Floating Water Plants - Floating Carefree

There cannot be another group of plants that need less help from you during the growing season, but when it comes to the colder months, some of them will need your tender loving care, whilstA barrow full of duckweed, for the second time that year - and look at the size of the pond! others will vanish as if by magic only to return again, just as mysteriously.
I don’t know why they have this appeal to me, but some of my favourite water plants are floaters. They float carefree, drifting around on the surface of the pool with no attachments to terra firma, their roots hang below them taking their nutrition directly from the water. Many of them are gross feeders and use up excess nutrients in the water; the same nutrients that algae would otherwise take advantage of. In this way they help to inhibit the algal proliferation, but also by shading the lower realms of the pool, they cut down the sunlight that algae also need for their growth.
This has a downside, which results in some species of floating plants receiving exceedingly bad press. Many of us know from bitter personal experience that if you are a ‘gross feeder’ then you grow. In the world of floating plants this also means propagation, proliferation and multiplication. Take the tiny Duckweeds, or LEMNA. There are 12 species, of which four are British, which between them seem to be able to cover any surface of unfrozen water in any part of the globe. Once you have one of them, you have got it for life, unless you keep ducks, which will gorge on it to oblivion. Some fish will love it too, making a highly nutritious supplement to their diet. Lemna minor is the most common, with small ovate fronds or leaves, light green above and deep green underneath with one rootlet per frond.
Lemna trisulca (Ivy-leaved Duckweed) is perhaps the prettiest, hiding itself submerged until the height of summer when it comes up to display light green, transparent fronds. The fronds divide with the new ones grow at right angles giving the ‘Ivy-leaf’ effect.
Fairy Moss, Azolla caroliniana
The Fairy Mosses or AZOLLA often get lumped with the Duckweeds and since we have been experiencing milder winters, their ability to cover a pool with a dainty mossy carpet that turns red in theLemna minor - duckweed Autumn has failed to endear it to many pool owners, since any amount of netting seems a vain attempt to keep it in check. Azolla caroliniana is the most common. It is a native of the Southern United States through to South America. Other species are found in Africa and Tropical Asia and Australia. Colonies of the blue-green alga Anabaena thrive with it symbiotically. It lives in the cavities of the underside of the leaves.
If you think they are bad then you haven’t seen the WOLFFIA – the Rootless Duckweeds. The worst is Wolffia arrhiza of which part of its infamy is linked to the fact that it is the smallest known flowering plant. Being no larger than a pinhead, it cannot be netted effectively and just persists as an ugly green scum on the surface of the water. Although most common in warmer climes, it has made forays into our climate zone and has settled in for keeps.
There is a close relative of the Duckweeds that is ironically the least hardy of all the floating plants commonly available to us in this country. That is the Water Lettuce, Pistia stratiotes. Looking like a caricature of a young Webbs lettuce made of turquoise felt, it looks most unlike Duckweed. It is believed that the LEMNA group of floaters are an evolution from the Water Lettuce in its juvenile form. In the West Indies it was believed to produce malaria, although this was a belief construed from the association with the same water in which the malaria carrying mosquito larvae emerged as adults. Of course the flowers when they come may attract the adults, which are like tiny miniature Arum spathes.
As well as being very tender, it can be a very temperamental plant if left to its own devices. Another evolutionary factor may give a clue as to how it may be successfully grown. Assuming that its roots were originally designed for working in soil, it seems to thrive with them trailing down to just touch the soil of the pool bottom; therefore a position in the shallows seems to be its favoured habitat.
Salvinia natans is a member of a group of plants that is increasingly used in outdoor pools having been familiar to owners of cold water aquaria for years. This looks like a cross between a large Duckweed and a babySalvia natans struggling through the early part of the winter. It may just survive modern winters. Water Lettuce. It has thick, double ranked leaved standing upright on the water whilst the bright green young ones trail behind on the surface. They are very hairy, which makes them look even thicker. In Africa species of Salvinia are a serious pest, blanketing waterways and causing blockages with decaying plant debris. They are annuals that even though they create small fruiting bodies called sporocarps that sink to the bottom in autumn rising to the surface in the spring, the British climate still manages to catch them unawares. An early rescue bid, by floating them in a bowl of muddy water in shaded green house in very late summer may be effective.

