According to the OSM wiki, trees don't need to be "significant". If it is causing "unnecessary clutter" it is a problem with the renderer not the data source.  Take a look at ESRI's 3D tree layer for a good example of where this data is useful: https://www.arcgis.com/home/item.html?id=33383da8a75f4d24b4b6a0d0532abe6e