The side of a tree moss grows on is usually equatorial, meaning it depends on the hemisphere in which the tree lives.
Moss will grow on the north side of a tree in the northern hemisphere, and on the southern side of a tree in the southern hemisphere. There is no great myth or secret surrounding this - it’s simply due to the fact that moss tends to thrive in damp and shaded places. In other words, areas that get the least sunlight.
Moss ultimately needs water to survive due to the fact the species is non-vascular and doesn’t possess a biological network of vessels which supplies the plant with food and water. Instead, moss relies on absorbing water from its external environment. The species also needs water to successfully reproduce as the male reproductive cells reach the female cells through a film of water in order to carry out the fertilisation process. This can happen with a single plant but some species of moss will need to connect with another plant in order to reproduce. Without water, moss can’t reproduce. That’s why it tends to favour the shade - especially on the shaded side of a tree - as the sun may cause it to dry out.
Does moss grow in sun or shade?
Moss favours damp and shaded areas as it can thrive in the moist environment and use the water to sustain itself, grow and reproduce. It isn’t impossible for some species of moss to survive in full view of the sun, but the vast majority prefer a shaded environment. In terms of growing on trees, moss favours the side in antithesis to the view of the sun, although it can also grow in shaded crevices in the tree, or on surfaces in close proximity to the damp ground.
What causes moss to grow on trees?
Moss ultimately grows in any environment that welcomes moisture. So this includes trees as a prime example, yet it can also grow on rocks, buildings, fallen logs, walls and roots.
If we were to focus on trees, though, there are several reasons moss thrives upon them. The natural crevices that form on trees within the rough and irregular bark formation provide moss with a micro habitat that’s often sheltered and shaded. Here the rhizoids can anchor the moss and the spores can develop. This explains why you’re more likely to find moss on trees with rough bark, rather than smoother trees such as beech. Forever proving its resilience, moss tends to enjoy little to now competition when it grows on trees as you don’t see many other species that could grow in such a vertical environment.
Moss ultimately grows in any environment that welcomes moisture
Is moss on trees good or bad?
Mosses are not harmful to trees. Like their biological cousins, algae and lichens, they don’t pose a parasitic risk to the tree, either. It’s actually the opposite, as mosses that grow on trees contribute hugely to biodiversity in providing a microcosm in which miniscule organisms thrive - including rotifers, tardigrades and nematodes. These creatures are much too small for the human eye. Yet, thanks to the moss that grows on trees, they can thrive and survive in their own little habitat.
Although moss growth on trees isn’t harmful, it can contribute to other potential problems. For instance, moss can make it difficult to spot health issues upon older trees as it may literally shield the problem from sight. If there’s an abundance of moss growing on a tree, it may add extra weight that destabilises the tree and puts it off balance, which could be a major problem in windy conditions. In the wider picture, though, these problems aren’t overly common so we can safely conclude that mosses aren’t harmful to trees.
Does moss die in winter?
Mosses don’t die in the winter as they are extremely resilient and have a tolerance for low temperatures. In fact, they can still reproduce despite the harsh winter environment, which is why you’ll often see flourishing green moss during the winter months.
