Small Pondweed (that’s it’s name – not just a description of its stature!)

Small Pondweed (Potamogeton berchtoldii) seems to be growing well in the New Pond. This native plant - which occurs the length and breadth of Britain, should be within everyone's reach to grow in a clean garden pond

Most garden ponds have a pretty poor and unnatural selection of submerged plants.

This is down to a combination of factors:

– Native water plants can be quite difficult to get started;  clean, unpolluted, water is more or less a pre-requisite, and even then they don’t always take.

– Garden centres don’t supply any native submerged water plants except (if you’re lucky) Rigid Hornwort and Spiked Water-milfoil. Worse, many still provide what they call Elodea crispa – more correctly known as the non-native Curly Waterweed (Lagarosiphon major) – which originates from Southern Africa. This plant has escaped into the countryside where it is probably competing with native plants and, at least in some places, adding yet another threat to our native freshwater wildlife.

– The best source of native submerged water plants – the wild – is often apparently ‘out of bounds’ with many organisations repeating the misleading idea that it is generally illegal to collect any wild plants (it isn’t – except for some specially protected species it is legal, with landowners permission, outside of protected areas). It is understandable why conservation organisations have opted to promote this simple message – (see here for example) – but this message certainly hasn’t helped reduce the spread of non-native plants in freshwater. It is worth remembering that 6 out of 10 garden ponds have non-native species whereas only 1 in 10 in the countryside do, so the safest place to get native submerged plants is the ‘wild’ rather than other garden ponds.

All in all, in my experience, most garden ponds are a bit of a disaster area for plants. But it doesn’t need to be like this.

So in my New Pond – to which we are adding plants – we’re pleased to see the signs of native aquatics getting going. Stoneworts from the local gravel pits are beginning to take; the plant above – Small Pondweed (Potamogeton berchtoldii) – looks to be growing well, we have some little bits of Water-violet (from another local source – a pond we created to strengthen the population of this and other  uncommon water plants in another part of Oxfordshire) and we are hopeful that Blunt-leaved Pondweed (Potamogeton obtusifolius, from Pinkhill Meadow near Farmoor) and Least Pondweed (Potmogeton pusillus) from a village pond in Appleton about 5 miles away will also take.

Already with three aquatic plants growing successfully, and perhaps as many as five in due course, this pond has more submerged plant species than the average countryside pond – shockingly this is just 1 species of submerged plant (read the report here) – and about the same number as the average for top quality unpolluted sites.

The question now is whether garden ponds could actually help spread our threatened native water plants or are merely places where plants collected in the wild come to die.

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10 Responses to “Small Pondweed (that’s it’s name – not just a description of its stature!)”

  1. Tristan Hatton-Ellis Says:

    Hi Jeremy,

    Interesting that you’ve had this one grow well. I’ve not tried this one but the similar least pondweed (Potamogeton pusillus) is a bit scrawny for me – I think it likes more nutrients! P. pusillus, obtusifolius and berchtoldii are ‘annuals’ – each year the plant dies back but releases a lot of baby plantlets called turions, which float about and come up the next year. They may need some disturbance to persist.

    My favourite garden pondweed is Various-leaved pondweed Potamogeton gramineus, which produces attractive olive-green transparent underwater leaves and a smattering of floating leaves later on. It spreads by runners but it never forms too dense a canopy. Unfortunately it’s rather uncommon in the wild. This and most other native pondweeds need to be established from pieces of rhizome like you would a perennial, not the ‘Canadian pondweed’ method of just throwing in a piece of leafy material. They take a season or two to get going.

    Tristan

  2. Jeremy Biggs Says:

    Hi Tristan

    Would you like to write some more about the plants you’ve managed to grow?

    All the stuff you sent me ages ago which I still haven’t got round to using would be good to talk about as this whole area of getting decent native plants to grow is important.

    Jeremy

  3. pondolive Says:

    Hi Jeremy,

    I will. In fact, I’ve been inspired! See pondolive.wordpress.com to see what I mean. It’s pretty embryonic at the moment but I’m working on it.

    Tristan

  4. Perry Says:

    Hi Jeremy

    Hope my pictures have come through by now and as you can see I’ve changed my mind AGAIN! Hope you can give me some ideas, thanks, the blog is great.

    Perry

  5. linda Says:

    Very interested in this article. Have just installed a pond in my garden and have some water iris and oxygenating plants growing. Thought they might keep the water clean. I am keen to introduce other species. Garden centre plants are very expensive and besides next year I would like to attract some wildlife. Have no idea what pondweed is or where I can get it? How can I recognise it? Regards linda

  6. Jeremy Biggs Says:

    Hi Linda

    You’re right that finding these non-standard plants is more difficult.

    If you can give me an idea of where you are in the country I’ll see if I can make some helpful suggestions.

    Jeremy

  7. Jon Britton Says:

    Hi there,

    We created a small pond in my garden last year. Because we weren’t too knowledgeable we bought a pond plant pack which happened to include Lagarosiphon major. We didn’t know this was an invasive species until now and now we’re considering what to do with it. It’s got pretty bushy this year and fills a lot of our pond.

    Should I just remove it? What other plants would be a suitable alternative if I did?

    Any help would be appreciated.

    Cheers,

    Jon

    • Jeremy Biggs Says:

      Hi Jon – I wouldn’t be too hasty to get rid of the Lagarosiphon because there will be creatures living in it and if you do you might not be able to get anything else to grow in it’s place. It’s tolerant of less than perfect water quality and if you’ve any water quality issues it might not be such a bad bet.

      However, native aquatics that would be alternatives include Spiked Water-milfoil, one of the starworts or Rigid Hornwort if water is a bit nutrienty. If you’ve got low nutrient rain water, you could have a go with more sensitive species such as some of the pondweeds I’ve been mentioning though the difficulty with these is you might need to source these yourself.

      If you’re interested we can give note detailed advice to Pond Conservation members (if you are a member already let me know!).

      Hope that helps.

      Jeremy

      • pondolive Says:

        Jeremy and Jon – Lagarosiphon is an interesting species because it actually causes poor water quality that favours its growth! The way in which it photosynthesises causes pH to rise to high levels – sometimes above 10 – which gives it a competitive advantage over other plants. pH levels this high would be harmful to many pond animals too, I expect. See http://www.nerc-wallingford.ac.uk/research/capm/information%20sheets.htm

        So my advice is to chuck it on the compost heap. This would also reduce the risk of it escaping into the countryside.

  8. pondolive Says:

    Here is my post on Small Pondweed. It’s interesting how it has responded to the recent drought.

    http://pondolive.wordpress.com/2010/07/13/small-or-smaller-pondweed/

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