Creature Comforts Brewing Co. is growing so fast that its supply chain can’t keep up.

The brewer has had so much trouble finding enough of a special type of hops called citra—the plant that gives its popular Tropicália ale its bitter flavor and fruity aroma—that it has been forced to reject orders for about 8,000 barrels of beer during the past year. That is more than $2 million in revenue and enough beer to nearly double production.

The Athens, Ga.-based brewer isn’t alone. A host of smaller, regional brewers including Wicked Weed Brewing of Asheville, N.C., and MadTree Brewing of Cincinnati have run into similar constraints.

The shortages are contributing to the sudden slowdown in craft beer sales. During the first half of the year, independent brewers’ volumes grew about 8%, ending six years of double-digit growth, according to the Brewers Association, which represents the industry.