Buzz
What do you picture when you think of spending time in the garden? For some, it’s a peaceful retreat to bask in the sunlight, read, and maybe fit in a bit of exercise. For others, the garden becomes a gathering place for friends, outdoor picnics, grilling up a feast, and socializing.
At ground level, however, gardens can resemble battlegrounds— with plants, insects, small birds, and mammals all competing for space and sustenance. To thrive in this garden ‘jungle’, you have to use whatever tools you have, including chemical weapons.
10. Fungi That Kill Trees
Many fungi are indeed linked to poison, and rightfully so, as several toadstools and mushrooms contain potent toxins (often with names like ‘Death cap’ and ‘Satan’s bolete’ that sound as dangerous as they are). These toxins serve as a defense, deterring insects and mammals from consuming the fungi.
Some fungi, however, take a more direct approach in their chemical warfare tactics. Take the bracket fungus (Fomitopsis betulina), for example, which grows on birch trees. When the tree is weakened, the fungus produces digestive enzymes that break down the tree’s internal material, allowing the fungus to consume the decayed tissue.
Not everything about these fungi is harmful, though; some of the chemicals found in the ‘brackets’ (the disc-like structures growing from the infected tree) actually have practical uses for humans, as they possess antiseptic and anti-inflammatory properties. This particular fungus has been utilized in some alternative medicine practices and was even found among the belongings of a 5000-year-old mummy from the Alps, sparking theories that it was used for medicinal purposes.
9. Insects as a Tool for Attack
Another fungus that manipulates its environment is the sac fungus (Ascomycota), which targets elm trees. This fungus relies on elm bark beetles, which lay their eggs in dying elm trees. If the fungus is present, it releases spores that attach to the young beetles, which then carry it to other trees. As the beetles feed on healthy trees, the spores infiltrate the tree, particularly attacking its water and nutrient transport system. This leads to the tree’s demise as it can no longer support itself, causing its leaves to turn yellow and wilt year-round (not just in autumn) and its shoots to die off. Known as ‘Dutch elm disease’, this infection has decimated a large percentage of elm trees worldwide, with its name stemming from its initial discovery in the Netherlands.
The story doesn’t end there, though; some trees seem to be resistant to this disease. For instance, the European White Elm (Ulmus laevis) produces a chemical called Alnulin in its bark. Elm bark beetles seem to avoid trees containing Alnulin in their bark, allowing these elms to escape infection. Natural chemical defenses could be the key to resisting Dutch Elm disease.
8. The Wood-Wide Web
Despite the previous examples, fungi are not all harmful to garden and woodland plants— in fact, they’re often quite beneficial. The mushroom or toadstool you see above the ground is only a small fraction of the fungus; beneath the surface lies a vast network of root-like structures known as mycelium. This underground network greatly benefits surrounding plants by decomposing dead leaves and wood, enriching the soil, and even boosting tree immune systems by stimulating the production of defensive chemicals. Recent studies have revealed that mycelium has even more remarkable capabilities, sometimes acting as a communication system (earning it the nickname the ‘wood-wide web’). This communication can involve simple nutrient transfers between trees, but more intricate exchanges also occur— for example, when one plant is under threat (like from aphids), others in the network may release defensive chemicals to protect themselves. The full range of chemical signaling in this system is still not completely understood.
7. Insects Skilled in Crafting Chemical Weapons
Chemical warfare in the garden isn’t restricted to fungi and trees; many insects are also adept at producing toxic substances to deter or eliminate their predators. Ants are a prime example of this; with over 12,000 species spread across most continents, ants deploy a variety of fascinating chemical defenses. Some of the more remarkable examples come from Central America, like the bullet ant (Paraponera clavata), whose sting is said to be excruciatingly painful due to the injection of poneratoxin, a potent neurotoxin. However, it’s not just the exotic ants that rely on chemical defense; even the common black garden ant (Lasius Niger) uses formic acid to protect itself.
6. Plants Create Natural Insecticides
Left to their own devices, insects can devour large quantities of plant matter. Since most plants can’t move to defend themselves or kill the insects (except for a few carnivorous plants like the Venus flytrap…), it’s no wonder that many plants have developed chemical defenses. While there are well-known examples like deadly nightshade and poison ivy, even some of our more unremarkable garden plants can produce toxins that are potent enough to keep insect predators at bay. Take the humble mint plant, for instance— while it’s used by humans to create a tasty sauce for lamb, from an insect’s perspective, it produces a cocktail of harmful chemicals. The most powerful of these is pulegone, a substance that can damage the nervous system of insects that come into contact with it.
5. Survival Strategies of Aphids
Aphids are small but fascinating creatures that gardeners typically don’t favor— they weaken plants by feeding on their sap, harm new growth, and spread viruses between plants. While they are part of the food chain and have natural predators like ladybirds and wasps, there are times when aphid populations can get out of hand and cause significant damage to the plants they infest. Aphids have an interesting chemical tactic to protect themselves: they excrete honeydew, a sugary liquid derived from the sap they consume. This honeydew attracts ants, who are so fond of it that they become extremely protective of the aphids. Ants have been known to fend off the aphids’ natural predators and even move aphids from wilting plants to healthier ones to continue feeding.
4. Aphids Don’t Always Have the Upper Hand
However, despite their symbiotic relationship with ants, aphids are not immune to all chemical dangers in the garden. Strong-smelling plants, like garlic and onions, seem to have an impact on certain aphid species. Alliums, including garlic, contain a mixture of sulfur-based chemicals, which likely alter the aphids’ behavior— for example, by masking the scent of the plants they would normally prefer to feed on.
Some plants, however, take a different approach. Instead of producing chemicals to directly ward off aphids, they create substances that attract aphid predators. For instance, chamomile flower buds emit a volatile compound that draws ladybirds. The process of selecting plants to attract aphid-eating creatures is intricate, and there's some debate on how effective it truly is as a method of pest control.
3. Venomous Mammals
Venom is rare among mammals, as most of them use claws or teeth to immobilize their prey. However, there are a few venomous mammals. A surprising example is the European mole, often regarded as a nuisance when it appears in gardens (although it plays a valuable role by aerating the soil while digging). Moles are typically viewed as cute, furry creatures that consume earthworms and insects, but their feeding habits are far more fascinating (and gruesome). Their saliva contains a toxin that paralyzes their prey, which the mole then drags into its underground tunnel system. The still-living prey is stored in the mole's “earthworm pantry” for later consumption. The European mole is the only known mammal to exhibit this behavior, though certain species of shrews can also deliver venomous bites to their prey.
2. Do Birds Rely on Chemical Signals?
If small birds are frequenting your garden, it's a good sign as it indicates an abundance of insects for them to eat. It was once believed that birds had no need for a sense of smell, assuming that they used vision and hearing to detect prey and predators. However, recent research suggests that some bird species do indeed rely on their sense of smell. Starlings and blue tits, for example, have been observed incorporating leaves from aromatic plants into their nests. It is thought that these birds choose plants based on their scent, but the question remains: Are these plants chosen to repel predators, or do the chemicals they contain help keep bacteria in the nests under control?
1. The Protein Chemistry of Spiders
Spiders excel in protein chemistry. The silk that forms their webs is composed of long protein molecules tightly packed together to create a fiber. Proteins, in turn, are made from smaller molecules called amino acids, and the spider can adjust the types of amino acids in any given strand of silk. This allows spiders to produce different kinds of silk with varying properties – some strands are tough to maintain the structure of the web, while others are more elastic, making them ideal for ensnaring and holding prey that flies into the web.
