His working life was closely connected with trees and their role in land stabilisation, commercial uses, protection forestry, farm forestry, watershed and riparian protection, treescaping and landscaping.
Mr Knowles said at least until the late 1950s the Queen Elizabeth Park trees were properly maintained by pruning, trimming and removing wind damaged limbs after gales.
But over "quite a few years" tree management had not been adequate, he said.
"Trees that toppled on the lake island were left lying in the lake, wind damaged branches left hanging and diseased and dying specimens left unattended.
"The oak avenue on Memorial Drive is an example of where judicious thinning to open-row spacing and form pruning for shape should have been done years ago to retain the memorial's integrity."
Mr Knowles said elsewhere in the park there were several hazardous trees and others that were "over-mature".
He hoped the felling and maintenance work about to be done would solve problems caused by "deferred maintenance".
Mr Knowles said even when he was living in the park there were trees that had to be felled for public safety and in the late 1950s safety requirements led to lower branches on many trees being removed to increase visibility.
In later years the number of deciduous trees had been reduced to ease the problem - and the cost - of clearing away seasonal leaf fall.
In tandem with that, Mr Knowles said he believes passive, recreational use of the park dropped and greater emphasis was put on sporting use.
"Lack of public use justified a lower level of input in effort, finance and direction so maintenance dropped and tree management was neglected."
Part of the blame for lack of park care rested with widespread local government reorganisation in 1989, he said.
That did little to help with managing facilities as it required local bodies to divest operational and specialist activities to commercial contractors, who were profit-driven.
He said most parks established in New Zealand in the late 1800s mirrored English styles with a wide selection of tree and shrub species in arboreal form with trimmed hedges and beds of perennial and annual flowering plants.
"These were set out amongst mown lawns separated by gravel paths. Some featured an oval for cricket, a grandstand, a band rotunda and a lake for ducks swans and boating. They were well used for passive recreation and enjoyment."
He wondered if the makeover of Queen Elizabeth Park meant that the English theme is to be abandoned. Mr Knowles said, as an aside, he feared there is a problem looming in the Masterton Cemetery caused by indiscriminate tree planting throughout the plots.
The likely size of mature trees was often overlooked when people planted juvenile specimens.
"While doing some genealogical tracing I discovered a large specimen growing out of about the chest area of an ancestor but at least the headstone remained clear and intact, " he said.