Bees forage for four substances: nectar, pollen, water and propolis 1 . In addition, collected nectar is converted into honey, which acts as an essential food reserve for the colony. The amount of the four foraged substances needed by a hive is unknown, and naturally this will vary between colonies. However, there has been some research suggesting required amounts of nectar and pollen. Grissel 2 (2010) suggests that a typical hive requires 250 pounds of nectar and 40 pounds of pollen, while Standifer, et. al. 3 (1977) estimates 300-500 pounds of nectar and 50-75 pounds of pollen. As much as 700 pounds of nectar has been estimated as the required amount for a colony 4 .
So how many flowers are needed to produce 700 pounds of nectar? This is not easy to determine. Flowers are of varying shapes and sizes; therefore, they produce varying amounts of nectar. In addition, in oversimplified terms, nectar is sugar water and flowers produce nectar of varying sugar concentrations.
Though an exact amount of nectar or flowers needed cannot be determined, aiming to provide an abundance of quality food sources for a hive year-round will promote colony health. Knowledge of preferred food sources and the preferred variety of such sources will be useful to meet this goal.
Preferred Food Sources
Bees tend to forage on flowers that will provide them the greatest food rewards 5 . However, the greatest profit is not always associated with high-food producing flowers but is dependent on other factors such as number of bees already foraging on the flowers and how attainable the nectar source is to the bee 5 . Bees are attracted to flowers due to their colours and scents. In terms of attractive colours, bees are sensitive to ultraviolet light, and the colour red appears black through a bee’s eye and is therefore unappealing.
Plants that honey bees prefer include borage, buckwheat, buttercup, catnip, centaurea, comfrey, dandelions, fireweed, foxglove, lupine, oceanspray, phacelia, sunflower, witch hazel, and yarrow 6 (Anylese Weiler, personal communication, 2012). Tree and shrub fruits such as apple, cherry, red-flowering currant, blueberries, Oregon grape and raspberries are also preferred sources of nectar, as well as herbs that include basil, lavender, mint, oregano, rosemary, and Russian sage 6 (Anylese Weiler, personal communication, 2012). In addition, cover crops such as alfalfa, bush clover, white-clover, and legumes provide an abundance of flowers that are beneficial to honey bees, as well as native bees 6 . Bees can be found to exist near fencerows or hedgerows and riparian buffers; areas with wide variety of plants or weed species 6 .
Though many preferred flowering species have been mentioned, this is not a complete list. Bees enjoy a wide variety of nectar sources and are not limited to few kinds. However, there are some plant species that are toxic to bees. These include: azalea (Rhododendron molle), azure (Aconitum carmichaeli), black hellebore (Veratrum nigrum), California buckeye (Aesculus californica), Chinese alangium (Alangium chinense), Chinese bittersweet (Celastrus angulatus), jimson weed (Datura stramonium), plume poppy (Macleaya cordata), happy tree (Camptotheca acuminate), Summer Titi (Cyrilla racemiflora), tea (Camella sinensis) and oil-tea (C. olelfera).
Note: To comply with the Canadian Organic Standards, the main source of bees forage should consist of organically produced plants and wild vegetation 7 .
Preferred Variety of Food Sources
Flowers express a wide range of diversity regarding their morphologies, scent and blooming times 5 . Bees and other pollinators forage for food sources using a search image technique; associating flowers and their corresponding pollinator rewards with their morphologies 5 . Providing a variety of flowers that have a distinctly different morphology among different species but uniform features within the same species results in more efficient use of the search image technique. In other words, with physical similarities between different flower species, bees tend to go astray, possibly feeding on flowers that provide less profit and resulting in an energetic cost 5 .
However, there is a downfall to this kind of flower diversity. Some flowers, such as the orchid Calopogon pulchellus, do not provide rewards to pollinators yet still rely on them 5 . Therefore, with the presence of the kind of flower diversity mentioned above, bees would quickly recognize these non-rewarding flowers and avoid them. Non-rewarding flowers are commonly dependent on varying morphological features within the species and inexperienced pollinators 5 . Another method shown to increase the likelihood for pollination of non-rewarding flowers is the simultaneous bloom and intercrop with a flower that does provide rewards. Combined morphological features can attract bees, while the reward-providing flower keeps the bees in the area long enough for them to also pollinate the non-rewarding flower 5 . Planting a rewarding flower with similar morphology and a bloom period before that of a non-rewarding flower will also increases the chances for pollination of the non-rewarding flower 5 . In addition, Heinrich (1975) demonstrates that having a variety of flowers that are morphologically distinct (resulting in increased efficiency of the search image technique) results in a lower diversity of pollinators required. Therefore, this possibly negatively affects pollinator populations due to the reduced need for them.
Heinrich (1975) determined that “the greater the variety of the flowers in a community the less likely that the pollinators will roam and the better are the chances that pollen will be deposited from one flower to another of the same species.” The roaming of bees not only results in an energetic cost (loss of profit) to the bee but also to the flower due to the waste of nectar and pollen resulting from inefficient pollination 5 . Methods to prevent bees from straying to less profitable flowers include different times of blooming and/or alternative arrangements of the flowers within the ecosystem 5 . Different blooming times not only provides food sources for a longer period of the year but also reduces competition between the flowers therefore increasing the chance of pollination 5 .
Summary
In terms of honey bee forage, providing the greatest variety of flowers possible and including flowers with distinctly different physical characteristics between species will increase honey bee efficiency.
I planted a wildflower meadow and in the first year I had a large number of Papaver rhoeas plants in bloom. They provide no nectar but do provide a great deal of pollen. The sound of honeybees gathering from them was loud and multiple bees could often be found working a single flower. Bumblebees, for whatever reason, didn’t seem to find them palatable but honeybees really did. One study said California poppy in particular is a high-quality pollen, considering the quantity of pollen. Certain clovers are better in terms of amino acid completeness but the amount of pollen each floral head provides is very low. Dandelions are weak for both pollen and nectar quality but are necessary due to scarcity of resources thanks to human development. Sunflower pollen is also not a particularly high-quality resource for bees but it’s better than nothing. Unfortunately, pollen-free cultivars are becoming more prevalent.