The message tree is a hawthorn. Before the park was create a Sailors Trod ran from Newport to North Ormesby.
Its said that sailors left messages for each other under a piece of ironstone in the tree, which is still there with the tree having grown around it.
I like the story, but having checked the first OS map of the area the only footpath seems to co-incide with the one currently running through the centre of the park with this location being in the middle of a field. Although there’s then a 30 year gap until the next OS maps when the park is fully layed out so its possible the footpath moved.
UPDATE 23/11/2011 :
Prompted by Mikes comments I overlayed the first OS map onto Google Earth by aligning points that still exist today, this shows the path running east-west exactly where Mike says south of the Longlands Club
This also puts the path further north in the park than I originally thought, but it still doesn’t run next to the tree.