Bush-harvesting of the sedge Caustis blakei reduces vegetative growth and seed set

Abstract

Summary. Substantial quantities of the native sedge, Caustis blakeiKukenthal (commonly called koala or foxtail fern) are harvested from naturally occurring populations in south-east Queensland as cut foliage and exported to Europe, USA and Japan. Light harvesting (30%) of stems of C. blakei reduced the number or size of marketable stems but did not alter the number and length of new stems. Moreover, mean dry weight of harvested stems significantly reduced over time, suggesting that even light harvesting was probably not sustainable under the dry conditions experienced. Plants that were harvested 3 times per year had more marketable stems than plants that were harvested once or twice per year at the same annual intensity.

Despite the infertility of the soil in the experimental site, the amount of nutrients removed by harvesting stems was low and may not be the major factor reducing growth. We suggest that limited carbohydrate supplies due to low water supply and harvesting (particularly moderate and heavy harvesting) might be the major causes of reduced growth. Regeneration of fire-sensitive species such as C. blakei is likely to be prejudiced by harvesting. Harvesting removed spikelets and reduced the number of spikelets on new stems. Although only a small number of fruit were removed in this experiment, the commercially harvested stems represent the current season’s stems and are the most fecund. This loss could be significant as C. blakei sets few fruit in any one year.

It is recommended that harvesting should be limited to only 30% of the current season’s stems with a limit of 15% during dry seasons, instead of the present harvesting limits of ‘30% of green stems’ or ‘30% of the plant’. In the longer term, propagation and commercial production will be necessary to supply the demand for cut stems on both export and domestic markets.