Salient Aspects of Huisache Seed Germination

Germination of huisache (Acacia farnesiana [L.] Willd.) seeds is restricted by an impermeable seed coat. Mechanical scarification or soaking seeds in concentrated sulfuric acid for 45 to 60 min resulted in 65 to 70% germination. More huisache seeds germinated at 30 C than at 16, 21 or 38 C. At the optimum temperature, germination was not reduced by osmotic pressures of 4 atm. Germination and seedling growth were favored by a pH range of 6 to 8. Huisache seeds were not light sensitive, and optimum seedling emergence from soil occurred when seeds were planted 2 cm deep. Percent germination at 30 C was not reduced by less than 5,000 ppm NaCL or MgC12 in aqueous solution but seedling development was inhibited by 300 ppm NaC1 or 150 ppm MgCl2. Huisache (Acacia farnesiana [L.] Willd.) is an introduced woody plant which inhabits almost 2.5 million acres in the Gulf Prairies and marshes and South Texas Plains physiographic provinces of Texas (Smith and Rechenthin, 1964). The species is established as far north as College Station in Brazos County, Texas. Huisache grows rapidly and may develop into a many-stemmed shrub or a thorny tree (Fig. 1). Huisache leaves are pinnately compound, alternate and 3-10 cm long with 2-8 pairs of pinnae. Plants flower in February and March, producing yellowish heads 1-2 cm in diameter (Vines, 1960). Fruits are usually 5-7 cm long and purple or black. Huisache is adapted to tropical or semi-tropical conditions (Vines, 1960). Climatic conditions in its center of distribution in Texas are typified by a growing season of more than 300 days, warm temperatures and relatively high humidity (Gould, 1969). Rainfall in the distribution range varies from less than 50 cm annually in the west to about 130 cm in the east. Soils in the center of huisache distribution are typically acid sands, sandy loams or clays (Gould, 1969); many are only slowly permeable and drouthy by nature. Vegetation of such 1 Approved by the Director, Texas Agricultural Experiment Station as Technical Article 9690.