• Piet Stoker (PhD)

The bee-value of South Africa's trees

Updated: Jul 23

The miracle of bees – a vital link in our food chain.



A study to document the value to bees of South Africa’s indigenous trees was recently commissioned by SANBI (South African National Biodiversity Institute). The study formed part of a global pollination project, in which 7 countries participated. Although the focus was on the role and importance of bees in agricultural production, it went further to also study the value to bees of our indigenous flora, including trees and shrubs.


As a service to visitors of our website, we decided to incorporate the findings of the above study in the descriptions of our tree products. By doing so we hope to encourage you to plant trees that will benefit our honeybees.


You can make a difference

Honeybees are generalist feeders. They contribute to the pollination of many of our indigenous plants, thereby playing an important role in sustaining South Africa’s diverse eco systems. To maintain their colonies, bees need pollen and nectar. Our indigenous trees are an important wild source for these substances, and planting them in your garden will not only help honeybees to survive and multiply, but will also increase the viability of our trees’ seed production.


Indexing the bee-value of South Africa’s Indigenous trees

We indexed our trees’ value to bees using the data and scale presented by Johanssmeier2 as follows:


Pollen P and Nectar N, are each quantified by a 5 point scale, 0-4, where 0 indicates that no nectar/pollen is available to honeybees; 1 indicates that the tree is a poor to minor source; 2 that it is a minor to medium source; 3 a medium to good source and 4 a very good to major source.


Nectar and pollen availability of a particular plant species may vary significantly due to historic and prevailing weather conditions, plant health, variation of values reported by different sources and more. In such a case bee value is indexed as a range, for example, N0-2 and P0-3, where 2 and 3 indicates the maximum value measured for a species under ideal conditions. P1? and the like indicates that Pollen is collected by bees. The question mark reveals that the extent is uncertain. Other indexing codes are also used:

  • N?P Uncertain if honeybees collect nectar. Pollen is available and collected, but quantity is unknown.

  • EN Extrafloral nectar is available. Usually secreted by the leaves.

  • HD Honeydew, a sugary solution excreted by plant sucking insects – usually aphids

  • PR Propolis, a plant based resinous material used by bees to water-proof and insulate their nests, to line brood cells and to cover foreign animal matter that they can’t remove from the nest.

Also of interest is the trees’ flowering time. This is indicated by a month code, for example 4-6 for April May and June. Most likely month(s) for flowers is indicated in brackets for example (5)

Some indigenous tree species are not yet indexed. In these cases we indicated bee-value as “Unknown”


How to search for trees based on their bee-value.

Treeshop recently added a powerful Site Search tool (SS360) to our website. Please read this post to learn more about the tool. We will now apply it to research our trees’ bee-value.


Nectar value:

  • If you want to find trees that provide a very good to major source of nectar, enter N0-4 in the search box. (Top left. Results are displayed on a dedicated site search page) Only Senegalia galpinii (Monkey thorn) provides nectar in such abundance.

  • What about trees that are a medium to good nectar source? Enter N0-3 in the search box. 18 trees meet this requirement. Note that some are indexed as N0-3?, implying that there is some uncertainty in regards of nectar collection at this level.

  • If you want to plant trees that will not attract nectar searching bees. Enter N0. 6 trees meet this criterion; 4 Ficus species (because their flowers are embedded in their fruit. Flowers are pollinated by insects, for example ants.) Flowers of the other two trees (Mundulea sericea and Millettia grandis) are not accessible by bees.

Pollen value:

Follow the same search strategy as above, for example:

  • To find trees that have no or little pollen value, enter P0-1 in the search box. 20 trees meet this requirement, including all Ficus species. Persons allergic to pollen will find this outcome quite useful.

Other values, for example Propolis

  • Enter propolis (or PR0) in the search box. 6 of our tree products meet this bee-need, amongst others all the Ficus species!

Taking a tree view

Let’s say you want to study the value to bees of the genus Vachellia. Enter “vachellia”+”bee-value” in the search box. Note quotation marks! You are instructing the search engine to look for 2 exact text strings (ignoring capitals). Also note the “+” operator. You are instructing the search engine to list pages that contain BOTH text strings (a so-called “AND” operator). SS360 returns 5 tree species which meet this search. Their respective text snippits all contain N and P codes (2xN0-3; 1xN0-2 and 2xN0-1) and (1xP0-3, 2xP0-2 and 2xP0-1). Clicking on the snippit will take you to the tree’s page. Use the “go back arrow” of your browser to go back to the SS360 page.


Productive bee-tree research!

Piet Stoker


REFERENCES

1) Bee video by Linky de Bruyn.

2) JOHANNSMEIER, M.F. 2016. Beeplants of South Africa. Sources of nectar, pollen, honeydew and propolis for honeybees. Strelitzia 37. South African National Biodiversity Institute, Pretoria.

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