The last drop

What is a desert? Per definition, the answer to this question is simple. They are areas of land with little to no flora. Though they are dry, they are not all hot. Take Antarctica, the largest desert in the world. Because it's so cold there, it is just as dry as the Sahara, the biggest hot desert on the planet. 

Generally speaking, when we think of a desert, we think of inhospitable, sandy and furiously hot regions. We think of towering dunes, sand storms and temperatures that bake by day and chill by night. One thing we are unlikely to think about are the plants that thrive in these unfriendly conditions. But they are out there. In the Sahara alone, there are 1,400 different plant species. Some of them, cacti.

Green giants

Carnegiea gigantea is one of them. It is a succulent plant, which means it can retain its own water supply. This cactus grows in the North American Sonoran Desert and can reach heights of 16 meters, collecting enough water inside to keep it moist for a year.

To do this, it relies on a root system that lingers just below the surface. That's not their only trick, for these prickly giants can live to a ripe old age of 220. When they hit 40, the age at which life reputedly begins, they start to bloom. At that stage, they're 2.5 meters tall. By the time they hit 65, they've soared to heights of six meters.

As if by magic

A much smaller and unlikely looking desert survivor found in North Africa and the Sahara goes by the name of the Rose of Jericho. With its olive green foliage and white flowers, it grows to around 10 centimeters. When the rainy season ends, it folds in on itself so consequently that it almost becomes a ball.

In this state of hibernation, it is brittle and more brown than green, and could easily be given up for dead. But it can just as easily be resurrected if put in water. Its cells absorb the liquid and the plant unfolds, leaving it looking almost as fresh as a daisy. Its dry casing serves to protect the seeds which, in the event of a heavy downpour, quickly begin to germinate.

Dig, dig, dig

Once upon a time a single Acacia stood in the middle of Niger's Ténéré desert. It was the only tree for 400 kilometers, and was considered the most isolated one in the world. 

For decades, it was the sole specimen, offering travellers a shady place to rest, but also posing questions about its tenacity. In the winter of 1938/39, those who wanted to know how the tree managed to survive, started to dig a shaft nearby. They spent a long time excavating hot sand, but once they got to a depth of 30 meters, they hit upon the explanation: groundwater and the tree's roots.

So-called taproots are strong and grow vertically allowing plants to grow on rock cracks, not only in the desert. Oaks, pines, dandelions and carrots also have taproots.

In the cool depths

Other plants more or less grow under the earth allowing just their tip to peep out of the ground. Fenestraria, which is also known as baby toes or window plant is a perfect example. The waxy leaves of this plant, which grows in Namibia, are sometimes completely covered, with their roots penetrating deeper into the ground.

The tips of their club-shaped leaves form a kind of window, so-called because it is transparent and conducts the light from above into the darkness of the earth below, ensuring that the plant grows.

How species survive in the Namib desert