The development of 157 tanoak [Lithocarpus densiflorus (Hook. and Am.) Rehd.] and 130 Pacific madrone (Arbutus menziesii Pursh) sprout-clumps 1 to 6 yr after cutting or burning was studied on a range of sites in southwest Oregon. The width and area of sprout-clumps originating from trees ≥ 2-cm stem diameter at 1.4-m height of both species was related to the size of the parent stem and time since cutting (tanoak, r2 = 0.77 and 0.75; Pacific madrone, r2 = 0.84 and 0.83). The sprouting capacity of tanoak develops slowly, and 5 to 6 yr after cutting, sprout-clumps produced by small tanoak 40 to 50 yr old averaged only 37 cm in diameter. Prediction equations, along with stem-diameter distributions of these species in forest stands, can be used to estimate hardwood foliar cover up to 6 yr after cutting.

Broadcast applications of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] pellets and foliar sprays were tested at four rates for hardwood control and safety to loblolly pine (Pinus taeda L.) at each of eight study locations differing in soil characteristics. Reduction in the number of hardwoods in the stand (hardwood density reduction) was greater with the pellet on soils with more than 60% sand, while the liquid formulation was most efficacious for finely textured soils. Hardwood density reduction with the pellet was negatively correlated with percent silt, clay, soil organic matter, and cation exchange capacity, and positively correlated with percent sand. With foliar sprays, hardwood density reduction was positively correlated with hexazinone rate and negatively correlated with soil pH. Pine mortality was positively correlated to percent sand with the pellet and negatively correlated to soil pH with broadcast sprays. Regression models incorporating pine height, herbicide rate, soil texture, cation exchange capacity, soil organic matter, and acidity could explain up to 78% of the variation in hardwood density change and 77% of the variation in pine mortality. Selective control of hardwoods in young loblolly pine stands is a function of hexazinone rate, formulation, and various soil factors.