Juniperus procera

Cultivation Details

Juniperus procera is a tropical highland species, where it is commonly found at elevations between 1,800 - 2,800 metres, though it also occurs in the broader range of 1,000 - 3,500 metres^[1]. It is found in areas where the mean annual temperature ranges from 5 - 20°c. Plants from the higher parts of its range have proven to be surprisingly cold tolerant, able to withstand short periods with temperatures down to at least -5°c, and are growing outdoors in the milder regions of the temperate zone^[2]. The mean annual rainfall in the forest belt where it is mainly found is 1,000 - 1,400mm, but the tree is also found in areas where the rainfall can range from 300 - 2,000mm. Individual trees can survive in hot and dry conditions, once established, but in areas with low rainfall, the trees are generally of poor form and small size. Where rainfall exceeds 1,400mm the forests dominated by Juniperus procera are gradually replaced by moister types of evergreen forest in which Juniperus procera becomes increasingly rare^[1]. Requires a sunny position^[1]. Prefers rocky soils, with a light to medium texture and free drainage^[1]. Found wild in sand, loam or clay soils over various rock types, including basalt, volcanic ash and cinders, granite, limestone, and metamorphic rock^[3]. The tree is assumed to be deep-rooting, like other Juniperus spp., but the characteristics of its root system are poorly known^[1]. Growth, especially of young plants, is slow. In Ethiopia 10 - 15-year-old plantation trees were 6 - 9 metres tall, with a bole diameter of 8 - 16cm, whereas 30 - 40-year-old plantation trees were 17 - 21 metres tall, with a bole diameter of 16 - 29cm. In a 200-year-old stand, the trees were 37.5 m tall, with a bole diameter of 107cm^[1]. In the Usambara mountains in Tanzania (at an elevation of 1,450 metres, an average annual temperature 18°c, and an average annual rainfall of 1,070mm) 61-year-old trees in a density of 182 trees/ha had an average height of 32.5 metres and an average bole diameter of 47cm. The standing volume was 247 m³ per hectare^[1]. A naturally regenerated 15-year-old stand in Kenya, the result of an earlier fire, had an average tree height of 14.7 metres and an average bole diameter of 23cm; 35 years later the trees in this stand (density 262 stems/ha) had an average height of 23.5 metres and an average bole diameter of 39cm^[1]. The growth of plantations ranges from 3.5 to 13 cubic meters per hectare per year, averaging 7.5 cubic metres, considerably less than that of some exotic species on the same sites, such as Eucalyptus globulus which produces 50 cubic metres^[1]. The tree has irregular flowering and fruiting periods, only flowering once every several years. It is wind pollinated and seeds are dispersed by birds^{[1, 4]}. Juniperus procera is a prolific seed-bearer and the seeds, though sometimes damaged by seed-boring insects, are usually fertile^[1]. Young seedlings are very light demanding and absolutely intolerant of any decomposing organic matter covering the ground. Therefore the seeds can only germinate freely in open, grassed areas or among shrubs, such as in glades or forest edges, where there is adequate light and mineral soils. Consequently, Juniperus procera forests can only develop in two principal ways: either saplings are found growing under the shelter of bushes at forest edges, or natural regeneration occurs after a fire or in large clearings of other origin, giving rise to usually very dense, even-aged stands of trees with long, branch-free boles. Due to these strict requirements, artificial regeneration appears to be the easiest and fastest way to maintain Juniperus procera forests^[1]. The production of suitable logs for the sawn wood and veneer market may be possible with a rotation period of 70 - 100 years^[1]. A dioecious species, both male and female forms need to be grown if fruit and seed are required^[1].