Received wisdom (i.e. knowledge often of the most unreliable kind) is that thickets of plants provide good places for criminals to dwell and hone their craft.
Well, it turns out, in Philadelphia at least, that vegetation, well maintained, can lower crime rates. Aggravated assault, robbery and burglary all drop when you clip your hedge. But first you have to grow a hedge.
A study out of Temple University, in Philadelphia PA, found that 'the presence of grass, trees and shrubs is associated with lower crime rates'.
Jeremy Mennis and Mary Wolfe used satellite imagery and crime statistics - after discounting the effects of poverty, education levels and population density - to come to this conclusion. Their results are published in the journal Landscape and Urban Planning but unless you want to pay $42 you'll have to, like me, get the gist of the study from their media release on Eurekalert!.
Mennis and Wolfe argue that 'well maintained greenery' is good for social interaction and what they call 'community supervision' (which I assume is like Neighbourhood Watch). It also calms us down, they say. Calm people, it seems, are less likely to commit crimes.
They add that vegetation also reduces stormwater run-off and improves the quality of our lives in other ways so this crime reduction is an added bonus.
They don't, at least in the press release or abstract, explain why the vegetation has to be well-maintained and what that really means. However they do confess that theft doesn't go down in vegetated areas. Presumably thieving criminals still find a dense thicket of plants a useful cover.
So for a safer city, but possibly fewer personal belongings, we should fill our cities with neatly pruned plants like these.
Images: Neatly trimmed hedges in Madrid (Spain), Powis (Wales), Sissinghurst (UK) and Versailles (France).