In ASL there are several ways to sign the concept of
cactus.
One of the more common ways is with a four handshape and a one handshape.
CACTUS: 4/1 version:


Animated GIF: CACTUS-[4/1-version]

Notes:
CACTUS-[4-B-edge-version]:
CACTUS-[4-1-version]:
Notes: