Overcoming dormancy in New Mexico mountain mahogany seed collections

Mountain mahogany (Cercocarpus montanus Raf) is a useful reclamation species because it can occupy and improve poor soils. Literature regarding seed propagation of this species is varied and often contradictory, recommending stratification durations of 14 to 90 days, and sulfuric acid scarification durations of none to 60 minutes. To assess variability in propagation requirements among seed sources, 8 New Mexico seed sources were tested with factorial combinations of scarification and stratification treatments. Sources were selected to encompass both a range of latitudes throughout New Mexico and a range of elevations at Questa, N. M. Seeds were scarified 5 or 10 minutes in concentrated sulfuric acid, tumbled 5 or 10 days in course grit, or unscarified (control). Seeds underwent subsequent stratification for 0 (control), 30, or 60 days. Averaged across scarification treatments, the 2 southernmost sources lacked a stratification requirement, while northern seed sources achieved their highest germination following the longest stratification duration (60 days). Improvement in germination due to stratification was greatest for the 2 highest elevation Questa sources. Scarification treatments were less effective in improving germination than stratification treatments, and produced more variable results. A 5-minute soak in sulfuric acid was the most effective scarification treatment, but for 2 sources, this treatment reduced germination. Variability in the stratification requirement appears to be an adaptation to macroclimatic differences among seed sources, whereas differential response to scarification may be a response to microclimatic differences.