The Collaborative International Dictionary
Summer \Sum"mer\, n. [F. sommier a rafter, the same word as sommier a beast of burden. See Sumpter.] (Arch.) A large stone or beam placed horizontally on columns, piers, posts, or the like, serving for various uses. Specifically:
The lintel of a door or window.
The commencement of a cross vault.
A central floor timber, as a girder, or a piece reaching from a wall to a girder. Called also summertree.
Wikipedia
Summertree is a 1971 film directed by Anthony Newley. The screenplay was written by Edward Hume and Stephen Yafa, based on the 1967 play of the same name by Ron Cowen.
Usage examples of "summertree".
Lying down, Snake told herself to remember to take a few summertree seeds with her.
Closer, Snake could see that it was a dead summertree, close enough to the water to rot instead of drying.
The horse leaped across the shore and passed between delicate summertrees, shadows and delicate fronds flicking past, until suddenly the desert opened out to the horizon.
In a ring around the lake the summertrees stood like feathers, like a wreath of pale green silk.
The summertrees were brown and withered, rustling stalks surrounding a dark pond and deserted firepits.
The summertrees were dead, but the ground cover of grass and low bushes grew lushly.