Moss in the Grass
David Beeson
So, how do you gardeners rid your lawn of moss? Well, you’ll have to read on to find out!
When life started to emerge from the watery realms it, unexpectedly, was poorly adapted to life on land. Evolution needs time to work its miracle. LOTS of time.
The mosses and liverworts (known as Bryophytes) were the relatives of the algae that made the leap first. Today’s types of bryophytes are very distant relatives of the first terrestrial invaders – and your lawn grass is one of them.
Human sperm and eggs have just a single set of chromosomes – 23 in number. Egg and sperm’s DNA combine to give the two sets, 46 chromosomes, of the normal human.
Mosses (and liverworts) have a similar, but very different, pattern of changes in chromosome numbers. The moss plant you spot in the lawn, growing on a wall or under a woodland canopy has just a single chromosome set. This generates egg or sperm cells which, under WET CONDITIONS, can fuse. However, this zygote (fertilized egg with two chromosome sets) grows in situ on top of the green mossy plant – a spiky, small stem with a bobble (Capsule) on its end. Eventually, this capsule will burst open liberating spores which can grow on your lawn to a new green moss.
Mosses (Liverworts, horsetails and ferns) must have a wet environment at the appropriate time to complete the life cycle. That is not true for conifers or flowering plants … or humans … although a warm beach can be an inducement!
Mosses can never grow big as they contain almost no system for transporting water around the plant … you need to move on to the horsetails and ferns before that happens … which is why they can grow bigger.
The spore capsules contain vast numbers of spores. They are everywhere. On my garden wall these capsules are consumed by goldfinches over the winter. They sit nibbling them off most days.
Mosses do not like really dry conditions – because they cannot reproduce. But, they can survive dehydration for a while, so in the UK are seldom killed off by a hot summer as a wet autumn and winter follows.
Iron sulphate is deadly to mosses. So, lawn sand is a combination of fine sand and iron sulphate. The sand, in theory, carries the iron and lightens the soil. Except, I do not believe the latter unless you add tonnes. Much better to buy the iron sulphate and spread it with a gloved hand. Much cheaper.
BUT, the soil is full of enough moss spores to grow new plants for fifty years. So, sit back, admire the mosses and do not chuck unwanted iron sulphate to pollute the water supply. ‘Going for the mosses’ is a waste of time and effort.
Mosses show, like ALL land plants, alternation of generations. This is a flipping between an asexually reproducing phase and a sexual phase. In the case of mosses the two are attached, the one parasitic on the other. In other plant types they can be quite separate e.g. ferns.
Gametophyte = green ‘plant-like’ structure. The hair-like sporophyte is composed of seta and capsule (with its spores).
The gametophyte is haploid (each cell has only one set of chromosomes), the sporophyte is diploid (like us) and each cell has two chromosome sets but reduces that number in the spores via a nuclear division called meiosis.
I often spot goldfinches eating the spore capsules, but not the green gametophyte.
A similar life cycle occurs in liverworts.
In ferns, horsetails, conifers and angiosperms (flowering plants) the sporophyte is the dominant plant (what you normally see) and the gametophyte is much reduced. In flowering plants there are ‘male’ (Pollen, released) and ‘female’ spores (not released) and they germinated to form the gametophytes. The gametophyte has two forms: 1) Male spores grows into the germinated pollen (Pollen tube) or 2) the ovule containing an egg cell that is held within the carpel of the flower. All very confusing! Get a good botany book and check it all out. (Buy a second hand ex-uni library copy for just a small amount of money! The material will be bang up-to-date … it doesn’t change.)
Wildlife and Ecology, the Wildlife Encyclopaedia 