Optimization of flower and seed crop production in temperate eucalyptus orchards in South Africa through site selection and environmental manipulation.
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Date
2014
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Abstract
Temperate eucalypts are an important part of the commercial forestry landscape in
South Africa, comprising approximately 50% of the total Eucalyptus planted area. The
majority of the commercial temperate eucalypts grown in South Africa are reticent, shy
flowerers, and subsequently erratic seed producers. Disadvantages associated with
sub-optimum (inconsistent and sparse) flowering in Eucalyptus orchards include
decreased levels of out-crossing and compromised quantity and (genetic) quality of the
seed produced. Genotype, physiological age and a range of environmental factors are
known to influence flower bud production in temperate eucalypts. To date, winter cold
and paclobutrazol (PBZ), a plant growth regulator, remain the most effective treatments
for encouraging early and prolific flowering in temperate eucalypts. Disadvantages
associated with the use of PBZ in the outdoor environment include the toxicity and
recalcitrant nature and persistence of the chemical in soils, the high cost of PBZ and its
orchard application, and the need to re-apply the chemical approximately every five
years.
The main aim of this study was to provide a practical solution to the problem of shy
flowering and seed crop production in important temperate Eucalyptus species in South
Africa. The study focused on investigating key environmental factors associated with
optimum flower bud production in temperate eucalypts. The resultant data were used to
achieve optimization of flower bud production in temperate eucalypts in the summer
rainfall forestry areas of South Africa, via informed site selection and/or manipulation of
the environmental conditions. A subsidiary aim of the project was to lessen the
dependency on PBZ for achieving satisfactory flowering levels in temperate eucalypts
via improved site-orchard matching and environmental manipulation. The key objectives
in the study included definition of summer rainfall area site conditions for maximal floral
bud production in two important species, viz. E. nitens and E. smithii, investigation of
the effects of optimum flowering environmental conditions on post-initiation floral
development and seed maturation in temperate eucalypts, and development of a
method for supplementing winter cold and increasing flower bud production in orchards
located at marginal winter chilling sites.
Description
Ph. D. University of KwaZulu-Natal, Pietermaritzburg 2014.
Keywords
Eucalyptus -- South Africa -- KwaZulu-Natal -- Growth., Eucalyptus -- Growth -- Research., Theses -- Horticultural science.