These are incredibly simple but effective origami leaves.
You will need:
1 square of paper
a little time and patience.
Fold your square of paper in half
Unfold it
Fold the uncreased corners in to meet the centre fold - you can fold them in a little less to change the shape of your leaf.
Fold it back along the middle crease
Choose one end and fold it over in a concertina fashion. As long as the folds are fairly even you will still get the leaf effect.
Keep going until you run out of leaf and then unfold the two sides.
I would highly recommend not using card as I have here. Thinner paper works better as long as it's strong enough to create a firm crease.