March 2018

I have heard that grass doesn’t grow when the soil temperature is below 6 degrees C.  It is quite irritating then to find that despite the cold and dull weather that seems to have persisted for weeks, that our lawn needs mowing.  It’s even more irritating that it’s too cold and wet to get out there for the first mow of spring.  Grass is always a chore for gardeners, if it’s in the border it needs weeding out, if it’s not it probably needs mowing.

Unidentified, possibly Sweet Vernal Grass

It may however, be worth pausing as you empty the grass box, to marvel at one of nature’s most successful plants.  It grows just about everywhere from the high tide mark to well above the treeline and from the tropical rain forests to all but the driest deserts.  It comes in many forms – as grasses, sedges, and rushes, and even bamboo.  Incidentally, grasses, sedges and rushes are in separate families – Poaceae, Cyperacae, and Juncaceae respectively – and if you are not sure which is which then you need to remember the rhyme, ‘sedges have edges, rushes are round and grass stems are hollow right up from the ground’.  (That refers to the flowering stems which are triangular in the case of sedges.)  If you choose a grass species with fat seeds and fill a field with it, then you will have part of the world’s staple diet.  Where would we be without wheat or rice, or my own particular favourite, barley? (roasted and suitably mixed with another favourite native plant species Humulus lupulus, better known as the common hop.)  Another large part of our diet (too large in many cases) is derived from yet another grass – sugar cane.

Canary Grass

There are more than 10,000 different species of grass worldwide, and it is likely that your garden, however tidy you keep it, will contain a dozen or more different ones.  Identification of grasses is not easy and requires a lot of time looking for identifying features and following keys.  The botanical language used is different to that used for other plants because grasses have things like awns and stipules and spikelets that other plants don’t have.  Of course, the first thing you need to do to identify any type of grass is to stop mowing it and let it flower.  Grasses are wind pollinated and so they don’t need showy scented flowers to attract insects.  This means that the flower features are quite small and a hand lens is useful to see them clearly.  I have managed to identify a few species in our garden – Sweet vernal grass, which gives new mown hay its sweet smell, Quaking grass, Cock’s Foot, Field Wood-rush (a small but pretty species), Perennial Rye grass, and of course Common Couch grass.  Yet another species that I am trying to eradicate is Pendulous Sedge – if you have any, I recommend that you don’t let it flower!

Unidentified, possibly one of the False Oats

I find that the names of grasses have a sort of ancient and romantic feel to them.  Things like bents and fescues, crested dog’s tail, wood melick and canary-grass.  Believe it or not, there’s even one called Timothy.

Field Wood-rush

February 2018

I like writing this column because it forces me to check my facts before I write it and that means that I find stuff out.  We had some unusual visitors to our bird feeders recently – redpolls.  This was very unusual simply because we have never seen them on there before.  Redpolls are a small finch that breeds in this country, and we also get an influx from Scandinavia in winter.  When I looked up redpolls, it turns out that they could have been one of two species – the common redpoll, or the lesser redpoll.  Apparently these have only recently been split into two species, more recently than 2001 when my bird guide was published.  My bird guide did however, mention two sub-species depending on where in Scandinavia they bred, that correspond to the new species division.  So did we see Lesser Redpoll or Common Redpoll?  I haven’t a clue because the differences are small (one is slightly smaller and paler than the other) and I wasn’t expecting there to be two possible species when I saw them.  But it was a delight to see them and as long as they know the difference that’s all that matters.

Common or Lesser Redpoll - Carduelis flammea or cabaret

In last month’s column I briefly mentioned mosses and liverworts.  Apart from the fact that I could probably point out mosses or liverworts if I saw them, that was about all I knew, so I looked them up and it turns out that they are a very interesting group of plants.  As a group they are known as bryophytes and the group includes another set of plants that I had never heard of – hornworts.  Apparently hornworts are quite scarce in the UK which is probably why I haven’t come across them before (and if I had I probably would have thought them to be liverworts).  One thing about bryophytes is that they are not vascular plants.  Vascular plants (the plants we are more familiar with) have flowers, branches, and even trunks that contain sap which flows through the plant in a similar way to blood in veins – hence the term vascular.  Vascular plants grow, flower, set seed, which then germinate to form new plants, but bryophytes complicate matters with an extra stage. 

Bryophytes produce spores; those spores, usually dispersed by the wind, land somewhere favourable and grow into a new plant, but the difference between spores and seeds is that the DNA in seeds has the chromosomes from both parent plants, but bryophyte spores only contain the DNA from one parent.  (The technical term is haploid.)  When the plant that grew from the spore grows into a moss or liverwort, that stage cannot then produce spores.  Instead each plant is either female which produces eggs, or male which produces sperm.  The sperms are then usually dispersed by water (which is why bryophytes usually grow in very damp places) or by insects that carry sperm from one plant to another.  This egg and sperm stage is called the gametophyte stage, but you probably don’t need to know that.  The fertilized eggs are then dispersed from the gametophyte, again usually by water and having both the male and female DNA, they can then grow into the spore producing generation (called sporophytes, should you be interested).

From studies of their mitochondrial DNA it has been suggested that liverworts may well have been the first land plants to evolve from green algae more than 400 million years ago.  There are thought to be more than 1,000 species of bryophytes found in the UK and more than 20,000 worldwide. Though they are often overlooked, mosses and liverworts are an important part of the ecology and support a wide range of insects and other arthropods, not to mention the many birds that feed on those smaller creatures.  One day I hope to find a creature that makes its home only in moss – the tardigrade bear – that is almost microscopic and not actually a bear, but no less interesting for all that.