The frost hardiness temperature (i.e., the temperature that causes damage) and the lethal temperature (i.e., the temperature that causes death) were assessed in summer (January) and winter (July) for 35 Hebe species, cultivars, and hybrids. Frost hardiness was also assessed in both autumn and spring for a limited number of these selections.

Seeds of Carex trifida, Coprosma robusta, Cyperus ustulatus, Hebe stricta, Leptospermum scoparium, Muehlenbeckia australis, Myrsine australis, Phormium tenax, P. tenax 'Yellow Wave', and Sophora prostrata were assessed for germination and dormancy. Seeds of Carex trifida, Cyperus ustulatus, and Myrsine australis showed no germination in light or dark at 20 º C, but a high percentage of seed of Carex and Cyperus germinated after 12 weeks of low stratification. Despite high viability, germination of Myrsine australis seeds was low and occurred only after 12 weeks of low temperature stratification. Germination was low for Muehlenbeckia australis in the light, at 20°C, but increased after 4 weeks of low temperature stratification. After 12 months, 50% of Coprosma robusta seeds germinated but germination was greater after 4 weeks or more of stratification. No seeds of Coprosma robusta or Muehlenbeckia australis germinated in the dark. Rapid germination of Hebe stricta seeds was obtained, with 100% of the seed germinating in the light but 7% in the dark. Leptospermum scoparium had rapid germination, with 100% germinating in the light but 3% in the B02051;

A pot trial and two field trials evaluate the safety to stevia plants of 25 herbicides, many of which have been used for selective control in other Asteraceae crops. Pre-emergence herbicides that show potential for use in transplanted stevia include trifluralin, pendimethalin, oryzalin, bromacil, terbacil, linuron, methabenzthiazuron and alachlor. Post-emergence treatments that are tolerated reasonably well by stevia include many of the herbicides listed above plus clethodim, haloxyfop, propyzamide, thifensulfuron, flumetsulam and pyridate. Other postemergence herbicides that cause some crop damage but may merit further research include bentazone, ethofumesate, MCPB, picolinafen, chloridazon and metribuzin. Terbacil and bromacil are the most effective herbicides for weed control, although some crop damage did occur. Controlling weeds through frequent hand-weeding allowed a 30-fold increase in stevia production in one trial, although the best result obtained by herbicides was a 19-fold increase using bromacil immediately before transplanting stevia.

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