It’s
Easy to Plant Aquatic Plants, “Isn’t it?”
Reading my colleague Bernice Brewster’s article titled Plants and Fisheries (Sept 03) reminded me of a recent habitat enhancement project involving a private estate ornamental lake of about 2acres. The lake was built some 14 years ago then stocked with very large trout. Unfortunately the lake became very warm during spring and summer which led to the death of all the trout due to low dissolved oxygen! A year or two later, some small mirror carp were introduced, and that was it. The carp, better equipped for low oxygen levels, were left to their own devices and the years went by. During this time the lakes owner developed a fancy for ornamental water fowl. Several pairs of different and unusual species were purchased including a pair of black swans. Relatives and friends decided it would be a novel idea to purchase pairs of exotic water fowl for birthday and Christmas gifts. The collection began to grow and as they were all pinioned to stop them flying away, a small protected reserve connected to the lake, was built to keep foxes out. |
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| Most
of the water birds are vegetarian so consequently whatever aquatic
plant life that was established became extinct and the birds then
happily moved onto the surrounding terrestrial plants (much to the
consternation of the Head Gardener!). A very large percentage of the
birds waste is released into the lakes water causing it to become
eutrophic. These nutrients, along with leaf fall each year and the carp stirring up bottom sediments, created a constant green water scenario with no aquatic plants other than algae to use up those excess nutrients. Last year the owners decided to give the ornamental lake a face-lift, just plant it up with aquatic plants and provide some protection from the veggie waterfowl was the general idea, it would look great and what could be simpler? |
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| It turns out
that the lake had no marginal planting substrate at all; its margin
edge is sheer sided ranging from 2-3ft deep (11ft middle) and it has
a butyl liner which would cost a small fortune to replace if damaged.
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| Hydroponics was the answer. With the lake water rich in nutrients the plants don’t necessarily need a planting substrate as they can extract their requirements directly. With this thought in mind the problem became more about how to secure the plants to the margin without putting stakes through the butyl liner. | |||||||||||
This was solved with the use of pre-planted fibre Coir rolls that could be fixed to the bankside. The poles and pegs were supplied from locally worked sustainable hazel coppice. As you can imagine, it certainly looked different initially but as the aquatic plants (Carex, Iris, Juncus & Phalaris) and the bankside grasses began to grow their leaves and stems grew through the wire and slowly began to camouflage the mesh cage systems. |
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| The lake looked
fantastic this spring and summer with the plants providing a wonderful
splash of colour, particularly the flowering Iris. The lake has been
transformed from a drab looking pond into a beautiful ornamental lake.
The new habitat has provided food and shelter for a multitude of new
invertebrate life and in turn they have provided food for the young
carp fry from the hugely successful spawning this year, the margins
were full of small mirrors this August and they will also have some
cormorant protection this winter amongst the submerged plant cage
systems. The owners are utterly delighted with the new look and the
species diversity and habitat has benefited greatly as well. And the moral to this story is? Plants and fish go hand in hand; it’s the management of both that can sometimes get tricky but that’s a different story. |
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