Q. – I Am Soon Going To Increase the Size of My Pond
When I increase the size of my pond soon, up until now I have had pond plants in it, what to do? I know Koi purists would not advocate pond plants in a Koi pond but the Koi in my pond seem to enjoy the cover they offer and I don’t want to alter their environment too much so as not to frighten them. What is your view on pond plants and is there anything else I can add to my pond to provide my Koi with cover?
Answer …
I’m afraid I’m a bit of a Heathen like you too. Where there is water I like to see pond plants and I am sure the fish do as well. Unfortunately, Koi seem to appreciate them more for their nutritional or plaything value rather than their cover potential appeal. I have found on most occasions that pond plants need their own segregated area in which to flourish and if it is pool cover you are after then there are a few pond plants that will fit the bill of providing pool cover whilst their roots are tucked away safely.
Most lilies will fit the bill if you can provide the depth of water, but if the plants are in a shallow trough-like marginal area you might try Nymphoides peltata often known as Villarsia or water fringe lily. This is quite vigorous but easy to keep in check, it has small lily-like pads with a small funnel-shaped yellow flower, quickly covering a fairly large area whilst other pond plants are finding their feet. If you have 10cm of water then the water hawthorn, Aponogeton distachyos is worth a try. This is a deepwater plant that is quite happy in moderate shallows.
For proper marginal style plants, the Bogbean, Menyanthes trifoliate can also work in the shallow and provide a fair amount of safe and controllable cover over a pool. The pickerel weed, Pontedaria cordata, fits this bill too and is quite a bit taller and flowering blue in late summer. Mimulus guttatus and M. luteus, Sagittaria, Sauraurus, and Houttynia are also safe to try, although avoid the latter in a competitive trough situation.
Information On Pond Plants In General
THE GOOD AND THE BAD…
Oxygen dissolves from oxygenators into the water more effectively than by mechanical turbulence because it is in fact very difficult to dissolve oxygen into water. It needs to be done slowly and over a large surface area.
All pond plants that live happily underwater can be described as oxygenators. Out of these plants, there are bound to be one or two that are the best for the job we need them to do. There is no doubt they are specialized. Roots tend to be merely for anchorage and the nutrition absorption and gaseous exchange occurs on the surface of the plant directly to each cell.
The plant therefore has very thin walls and thin leaves to allow this to happen. This makes the pond plants floppy, which in fact becomes an advantage underwater as they are able to bend with the eddies in the water. Two pond plants that have made this a real specialty and thrive in streams are Water Crowfoot, the true Water Buttercup (Ranunculus aquatalis), and Curly Pond Weed (Potamageton crispus).
The Best By Far For the Pool or Pond
is also often referred to as “Curly Pond Weed” but is most rightly called aragasiphon major or more commonly Elodea crispa ( South African native). This has a tendency to take advantage of highly nutritious pond environments by filling them up, but at least you don’t get algae. It is easy to control by just snapping handfuls of it near to the source of growth. Fish love to spawn on or near it and it is dense enough to provide protection for the eggs and the subsequent fry.
For conservation and wildlife gardeners it is not entirely kosher since it is not a native plant. Indigenous plants in the USA are:
Butomus umbellatus – flowering rush
Cabomba caroliniana – fanwort
Egeria densa – Brazilian elodea
Epilobium hirsutum – hairy willow herb
Glossostigma diandrum – mud mat
Glyceria maxima – reed sweetgrass
Hydrilla verticillata – hydrilla
Hydrocharis morsus ranae – European frog-bit
Lagarosiphon major – African elodea
Ludwigia hexapetala – water primrose
Lysimachia vulgaris – garden loosestrife
Murdannia keisak – marsh dew flower, Asian spiderwort
Myriophyllum aquaticum – parrotfeather
Myriophyllum spicatum – Eurasian watermilfoil
Najas minor – slender-leaved naiad, brittle naiad
Nymphoides peltata – yellow floating heart
Sagittaria graminea – grass-leaved arrowhead
Spartina alterniflora – smooth cordgrass
Spartina anglica – common cordgrass
Spartina densiflora – dense-flowered cordgrass
Spartina patens – salt meadow cordgrass
Trapa natans – water chestnut, bull nut
Utricularia inflata – swollen bladderwort
These plants above are recommended by the Washington State Department of Ecology
For indigenous plants to the UK: Water Starwort, (Callatriche stagnalis), rampant but easy to crop to its source. Water Milfoil, (Myriophyllum spicatum), loves limey pools with high pH and does well where Elodea crispa fails. You get the bonus of little flowers in some years that look magical in certain lights. Hornwort, (Ceratophyllum demersum), is often confused with
Milfoil out of the water, but it feels much stiffer and has a more forked growth habit. This is one that does not mind a bit of shade on the pool. Water Violet (Hottonia palustris), a class act for the connoisseur; it has pretty little pink flowers above the water’s surface in May and June.
THE WORST…
The worst thing about some oxygenating plants is not that they are useless at their job, but that they are very often confused with the best, or they are sold as marginal plants and quickly run rampant, particularly in clay-lined ponds, and then are impossible to eradicate.
- Canadian pondweed (Elodea Canadensis), also known as Anacharis, can easily be confused with the weaker growth of Laragasiphon major. It will even grow on the surface of marginal plant baskets.
- Parrots Feather, (Myriophyllum proserpinacoides) This is causing some consternation in the States in areas where the frosts are not stiff enough to knock it back. Sold as a marginal here, it has submerged and surface foliage and will leap from one side of a small to another in less than a season.
- Mares tail (Hippurus vulgaris), often sold as a marginal. This plant has been around since time began, so it is not without a trick or two up its stem!
