Originally published July 2010
Hello everyone! Well here we are, post Solstice and looking forward with eager anticipation to the Summer hols. At present we don’t know whether to expect floods or hose-pipe bans; and of course this being England we wont know ‘til the the day we set off on that walking tour or camping trip! With this in mind my woodland ramblings this month have a seasonal warning for one and all, especially our little ones.
Anyone who has sauntered through our little Reserve lately will have noticed that the pond, if not quite brimming over, is at least two-thirds full. As the main feature of the Reserve, this is definitely good news, though the mystery as to where the water actually goes from time to time is still under investigation. I have referred to our ‘green highway’ before; during the summer months when the water is a carpet of small green leaves and tiny roots trailing below the surface. This is of course the ubiquitous Common Duckweed (Lemna minor); one of the smallest flowering plants in Britain, second only to Rootles Duckweed (Wolffia arrhiza). The 1mm flower is rarely produced as propagation is mainly by division. Put simply this means that when more than two or three leaves develop, the plant divides to become two separate individuals. With the ability, given the right conditions, to double its weight in 24 hours Lemna is one of the fastest colonising plants around. A handy trick for the survival of the species, but it makes life difficult for those of us wanting to keep our garden ponds clear so we can actually see down into them!
Duckweed is an important food source for herbivorous fish and birds, especially, as the nomenclature suggests, ducks. Donald is also credited with the spread of the plant across the water ways as the roots stick to his paddles and thus carried from pond to pond. Aquatic gardeners are only too aware that water plants bought in garden centres need to be thoroughly hosed off to get rid of the odd Lemna rootlet that is bound to be there somewhere.
Friend or foe? This really depends, like so many things in life, on your viewpoint. The plant has a very high protein value (just slightly lower than the soya bean!) and is used as a supplement in cattle feed. I’m sure that it is only a matter of time before us vegetarian types will be offered Duckweed burgers and sausages for our Summer barbeques!
Eutrophic (nutrient rich) water courses can be cleaned up with mats of Lemna mopping up the nitrogen before being mechanically harvested off the surface with a boom. Just be aware that once the plant is in situ it is practically impossible to erradicate!
A layer of Duckweed will decrease the level of evaporation from the water surface, a definite plus as far as our reserve pond is concerned. However, if too much of the pond is covered then oxygen levels will decrease in the water column and the wildlife will suffer. The moral of the story is definitely that good things come in moderation!
Now for that dire warning. Lemna has been associated with a certain evil faerie or river hag known by a variety of names depending which coloured rose your ancestors fought under or if they just watched the action from the Peak District or Offas Dyke. Stories abound as to how Jenny Greenteeth, also known as Ginny Greenteeth, Wicked Jenny, Peg Powler, Peg O’ Nell or the Béan-Fionn (the Irish relative!), lured children into the water to drown them. It is very likely that she is an invention to stop little ones from attempting to walk along our aquatic green highways; but of course this being the Mysterious Isle of Merlin et al. she has also been seen as a lingering memory of human sacrifice carried out in the dark recesses of ancient history.
Mother, may I go out for a swim?
Yes, my dearest daughter.
Hang your clothes on a rowan limb,
And don’t go near the water.
Another custom this Fair Isle is famous for is having traditional nursery rhymes which make no sense whatsoever! Let me know your thoughts at email@example.com
Enjoy the Summer.