Aspen Wood Chip and Stone Mulches for Landscape Plantings in Interior, Alaska

Five woody landscape plants were grown on five mulch treatments: 2.5 or 5 cm (1 or 2 in) crushed basaltic rock, 5 or 10 cm (2 or 4 in) of aspen wood chips and a non-mulched control, to determine the usefulness of these mulches in subarctic landscape plantings. Weed control was best, but growth and plant nutrition poorest on the wood chip mulches. White spruce, Siberian crabapple, Peking cotoneaster, and rugosa rose had low levels of leaf nitrogen on the wood chip plots, and all species except cotoneaster and lodgepole pine showed significant N deficiency symptoms after 2 years. With the exception of the roses, all species grew best on the stone mulch plots. Roses grew vigorously on the stone mulches and the unmulched soil, but were subject to winter dieback. After 3 years, their total biomass did not exceed the recumbent, spindly and nitrogen deficient roses that were growing on the wood chip mulches. Plant growth, nutrition, and weed control were best achieved on the 5 cm (2 in) stone mulch plots.