The TGS 2D Foliage Mega Pack contains plenty of trees, bushes, vines, etc., in high resolution, medium resolution, low resolution, and silhouettes.
There is also a simple sprite for grass included in this package.
This package also includes a small demo scene which can be seen in the video below.
Also includes 3 sample background images, and a parallaxing camera script that adds depth to your 2D scene. A great way to prototype levels,
or use in your own game!
*Update* May 18th 2017
Added 9 trees, 3 bushes and 3 vines
New trees, bushes, vines, cactus will be added in the coming months.