On behalf of the Street Society Nina Fry contacted Stephen Clark at Mendip about the trees in Merriman Park. This is the relevant part of the reply:

Merriman Park has a good selection of trees, I�m not sure they would be considered rare but there are some species that you don�t often see in this area. Most of the trees are in reasonable condition as we have carried out remedial work around the park over the last few years. Unfortunately this has also meant the removal of a few trees, one of which you may be interested in, an Indian Bean Tree (Catalpa bignoniodes). There is a Ginkgo biloba on site, that is doing well. Although these days it may not be considered rare.

Some members of the Street Society had found that the park was originally planted with rare species. Evidently these species have now become more common. I repeat my feeling that the whole park now needs to be redesigned for present-day use.