Seed dormancy, germination, emergence and seed longevity in G alinsoga parviflora and G. quadriradiata

Summary Galinsoga quadriradiata (hairy galinsoga) and G alinsoga parviflora (smallflower galinsoga, gallant soldier) are very troublesome weeds in many vegetable row crops in E urope. To optimise management strategies for G alinsoga spp. control, an in‐depth study of germination biology was performed. Germination experiments were conducted to evaluate the impact of light and alternating temperatures on germination of a large set of G alinsoga populations. Seedling emergence was investigated by burying seeds at different depths in a sandy and sandy loam soil. Dormancy of fresh seeds harvested in autumn was evaluated by studying germination response in light at 25/20°C with and without nitrate addition. Seed longevity was investigated in an accelerated ageing experiment by exposing seeds to 45°C and 100% relative humidity. Galinsoga spp. seeds required light for germination; light dependency varied among populations. Seedling emergence decreased drastically with increasing burial depth. Maximum depth of emergence varied between 4 and 10 mm depending on soil type and population. In a sandy soil, emergence percentages were higher and seedlings were able to emerge from greater depths than in a sandy loam soil. Freshly produced G . parviflora seeds, harvested in autumn, showed a varying but high degree of primary dormancy and were less persistent than G . quadriradiata seeds that lack primary dormancy. Lack of primary dormancy of freshly harvested G . quadriradiata seeds and light dependency for germination may be used to optimise and develop G alinsoga management strategies.