Start with a plane. Scale it into a rectangle which would fit the leaf inside of it. Select one end edge and scale it to 0 to make it a point. Then do on loop cut down the centre. Then do about 4 or 5 loop cuts down the middle. Select the edges each of those loop cuts made.
Press ctrl b to bevel and increase the segments to 2 and increase the offset to the size you want the bit where the leaf goes in to be.
Go on by one grabing the mid points of each bevel and moving it inward to make in in bits of the leaf.
Turn on proportional editing and set the fall off type to sharp. Drag up and down vertices until you have the curve of the leaf.
Merge the end points
Select the edge loop which goes from top to bottom of leaf. Disable proportinal editing and then grab it and move it down a bit on the z axis.
Then add a solifiy modifer to make the depth of the leaf and you are finished.