The Australian Acacia longifolia (Andr.) Willd., owes its success as a weed in South Africa amongst other things to the excessive production of long-lived seed banks under existing stands of the weed. A fairly intense fire (circa 24 900kW m−1) was found to reduce the number of viable seeds in the seed bank to 8% of the original by either destroying or stimulating the germination of a large proportion of the seeds. Only 3% of the seeds present in the seed bank before the fire, established as seedlings after the fire, while the remaining seeds that were viable appeared to be buried too deeply to be stimulated to germinate. This was confirmed by a separate trial where seeds buried 10mm below the soil surface were destroyed by fire. Most seeds buried 20mm deep were stimulated to germinate while seeds buried 30mm or deeper were largely unaffected by fire

Moringa oleifera (moringa) trees excel mainly in tropical and sub-tropical regions and are known to thrive in a wide range of soil types. The recent rise in moringa production in various agro-ecological zones of South Africa could be attributed to its multiple benefits, including nutritional and medicinal properties. Since its introduction as a cultivated crop, there has been a growing interest from farmers, researchers and government on various aspects of the tree such as its morphology, chemistry, growing conditions, production, processing and utilisation. We reviewed the work done on moringa within the South African context in terms of production, growing conditions and cultivation practices. The involvement of government departments on moringa-oriented activities and its consumption as food were also reviewed. In addition, gaps were outlined on its utilisation that need to be addressed, and recommendations provided on what could be done to ensure successful production of moringa in South Africa.Significance: This review highlights moringa research that has been done on growing conditions, production and human consumption in South Africa. The review further addresses the potential commercialisation of moringa and existing knowledge gaps.

Apart from the last 40 to 50 years, weed control in crops has always been a labour-intensive and time-consuming mechanical practice. Relief came in the form of chemical compounds that could control weeds, in particular selective herbicides. The development of highly effective selective herbicides has resulted in farmers becoming increasingly reliant on chemical weed control. Continuous application of herbicides with the same mode of action, however, selected for resistant mutations within weed populations to become dominant, rendering the herbicides less effective. Herbicide resistant weeds currently occur in 187 weed species distributed over 60 countries worldwide. South Africa is no exception and resistance in 15 weed species to herbicides in seven modes of action groups has been verified. This situation is compelling farmers to consider alternative weed control strategies and cropping systems. The most effective strategy to manage resistant weeds would most probably be an integrated weed management program that does not rely on any one type of weed control method alone. Farmers will therefore have to adapt weed management systems and cropping systems to delay the onset of herbicide resistance or, if it is already present, to manage it effectively in order to keep future crop production profitable and sustainable.

The population dynamics studies of Acacia longifolia (Andr.) Willd. differed greatly in the absence or presence of fire. In the absence of fire few seedlings established under the living parent plant even though a large quantity of seeds is incorporated into the seed bank annually. Fire caused the destruction of the parent trees but resulted in the establishment of a dense, even-aged stand of seedlings. However, this treatment depleted the seed bank of this weed by 90%. The implications of these findings for integrated control are discussed.

The effect of different pre-treatments on the dormancy of the hard-coated seeds of Acacia longifolia Andr. Willd. was determined. A final germination figure of 100% could be obtained with hot water treatments, acid scarification and manual scarification. However, if germination rate was taken into consideration, acid scarification proved superior to all other treatments.

Acacia mearnsii is an important invasive plant in most of the higher rainfall areas in South Africa. The production of long-lived water-impermeable seeds results in the establishment of large soil-stored seed banks. One way of controlling these seed banks is by felling the plants and burning them to destroy or to stimulate seeds to germinate, so that the resulting seedlings may be controlled. In order to save costs, the hypothesis that the plant population can be burned without felling beforehand, was investigated. A wildfire that swept through a standing population of A. mearnsii plants provided an opportunity to investigate the effects on the population. The mortality of the pre-fire population, the subsequent establishment of seedlings, mortality of seedlings and the spread of the population after the fire were investigated. It was found that the above-ground population increased by a factor of ca. 21,8 due to coppicing of young plants and the mean distance of spread from the edge of an infestation was ca. 20 m. About 90% of seedlings that established, died within two years. Due to the growth of the population, and the dificulty of controlling coppicing plants, a standing burn is not recommended as a control measure for A. mearnsii.