Expedition no. 26: Tree Society visit to Ivordale Farm: 19 Oct 1997-

Tree Society visit to Ivordale Farm


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Description

Happily, although mid-October, the day was not unduly hot. Over thirty members led by Phil Haxen set off up the gradually sloping granite outcrop. Being on shallow rocky soil, the emergence of new leaf was a bit retarded, but the early species had sufficient new leaf to assist in identification, whilst in the others still devoid of leaf, identification was by characteristics of form, shape, and bark.

The 'zigzag' Euphorbia matabelensis with latex and three-lobed fruit, was much in evidence. Commiphora mossambicensis was plentiful showing the characteristic 'apricot-like leaves' and the rippled bark effect where spurs came off the main limbs. Then came Vitex payos, the 'Chocolate Berry' with deeply and vertically striated bark and palmately compound leaves. Strychnos spp. was common with its three-veined leaves, probably Strychnos innocua with light coloured and sometimes flaky bark. Both Erythrina abyssinica and Erythrina latissima were seen, the latter with much larger and rounder leaves and larger lucky bean seeds.

A fine specimen of Sterculia quinqueloba with five-lobed leaves attracted attention, and we learnt that the genus was named after the Roman God of 'privies and manuring', Sterculius, because some species smell a bit! Further on, the regular twist to the leaf apex assisted in identifying Combretum apiculatum which was common in this relatively dry habitat. Cussonia arborea, one of the 'cabbage' trees with five-lobed compound leaves and Pseudolachnostylis maprouneifolia, the Duiker berry were both seen. The latter, Phil explained, has the longest name on the Mashonaland Field Card, the name deriving from a resemblance to Lachnostylis, a tree of the Cape Province. The leaves are very like those of Maprounea africana, another Euphorbiaceous species, so hence the specific name. It all helps one to understand and hopefully remember! Anyway, Duiker relish the fruit, in fact all ungulates do so, which is acknowledged in the common name as well as the vernacular name, Mudyamhembwe. In South Africa the name is Kudu berry (has the Duiker been exterminated there?). It is a pretty tree, the more so when in autumn foliage.

Several specimens of Pod Mahogany, Afzelia quanzensis, were present and Phil pointed out the yellow border to the margins of the leaflets which is diagnostic. Nearby was Julbernardia globiflora, and using a hand lens, we were able to see the white rim to the leaflets as white bristles fringing the leaflet margin. The latter genus was named after M. Jules Bernard – an interesting anecdote from John Cottrill. The derivation of scientific names is of interest – Bob Drummond’s book entitled Common Trees of the Central Watershed Woodlands of Zimbabwe is very helpful in this respect and no member should be without a copy.

The 'ball and claw' shaped terminal bud of Zanha africana was just visible at this early stage of leaf emergence, while the red coloration of the underbark when newly sloughed, was clearly visible and helpfully diagnostic. The specimen of Ozoroa insignis available to us was struggling for existence on the poor rocky and sandy soil, but evidently, in more favourable habitats, it grows into a majestic tree. Hence its generic name derived from the Ethiopian word for queen, ozora. Sadly, the tree is abused locally, the bark supposedly having aphrodisiac properties. Still leafless was Lannea discolor, but recognisable by the 'dead man's finger' leaf buds about to burst and the texture of the bark, described by Drummond as 'pale grey, irregularly fissured'.

Pavetta schumanniana, confirmed as poisonous to cattle, was seen to have black spots on the leaf when held up to the light. The quilted appearance of these hairy leaves is evidently to conserve moisture.

Pterocarpus angolensis, newly in leaf, was not uncommon but weakly grown on the shallow rocky soil. On deeper soil this tree yields the very fine furniture wood, Mukwa (Kiaat in S.A.), so widely exploited. It has the feature of exuding a blood-like sap when the bark is slashed, hence the vernacular name Mubvamaropa. Unfortunately, this phenomenon is common as the tree is widely used for muti purposes. The deeply serrated leaf margin and midrib raised on both upper and lower surfaces helped us identify Ochna puberula.

