Anja Murray: Bow down to the impressive  superpowers of plants 

For those that escape the sprays, mowers, and strimmers, pollinated flower tubes will develop into pea pods. Ripe seed pods become taut before bursting open to disperse half a dozen small wild peas. Closely related are several species of vetchling. Meadow vetchling is common and easily seen with its bright yellow flowers. These wild pea plants are the original ancestors of both garden variety sweet peas and the peas we often eat for dinner, all with the same genetic inclination to climb upwards. Sweet peas have been cultivated and bred to produce the highly scented, large-flowered varieties that gardeners of today love growing.

In the vegetable plot, garden peas also climb upwards, growing as much as two metres in a single season, producing copious quantities of delicious peas that are best eaten straight away, as soon as they’re popped out of their pods. Peas are one of the oldest cultivated crops. These days we mostly consume them via a packet in the freezer, a tin can, or from dried stores. All varieties of edible peas originate from the wild pea family, also referred to as legumes.

What each member of this wide family of plants has in common is the ability to ‘fix’ nitrogen.

Nitrogen gas makes up 78% of the Earth’s atmosphere, though in this gaseous form, the nitrogen atoms are so tightly bonded together that it's almost impossible to break them apart and recombine into more useable forms of nitrogen. Most living things aren’t able to absorb this ‘free’ or gaseous nitrogen, yet nitrogen-containing compounds are found in all living things, including amino acids that make up proteins that both plants and animals need to grow and repair cells. Nitrogen is even found in the nucleus of every living cell as one of the chemical components of DNA.

So where does this nitrogen come from? In nature, certain bacteria and blue-green algae (cyanobacteria) convert nitrogen gas from the air into nitrogen compounds that are useable by plants and animals. These tiny lifeforms convert around 90% of nitrogen.

Human-engineered procedures for fixing nitrogen were only pioneered in the early 1900s, millions of years after bacteria figured it out. Our industrial processes for fixing nitrogen require high pressures and high temperatures and thus are costly and inefficient. These processes are now the basis for making explosives, bombs, and chemical fertilisers, among other things.

Early in their evolution, plants in the pea family teamed up with these bacteria, hosting them in small root nodules, and learned to harvest the nitrogen directly from the bacteria. This symbiotic relationship with nitrogen-fixing bacteria is what has made legumes (another name for those plants in the pea family) such a successful family of plants across the globe. Nitrogen is a key component in proteins, which is how green peas, chickpeas, soya beans, lentils and even peanuts are rich sources of protein.

Vetches are one of the earliest crops known to be cultivated by humans. It is thought that one of the common, wild-growing species of vetch, common vetch, was brought to Ireland by early farmers thousands of years ago as a protein-rich fodder crop for cattle. Tufted vetch, for example, is widely known as ‘cow vetch’. Vetches and other legumes are still widely used across the world as a forage for farm animals, though here the practice has switched to using soya beans imported from afar to feed our cattle instead.

As well as feeding legumes to cattle, there is great benefit in having clovers growing among grasses to enrich the nitrogen content of the soil. In ancient legends and folklore, ‘plains of blossoming clover’ always depicted the fertility of the land and associated prosperity. We now know that the nitrogen-fixing superpowers of clover’s bacterial accomplices are why these plants are so closely associated with fertile land. This same special relationship between clover and nitrogen-fixing bacteria contained in root nodules is why farmers have been utilising clovers for aeons to enhance nitrogen levels in the soils of grass-based systems.

In recent years there has been a good deal of research about how the presence of both red and white clover enhances grass growth, negates the need for fertilisers, improves the quality of silage, and increases the resilience of grassy fields to drought. Farm advisory services and special farm payment measures have been designed to encourage more clover in grazing and silage swards. Because clover offers an alternative to artificial fertilisers, it is also considered a cornerstone of grass-based organic farming.

Like many things, a resurgence of old knowledge has much to offer in these challenging times. Not only do clovers have enormous benefits for farmers, reducing inputs and costs, but they also provide nectar and pollen for wild bees, butterflies, hoverflies and other pollinators. Clovers, as an alternative to fertilisers, offer a path to reducing the glut of water pollution that is currently destroying wildlife in lakes and rivers across the country.

So next time you are out on a stroll, keep an eye out for the flowers of vetches and their characteristic spiral tendrils. Watch as bees clamour to clover. Remember that whatever our innovations, plants have probably got there first. With a little humility, we might acknowledge the power of plants to provide us with all the solutions we need.