Ecology and Biology of Uapaca kirkiana, Strychnos cocculoides and Sclerocarya birrea in Southern Africa - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 327

have been made at ages of up to 200 years for many large individuals of the
subsp. caffra in southern Africa (Hall et al ., 2002).
The onset of flowering in planted S. birrea subsp. c affra was reported to be
4-5 years in Malawi and Israel (Nerd et al ., 1990; Maghembe, 1995). On the
other hand, Shone (1979) indicated an age of 7 years for the onset of fruiting
in wild South African plants. From observation made in Israel and Malawi,
early fruit crops are small and are usually very small (Nerd and Mizrahi, 1993;
Bwanali and Chirwa, 2004). Bwanali and Chirwa (2004) found that the onset
of fruiting also depended on the provenance or family being tested. Older
planted trees (14-15 years) of subsp. caffra in Botswana have been reported to
produce 1000 fruits (Campbell, 1986). In a S. birrea provenance trial in
Mangochi, Malawi, the provenance from Mozambique started to fruit after
6 years (Akinnifesi et al ., 2006).
The leaf flush of S. birrea subsp. caffra coincides with the transition from
the wet to the dry season in southern Africa (Teichman, 1982; Hall et al .,
2002). Trees are in full leaf during the mid to late rainy season and leaf fall is in
the dry season. Hall et al . (2002) give details of the flowering and fruiting
phenology of Sclerocarya in relation to the dry months (rainfall <50 mm) as
flowering is a dry-month event. Flowering has been described as precocious
but it is also associated with the flush of new foliage (Shone, 1979; Teichman,
1982; Hall et al ., 2002). Periods given in the literature for the duration of
flowering are variable, with periods of up to 4 months or much less, especially
for subsp. caffra (Hall et al ., 2002). The period of fruiting is usually within the
rainy season but is also said to be very variable, with a period ranging from 2
to 8 weeks in Botswana (Taylor and Kwerepe, 1995). Lewis (1987) reported
that the fruit-fall period ranged from 1 to 3 months.
Although male and female flowers occasionally occur on the same tree, the
species is considered dioecious. There have been a few cases in a number of
studies done in South Africa where monoecy has been reported. In many cases
this has primarily been due to the presence of occasional female flowers in one
or two of the most proximal inflorescences of the shoots on predominantly male
trees (Hall et al ., 2002). In some cases there has been a rare occurrence of
bisexual flowers. Male flowers are borne in groups of three on racemes below
new leaves. The female flowers occur below the leaves on long peduncles and
consist of four curling petals. They have numerous infertile stamens and a long,
shiny ovary. Hall et al . (2002) give details of studies in which observations have
been made during anthesis and pollination, with honey bees usually cited as the
major pollinators. Secondary pollinators include flies and wasps.
The development of the seeds and fruit of S. birrea subsp. caffra in South
Africa has been discussed by Hall et al . (2002). Fruits are borne in clusters of
up to three at the end of the twigs and always on the new growth. The fruit is a
round or oval drupe, usually wider than it is long, with a diameter of
30-40 mm. The shape and number of nuts per stone determine the final shape
of the fruit. The fruit has a thick, soft leathery exocarp with tiny, round or oval
spots, enclosing a juicy, mucilaginous flesh that adheres tightly to the stone and
can be removed only by sucking. The flesh tastes tart, sweet and refreshing,
although the fruit has a slight turpentine-like aroma and can give off a very