Returning to the car park area, we skirted around the foot of the outcrop where the soil was much deeper and subject to run-off from the sloping rock above. Tree specimens were much more strongly grown under the favourable conditions. Fine examples of Dalbergia nitidula, well leafed but not yet in flower were present. This species has a very attractive purple-red heartwood, different from the ebony black colour of its relative Dalbergia melanoxylon, both of which are used for carving. A splendid Pod Mahogany, Afzelia quanzensis, was in flower here and we were able to examine the single pink petal and smell the sweet nectar easily as the adjacent sloping rock slab allowed a close-up 'bee-eye' view. Kirkia acuminata was common and newly in leaf while the genus Ficus was represented by two species, Ficus thonningii, the notorious Strangler Fig, and Ficus glumosa, the Rock Splitting Fig.

Nearer the parking area one observant member pointed out three heavily weathered grinding holes in the granite, explaining that gold bearing ore was ground in these before panning it for the precious metal. Recovered gold was commonly stored in porcupine quills and, together with ivory, was the basis of the early trade in these regions with Arab, Portuguese and subsequent visitors.

The afternoon session began with a fine specimen of the Violet Tree, Securidaca longipedunculata, in full flower, at eye level, thankfully. Just think how frustrating it would be if the flowers were out of reach! This tree, happily, was not damaged, since its roots are also commonly preyed upon for muti. The roots contain methyl salicylate and when fresh, smell strongly of wintergreen. We were now in semi-vlei land with strongly grown thatching grass subject to fierce bushfires at times. The species in this vicinity were fire proof generally, exemplified by Terminalia sericea, Ziziphus mucronata, and Flacourtia indica. Well grown Parinari curatellifolia were present. This species sometimes gives off an unpleasant odour and is pollinated by a specific butterfly, although bees and flies were observed in attendance. The wood is evidently borer proof, but is seldom sawn due to the abrasive silica content and the fact that the tree produces a not unpleasant fruit. Also present were Syzygium guineense and the prostrate Syzygium huillense, with its underground contorted stem, well protected from fire and sometimes collected for ornamental purposes. The yellow flowers of Senna singueana were pretty, and the 'bee sting' like stipule between the terminal leaflets was visible.

The diehards then climbed part of a neighbouring granite hill with similar, but better grown vegetation than that seen earlier. The Euphorbia matabelensis were now handsome well grown specimens, presumably reflecting better soil between the granite slabs.

Pericopsis angolensis, Muwanga in Shona, was identified, not huge but fairly well grown. The wood of this tree is so durable that fencing posts made of it over fifty years ago are still standing as strong as ever to this day. Its future preservation seems assured because few axes, or the men that wield them, are strong enough to deal with the hard heartwood. In fields, too, it is mostly spared since the clear trunk and high foliage interfere little with crops underneath.

Among the 'resurrection' plants, green from rain the previous week, large Combretum zeyheri seedpods were seen and eventually the tree was spotted. Also visible were several small Elephantorrhiza goetzei trees with golden flower spikes. This tree derives its name from the 'elephant' sized roots below ground level. An interesting and informative outing well led by Phil whose perception in matters arboreal was as captivating as ever.

Thank you to the organisers and to the owners of Ivordale, Mr. and Mrs. Pascoe.

John and Wendy Wilson.


Copyright: Mark Hyde, Bart Wursten, Petra Ballings and Meg Coates Palgrave, 2002-17

Hyde, M.A., Wursten, B.T., Ballings, P. & Coates Palgrave, M. (2017). Flora of Zimbabwe: Expedition no. 26: Tree Society visit to Ivordale Farm.
http://www.zimbabweflora.co.zw/speciesdata/outing-display.php?outing_id=26, retrieved 13 December 2017

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