Switch to vertex selection and scale the vertices to get a leaf shape.
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Switch back to Object Mode and Activate your Move Tool. Hit the Insert key, hold down V to snap to vertex, and move the pivot point for the leaf to the top vertex.
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Move your leaf and position it so that it looks like it is attached to the stem.
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Duplicate the leaf using Shift+D and move it to the right. Do not De-Select the leaf you just duplicated when finished.
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Now hit Shift+D repeatedly to get a result similar to the one below.
