If you look at our experience fishing the lower Blackfoot River in our Small Streams report today there are words on the effects of aquatic weeds breaking up. Those words apply, as well, to sections of the Henry’s Fork that “weed up” during the growing season. That includes such as the Harriman State Park reach, the River above Mack’s Inn, above Coffee Pot Rapids, and others. What is important regardless of the water you fish, weeds breaking up this time of year release life forms that therefore become more easily available to foraging fish. Thus because of availability they will key on these life forms and your response should be to simulate them in the flies you offer.