Understanding the role of insects in gardening

While many types of insects, birds and animals seen in the home are unwanted intruders, others play a vital role in pollinating plants and moving seeds from one place to another.  In fact, without these animal and insect helpers, most plants would be unable to reproduce.

Even though most gardeners understand how important this cycle of pollination and seed disbursal is, few fully understand why it occurs, or how it benefits both the plants and the animals.  

The rewards of pollination and seed disbursal to the plants are easy to determine – they get to spread their seeds far and wide, and start new plants in far off locations.  The rewards the insects, birds and mammals derive are many as well, and they include:

• Nectar 

nectar is actually a sugary solution, and therefore it is highly prized by all kinds of animals both for its good taste and for the ample energy it provides.  Getting at this nectar is what prompts most pollinating insects, birds and animals to do such a good job.  Nature has provided plants with various ways to attract pollinating insects, birds and animals.  Many types of flowers store their nectar in special glands called nectaries.  These nectar glands are most frequently found in flowers, but they are also sometimes contained in leaves or other parts of the plant as well.  Most plants are designed to protect their nectar stores from non-pollinating insects and animals, through the use of special storage locations that only pollinating insects can reach, for instance.

The use of nectar and the plants, insects, birds and animals that depend on it is a fascinating study in co-evolution.  The sugar concentrations of many plant nectars have evolved to match the energy requirements of the types of animals, birds and insects that pollinate them.  For instance, bees require a 30-35% concentration of sugar in order to make the honey needed by their larvae in the winter.  Therefore, bees will not visit flowers whose nectar contains less than 30% sugar.  Therefore, the flowers and plants that depend on bees for pollination have evolved high concentrations of sugar in their nectar to attract these pollinators.

• Pollen 

 Pollen is also used by flowers and plants to attract the insects, birds and animals they need.  Pollen is eaten by bees, and it is also used to make a substance called bee bread, which is a high protein combination of pollen and nectar.  This bee bread is used to feed the larvae, which require a high concentration of protein to grow and thrive.  Some plants, such as peonies, poppies and roses, use only pollen as a reward and produce no nectar at all.  Other types of plants produce two types of pollen – their normal pollen and a sterile pollen with is attractive to pollinating insects.  This evolutionary strategy ensures that the good tasting pollen will be eaten while the reproductive pollen will be spread to other areas by the insects, birds and animals that visit the plant.

Of course, this pollen and nectar does the plants no good if the birds, insects and animals cannot find it, and plants and flowers use their bright colors and strong scents to attract these animals and let them know that pollen, nectar, or both await them.  

Some pollinating species rely primarily on their sense of sight, and the bright flowers are used to attract their attention.  Other species, particularly nocturnal ones, rely primarily on smell.  It is the scent of the flowers that attracts these scent oriented pollinators.

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