Chapter 3 Bee forage and floral calendars

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A. Honey plants and pollen plants
B. Floral calendars
C. Assessment of areas for beekeeping


Honey and most other hive products do not originate directly with honeybees: they are natural products which the bees have collected and processed.

The bees visit flowering plants to obtain nectar, which is the source of honey, as well as pollen. As was seen in Chapter 2, many plant species possess, inside their flowers near the base of the petals, glands called nectaries, which secrete nectar. (Some plants have nectaries unconnected with their flowers, called extrafloral nectaries.) It should be recalled, however, that not all plant species have nectaries that secrete enough nectar to attract bees.

The concentration of sugar in nectar depends on several factors: the plant species and variety, the soil type, the time of day of collection, the temperature and relative humidity, etc. As a rule, plants with a higher sugar concentration in their nectar are more attractive to bees than those with weaker nectars, because in the process of making honey the bees are obliged to get rid of excess water in the nectar, so that in treating more highly concentrated nectars, they need to expend less time and energy.

When the excess water has been evaporated from the nectar and the enzymatic reactions in the conversion of nectar to honey have been completed, the honey is ready for storage, to serve as the bees' reserve of carbohydrates to cover the colony's energy requirements. In the broad sense, then, honey is the colony's energy reserve, all or part of which will be expended in the process of foraging.

From the standpoint of the beekeeper, a colony is "productive" when it stores a surplus of honey, i.e. when it can collect and convert into honey more nectar than it consumes. The beekeeper harvests all or most of this "surplus" honey. In some beekeeping systems, he may have to provide the bees with sugar syrup to replace the honey harvested, particularly at times when the colony requires additional food.

In both stationary and migratory beekeeping, the beekeeper seeks to place his colonies in or near areas where a sufficient quantity of honey plants - be they crop or pasture plants, weeds, shrubs, forest trees, roadside planting, etc. exists, in season or throughout the year, within the economical flight range of the foragers. Planting special crops for bees is not likely to yield a good economic return: arable land will provide better returns if it is used for other agricultural purposes. Beekeeping is thus one of the rare forms of agriculture in which the planting of crops is not specifically required.


A. Honey plants and pollen plants

In order to survive, prosper and be productive, honeybee colonies, as has already been observed, must have a supply of both nectar and pollen in adequate quantities. Not all plant species are equally good for beekeeping. Some supply both nectar and pollen abundantly when in bloom, and these are often called honey plants, because they are best suited for honey production. Plants producing nectar but little or no pollen are also considered to be honey plants. Other plants, however, may yield pollen but little or no nectar. These pollen plants are also important in beekeeping, especially at the time of colony build-up, when the bees need large amounts of the protein contained in pollen for their brood-rearing.

Ideally, a good beekeeping area is one in which honey and pollen plants grow abundantly and with a relatively long blooming season. Such areas are however not always available or easy to find. The beekeeper therefore combines his skill in colony management with migratory practices in order to provide his bees with good, productive foraging environments. He must know the time and duration of the blossoming season of every major honey plant, including the environmental factors affecting them, and make a reasonable assessment of the supporting capacity of each area, i.e. the number of colonies that can be put to productive work there.

Since the practice of modern beekeeping is relatively new in Asia, the compilation of economic bee forages and the identification of areas suitable for beekeeping are still far from complete. Asian beekeepers may find useful information in many internationally-published books, pamphlets and technical articles which contain lists of honey and pollen plants, some of which may already be abundant in parts of Asia, waiting to be exploited by beekeepers. A list of some commonly-known honey plants recorded in some Asian countries appears in Table 2/1.

Table 2/1. Some Important Asian Bee Forage Plants

Species Family Common Name
Aesculus turbinata Hippocastanaceae Japanese horse-chestnut
Astracalus sinicus Leguminosae Chinese milk vetch
Bombax ceira Bombaceae silk-cotton tree
Brassica campestris Cruciferae rape
Brassica spp. Cruciferae mustard
Calliandra calothyrsus Leguminosse calliandra
Castanea pubinervis Fagaceae sweet chestnut
Ceiba pentandra Bombaceae kapok
Cirsium spp. Compositae thistle
Citrus spp. Rutaceae orange, pomelo
Clethra barbinervis Clethraceae  
Cocos nucifera Palmae coconut
Croton spp. Euphobiaceae  
Cucumis spp. Cucurbitaceae cucumber, melon
Cucurbita moschata Cucurbitaceae pumpkin
Diospyros kaki Ebenaceae persimmon
Eriobotrya japonica Rosaceae loquat
Eucalyptus spp. Myrtaceae eucalyptus
Eupatorium odoratum Compositae snakeroot
Euphoria longan Sapindaceae longan, lam yai
Fagopyrum esculentum Polygonaceae buckwheat
Gossypium spp. Malvaceae cotton
Helianthus annulus Compositae sunflower
Hevea brasiliensis Euphobiaceae rubber
Ilex pedunculosa Aquifoliaceae gallberry
Ilex rotunda Aquifoliaceae  
Lespedeza spp. Leguminosae bush clover
Ligustrum japonicum Oleaceae privet
Litchi chinensis Sapindaceae litchi
Malus pumice Rosaceae apple
Medicago sativa Leguminosae lucerne, alfalfa
Melilotus alba Leguminosae sweet clover
Prosopis cineraria Leguminosae mesquite
Prunus spp. Rosaceae cherry, apricot, peach
Pyrus pyrifolia Rosaceae pear
Rhus spp. Anacardiaceae sumac
Robinia pseudoacacia Leguminosae black locust
Salix spp. Salicaceae willows
Sesamum indicum Pedaliaceae sesame
Styrax japonica Styracaceae snowball
Tilia japonica Tiliaceae linden, lime
Tilia maximowicziana Tiliaceae linden, lime
Tithonia tagetifolia Compositae Mexican sunflower
Trifolium pretense Leguminosae red clover
Trifolium repens Leguminosae white clover
Tridax procumbens Compositae  
Ziryphus jujuba Rhamnaceae Chinese jujube


B. Floral calendars

A floral calendar for beekeeping is a time-table that indicates to the beekeeper the approximate date and duration of the blossoming periods of the important honey and pollen plants in his area. The experienced beekeeper will have acquired much of this information over the years, but published charts are also available for many areas.

