Boron Tolerance of Twenty-five Ornamental Shrub Species1

Abstract

Boron (B) tolerance of 25 ornamental shrub species was determined in large, outdoor sand cultures. Tolerant species such as Natal plum ( Carissa grandiflora (E. H. Mey.) A. D. C.), Indian hawthorn ( Raphiolepis indica (L.) Lindl.), Chinese hibiscus ( Hibiscus rosa-sinensis L.), oleander ( Nerium oleander L.), Japanese boxwood ( Buxus microphylla Siebold and Zucc.), bottlebrush ( Callistemon citrinus (Curtis) Stapf), ceniza ( Leucophyllum frutescens (Berland.) I. M. Johnst.), and blue dracaena ( Cordyline indivisa (G. Forst) Steud.) were affected little, if at all, by 7.5 mg B/liter in the irrigation water. Sensitive species like yellow sage ( Lantana camara L.), juniper ( Juniperus chinensis L.), Chinese holly ( Ilex cornuta Lindl. and Paxt.), Wax-leaf privet ( Ligustrum japonicum Thunb.), laurustinus ( Viburnum tinus L.), thorny elaeagnus ( Elaeagnus pungens Thunb.), xylosma ( Xylosma congestum (Lour.) Merrill), photinia ( Photinia ☓ Fraseri Dress .), and Oregon grape ( Mahonia aquifolium (Pursh) Nutt.) were severely damaged or killed by 7.5 mg B/liter and moderately damaged by 2.5 mg B/liter in the irrigation water. B tolerance and B accumulation in the leaves were not correlated and no correlation was found between B tolerance and salinity tolerance.