And we owe it all to leaves.

A silhouette of acer leaves against a pale sky.In summer a breeze will work its way through the boughs of a tree and the resulting sound is one of the constants in our lives, a white noise of leaves dancing on their stems. Right now, in autumn the leaves are at our feet, or swirling around corners, collecting at the foot of a tree, or at the base of a wall. Leaves stimulate all of our senses; we calm down merely by touching a leaf due to our innate evolutionary programming, and the sight of them emerging in Spring is enough to quicken our heartbeat. When we give leaves a bit of thought, it’s a wonder every tree and shrub doesn’t have a group of people staring up at them in awe.

All plants grow in the same way, they need light, air, water, and food. For many millions of years plants have been converting carbon dioxide and light into chemical energy through photosynthesis, and it wouldn’t be an understatement to say that this chemical process is the foundation for all life on earth. Leaves perform this role in most plants, producing food and ejecting the waste product of oxygen through tiny openings called stomata. Half of the world’s oxygen bubbles up from the sea courtesy of photosynthesising plankton, plants, algae, and bacteria; the other half is produced by land plants and their leaves.

Aerial view of a rainforest
Rainforest from above.

Land plants vary enormously, from huge trees of Californian valleys to small stony African succulents, every plant is completely different while simultaneously being exactly the same. While animals can escape weather and danger, plants must deal with everything right where they are, and so have evolved in extraordinary ways. Needing to photosynthesise in every environment means that certain changes are necessary for leaves to perform, so here’s a quickfire series of adaptations…

In the dense tropical rainforests light is filtered through a canopy meaning that plants need to utilize what light there is. On the forest floor where light is at its lowest, and the most useful light wavelengths have been snaffled by the many leaves above, some leaves (such as Begonia pavonina) are structured in super thin layers; this refracts wavelengths of green light for use in food production leaving the surface glowing an iridescent blue. Further up the rainforest strata, intense rainfall means that leaves need to shed water, funnelling it down the leaf and through a tiny spout called a drip tip. In other environments there is too much light, plants have adapted to protect themselves with tiny white hairs reflecting light away. Cacti and succulents have adapted their leaves to become sharp spines, protecting themselves from thirsty foragers and leaving food production to the green stems. At altitude, pine trees have Giant Amazon water lily in the raised tropical pool of the Botanic Garden.rolled up, thin, needle like leaves that stay on the tree all year; the waxy coating stops them drying out as well as eliminating damage from snow and ice. In water, leaves lie flat to maximise light, and some, like Nelumbo nucifera, repel water with a bumpy, waxy surface. Grass leaves grow at the base of the plant to cope with frequent grazing. Antarctic hairgrass survives the rocky frozen wastelands of the southern most parts of the globe, its tough leaves hummocking from rocky outcrops. Some plants have adapted leaves to catch prey like Venus flytrap, others are laced with poison, such as oleander, or possess stinging attributes, such as nettles.

This is just a snapshot of the diversity of leaves, but one thing all leaves do, is to give us the air that we breath. Knowing this, there should be great reverence for the trees above us, the shrubs alongside us, and the plants around our feet. Looking at all the discarded leaves in November is awe inspiring; a mature acer is said to have around 100,000 leaves, while an oak could have upwards of 700,000. Every one of them is as important to us as anything can ever be, so as you kick up a pile of fallen leaves, issue a quiet thank you using the oxygen that they gave you.

Plants are our personal time machines

Fynbos flora on the cliffs overlooking Cape Town
Fynbos flora of South Africa.

There have been three occasions when our team have seen people reduced to tears due to plants. The first was in our New Zealand display. Now, don’t get me wrong, this is a very interesting display botanically, but many people wouldn’t note it as their favourite or the most beautiful in the Garden. In fact, most people walk straight through it on their way to the toilet or the glasshouses. There they were though, two people, a couple who were from New Zealand but had been in the UK a while, laughing and crying at the same time. It reminded them of the landscape of home. The second, a large South African man with a big beard in the glasshouses; he said he didn’t realise he was homesick until he saw and smelt the Fynbos plants and seeing them made him both happy and sad. Thirdly, a Brazilian woman who hadn’t been in Brazil for twenty years; the giant waterlily in the glasshouses reminded her of her childhood and made her feel reflective. These are the people we’ve seen, there may have been more.


Magical plants of the Summer Solstice

By Susan Stephens

Summer is officially here! The first day of summer in the UK was on 21st June, the summer solstice, which is when the sun reaches its highest point in the sky and it is also the longest day. Summer solstice has always been linked with plants and flowers as it is a time of fertility, abundance and growth.


Seasonal succession.

There’s something about May. It’s an incredibly uplifting month, particularly when there’s been a longer than usual winter; a very wet march and an icy easterly wind has kept the dregs of winter sloshing around up until the end of April. The sun’s position in the sky meant that the usual spring triggers applied for the likes of primroses, daffodils and tulips, but the temperature and wet weather meant that pollinators were out in dribs and drabs, a day on and a day off. Even my usually optimistic approach wavered and my bottom lip stuck out. But now the temperature is higher, Bristol is bright green again and plants are assertively growing from everywhere. (more…)