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The following article appeared in Tree Life no. 262 in December 2001.
My Saturday afternoon walk which had been planned for a farm near Lilfordia School was unfortunately cancelled at the last minute because of two incidents nearby, one of which was at the particular area we were due to visit.
At very short notice therefore, Fr. Hugh Ross was contacted and an alternative venue of St George's College arranged.
A surprise and welcome visitor was Hugh Glen from the National Botanical Institute in Pretoria who is visiting Zimbabwe as part of a Sabonet initiative.
The main aim of the walk was to re-visit the extraordinary crop of E Districts trees on the top of Hartmann Hill near a small water tower. This corner of the school grounds abuts the grounds of the National Botanic Gardens and is mainly ordinary msasa woodland.
At the top of the hill below the water tower, water cascades out and runs a short way down the hill before disappearing underground. A moister-than-usual environment is thereby created and around the tower grow a number of interesting species, some of which are more reminiscent of the E Highlands than the Harare area. When I was first shown these species a few years ago, I thought that someone had tried to create an E Districts garden, but both Father Ross and Rob Burrett have assured me that these trees have not been planted.
The 'E Districts species' together with some comments on their Zimbabwean distribution and the results of discussions with Tom Muller are as follows:
Macaranga capensis. A fine specimen occurs near the water tower but we also found a small one at the base of the slope in dry woodland. I understand that this is planted in the Botanic Gardens and I suspect that this is the source of this species. Tom later confirmed that this does behave as a weed in the Gardens.
Phyllanthus ovalifolius. The native distribution of this species is again the eastern and southern divisions of Zimbabwe. It is a semi-scrambling, woody species which forms large bushes several metres high and has fine pinnate-looking leaves. Although there is one up by the tower, it is quite common in the grounds of St George's College and there are many fine specimens on the other side of the fence in the Botanic Gardens. Again, I suspect the Botanic Gardens are the source of this species.
Polyscias fulva. This is an E Districts forest pioneer. There is a fine tree by the water tower. It is again planted in the Botanic Gardens and behaves as a weed there (again, per Tom).
Sapium ellipticum. Another E Districts forest species. Again, this is planted in the Gardens and escapes freely there. This might be the source or alternatively it might have a nearer source. It is planted at the base of the hill near the school buildings and in the woodland between the two places we saw a number of small specimens of Sapium ellipticum which looked self-sown.
Toddalia asiatica. Another common E Districts species but this is not confined to there but also occurs on some outliers, for example Hwedza Mountain which would probably be the nearest point. This species was also seen at the bottom of the hill. Like Sapium this could have originated from the Botanic Gardens or possibly the College itself.
Another species by the water tower is Maesa lanceolata. This is a high rainfall species which is very common in the E Districts but is certainly not confined to there. We come across it from time to time around Harare so its presence on the hill is not particularly surprising. Possibly the perennial water supply helps it.
Also nearby was the rhus with small, shiny leaves which we call Rhus natalensis. Tom mentioned that this also freely seeds itself around the Gardens.
In addition to these, there are three exotics
Homalanthus populifolius (Queensland poplar). This is commonly planted in Harare gardens and is occasionally naturalised around Harare but in a rather scattered way. I suspect that the size of this specimen is supported by the perennial water flow.
Ligustrum lucidum (a species of privet). Again, commonly planted in gardens and occasionally escaping, usually in my experience by rivers and streams.
Solanum mauritianum (Bug tree). A common
weed around Harare; its presence here is I suspect not
In conclusion, it seems that the Botanic Gardens are acting as a source of species of alien origin (alien to this part of Zimbabwe even though they are native in other parts) which are spreading into the grounds of the adjacent College, assisted in some cases by the perennial water provided by the overflowing water tower.
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