Plants that aren’t plants

that

PL L S

Some living organisms are neither plant nor animal. TIM ENTWISLE looks at lichens, fungi and other outliers that may be creeping around your garden

Not every living thing in your garden is a plant. There are animals, of course, but we don’t usually confuse them with plants – unless they are one of those fancy mantises or a stick insect.

Mushrooms and toadstools are often called plants, but they are the fruiting bodies of fungi, organisms more closely related to you and me than to the rest of the garden. Flowering plants, ferns and conifers all cluster together in the

Tree of Life, but fungi pop out on an entirely different branch – a side shoot of which is the animal kingdom.

If you think about it, that makes sense.

Fungi are, mostly, not green. And they don’t use the sun’s energy to convert carbon dioxide and water into sugars and oxygen – they don’t photosynthesise.

Instead, fungi feed on decaying material (saprophytes) or freeload off other organisms (parasites). Importantly for forests and garden plants, they also establish special relationships with the roots of many plants to provide nutrients in exchange for sugars (symbioses).

underworld connections

The intimate connections between plants and fungi have been publicised in recent years through concepts such as the Wood Wide Web, an underground network connecting trees of the same and different species. These so-called mycorrhizal fi laments (called hyphae) allow plants and fungi to not only share resources, but also communicate.

Fungal hyphae are often seen in the compost bin or rotting tree stumps. Take care with their fruiting bodies (they can be extremely toxic). Some, such as honey fungus (Armillaria mellea), are pathogens. Generally, though, you can encourage a diverse range of fungi.

wondrous lichens

You may not recognise the fungus in its alter ego, the lichen. Lichens are often considered a troublesome pest, but they are one of evolution’s truly wondrous achievements. They consist of an alga and a fungus living together in places where neither could survive alone.

When inside a lichen, an alga can survive in hot, dry places. The fungus, with access to its algal cuisine, gets to live on rocks and other non-decaying surfaces where it normally couldn’t exist. How the two organisms get about and re-form is still a mystery, but many release small packages that contain both fungal and algal cells.

So the fungus is not a plant, but what about the alga? That depends. Most lichenised algae are ‘green algae’, which means they are related to things such as sea lettuce and pond scum.

These green algae are to plants as fungi are to animals: an offshoot on the same larger branch of life. Less commonly, you fi nd yellow-green or blue-green algae, more distantly related to green plants and animals than fungi.

No matter what the alga or fungus, you can leave and even encourage lichen to grow on tree trunks, and even your roof – any damage to your tiles will be relatively minor and only become an issue after a century or two.

Calling a lichen a plant is a bit of a stretch. You are on safer ground with mosses or liverworts, which you can encourage to grow by smearing a damp surface with a mix of yoghurt and fragments of these tiny plants.

Taxonomically, bryophytes – mosses, liverworts and their close relatives – are tucked in close to ferns, conifers and flowering plants, and grouped into what are helpfully called the ‘green plants’. The difference here, as you may know, is the lack of fl owers and then seeds. Mosses and their kin produce tiny spores.

strange slime moulds

As a phycologist (algal expert) by training, I could rave for pages about the intricate lives of various algal groups, but the most fascinating plant that is not a plant is, perhaps, the slime mould.

In the fi rst instance, you might identify a slime mould as the rejected stomach contents of an animal (one’s called ‘dog’s vomit’). Slime moulds (myxomycetes) are neither plant, alga, animal nor fungus, but a group of unrelated organisms clustered together for convenience.

There are two main kinds: the cellular slime moulds that spend most of their lives as unobserved single cells, but every now and then coagulate into a slug-like form; and the ones that live their entire lives in this creeping slug form, called a plasmodium.

As the plasmodium moves around slowly, it lives off decaying material or other micro-organisms, and produces spores in a few different ways, including in foamy masses given the common names of ‘dog’s vomit’ and ‘wolf’s milk’. Others are more cheery and brightly coloured, resembling small coral. Again, you want these in your garden as part of a diverse and healthy ecosystem.

It often takes a fi ne eye, or a hand lens, to see the beauty of all these plant-like organisms. Most of them – here, I must give a shout-out to my algae, with their vibrant colours and eccentric shapes – are spectacular under a microscope. But even if you all you see is a small green cushion on the path, or a glaucous crusty coating on a downpipe, you can welcome most of them in to share your garden with the real plants. GA