Instructions
Gain experience points in your garden by tending to it and its Piñata residents. Get enough points to reach at least level 4.
Wait for Seedos, the wandering seed-lover, to enter the garden. He comes to the garden every in-game day. When he arrives, click on him to talk to him, and he throws a random seed on the ground. This may be a free watercress seed. If he does not give you one, or if you do not want to wait for him to arrive, buy one from the store for 13 coins.
Place the watercress seed next to the Squazzil. If the Squazzil does not eat the seed on its own, highlight and select the Squazzil, then select the seed to tell the Squazzil to eat it. When your Squazzil eats the watercress seed, the Squazzil will turn green.