Different flowers have many different methods of pollination. Some flowers rely on the wind for pollination. In order to achieve this, they may producethousands of flowers and masses of pollen which is carried by the wind, the volume of pollen ensuring that at least some lands on female flowers of their own species.
However, many rely on one of the gardener’s best friends which is the bee. Whatever kind of bee, from honey bees to the less gregarious carver and bumble bees, they are useful pollinators without whom many of our crop sand flowers would be lost. Flowers are devised especially to attract and encourage bees to pollinate them. The flowers are often scented and this tells the bee the flower is ready to be pollinated and they also provide food in the form of nectar which the bees take back to the hive or nest.
Plants pollinated by bees often have brightly colored flowers to attract bees and they are usually in the red or blue color range as bees see in ultra-violet and so these colours will stand out for them.Within the flower structure, the position of the nectaries and flowers male and female parts is so the bee has to brush the reproductive parts in order to reach the food and in doing so , picks up and transfer pollen. Many have mechanisms to prevent self pollination and encourage cross pollination such as having stigmas which brush against the bees body as they enter to collect pollen form their fur but are hidden under a flap as the bee exits to prevent them taking up their own pollen, newly collected on the bee from their current visit to the flower.
Stigmas tend to be shorter and above the food source so the bee has to pass down the flower and filaments are often shorter because they do not want their pollen lost to the air currents.
Some flowers have evolved to rely so specifically on bees for pollination that they would be lost without them. As an example, sweet peas (Lathryus odorata) have a flower structure designed to attract bees and only the weight of a bee allows access to the nectaries, which are held in a special structure called the keel at the base of the flower, formed by two joined petals. When the bee lands on the keel, it is pushed downwards and the stigmas and anthers inside the keel, move up to brush against the bee. The nectaries are above the filaments of the anthers so to reach them, the bee must pass the stigmas and anthers. The bee gets nectar and the flower is pollinated.
Pollen of bee pollinates plants tends to be spiky so it sticks to the fur of the bee’ body which is another adaptation for bee pollination.
So, bees pollinate plants by collecting nectar and inadvertently brushing against the anthers, collecting pollen on their bodies or in pollen baskets on their legs in the case of honey bees and the flowers have evolved to specifically use this behaviour to gain pollination.
Bees are in trouble at the moment due to a devastating disease and mites which can wipe out populations in areas so we must do all we can to provide them with nectar rich flowers to help them in their struggle to survive. They are the work force of the garden and without them, we ourselves would be in severe trouble.