Four years ago, when our pond was new, it had a small solar powered pump. The role of the pump was to keep the pond oxygenated for animal life such as tadpoles, daphnia, water boatmen, dragonfly and damselfly larvae and so forth. The pump though only worked intermittently, and after a few months we gave up on it. From then on, we left it to plants to oxygenate the pond.
Oxygen is formed as a by-product of photosynthesis, which, with chlorophyll as a catalyst, can be represented by:
Carbon dioxide + Sunlight + Water → Glucose + Oxygen
The glucose provides energy for plant growth, flowering and seed formation. Another story, another time. It’s the oxygen that concerns us now. Only certain plants get the oxygen into pond water (or aquaria or streams): underwater plants. Plants with leaves on the surface, like water lilies, give off oxygen but it goes into the air. With flags (pond irises) only that part of the stem and leaf that is underwater oxygenates the pond.
Filamentous algae is an oxygenator, but too readily takes over a pond with its green fibrous strands. We allow a little but pull it out in handfuls when it becomes prolific. The algae came uninvited, just a few cells stowing away on other plants. Two plants we did invite are elodea (Canadian pond weed) and hornwort, both oxygenators. It is interesting what has happened to them over the four years.
The elodea (Elodea canadensis) has flourished. It is everywhere in the pond, very easy to spot. Elodea has many small leaves up its stems in whorls of three, its roots are in the pond depths. Elodea readily forms more roots along its stem. So readily, that elodea in the wild can be a pest, blocking waterways and taking over lakes. Not our problem as it is easily controllable in a small pond. Elodea has the tiniest of white flowers on long thin stalks which rest languidly on the surface.
Hornwort (Ceratophyllum demersum) has been less successful. You have to look carefully to find the patches of it. Hornwort floats freely, having no roots, like many seaweeds. The leaves are thread-like, which give the stems a soft brush-like end.
Of the two, Elodea has taken over much of the pond, not allowing much space for the hornwort. Such is nature; our pond is as competitive as the savannah or the stock exchange. If we removed such plants, our pond would have little animal life. Oxygenators are vital for a thriving pond.
Earlier this week, there were strong winds. In the Cereal Project, the sweetcorn and the dwarf maize have a mass of wide ribbon-like leaves which in the wind acted as a sail. The force toppled the two plants, the soil in the cardboard boxes having insufficient weight to withstand its power. The fall, off their stands, was around 18 inches. We came into the garden to find them lying flat on the ground in their boxes. Fortunately there was little damage, though they had knocked over the barley and the rice in their wake. The barley was somewhat bruised, but the rice was unharmed. We put the plants back, did some tying, and screwed side supports onto the sleeper stands to make the maize more secure. Hopefully, they’ll stay put in the next strong wind.
A juvenile robin is a regular garden visitor. It has a mottled breast unlike the adult robin and is very tame. Perhaps too tame, as there are a couple of cats who prowl the garden as well as our resident fox family. I hope the young bird learns quickly, or it won’t live long.