The Water Hyacinth: OPPORTUNISTIC SUNLOVER

Another plant with a smutty reputation, abhorred in America and South Africa but adored in this country is the Water Hyacinth. In the swamps of Florida and the dams around Johannesburg the Water Hyacinth, Eichornia Crassipes, spreads alarmingly /(TRANNIE 7 or 8 or 9)/. Its long fibrous roots that make the perfect natural spawning mat for fish in a pool, become wrapped up in boat propeller blades in the wild, making waterways and vast areas of Lakeland water practically impenetrable.
Despite that, there is something appealing about its grotesquely inflated leaf petioles that look like vegetable water-wings, laid out in a rosette to support a flower spike of violet flowers. It needs a long hot summer in Britain to flower successfully and then all too briefly, but to see it is akin to spotting the temporal visit of a rare Camberwell Beauty amongst the butterflies. When winter comes, the first frosts turn it to a black mush, which is the saving grace for the waterways of this country.

Planting up a water hyacinth so that it will perhaps 'over-winter' in the cool greenhouse
Both the Water Hyacinth (Eichornia crassipes) and the Water Lettuce (Pistia stratiotes) can wintered indoors away from frost. Some growers have suggested resting them in subdued light, but many suggest that they survive best if they are potted into well-drained potting compost and then kept ‘just moist’. The time to float them again is late May.
The Water Chestnut (Trapa natans - other species are not generally available) is an annual and can be grown from the seed that forms after a long hot summer. They no bigger than the kernel of a small chestnut and can be just started off the following spring by floating them in a pan of tepid water in a warm greenhouse. The secret for keeping the seed viable is not to let it dry out.

The Water Chestnut is a plant much enjoyed by lovers of cuisine in China, India, Japan and Europe. These are the TRAPA which are annuals with creeping floating stems and triangular mottled dentate foliage. The stems to the leaves are swollen and can be rosy pink in colour. Trapa natans /(TRANNIE to come)/ used to be a native of Europe, is now extinct, but it is the species commonly available to the water gardener. T. bicornis and T. bispinosa are the species are the most commonly eaten.

Frogbit is one of those endearing little plants that just manages to get on with things quite happily all by itself. A sort of a ‘Miss Tiggywinkle’ of the plant world,
Hydrocharis Morsus-ranae (means “graceful in water, bitten by a frog”) has little floating kidney-shaped leaves about 25mm across. As winter comes, little buds form at the end of stems that drop off and sink to the bottom whilst the original form of the plant decays away. When spring arrives the buds bob up to the surface to form new little plants. Unfortunately it is very much relished by water snails, which in a small pool environment can spell its demise.
Stratiotes aloides - Water Soldier
Another ‘bob-a-job’ is my favourite, Stratiotes aliodes, the Water Soldier /(TRANNIE 10 or 11)/. It looks like someone has thrown a Pineapple top into the water, and that is what it feels like at first investigation, although the leaves are much more fragile. The narrow serrated leaves form a rosette from the centre of which emerges a little white flower. It was common on the Norfolk Broads but is becoming increasingly rare in the wild. It loves limey water, floating below the surface for much of the time but emerging in the warmth of July to flower. Male and female flowers are borne on different plants and apparently only the female normally occurs in this country.

HIGHLY SPECIALISED and REALLY WEIRD - THE BLADDERWORT

As you can probably surmise, the floating plant brigade are highly specialised and highly evolved. They have adapted to take especial advantage of very specific conditions. If those conditions areBladderwort - Utricularia vulgaris - it is an insectivorous floating plant.: It traps tiny little water fleas in the little bladders that dangle just under the surface of the water. just right then you may find that there is a bit of a ‘take over bid’.
One plant that will never be a real threat, not to us anyway, which some people put in the class of oxygenator and floater, is the Bladderwort, Utricularia vulgaris. This plant, which is another one that resorts to forming buds to ‘over-winter’, is native to this country and Europe. It has a multi-faceted appeal, since it floats submerged, whilst supporting rich yellow flowers well above the water surface. The flowers are unusual in themselves, looking like a cross between an orchid and a member of the Broom family, but it is what goes on down below that is really weird. Here it is a carnivorous plant. The little bladders, suspended on thin underwater leaves might that seem to be the float-supports for the plant, do in fact double as little traps for small crustaceans and water insects. Little bristles at the mouth of each bladder, when touched by a passing insect, trigger a flap that opens inward. Being full of air, water rushes inward, dragging the unsuspecting clumsy insect to be digested within the bladder. Stranger things don’t even happen at the movies.