DENVER (AP) — Colorado may ban collective marijuana growing under a bill that calls some patient-owned marijuana grows a “public nuisance.”

A bill up for its first hearing in a House committee Monday would ban co-op pot growing by setting a statewide limit of 12 marijuana plants per residential property.

The change would effectively force some medical marijuana patients to buy from a licensed grower instead of growing their own plants.

Supporters including Gov. John Hickenlooper say the change is needed to eliminate black-market pot growers.

Supporters say criminals are hiding under a Colorado law that allows medical marijuana patients to have as many pot plants as their doctor recommends, then selling that pot on the black market.

Patient advocates say increased tax revenue is the real goal of the change.