I have been to Gros Morne NP (ca. 1986) and hiked a good bit. I was most impressed with absolutely ANCIENT and enormous white cedar (Thuja occidentalis). I did not have a measuring tape but one tree took three arm spans which would be close to 19 feet dbh. However, I do not recall if it was a single trunk or multi-stemmed, but many were 3-4 foot diameter single stems. Up above treeline were some magnificent common juniper mats that could be super-old. It is a magical place well worth an ENTS visit.