Vermont on Sunday will end a decadeslong prohibition of recreational use of marijuana.

“It’s a huge deal. And it’s been a long time coming,” said Eli Harrington, a legalization advocate who co-founded the group Heady Vermont.

The state’s reform law, known as Act 86, was signed by Republican Gov. Phil Scott in January. The law takes effect July 1.

Vermont will allow adults 21 and older to carry up to 1 ounce of processed marijuana and grow a small number of plants at home, or on private property with the landowner’s permission.

The law limits cultivation to no more than two mature plants (with visible marijuana buds) or four immature plants.

Critics of the law worried that two mature plants might produce at least a pound of marijuana. Whatever is derived from two mature plants is permitted under Act 86 if secured at home.

Private sales or purchases remain illegal, though the law allows adults to share call quantities of marijuana — or cannabis — as advocates prefer to call it.

Act 86 expressly forbids consumption of marijuana in a public place — including parks, sidewalks, alleys, or in any facilities open to public accommodation — with a $100 fine for a first offense.

Furnishing marijuana to anyone under 21, or growing marijuana in larger quantities carry stiff penalties.

The law continues strict prohibition on driving under the influence, or consuming marijuana in a vehicle.

Vermont State Police now has its largest corps of specially trained “drug recognition experts” ready to prosecute violators.

Capt. Jim Whitcomb says troopers have received new training manuals that adjust to the changes made in Act 86.