What would be the easiest way to model green leaves (see picture) in SolidWorks?

An easy way is to start with a flat half-leaf without the stem and use the bend tool.
Attached is a leaf modeled using this method, but using displacement mapping and stuff to get the texture, instead of just a decal. Think I left the stem out of this one because the plant I put it on had them already.

  1. Step 1:

    Do a sketch on the Top Plane of half of the leaf, with the vein (midline) of it vertical and coincident with the origin, and make sure it's a closed sketch.

  2. Step 2:

    Create an extrusion from the sketch that is about 0.01", so you will have a flat half-leaf solid.

  3. Step 3:

    Next, use Flex tool (in Bending mode) to curl it slightly midway between the vein and outermost edge (this curl should be parallel to the vein).

  4. Step 4:

    Now curl it using Flex (bending) again, but this should be perpendicular to the first curl.

  5. Step 5:

    Use the Move/Copy feature to move (not copy) the half-leaf so that the vein was just over the right plane. This is sometimes necessary because the Flex Tool will curve the geometry slightly.
    Use Cut-Extrude to trim off the inner part that overlaps the right plane.

  6. Step 6:

    Use Cut-Extrude to trim off the inner part that overlaps the right plane.

  7. Step 7:

    Mirror this about the right plane so that you now have a whole leaf.
    Finish by making the stem with a swept boss. You can then project an image on it by using Decal. If you have a specific leaf you are shooting for, it might be good to use the same image as an Image Sketch and the Decal. Hope that helps! :)