Maine designated the white pine cone and tassel (Pinus strobus, linnaeus) as the official state floral emblem in 1895 (botanically, the white pine cone and tassel are not considered true flowers). The white pine (also the state tree of Maine) is considered the largest conifer in the northeastern United States. Maine's nickname is "The Pine Tree State" and the eastern white pine is also the state tree of Maine.

Selection of a state floral emblem was inspired by the "National Garland of Flowers" at the 1893 World's Fair, which was made of individual state flowers or floral emblems which were specified by each of the state legislatures (many states selected their official flower symbol as a direct result of this garland).

The resident's of Maine voted on three candidates: goldenrod; the apple blossom; and the pine cone and tassel. Though the pine cone and tassle is not a flower, the choice is not surprising for the citizens of Maine (considering the role of the white pine in Maine's history).

Source:

Maine State Symbols: Maine Secretary of State Kids Page

Links:

State Flowers - 50 States List
National Flower