noun
tree nursery; arboretum
Refers to a place where young trees are grown for planting or study. Can be a commercial nursery or a botanical collection.
この養樹園では、いろいろな種類の苗木を育てています。
This tree nursery grows various kinds of saplings.
苗圃 is a more technical term for a plant nursery, not limited to trees.
Compound of 養 (raise, cultivate), 樹 (tree), and 園 (garden, park). The word transparently means 'tree-raising garden'.