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Crassula helmsii / New Zealand Pygmyweed


 
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cormaggio
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PostPosted: Tue Jul 01, 2014 12:58 pm    Post subject: Crassula helmsii / New Zealand Pygmyweed Reply with quote

I installed a pond in my parents' house a number of years ago - it's a focal point of the garden, and has brought them much joy.

However, one of the oxygenators in the pond I've only recently identified as Crassula helmsii (New Zealand Pygmyweed) - which, I discovered at the same time, is on several Irish/UK/European databases of invasive species, and is one of the very few aquatic plants banned from sale in the UK. The plant is rampant in the pond, and choking the lilies, etc - though we have been periodically thinning it out to give the lilies a chance - and it is also growing in small areas around the verges of the pond.

What I'm asking is: what to do about this? Does anyone have experience of eradicating or controlling this plant from a small pond (roughly 10' x 6')? Is it realistic to keep this under control, or does it need to be completely removed? I have a few more specific questions below, based on what I've read around the web (e.g. [1], [2]).

I'm considering, as a fairly drastic solution, starting the entire pond again. My questions here are: could I re-use the butyl rubber lining, or is this contaminated with the plant's spores, etc? (I've noticed that there are some green spots on the lining, and the same spots on the C. hemsii itself - see pics [3] and [4] - are these spots part of the C. hemsii , or something else entirely?) And a related question: could I re-plant any of the lilies or other oxygenators from the current pond in the new pond, taking care to clear off any fragments of the C. hemsii - or would this inevitably re-introduce the C. hemsii (with fragments that aren't visible)?

An alternative to starting again would be to try to remove it entirely from the pond. There is plenty of the plant emerging from the pond [5], which could be treated chemically. (I don't want to introduce any chemicals to the water, as I don't want to kill other plants if I can help it - and also, birds and cats drink water from the pond.) Is chemically treating the emergent parts of the plant a viable solution on its own, or would it need another approach in tandem?

Thanks for your attention - any help would be much appreciated.

Cormac


[1] http://www.essexbiodiversity.org.uk/invasive-species/invasive-species-aquaticplants

[2] http://www.europe-aliens.org/pdf/Crassula_helmsii.pdf

[3] https://www.flickr.com/photos/cormaggio/14363572319/in/photostream/

[4] https://www.flickr.com/photos/cormaggio/14549265422/in/photostream/

[5] https://www.flickr.com/photos/cormaggio/14548633014/in/photostream/
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cormaggio
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PostPosted: Thu Jul 10, 2014 10:19 am    Post subject: Reply with quote

Any ideas (on any question)?
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tagwex
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PostPosted: Thu Jul 10, 2014 12:26 pm    Post subject: Reply with quote

Well for me anyway, and I would say for a lot of the others, this is a bit specialised and rare in that very few have a pond and even fewer have the weed you are asking about. You may have to go further in your quest. Frustrating I know and this response doesn't help you at all but it does give you an idea of why there are no responses.
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cooler
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PostPosted: Thu Jul 10, 2014 1:01 pm    Post subject: Reply with quote

Trying to separate the fragments of Pygmyweed from the other plants will be the devils own job and you just know you will miss loads. There is probably loads of fragment floating around in the water as it is.
You will never clear it this way, just control it.

So that's the first option. Lift everything, pick out the weed, suck out the pond water, running it through a fine mesh, then burn what was caught in the mesh and what you picked out. refill the pond with water and replace the worthy plants.

The other option is to suck out the pond water, running it through a fine mesh, then burn what was caught in the mesh. All the the plantlife remaining at the bottom and around the pool should be spray with roundup Shocked . When every thing is dead (3 or 4 weeks) you can burn the debris. Then fill and rinse, fill and rinse, fill and rinse the pool. Then begins the replanting.

The only options as I see it.

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Good guy
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PostPosted: Thu Jul 10, 2014 11:29 pm    Post subject: Reply with quote

What about consulting a professional nursery expert with a background in aquatic plants and their care? There are some UK companies that specialise in aquatics. Could be there are scientists at the Botanical Gardens who might advise, or maybe at Kew. What about a question to the BBC Gardener's World website?
I bought plants from Waterside Nursery in Leicestershire and got good advice from them: info@watersideplants.co.uk
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Greengage
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PostPosted: Fri Jul 11, 2014 5:36 pm    Post subject: Reply with quote

I dont know the answer to your question but thought this might interest you.
here is a short film by george Pilkington he produces a number of Nature films which can be seen on the BWARS website thought some of you might be interested in watching. Another site i patrol which compliments my interests with biodiversity ireland. ( Opps nearly forgot to post the link)
http://www.youtube.com/watch?v=vn1G0MBxthw
After posting this found the link so I will repost it there
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cormaggio
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PostPosted: Sat Jul 12, 2014 7:30 am    Post subject: Reply with quote

Thanks very much for all the replies - particularly since, as tagwex says, this is a pretty specialist question. Much appreciated. Cooler, those options are along the lines I'm thinking - but can I check, what do you mean by "fill and rinse, fill and rinse, fill and rinse the pool"? Is this to do with reusing the butyl rubber, and to get any unwanted stuff off? Do you have to fill it a few times and pump out the water each time? I'll also be doing what Good guy suggests and ask an aquatic specialist and biodiversity experts (who wrote the pages I linked to). And that's a wonderful pond, Greengage - the kind of thing I aspired to when making mine Smile
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tagwex
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PostPosted: Sat Jul 12, 2014 9:40 am    Post subject: Reply with quote

Or maybe a good blasting with a power washer...........
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This boy can really sing http://youtu.be/Dgv78D2duBE
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