from Duncan Slater on LinkedIn:

No. 993: Tree Planting Shouldn’t Be A “One-Hit Wonder”

It requires more than an initial physical effort & financial contribution to grow a tree successfully. We should never accept a count of “trees planted” as a meaningful statistic for urban greening – it should be “trees well-established in suitable locations” – or “sustainable canopy cover added to our city after a decade”: although, few involved seem to want to wait for such a metric! 😔

Urban locations are often challenging to plant up with trees, & three key factors are associated with planting failure:

🔹The planting location is unsuited to the species planted in it (e.g., soil compaction, soil volume accessible, soil pH, dryness/wetness).

🔹The technical aspects of the planting are carried out poorly (e.g., planting at the wrong depth, planted in the wrong season, transplant has an inadequate root system in the first place).

🔹After-care is not implemented when it is needed (e.g., no irrigation or weed control in place).

A mix of these three factors accounts for the majority of failed urban tree plantings & this is compounded by a further factor that I have found to be very common in my revisits to sites:

🔹Few failed trees are replaced – the planting was a “one-hit wonder”

Obvs, if the site condition doesn’t suit the species planted, or is inhospitable to most tree growth, it is understandable not to try again on the same spot. However, there are means to make most urban locations more suitable for tree planting by soil amendment or artificial creation of underground soil resources. Potentially expensive, but, if it’s a good spot for a tree in an urban area of poor canopy coverage, it may well be worthwhile to amend the site conditions to achieve good tree establishment.

That the planting may have been poorly enacted or that there was no aftercare in place are more easily overcome by education. I have a current MSc student investigating the benefits of empowering local residents to carry out basic aftercare for trees outside their houses – and the findings look good! 😊🌳🚿

My time-lapse shows a failed urban planting: pit created, metal guard in place, tree planted (all at quite a cost to the taxpayer) – but no re-attempt to do a replacement planting: the initial tree is still there, shattered into pieces on the ground!

LESSON LEARNT: Urban foresters are not just ‘guardians of the trees’ – but, by necessity, they must be ‘guardians of the soil’ too. Soil conditions drive what can be planted & achieved on any site, making some sites unsuitable for tree establishment entirely, unless amended. All urban forests are an “experiment in action” – as the concept of an urban forest is fairly new – as is the science behind their establishment & care. Where an experiment fails, don’t give up by default: review – and learn the lessons of each failure!