It seems the phrase "You are what you eat", doesn't just apply to humans. A Tiny Forest with super powers needs super, superior soil with optimum nutrition and drainage to thrive and succeed.
Whilst Terry Gordon, retired Geotechnical Engineer dug for samples at Morgan Jones park, we chatted about what he was doing and why:
Lynn: Do you know anything about the history of this site?
Terry: Before Morgan Jones park was developed in 1934, this was a field. The geology map shows part of a terrace of glacial ‘sand and gravel’ deposited 10,000 years ago as the Cwm-yr Aber glacier melted and retreated
Lynn: One of the residents told me this little hill was the site of a famous battle in Caerphilly and that they built the hill up to fire at the castle. I'm not sure if this is based on any historical evidence or local folklore? I can't find anything online.
Terry: Hmm, I would say that is unlikely...
Lynn: Can you describe to me what you are doing and why?
Terry: I’m going to keep digging this trial pit until I get to a metre depth, taking notes and photographs of the material I find. I will take samples of each layer to further examine, weigh, sieve and test at home. Then I will start on the second trial pit to make sure we see the same material in this slightly different location.
Lynn: If it were not for social distancing restrictions, I would help you, sorry!
(Terry digs whilst Lynn throws sticks for her dog)
Lynn: So you’ve reached a metre now, have you found what you expected?
Terry: Yes, we have found the expected glacial ‘sand and gravel’, which is a roughly equal mixture of soil and stones, (the soil being mainly sand and silt and the stones mainly ranging from large gravel to cobble stones). It is all topped with a thin layer of organic topsoil consistent with the site’s previous farming use!
Lynn: It doesn’t sound the sort of soil that would allow for the rapid growth of a Tiny Forest?!
Terry: No, it’s not! We will need to do quite a bit of work to modify its properties and make it into ‘super soil’!
Lynn: So what exactly will we have to do?
Terry: At the moment, the soil and stones are too dense to allow the tree roots to penetrate down, so we have to dig the area down to a 1 metre depth using a mechanical excavator and then put it back in a nice, loose, root-friendly condition!
Lynn: Is that all?
Terry: No, because the material is inorganic and does not have the nutrients the trees need to thrive. Also, it needs to be better at holding moisture. So as well as loosening it, we will be adding organic matter.
Lynn: Such as fertilizer?
Terry: We prefer to use organic, natural additives, like manure, mushroom compost and straw. When these are thoroughly mixed with the existing soil, we hope to produce a ‘super’ soil that will allow the Tiny Forest to take off!
Lynn: I saw a time lapse of the speedy growth (see link below) and I believe the trees can achieve 100 years growth in 10 years with the optimum conditions and the close planting makes them compete with each other for light! Super forests indeed!
Follow the link to see a two year time lapse of Tiny Forest growing.