Garden pond plants For koi ponds, cover and shade

I am soon going to increase the size of my pond and up until now I have had plants in it. I know Koi purists would not advocate 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 ...  Im afraid Im a bit of a Heathen like you too. Where there is water I like to see plants and Im 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 plants need their own segregated area in which to flourish and if it is pool cover you are after then there are a few 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 a 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 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 Bog bean, Menyanthes trifoliate can also work in the shallow and provide a fair amount of safe and controllable cover over a pool. The pickeral weed, Pontedaria cordata, fits this bill too and is quite 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 plants that live happily under water 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 specialised. 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 plants floppy, which in fact becomes an advantage under water as they are able to bend with the eddies in the water. Two plants that have made this a real speciality and thrive in streams are Water Crowfoot, the true Water Buttercup (Ranunculus aquatalis) and Curly Pond Weed (Potamageton crispus).

Where to buy pond plants

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 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. 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 looks magical in certain lights. Hornwort, (Ceratophyllum demersum), this is often confused with
Milfoil out of the water, but it feels much stiffer and has more forked growth habit. This is one that does not mind a bit of shade on the pool.

Water Violet (Hottonia palustris), class act for the connoisseur; it has pretty little pink flowers above the water surface in May and June.

Where to buy pond plants

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!

Where to buy pond plants