Lemax makes tons of collectible items, most of which are useless for prehistoric settings. Recently I purchased a few trees that are quite compatible with antideluvian times: small and medium cypress trees and small and medium palm trees. Cypresses have been around since at least the late Triassic and the oldest known fossils are from about 200 million years ago, while palm trees first appear in the later Cretaceous around 80 million years ago. While the palms can be used as is from the end of the Mesozoic until modern times, I will also use them for earlier palm-like plants such as giant tree ferns.
The Lemax small trees are about 4″ tall and come two to a pack. In the case of the palm trees these are a pair on a single base. A 4″ tree scales out to about 33 feet in 15mm. The medium trees are packaged as singles and are about 6″ tall, so approximately 50 feet at 1/1ooth scale. The trees are very nice, but a bit pricey at 6.99 per package. Contrast this with a Woodland Scenics economy pack with 33 trees for under 30.00. If you are lucky you can snag some on sale after the holidays. I think the cypress trees are part of the Christmas collection, while the palm trees are in the Halloween range (for some odd reason!)
The pictures show the trees with 15mm Lambeosaurus and Tyrannosaur from Primaeval Designs, a Khurasan Miniatures Ankylosaur, and a Schliech Brachiosaur toy(this is about 1/100th scale)