Flowering and capsule production of bellyache bush (Jatropha gossypiifolia L.) in northern Queensland

Abstract

In this paper we conducted flower initiation and subsequent capsule production of the exotic weed bellyache bush (Jatropha gossypiifolia L.). A field trial observed times to first flowering and capsule production, and growth rate at three sites (cleared, rocky embankment and grazed pasture). A pot trial examined the effects of five plant density treatments (20, 40, 80, 160, and 320 plants m-2) on flowering and capsule production of bellyache bush. After one and a half years, the proportion of tagged plants that had flowered and produced capsules in the cleared, rocky, and grazed pasture sites had a mean 95, 26, and 32% and 95, 15, and 25%, respectively. For those bellyache bush plants that reached reproductive maturity, time to first flowering had a mean 74.0 ± 0.9, 294.0 ± 48.2, and 454.0 ± 1.9 days in the cleared, rocky, and grazed pasture sites, respectively. In the density trial, the percentage of bellyache bush plants that flowered and produced capsules reduced exponentially with increased density. In contrast, increasing plant density caused exponential increases in times to first flowering and capsule production. At the lowest density (20 plants m-2) of bellyache bush all plants produced capsules, with the time taken a mean 64.8 ± 7.7 days following germination. In contrast, no plants within the highest density (320 plants m-2) had reached reproductive maturity after three and a half years. These results highlight the speed at which bellyache bush can flower and set seed, but also suggest that competition should be investigated further with regard to its potential role in slowing down the process.