Nectar is a sugary liquid produced by some flowering plants to attract pollinating insects such as bees, hummingbirds and butterflies and is secreted by specialised glands called nectar glands, which are found inside flowers. These glands produce nectar as a reward for insects that visit the flowers in search of food.
Nectar is therefore an essential source of energy for pollinating insects, as it contains easily assimilated sugars such as glucose and fructose. In fact, insects collect nectar with their proboscis or tongue, and while feeding, can incidentally transfer pollen from the flowers of one plant to another, thus contributing to cross-pollination and plant reproduction.
In short, nectar is a substance at the basis of life for these insects! Researchers in Bristol wanted to investigate what the main sources of nectar were and, for this very reason, observed nectar production from March to October in certain portions of land they rented. These analyses revealed that the plants producing the largest share of nectar are shrubs. This is due to the fact that they are plants with a high density of flowers, which makes them suitable even for small spaces.
Not surprisingly, in cities, one can find many gardens with different varieties of flowers, which makes an urban space more pollinator-friendly than a rural space. This is because a greater variety of plants ensures that pollinators have a constant source of nectar throughout the year!