Many plants have thorns or needles… but that doesn’t stop them from being beautiful. Think of roses, spruce trees, and barberries, three popular plants you wouldn’t want to get too close to. But what are these thorns really for? You’ll probably be surprised by the answer!
Defense
That’s the most obvious answer. Yes, thorns are often used to keep unwanted animals away. Producing beautiful large leaves and stems only to have them eaten a few weeks later is a great loss for the plant and can even kill it, especially if the action is repeated. A few thorns here and there and most large herbivores will look elsewhere.
Humans can take advantage of this defensive action to protect their homes or property. It is well known that thieves will not enter through a window under which a thorny plant, such as a rose bush or barberry, is growing. And before the era of barbed wire, farms were surrounded by thorny hedges to keep predators out… and livestock in!
In fact, legend has it that Scotland was saved by a thistle. In 1263, the Viking king Haakon had already conquered most of the country and was preparing to attack one of the last Scottish strongholds at Largs. Preparing for a surprise night attack, he asked his men to remove their shoes so as not to make any noise, but one of the Vikings stepped on a thistle leaf and let out a cry, alerting the Scots. Not only did the Scots win the Battle of Largs, but this victory sparked a renewed enthusiasm and the Vikings were driven out of the country. Since then, the thistle has been the floral emblem of Scotland.
A Climbing Aid
Several climbing plants use thorns to cling to their support. Climbing roses and brambles, for example, produce long, arching branches that would collapse to the ground without support. But when they grow in dense brush, the branches pass through the less flexible stems of the shrubs and lean against them. The thorns prevent the branches from sliding down.
A Source of Water
Desert plants have a surprising use for their spines: dew condenses on them and falls to the ground, providing them with water. In fact, there are cacti called Copiapoa that live solely on dew, since in some parts of the Atacama Desert in Chile where they grow, it has never rained in living memory.
A source of shade
Despite their thinness, the spines also serve to shade certain plants, such as cacti and euphorbias, from the intense sun. In the height of summer, when the sun is intense, these plants shrink like an accordion and the spines provide good shade. During the winter rainy season, the “accordion” swells and allows the now weaker sun to penetrate once again.
A Means of Transportation
Yes, some plants use thorns as a means of transportation. You have probably encountered burdock fruits that have stuck to your clothes, much to your dismay. They are covered with spiny hooks designed to attach themselves to animal fur. When the animal moves, the fruits begin to irritate it and it scratches to remove them. This transports the seeds away from the parent plant, where they can start a new generation of burdocks.
Several other plants have clinging seeds and move in the same way. And it’s not just seeds! How many hikers in Arizona or Mexico have discovered the hard way that the spiny pads of certain cacti (Cylindropuntia) break off and stick to the legs of passers-by! It’s extremely painful, and when you finally remove the intruder with tweezers and throw it on the ground in disgust, it takes root and produces a new leg-hanger.
Useful Thorns
That’s it for plants and their uses for needles. Humans also find several uses for these growths. Curved needles were the first known fishhooks. Agave thorns are used as sewing needles. The very prickly fruit of the teasel was used (and still is) to card wool. And the list goes on.
The next time you feel a thorn pricking you, rather than complaining, marvel at the many uses of this simple yet effective structure.
Larry Hodgson has published thousands of articles and 65 books in French and English during his career. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil on July 30, 2011.
Roses actually have prickles that are really just modified hairs on the outer skin to the rose cane and can be removed without damaging the cane… Unlike thorns or spines, prickles do not contain vascular bundles: the pathways that transport nutrients up and down the stems.
Very informative. Enjoyed reading how the thistle became Scotland’s national floral emblem