National Recovery Plan for the Eneabba Mallee (Eucalyptus Impensa)
Gillian Stack and Gina Broun
Wildlife Management Program No. 179
Department of Conservation and Land Management, June 2004
About the document
Eucalyptus impensa was discovered in 1987, but was not seen in flower until July 1991. Seed was first collected in 1994. The taxonomic description was published in 1993, and the species was named 'impensa' from the Latin (impensus - large, strong), alluding to the leaves and fruit. Five populations are known from a Nature Reserve, and one from private property, over a range of approximately 3 km.
All populations are known to have been burnt in recent years. Population 1 was burnt in 1990 or 1991. Population 3 was burnt in 1993. This population occurs in buffer vegetation which is currently prescription burnt approximately every 12 years. Populations 4, 5 and 6 burnt in summer 1995. An intense fire in December 2002 burnt all populations. Regeneration through resprouting has been noted on plants in Population 3, and in March 2004 was approximately 40 cm high and insect damaged. Almost all shoots were eaten or damaged, and almost all leaves have suffered insect damage. Charred stems remain and bear some burnt fruits, indicating that the species flowers within 10 years post-fire. It is not known, however, if these fruits contained seed. Eight fruits collected in November 2002 contained seven seeds in poor condition. Their viability has not been tested as there are so few in storage.
Eucalyptus impensa is a straggly mallee to 1.5 m tall. It has smooth stems which are coloured grey over pale copper. Mature leaves are pale green to yellow-green, and have short, stout stalks up to 1 cm long. Leaves are large and stiff, up to 14 cm long and 8 cm wide, and usually in opposite pairs. Pink flowers are held in the leaf axils, on a thick stalk up to 2 cm long. The bud has a hemispherical floral tube and beaked cap, which is slightly ribbed. Buds are up to 2.5 cm across and 5 cm long, including the stalk. Hemispherical fruits, up to 2.5 cm long and 6 cm wide have a conspicuous raised disc and 5 protruding valves. The brown seeds are an asymmetrical pyramid shape. The large fruits are similar to those of E. macrocarpa, but E. impensa has leaves on short stalks, with no whitish bloom, and the plants are smaller than those of E. macrocarpa (Brooker and Hopper 1993; Brown et al. 1998).
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