Hypoxia improves germination of the problematic invader garlic mustard (Alliaria petiolata) of North American forests.
Garlic mustard [Alliaria petiolate (M. Bieb.) Cava & Grande] is a problematic European invader of temperate Eastern North American forests. We studied its germination response at reduced oxygen (O2) concentrations. Seeds of garlic mustard were exposed to different O2 concentrations (20.9, 15, 10, 5, and 2.5%) in two laboratory experiments. Germination rate increased, and it took fewer days to attain 50% germination (t50) at 15% O2 than at 20.9% O2. Germination declined at 5% O2, and seedlings became stunted at 2.5% O2. The ability of garlic mustard to thrive under low O2 concentrations may allow it to invade a wide variety of suboptimal habitats, such as shady understories where leaf litter cover the forest floors and on compressed and compact soils. Its ability to grow at low O2 levels may contribute to its invasiveness.