The Weed Control Act is legislation in Alberta that directs all landowners to prevent the growth, propagation and spread of regulated weed species. The Weed Control Act lists specific weed species as either Noxious or Prohibited Noxious.
Noxious weeds are generally present in the province already in large numbers. Noxious weeds are required to be controlled (inhibit the growth or spread) by landowners.
Prohibited Noxious weeds tend to not be present in Alberta or in very low numbers. Prohibited Noxious weeds are required to be destroyed (kill all growing parts, render reproductive mechanisms non-viable) by landowners.
These species are not native to Alberta thus they are here without their natural control mechanisms. Typically they have been introduced either intentionally or accidentally, tend to inhabit environmentally sensitive areas and will displace native vegetation that wildlife require for survival.