Sandy’s Garden ... Let Them Eat Duckweed

Sandy Simpson
Sandy Simpson

We start this week with a quotation from the 18th century philosopher and writer Jean-Jacques Rousseau.

Born in Geneva in 1712, Rousseau died in France in 1778. In his massive autobiography entitled Confessions, we read, “Je me rappelai le pis-aller d’une grande princesse à qui l’on disait que les paysans n’avaient pas de pain, et qui répondit: ‘Qu’ils mangent de la brioche!’” For readers whose French is a trifle rusty, this can be translated as, “I recalled the spur-of-the-moment answer of a grand princess who, on being told that the peasants had no bread, responded: ‘Let them eat cake!’”

This saying is usually attributed to Marie Antoinette but, since she was a mere nine years old when Rousseau wrote of ‘remembering’ this incident, there is no way that the story began with the lady who was Queen of France from 1774 until 1792. And what has this to do with duckweed? Well, as the world’s population continues its seemingly-unstoppable increase, we may well need to exploit seemingly-unlikely sources of nutritious food; and duckweed assuredly comes into this category. Might we be moving towards a time when, on being told that some people have no bread, we may reply, “Then let them eat duckweed”?

So what is duckweed … or, more properly, what are duckweeds? Here is another quotation, this time from the internet. “Duckweeds are tiny free-floating vascular plants found throughout the world on fresh (or sometimes brackish) waters.” And vascular plants are, “A large group of plants that are defined as those plants that have lignified tissues for conducting water and minerals throughout the plant,” or, in short, most plants. Duckweeds have neither stems nor proper leaves, usually consisting of a few, small fronds varying in diameter from about 2 mm to 20 mm depending on the species, forming green mats of plants floating on the surface of still or sluggish water. All species of duckweed thrive in a wide variety of habitats and temperatures, although they do particularly well in tropical and subtropical areas. In ideal conditions, duckweeds can double their mass in less than a day, making them one of the fastest biomass producers on Earth, a characteristic which, combined with their very high protein content, could make the plants providers of sustainably-produced protein to a growing global population in, perhaps, fewer years than we may imagine.

At present, fresh duckweeds are used to feed some varieties of fish in fish farms and dried duckweeds are used in animal feedstocks, although the high water content in duckweeds makes them expensive to dehydrate in countries where the plants must be dried artificially. And fresh duckweeds are eaten, as highly nutritious vegetables, in some countries in the Far East, mainly by economically-disadvantaged persons – today’s politically-correct terminology for people who were previously known as ‘peasants’. Unfortunately, duckweeds’ enthusiasm for growth and for reproduction makes them gross feeders which ingest virtually any chemicals they find in their watery habitats, meaning that duckweeds farmed for widespread human consumption would need to be grown under carefully-controlled, sanitary conditions, subject to regulation and inspection. But none of these restrictions present insurmountable problems; if the need is great enough, successful strategies will be found.

Gardeners whose ponds are infested with duckweeds … and the plants are seen as a real problem by most pond-owners in this country … may not be impressed to learn that these presently unwanted plants may be seen as a valuable food source in the not-too-distant future. But perhaps it is too soon to suggest regarding the garden pond as part of the kitchen garden!