EATING is vital to life, and can transport us to sublime heights of delight. But our emotional relationship to eating colours how we see plants, blinding us to their own intriguing methods of consumption.

It is spring in the northern hemisphere. Throughout Britain, hedges and verges, garden and field are lush and swelling with leaves and buds.

The annual explosion of plants is here once again. Plants reorient the environment with their bodies, enriching and depleting soil, ripping through pavements and walls, blocking out the light, housing and feeding insects and birds.

Plants split from the ancestors of other life-forms around 1.5 billion years ago, when a single-celled organism engulfed a photosynthetic bacterium, maintaining the bacterium’s light-harvesting function even after it had entered the cell.

The bacterium became a permanent “organelle” within the plant cell, which we refer to as a chloroplast. This is what allowed plants to start absorbing energy from the sun, converting the carbon from the environment into their own material in the process.

A permanent arrangement like this has actually happened twice, once to produce all the plants and algae that we know, and once in a little-known “amoeboid” we call Paulinella much more recently — only a couple of hundred million years ago.

Although the amoeboid is a minor player on the world stage of ecology, the discovery of a second evolutionary occurrence makes it a fascinating flashpoint for biologists who want to learn how plants evolved after first engulfing the chloroplast’s ancestor.

The engulfment meant that plants could harvest energy from the sun and take in carbon from the atmosphere. This change freed them from the need to eat so much through other means, unlike animals.

In a sense, almost all animals are predators. When they eat, they usually take bites of other organisms using teeth or hard or sharp mouthparts, and move the tissue into their body, or perhaps swallow it whole. There, enzymes released by the animal’s body slowly start to disassemble the complex molecules of the preyed-on food, gradually releasing the resulting nutrients into the predator to use as energy and to build or maintain its life processes.

The complex structures and molecules that make up our food are broken down all over again, requiring more energy and digestive resources. There are a very few exceptions to this process in the animal world.

One outstanding example is a group of sea slugs that take fully functioning chloroplasts into their translucent bodies and maintain their function there, though they are still separate to the animals’ own bodies and cells. They are denoted “kleptoplasts,” because they are stolen.

Research is ongoing into how exactly the chloroplasts benefit the slug. Unlike in plants, which take control of some, although not all, of the genetic control of chloroplasts, these aquatic slugs have not fully integrated chloroplasts into their body plan. Though we don’t know the odds, it might only be a question of time (albeit on the order of millions of years).

We often view the eating that plants do, as with so much else of their natural state, as a passive process. But again it is a question of timescale. Our attitudes to the passivity of plants come from our animal perspective, and neglect the sorts of powerful directed movement that plants are capable of.

Plants move, release toxins, aggressively occupy space, strangle and smother other plants or tap directly into host plant bodies as parasites. Some even trap and digest animals just as animals do.

These carnivorous plants, a staple of sci-fi horror, show us what plant killing looks like. Among the most celebrated carnivorous plants are the pitcher plants. In pitcher plants, an adapted nectary — the part of a flower containing the reward of nectar that attracts insects — grows to enormous size, filling with a large quantity of sticky nectar fluid.

Instead of letting insects leave with nectar and some pollen, this bucket of sticky liquid acts much like a stomach, trapping the lured insect which is eventually drowned and decomposed.

These plants even hunt, having adaptations to their outer surfaces allowing them to attract insects — bright colours and shapes, delicious lemony scents that lure prey towards them.

In some species, once they arrive at the trap specially adapted surfaces around the rim of the pitcher even change depending on the weather. Ants get into a habit of walking freely on the lip, before wet conditions turn them into an ultra-slippery aquaplane that shoots them straight into the pitcher.

In fact, the evolution of pitcher plants has produced even more physical adaptation. Researchers at the University of Exeter have taken a particular interest in a “springboard mechanism” — the lid of the pitcher makes an attractive surface for ants to walk about on, unlike the slippery lip.

It’s covered in grippy wax, stays dry in rain and is as stiff as a board. The stiffness of the lid is vital to the action of the pitcher plant — when impacted by a heavy droplet of rain, the lid jerks like a loaded spring, and the ant standing on the underside is propelled immediately into the pitcher’s mouth.

This mechanism is a consistent method of prey capture and appears to have evolved separately in two species separated by thousands of miles of ocean, through a combination of luck, anatomical tendencies, and the ubiquity of ants.

Convergent and repeated evolution of this kind, much like the engulfment of photosynthetic bacteria by different organisms, are exciting because of the ways that they allow us to compare evolutionary trajectories.

Plants that kill and eat animals are eerie because they seem more active than other plants. But our perception of other plants as passive is misplaced. What we project onto plants reflects our own values.

The reality of the plant world is much more exciting than that. For better or worse, consumption and colonisation can happen slowly and creepingly as a plant just as well as in the chewing and scuttling forms of animals.