This root-over-rock marijuana bonsai is pretty amazing — and entirely legal in my state, and many others.
Root over rock marijuana is done just like root-over-rock chrysanthemums. Start a seed or sprout in soil on a rock, with the soil held to the rock using saran plastic wrap. As the plant develops, and roots extend to the soil below the rock, you remove the saran wrap. The trick is to keep everything watered; a gravity drip system can help.