One of the smallest flowering plants: each individual is a flat frond a few millimetres across with a single root
Common duckweed.
Nature · Ferns, grasses & other plants
Common duckweed
Annual to perennial · fronds 1.5–4 mm
Lemna minor — Araceae (Lemnoideae)
Common duckweed is among the smallest and simplest of all flowering plants: each individual is a flat green frond a few millimetres across, with a single hair-like root and no distinction between stem and leaf. It almost never bothers to flower, budding off daughter fronds instead, and can double its population in a couple of days, so a still pond can be sheeted over in a fortnight. Its relatives include the world's smallest flowering plant, Wolffia.
How to spot them
- ▸A carpet of tiny bright-green oval fronds lying flat on still water, each 1.5–4 mm long
- ▸One single thread-like root hanging beneath each frond
- ▸Fronds joined in twos and threes where daughters have budded off, then breaking free
- ▸Three faint veins in each frond; no lobes, no stalk, no leaf and stem distinction
- ▸Still, nutrient-rich water — pond, ditch, canal backwater and water butt, never fast current
How to know it
It scarcely ever flowers, reproducing instead by budding daughter fronds from a pocket in the parent
Common duckweed; the flowers, when they do appear, are microscopic and lack petals.
Molecular work moved this family out of its own order and into the arum family, alongside the cuckoo pint
Common duckweed — Lemnoideae are now a subfamily of Araceae.
No weedkiller is approved for home gardeners against it, so raking, netting or a floating boom is the only control
Common duckweed, according to RHS advice.
A single population can double in a couple of days, sheeting a still pond over within weeks
Common duckweed — among the fastest-growing plants known.
Its even smaller relative in the genus Wolffia is the smallest flowering plant in the world
Common duckweed's family; Wolffia fronds are under a millimetre.
Quick-fire facts
- •Each plant is a single flat frond, 1.5–4 mm long, with three faint veins and one root
- •Now classified in the arum family, Araceae, as part of the subfamily Lemnoideae; it was formerly given its own family, Lemnaceae
- •Reproduces almost entirely by vegetative budding; flowers are minute and very rarely seen
- •Among the fastest-growing of all flowering plants, capable of doubling in a few days
- •Food for ducks, moorhens, coots and swans, which give it its name
- •RHS notes that no chemical control is approved for gardeners; raking, netting or a floating boom is used instead
- •A thick blanket cuts light and oxygen to the water beneath, which can kill fish and submerged plants
- •Studied as a high-protein crop and for treating waste water, because it strips nitrogen and phosphate so fast
- •The genus Wolffia, in the same subfamily, contains the world's smallest flowering plants
Drill it — 6 cards
1 / 6new card
Sources
- Royal Horticultural Society — Duckweed
- Royal Horticultural Society — Lemna minor — common duckweed