Your houseplants were 'forged in the war of nature' to be pretty and poisonous, says an evolutionary biologist

• Evolution has led to a variety of defense mechanisms for plants.
• This means that every plant, from hemlock to houseplants, is probably toxic to some form of life.

Evolutionary biologist Noah Whiteman has a poison garden outside of his home.

"There's nothing illegal in there," he told Business Insider. "Pretty much any plant, I think of as poisonous because it is to some critter."

For example, the California pipevine (Aristolochia californica), which his husband plants, contains aristolochic acids that can cause kidney failure in humans.

In fact, in the early '90s, some women taking certain weight loss supplements started experiencing kidney disease. It was later found that the slimming pills contained aristolochic acid.

But a type of butterfly, the pipevine swallowtail, has no problem with the plant's toxins.

"These [are] beautiful, blue-green, big butterflies that are native to California," Whiteman said. The butterflies ingest the plant as caterpillars and become toxic to predators themselves.

Plenty of people invite toxic plants inside their homes in the form of houseplants, Whiteman said. The toxins are "most often used as defenses," he said. "That means that they have the potential to cause harm, at least to some organisms."

From the rainforest to your living room

In his book "Most Delicious Poison" published in October, Whiteman describes a friend who got squirted in the eye with goo from a spurge, a type of euphorbia plant.

He'd mistaken it for a relatively harmless cactus until his eye started to burn. The plant had launched latex, which has the potential to lead to blindness if left untreated.

The plant keeps its latex toxin under pressure so when the toxin-containing cells break, the plant is armed and ready. "It doesn't drip out," Whiteman said, "it shoots out into your face."

Luckily, Whiteman's friend made a full recovery and did not lose his vision.

From the plant's perspective, it's a great defense against herbivores, he said. "The deer's going to back away, probably, and not eat it again," he said.

The same is true for dieffenbachia, a plant Whiteman often sees crop up on Instagram. "In tropical rainforests, they're fighting for survival," he said. "They were forged in the war of nature, and we should never forget that."

Look at a dieffenbachia under a microscope, and you'll see what look like tiny needles, Whiteman said. These are called raphides, and they're sharp crystals made of calcium oxalate, which can cause

Oxalates can cause "swelling, drooling, and loss of speech" if swallowed, and can irritate any exposed skin and eyes, according to Poison Control.

"They've evolved the ability to really cause a lot of pain for an organism that's going to start chewing on its leaf and be toxic in addition to that," Whiteman said.

Plants are just doing what they do best: survive

It's not as if a plant has bad intentions. It just wants to live, which is something Whiteman wants people to understand and respect.

"None of these things evolved for our sake," Whiteman said. "We can think of them as tools that were not invented for us so we had better be very careful in thinking about what we're using them for."