| dc.description.abstract | Leucospermum plants have a relatively short flowering period and peak flowering periods
often coincide with low prices on the export market. Two field trials were therefore carried
out at Pinfields farm Ruwa, Zimbabwe from 2002 to 2004 to investigate the effect of two
cultural practices, pruning and deheading, on the flowering behaviour of two Leucospermum
cultivars: Scarlet Ribbon and Saxosum. The first trial investigated the effect of pruning and
deheading two different aged plants (2½-3years ‘old’ and 1-1½ ‘young’) of Scarlet Ribbon.
The second experiment compared the response to pruning and deheading of two cultivars,
Scarlet Ribbon and Saxosum, on flowering time. Measurements taken in all experiments
included the period from pruning to harvesting, the extension to harvest time after deheading
of the primary inflorescence, length of harvested flowering stems, inflorescence diameter of
harvested flowering stems, grading of stems and losses in harvest due to pruning and
deheading. Pruning of plants was carried out at different times from January to July,
including the control treatment (normal farmer practice) for both experiments. Deheading of
the primary inflorescence bud was at 0-5 mm, 6-10 mm, and 15-20 mm and was compared
with a control (disbudding all but the primary bud). Pruning and deheading treatments
significantly (P<0.05) extended harvest time for all the experiments. The extension to harvest
varied with pruning time, deheading diameter, age of plants and cultivar. Pruning early
(Jan/Feb) and deheading early in the induced reproductive phase resulted in a longer
extension to harvest time compared to late pruning (May/Jun and Jun/July). Old plants had a
shorter extension to harvest time compared to young plants. Harvesting of flowering stems
post pruning was earlier for old plants by 2 weeks compared to young plants of Scarlet
Ribbon. The significant (P<0.05) age x deheading diameter interaction resulted in long stems
for old plants for all the deheading diameter treatments. Quality and quantity of stems and
earnings from old plants were higher than for young plants. Pruning and deheading old plants
of Scarlet Ribbon resulted in the least losses (10%) with regards to harvested stems compared
to young plants (12.5%). Results indicate the ability of old plants with more plant matter to
effectively resume growth and development to the flowering stage due to more assimilates
facilitating this compared to young plants. When the two cultivars were compared, Scarlet
Ribbon had a longer extension to harvest time than Saxosum. The result was similar when
comparing the extension to harvest after deheading. The effects of pruning and deheading are
cultivar specific as was demonstrated in this study. Although in Zimbabwe both Scarlet
Ribbon and Saxosum are regarded as early flowering in the industry, Saxosum was harvested
much earlier by 2.4 weeks than Scarlet Ribbon. Flowering and harvest period for Saxosum
was shorter (5 months) compared to Scarlet Ribbon (7 months). In addition, a difference in
flower head complexity resulted in early flowering for Saxosum. Saxosum is naturally
multiheaded thus exerting less apical dominance through correlative inhibition of the
secondary bud. The secondary bud resumed growth and flowered earlier than Scarlet Ribbon,
which produces solitary inflorescence naturally. Scarlet Ribbon produced longer stems than
Saxosum. The significant (P<0.05) cultivar x pruning time interaction showed a reduction in
stem length for Saxosum. There was no significant difference to the inflorescence diameter of
harvested stems for both cultivars. Losses in harvest were high for Saxosum (16.7%) than for
Scarlet Ribbon (12.5%) when the plants were deheaded at 6-10 mm. Deheading late in the
season from late July to September at a diameter of 15-20 mm produced the highest losses.
Deheading resulted in different quality stems for the two cultivars however, the stems were of
marketable quality. Scarlet Ribbon produced more flowering stems of higher quality and
correspondingly high earnings compared to Saxosum. Scarlet Ribbon had the most
favourable response to pruning and deheading on flowering time compared to Saxosum. It is
therefore recommended that pruning be done early (Jan/Feb and Mar/Apr) and deheading at
0-20 mm diameters up to mid July as harvest period can be extended up to November for
iv
Scarlet Ribbon with good quality stems, earnings and minimal losses in the Ruwa farming
area. Old plants respond better to pruning and deheading than young plants. | en_US |
