Seedling survival, post-harvest recovery and growth rates of the woodrose-producing mistletoe Erianthemum dregei (Loranthaceae) on Sclerocarya birrea

The mistletoe Erianthemum dregei (Eckl. & Zeyh.) V. Tieghem produces a wood rose type haustoriurn on host trees. In some rural areas of southern Africa woodroses are harvested for their unique ornateness and prepared for sale as curies. Concern for the sustainability of mistletoe populations led to t his study. Sclerocarya birrea (A. Rich.) Hochst hosts were artificially ino culated with hand-excised mistletoe seeds and post-harvest recovery of mist letoes on 12 S. birrea trees were investigated a year after disinfection. E . dregei exhibited 25% germination after 5 days but no seedlings survived a month in the field. Seventy-eight living E. dregei removed in 1994 were re placed one year later by 68 'new' plants probably through resprouting from internal, longitudinal cortical strands which allow for rapid vegetative re covery after removal. Poor seedling establishment and the occurrence of new recruits on branches between 0.0002 to 0.025 m(2) cross-sectional area cou ld indicate resprouting rather than recruitment from seed. The growth rates of 22 E. dregei woodroses growing on S. birrea were assessed over a 12 mon th period during 1994/5. These woodroses varied in size from seedlings to i ndividuals with a diameter of 25 cm. Absolute growth rate increased linearl y with woodrose size, with most growth occurring during the first 6 months (August-February) relative to the second (February-August). Relative growth rates declined (negative In function) from very high rates for very small woodroses to fairly similar slow rates of growth for all other sizes. Woodr oses of diameter 10 cm and 25 cm are typical size classes sold as curies. U sing the growth data, it is estimated that woodroses of these sizes are 40 +/- 25 (S.D.) and 56 +/- 35 years old respectively. These slow rates of gro wth must be taken into consideration when determining sustainable harvestin g limits.