For making such leaf you should insert the hook into back loop of each chain stitch of previous row and work dc/sc.
Diagram of leaf:
Make chain foundation of 14 chs.
1 row: work (from second chain from hook) 12 dc/sc in chain foundation.
Make 3 chains and continue work on opposite side: work 9 dc/sc.
In each next row no work the last three stitches and insert the hook into back loop of chain stitch of previous row. This is important!
Turn and work 2 row: make 1 chain, work 9 dc/sc into back loop of previous row, than work in space of 3 chains: 2 dc/sc, 3 chs, 2 dc/sc. After that work on opposite side 9 dc/sc.
Below are the pictures shown this step:
Turn and work next rows in this manner.
Our leaf and the diagram consists of 9 rows. But you can increase the number of rows for a longer leaf.
After reaching the desired length of the leaf you can crochet the last row with reverse dc/sc.
leaf with bend crochet in the same manner but in the place of increasing of stitches (place of 3 chans in each row) it is needed to work another number of stitches.
In the 2 row work in the space of 3 chans: 1 dc/sc, 3 chans, 2 dc/sc. In 3 row over this stitches work: 2 dc/sc, 3 chains, 1 dc/sc. Repeat 2 and 3 rows increasing for all next rows.
If you change the number and order of increasing stitches you get a
bend in the opposite direction. For that in the 2 row work in the space of 3 chans: 2 dc/sc, 3 chains, 1 dc/sc. In 3 row over this stitches work: 1 dc/sc, 3 chans, 2 dc/sc. Repeat 2 and 3 rows increasing for all next rows.
If you change the number and order of increasing stitches and change the number of rows you will get all the variety of lengths and shapes of such leaf.