Dormancy of spurred anoda [ Anoda cristata (L.) Schlecht] seeds was not broken 60 days after harvest by stratification, presoaking in tap water, or by treatment with thiourea, potassium nitrate, or kinetin. Dormancy was broken by scarification or treatment with concentrated sulfuric acid. A high percentage of seedling emergence was obtained when scarified seeds were planted in soil at depths of 7.5 cm or less. Emergence decreased as planting depth increased. No seedlings emerged at depths of 12.5 cm or greater. Even at depths of 15.0 cm germination occurred, but no seedlings emerged.
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Solano et al. (1974) studied this question.