Teucrium racemosum, also commonly referred to as either the grey germander or forest germander, is a species of flowering plant in the family Lamiaceae. It is endemic to Australia and is found in all mainland states, the Northern Territory and the Australian Capital Territory. It grows in floodplains, dry lake beds and open woodlands. A perennial herb, it has four-sided, densely hairy stems, narrow egg-shaped leaves, and white flowers usually arranged singly in leaf axils. It grows to be between 15 and 40 cm tall.
Description Teucrium racemosum is a perennial herb that grows to a height of between . It is a root suckering plant, meaning that it spreads by pushing up new shoots around the perimeter of its original base. Due to this root suckering ability, it is not uncommon for the Teucrium racemosum to spread to a diameter of several metres. The stems are white or greyish and densely covered with curved hairs pressed against the stem but that are usually lost from the stem's ridges. The leaves are a narrow oval shape, densely hairy, especially on the lower surface, usually long and wide. The edges of the leaves are sometimes somewhat lobed, rolled under or wavy. The flowers are usually arranged singly in leaf axils near the ends of branches on a pedicel that is long. The pedicel is often horizontal near its far end with the flower held erect. The sepals are long, densely hairy and fused at the base for about half of their length. The petals are long, with the lower middle lobe usually long, the four stamens long. Flowering occurs from September to June.
Taxonomy Teucrium racemosum was first described in 1810 by Scottish botanist Robert Brown in his Prodromus Florae Novae Hollandiae. The specific epithet (racemosum) means 'racemose'.
Distribution and habitat Teucrium racemosum is found in all states and territories of Australia apart from Tasmania. It grows on floodplains, dry lake beds and open woodlands. It is also often found around ephemeral lakes or disturbed areas.Teucrium racemosum - Plant Selector, 2021, Botanic Gardens of South Australia, http://plantselector.botanicgardens.sa.gov.au/Plants/Details/2879
Reproduction As is the case with many Lamiaceae, Teucrium racemosum uses gynodioecy as a method of reproduction.Floral Construction and Pollination Biology in the Lamiaceae, Claßen-Bockhoff R., Annals of Botany, 2007, 100 (2), p. 350-360,https://doi.org/10.1093/aob/mcm157 Gynodioecy is a breeding system consisting of male and hermaphroditic plants in a population.Gynodioecy in Teucrium racemosum, O'Brian E.& Walsh P., 2013, Muelleria, Volume 31, p. 77-80 Gynodioecy occurs as a consequence of genetic mutation that prevents a hermaphroditic plant from producing pollen, while keeping the female reproductive parts intact.A Model for the evolution of Dioecy and Gynodioecy, Charlesworth B. & Charlesworth D., 1978, The American Naturalist, p. 975, The University of Chicago Press journals In gynodioecious species, female plants often have much smaller anthers (the part of the stamen where pollen is produced) and as a result produce little to no pollen, whilst in hermaphroditic flowers both male and female sexes are functional.Recent Advances in the Study of Gynodioecy: the interface of theory and empiricism, Bailey M. & McCauley D.E., 2009, Annals of Botany, 104(4), p, 611-620 Genetic conflict often arises in these plants, and it is a common observation for female plants to produce more seeds and healthier, higher quality seed than the hermaphroditic plants.Effects of male sterility on reproductive traits in gunodioecious plants: a meta-analysis, Shykoff J.A., Kolokotronis S.O., Collin C.L. & Lopez-Villavicencio M., 2003, Oecologia, 135(1), p. 1-9 This is thought to be because of the extra energy that female plants have access to as a result of not producing pollen. Gynodioecy is an extremely rare form of reproduction, with the Teucrium racemosum being part of just 1% of all plants that exhibit a gynodioecious mating system.Pollen-Stigma interference in two Gynodioecious Species of Lamiaceae with Intermediate Individuals, Rodriguez-Riano T. & Amots D., 2007, Annals of Botany, 100(2), p. 423-431 Flowering occurs from September to June.
Conservation Teucrium racemosum is listed as "not threatened" by the Western Australian Government Department of Parks and Wildlife, and as "least concern" under the Queensland Government Nature Conservation Act 1992 and the Northern Territory Government Territory Parks and Wildlife Conservation Act 1976.
See also List of Teucrium species
References