The floral calendar is one of the most useful tools of the apicultural extension worker. It enables him to inform the beekeepers on what to expect in bee-forage availability, and when, so that they can manage their colonies in the most rational manner. Beekeeping in any specific area cannot develop without an understanding of the calendar, and for migratory beekeeping, special calendars for the different foraging zones along the migration route are required.

Assembling a floral calendar for any specific area is simple but time-consuming. It requires complete observation of the seasonal changes in the vegetation patterns and/or agroecosystems of the area, the foraging behaviour of the bees, and the manner in which the honeybee colonies interact with their floral environment. The accuracy of a floral calendar, and hence its practical value, depend solely on the careful recording of the beginning and end of the flowering season of the plants and how they affect the bees. The preparation of an accurate, detailed calendar will therefore often require several years of repeated recording and refinement of the information obtained.

The steps normally taken in building up a floral calendar are as follows:

1. The beekeeper makes a general survey of the area, drawing up a list of flowering plants found, special attention being paid to plants with a high floral population density per unit area or per tree.

2. He places several strong honeybee colonies in the area, inspecting the hives regularly and observing changes in the amount of food stored within the hive to determine whether it is depleted, stable or increasing. Any food gains or losses can be monitored accurately by weighing the hives.

Fig. 3/1. Floral calendar, in the form of a circular chart, indicating the periods of availability of major nectar and pollen sources in northern Thailand

3. At the same time that he monitors the hives' food stores he surveys areas in the vicinity of the apiary and within the flight range of the bees, to record the species of plants that the bees visit.

4. He determines whether the plants are visited for nectar or for pollen. Pollen-foragers will have pollen pellets attached to their hind legs. To determine whether the bees visit flowers for nectar the observer squeezes the abdomen of individual bees to obtain a drop of regurgitated nectar, tasting it for sweetness or measuring the nectar concentration with a hand refractometer.

5. He studies the frequency with which the bees visit each flower species, in relation to changes in the level of the colonies' food stores. If there is a continuous increase in food stores, in direct response to the availability of the plants visited, the plants are good forage sources. When the food stores remain stable, the plants can be depended upon to meet the colonies' daily food requirements, but they cannot be classified as major honey sources.

6. He carefully records all the changes in the blossoming of the plants visited. When the colonies begin to lose weight, the flowering season is finished for all practical purposes.

Once all the data on forage species have been assembled and repeatedly verified, they should be judged as they relate to the actual performance of the honeybee colonies. The calendar can then be drawn up in the form of circular or linear charts, showing the weekly or monthly availability of each plant and their flowering sequence.


C. Assessment of areas for beekeeping

Productive beekeeping depends on good colony management and good beekeeping areas, and in order to promote it as a profitable agricultural occupation, areas with a good potential for beekeeping must be located and evaluated. Asia is rich in places inhabited by feral swarms of native honeybees, and this fact often inspires premature judgements to the effect that beekeeping can be promoted almost anywhere in the continent where native bees are found. The truth, however, is that most feral colonies of Asian honeybees adopt a migratory strategy, moving with the seasons and the availability of forage. Thus, the temporary presence of a few feral swarms of honeybees here and there, for short periods, does not necessarily indicate that there is enough forage in the area to support year-round commercial beekeeping.

As in the assembling of floral calendars, weighing the hive is one of the most accurate ways of assessing the suitability and supporting capacity of an area. One major problem in this respect is how to select sites for assessment. The following guidelines for the exploration and evaluation of potential beekeeping areas may be found useful:

1. Referring to lists of known major honey plants in other countries or regions with similar vegetation patterns, agro-ecosystems, climate and edaphic conditions, determine whether similar plants are to be found in the area under study.

2. The seasonal occurrence, in unusally high numbers, of feral nests of native honeybees can often indicate that there is ample forage in the area, at least during the period in question.

3. The mere presence of flowering trees and shrubs in limited numbers, or of a few hectares of land covered with good honey plants preferred by bees, does not necessarily indicate that the area has potential for commercial beekeeping.

4. Practical, large-scale beekeeping operations call for large areas, usually hundreds or thousands of hectares of nearby land bearing good forage with high population densities. Good honey plants are characterized by relatively long blossoming periods, generally in terms of several weeks or months; high density of nectar-secreting flowers per plant or unit area; good nectar quality with high sugar concentrations; and good accessibility of the nectaries to the bees. The foraging land should be well proportioned, in terms of length and width, so as to promote foraging efficiency.

5. The supporting capacity of an area for honey production is best determined by monitoring weight changes in the bee colonies. Among other factors that affect the economic value of an area for beekeeping are average hive yields, prevailing honey prices in the area, as well as costs of colony-management inputs.

6. The fact that a flower is brightly coloured or that it has a strong scent does not always indicate that it is good for bees, unless the fact is confirmed by the criteria set out above.

7. The large-scale planting of honeybee forages has never been proved to be a profitable approach in terms of net economic return, except in integration with other agricultural activities, such as reafforestation, roadside plantings, animal pasture, etc.

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