Coupled with this, the larger and older the imported tree, the greater the ecology it brings with it. Not only that, the pH of the soil in many of the German nurseries is very low at about 5.5-6.0 in comparison with sites in Bristol that usually have a pH of 7.5-8.0. I worry about the shock to such a large tree in making it’s journey so far away from it’s mates (yes, trees apparently do bond and care for each other) and then suddenly giving them a different diet – a lifetime of lemon juice switched to milk overnight!!

Since coffee with Jules and Lyn I checked with Wyevale if ‘tree travels’ are as they were 15-20 years ago or whether they’ve changed since COVID and Brexit, and of course some things have changed.

  • Propagation of transplants are now all done in-house at Wyevale in Herefordshire but they only focus on native species. Root stocks are still imported from the Netherlands.
  • Wyevale supply their stock to projects in the UK with whips, standards and ANS trees but semi-matures are still imported from Germany.
  • Trading has become more difficult and expensive since Brexit with plant health inspections being more intensive (they were already rigorous).
  • Exporting to the EU has become impossible.

As I said, the nursery trade is fascinating and complex but made more-so by climate change prospects and Brexit. The suppliers are preparing stock that may survive for 500+ years or more.  Focussing on the production of native species as a response to Brexit is somewhat worrying as most of our natives are subject to various diseases such as Chalara fraxinilolia, Phytopthera, Dutch Elm etc. Species migration is happening northwards at a rate of 80km per decade due to climate change so species such as Beech won’t necessarily survive in their current locations. As a result we do need to plan for resilience for the future, particularly given the lifespan of trees and include some non-natives into our projects as a back stop’.

Led by Design, 4D embrace key environmental issues including infrastructure, sustainability, biodiversity, flood mitigation and watershed management. Check out 4D Landscape Design or contact Michele at michele@4dld.com to find out more about their fascinating work.