Step one:
First draw a circle.
Step 2:
Use an arc around the circle to draw a flower shape.
Step three:
Then draw two arcs from the flower, a bit like an oval but do not connect them.
Step 4:
Then draw a rectangle underneath.
Step 5:
Draw a larger square.
Step 6:
You also need to draw a little texture on the cactus with arcs.
Step 7:
Use small short lines to draw the thorns of the cactus on the texture, and draw a flower at the back.
Step 8:
Finally, apply a nice color and the cactus is finished.