Lost Crops of Africa, Volume 3: Fruits by the National Research Council

I give this book 8 out of 10 acorns. It would be of particular use to readers in Africa, but also smallholders in other tropical zones out to Mediterranean climates and even warm temperate areas.

Again, I would like to draw the reader's attention to some of the issues involved in removing some of these plants from Africa, both in terms of social justice and in terms of biosafety. I request that you read the first part of my review of Volume 1 of this series: https://permies.com/t/57007/books/Lost-Crops-Africa-Volume-Grains. While a few of the plants discussed in this book present cultivation opportunities outside Africa, I would again implore the reader not to attempt to circumvent important legal and cultural norms in these matters.

While I am always on the lookout for new fruits to try, I especially think it's important to be aware of the fact that I'm not alone. The main reason plants produce edible fruits is in order to encourage their distribution by animals. Many of the overbred species found in our gardens now require attention in order to survive long enough to fruit, although others, such as the raspberry (Rubus idaeus) hybridise readily with wild ones. It is reasonable to expect that some species described in this book may become opportunistic given suitable conditions: indeed some are adapted to difficult soil and climatic conditions. Germplasm, unless carefully checked by an expert, may contain pests and diseases that may quickly find a home elsewhere. This is not to say that one should not introduce some of these fruits to other areas where they may do well, but that the grower should be very cautious when doing so. At the same time it's important not to undermine actual and potential export markets bringing farmers out of poverty.

As with the other volumes in this series, this book discusses the uses, potential and propagation of a number of plants which have been widely ignored by organised (or even disorganised) breeding and other scientific efforts, with the aim of encouraging the use of these crops for food and other purposes, some economic. Each is examined for likely relevance to survival and social stability: nutrition, food security, rural prosperity, and general landcare. There is a detailed description of each plant, its known uses and its requirements for growth and propagation. In many cases these plants are adapted to very difficult conditions, including poor soils, aridity, and witheringly high temperatures (one comes from the Kalahari desert!). Most are adapted to the tropics, but many have been found to do well into subtropical, warm temperate and Mediterranean regions.

I'm going to ignore those species that I expect will be familiar to the reader, such as melons and watermelons (although the smallholder might be well advised to examine as many varieties of both as will grow in their habitat, for a range of good reasons), as well as those presenting particular opportunities for African export markets such as marula (Sclerocarya birrea), those likely to become invasive such as balanites (Balanites aegyptiaca), or those unlikely to do well outside Africa. I would, however, very much encourage African readers to pay due attention to these plants. Marula, for example, is apparently aesthetically pleasing and thrives in difficult conditions, while presenting economic development opportunities. Balanites is an incredibly useful plant, suited for extremely arid regions. but is a known invasive species, and has infested the island of Curaçao: it should be left where it is.

The authors are of the view that baobab (Adansonia digitata) (which I have already mentioned in my review of Volume 2) is unlikely to find much of a home outside Africa, it will grow elsewhere, such as northern Australia. I think that, with sufficient experimental space, it may be worth growing as part of a tallforest. Little else grows under it, perhaps due to massive nutrient demand, perhaps due to alleleopathy, and it may make a good firebreak plant. Most parts of the plant have extrinsic value. I especially commend it to African readers, particularly those in drylands, but those in other arid regions may wish to pay proper attention to this tree. It's a tropical plant, and is frost sensitive, but established plants may tolerate a light frost: with the right conditions it might be worth trying into the subtropics and Mediterranean regions. Readers may also be interested in examining the seven other Adansonia species.

Butterfruit (Dacryodes edulis) already exists in agroforestry systems, and contains impressive quantities of protein, as well as being a viable oil plant. It's treated more as a vegetable than a fruit. It is a tropical plant, but seems to do well elsewhere, and seems to be only moderately frost sensitive. It might do well in agroforestry systems elsewhere, and I hope to experiment with it, although it has a number of issues, not least its dioecious nature, and the lack of clarity over its potential range.

Carissa (Carissa macrocarpa), known as “big num-num” in South Africa, which has to be great free advertising, presents us with an edible spiny hedging plant, with fruits that can be eaten out of hand. It is known elsewhere, such as California, and may well produce opportunities in other subtropical, warm temperate and Mediterranean regions. A related species (Carissa haematocarpa - “bloody num-num”?) does well in arid regions. You can also make jams, jellies, fruit vinegars and wine out of it. A definite win. It may do especially well in polycultures where many nocturnal pollinators can get at it. I've been looking for hedging that is resistant to wild boar (Sus scrofa) and this may be part of the solution.

I'm familiar with the Horned melon (Cucumis metulifer) by one of its trade names. It grows in New Zealand, from which it was commercialised as a novelty crop. It's also now grown around parts of the Mediterranean basin. The ones I've eaten have verged on tasteless, not unlike a cucumber, to which it's related, but these may have been picked under-ripe for export. Apparently sweeter versions do exist, but I think it needs breeding work: indeed there is much potential for hybridisation for fun and profit. There is some evidence that the plant may become opportunistic, but this is patchy: I recommend vigilance, however.

Kei apple (Dovyalis caffra) may be another part of the solution to that hedge problem: like Carissa (above) it has nasty acacia-like thorns and has been used as hedging in the past. It produces small, golden, apple-like fruit that are apparently extremely sour (although sweeter ones are now available) as a result of large concentrations of vitamin C (although I'm not sure this is the whole story, as less sour fruits sometimes contain more). Few people like this, but it can be processed to add zest to other things or to convert into fruit leathers and so on. It's known to grow in Mediterranean climates, as well as California, Australia and elsewhere. They are dioecious, but produce fruit profusely and for an extended period. There are about 15 species in the Dovyalis genus, and there is good evidence they hybridise. The enthusiast might have a great deal of fun with these, perhaps breeding sweeter fruit or thornless varieties.

There is a strong case, which I won't go into here, for readers in the tropics to consider growing Tamarind (Tamarindus indica – a misnomer, since it's clearly African). The book has the usual details on its uses and cultivation, and I would say it has a clear place in the tallforest of those readers who can accommodate its needs.

A number of other wild fruits are also examined, but without a detailed discussion of their potential ranges. A number are sweet, nutritious foods that are resistant to appalling conditions and may well be important lifesavers in worsening climatic conditions, and I would especially recommend that African readers have a close look at all of them for their own conditions. I'd be especially interested in having a more detailed look at the custard apples (Annona spp), a larger family than I believed, and which might well be suited to cultivation in a Mediterranean climate and with potential for hybridisation. The problem outside Africa would be sourcing germplasm, but this might be less of an issue for African readers.

This book is a truncated version of part of a longer series that was planned, and a number of species were omitted from a shortlist of a much longer one provided by a number of interested parties. The shortlist can be found in an appendix to Volume 1, and this might be worth examining for other ideas.

All in all, a good book. The further from the tropics you go, the less use it's likely to be, but there are many fruits in this book that could be grown in Mediterranean or even warm temperate zones. Many of the plants in this book are adapted to poor soils, low and unpredictable rainfall and extreme heat, and may well be adapted to our increasingly disrupted climate.