I am interested in people's thoughts on the planned lifecycle of urban trees. I am thinking particularly of street settings, as opposed to semi-natural settings such as parks.
The growth and development of trees in a natural setting could be considered in three stages - growth, maturity and decay. In a tree grown without intervention, it is the end point of the latter which is usually taken as the lifespan. For trees in settings with more intervention, I would anticipate that they would pretty much never reach the natural end through decay, so the effective lifespan is shortened.
I am interested in views as to what the expectations of lifespan would therefore be. I suppose the simple ones are short-lived trees such as flowering cherries, which will probably not ever outgrow a space. However, I can see the potential conflict in, say, removing a row of street limes because their trunk diameter and root structure is now blocking the pavement, even though their crowns are well maintained in the available space. I have seen plane trees of 2m across in parkland, where in a street setting they would block the road, let alone the pavement.
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Any thoughts on how these expectations are managed?
I am particularly interested because of the current position with elms. There are now elm strains and hybrids which have proved highly resistant in controlled testing and are now fairly widely planted in The Netherlands, but of course nobody knows how resistant they will be in the field, or how they will perform over their lifespan. The most controlled approach would be to plant out and monitor in settings which do not matter, but 300yrs of monitoring is a bit much! Hence the interest in thoughts as to what would be satisfactory for a realistic specification?
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