Plan, prepare, plant… repeat! What do our scientists do before planting a new Tiny Forest?
21st March 2023
Here at Earthwatch Europe, so much goes on behind the scenes to prepare for planting a new Tiny Forest. All of our Tiny Forests are unique and a lot of work goes into making sure that they have the best start in life. Our Science Coordinator, Eve Horsfall, takes us through the steps that lead up to a Tiny Forest planting day.
Eve doing ‘some light weeding’ in a Tiny Forest
Meet Eve, our Science Coordinator for the Tiny Forest programme
Hi, I’m Eve. I started with the Tiny Forest team in June 2022, so the current planting season (October 2022 to March 2023) was my first tree planting season. It has been very exciting putting all that I have learnt into practice, and getting out there to plant some trees.
My background is in Geography and Archaeology, with a brief stint as a cheesemonger. Everyone in the Earthwatch Science Team has such interesting and varied backgrounds. It’s lovely to be part of this team!
A Tiny Forest consists of 600 trees planted densely in a tennis-court size plot.
Step 1: Site checks
The site for the Tiny Forest is selected by another part of the Tiny Forest team. After a site is selected (often in a school or a park) some important checks are carried out. We get the utility maps for the area and check that the site isn’t right over any pipes or cables. We do this using a GIS (Geographic Information Systems) program, which allows us to overlay utility maps onto a map, add buffers (these are an exclusion zone that show areas that are too close to pipes or cables, so that we know not to put the Tiny Forest within these zones), and highlight where the Tiny Forest could go. If landowners and the local community are happy with this placement, the site gets the green light!
Sometimes the site has to be moved slightly within the preferred area to avoid utilities, but as the Tiny Forest sites are only the size of a tennis court, this isn’t too much of a bother. We also check that the area isn’t too close to conservation areas like a Local Nature Reserve, or a Site of Special Scientific Interest, as it is important to keep these areas with as little disturbance as possible.
A soil corer that has been used to look at soil in a Tiny Forest site.
Step 2: Soil sampling
Once we’ve agreed the Tiny Forest location, we send someone out (sometimes one of the Tiny Forest team, or sometimes a volunteer) to do a site visit and take soil samples. We use a soil corer to look at how the soil changes below the surface, record the soil colour, and get muddy identifying soil type – using the same methods as you use when collecting data on your Tiny Forest’s soil colour, compaction and texture. What does the soil look like in this core? Do you think it changes with depth?
Soil samples are important as different species of tree like to grow in different soil types. Soil testing gets very muddy, but that’s all part of the fun!
We use a tool called a penetrometer to measure how compacted the soil is. Compaction describes how dense the soil is. The higher the compaction the more force is needed to dig into the soil; for instance, soft sand at a beach has a low compaction, but a path in a park that has been walked on a lot has a high compaction. If a site is very compacted then tree roots will find it difficult to grow through the soil, stunting the growth and impacting the health of the forest.
Soil nutrient testing is a colourful exercise!
Nutrient levels are also vital to ensure a healthy forest. Soil samples are tested to assess the nutrients potassium, phosphate, and magnesium. The soil pH (how acidic or alkaline the soil is) is also tested. These tests are quite fun to do as the samples change colour which is cool to watch!
All of these measurements guide our tree selection so that we only choose the species best suited to the location.
Selecting the most suitable tree species in advance is important. All trees will be tagged on the planting day for monitoring purposes.
Step 3: Tree species selection
Now comes quite a technical bit. We have a list of 38 native tree species from across the UK that could go in the Tiny Forest. Our job is to now narrow these down into which tree species that are best suited to this location. For instance, willow trees are well suited to wetter soils and water-logged conditions, but Sessile Oak prefers loamy and clayey, well drained soils.
Another thing that we have to look out for is making sure that there are not too many pioneer species. A pioneer species is a tree that grows quicker than other trees in order to get a good head start in a new location – for instance, Silver Birch is a pioneer tree species. It’s okay to have a few pioneers but if there are too many then they grow too quickly and impact on the growth of the other trees around them which are slower growing (like the oaks).
Forest layers (image credit: Sabine Eiche)
What is special about the way that we plant trees is that we plant all layers of the forest at the same time (canopy, sub-canopy, understory and shrub), which means that we could be planting big trees like oaks at the same time as planting smaller plants like heather. So, in deciding which trees to plant, we have to balance the forest layers to make sure that the right number of trees are in each layer. The trees are also planted really close together, with 600 trees of around 15-20 species in a 200m2 area.
The planting approach that we use was developed by the Japanese scientist Dr Akira Miyawaki in the 1970s, and has been used all over the world, most notably in Japan, India and The Netherlands.
The idea behind this is that if lots of trees are planted in a small area, and lots of species are planted at the same time, then the forest grows up quicker, and reaches its full potential in a matter of years, rather than decades.
This is very different to conventional planting where the trees are all spaced in neat lines, and only a few species are planted at a time.
Thankfully, we have developed a tool (with the help of students from the University of Oxford) that allows us to put in the information about the soil and site conditions. It works out which tree species to plant, categorising them into ‘good’, ‘medium’ or ‘bad’ depending on the local conditions and tree species which are in nearby forests.
Step 4: Deciding what to add to the soil
Most of the soil that the trees will be going into needs some extra help and nutrients to be the perfect place for the trees to go. We excavate the site to either 50cm or 1m – making this decision based on how compacted the soil was on our site visit. If the soil was very compacted then we will dig down to 1 meter to loosen the soil for the trees to grow in. Occasionally we rotavate to a shallower depth instead of a full excavation, but only if the site requires it and the soil isn’t compacted. When we put the soil back into the hole, we mix in the supplements the soil needs – a combination of compost – to make the soil more nutrient rich for the trees, then organic manure – to add structure to sandy soils, or straw – to improve drainage in clayey soils.
Two different Tiny Forest shapes (designed with SketchUp)
Step 5: Creating the design
When you hear that a Tiny Forest is the size of a tennis court you might automatically assume that it’s always rectangular. Not so! We have loads of designs in all sorts of wacky shapes! Which one of these is your favourite?
Designing the shape of the Tiny Forest is one of the most fun bits. We use a 3D design software called SketchUp for this. As long as the forest is 200m2 and there aren’t any sections that are less than 4m wide then any shape is possible. We often add classroom areas with benches in, and have paths that wind through the forest. When the trees are all grown up, you really will be able to get lost in these little patches of green.
Finally we can plant some trees! The most exciting day in any Tiny Forest planning is of course the day that we get to see it all come together – the planting day. It’s a lovely day and the whole community get involved; local residents or the local school community – sometimes both! It’s a fun (and very muddy) day that makes all of the hard work worth it.
Eve handing out saplings at a Tiny Forest Community Tree Planting Day in Belfast.
Find out more about our Tiny Forest programme. The next Tiny Forest tree planting season will take place from October 2023 – March 2024. Keep an eye on our Events page, where we will announce all Community Tree Planting Days in advance. During the warmer months, we invite you to join our Science Days to help us monitor the benefits of our Tiny Forests.