Ecological life cycle and temperature relations of seed germination and bud growth of Scutellaria parvula ( Lamiaceae, Tennessee).

Scutellaria parvula (Lamiaceae) is an herbaceous skullcap that grows in prairies, meadows, open woods and cedar (limestone) glades throughout much of the eastern United States. In the middle Tennessee cedar glades, plants flower, set seeds and form moniliform tubers in May and early June and then die in late June, leaving only the seeds and tubers. Most of the seeds are dormant at maturity, but they quickly afterripen and consequently are nondormant in late summer and autumn. Some seeds may germinate in late July and August, but most germinate in September and/or October. After germination, overwintering rosettes are produced. Age of plants when they first flower in the field is unknown, but in a nonheated greenhouse plants from seeds that germinated in autumn flowered, set seeds and formed tubers the following spring. Each tuber has a terminal bud which gives rise to the shoot. These nondormant buds grow slowly, even at optimal daily thermoperiods (30/15 and 20/10oC) in continuously moist soil. In the cedar glades, some shoots may emerge in July and August and produce seeds and tubers in autumn, but most do not emerge until September or October. These autumn-emerging plants form rosettes and overwinter in this condition. During the winter the tubers decay, and in spring plants flower, set seeds and form new tubers. -Authors