hornwort vs Can. pondweed

hi folks,

yes its me YET AGAIN.
youre fully entitled to groan but hey, you cant knock my enthusiasm.

this time to ask;

is our native HORNWORT (ceratophyllum demersum) as good an oxygenator as CANADIAN PONDWEED (elodea cadensis)?


got a bit of both flora at the mo but considering going "alien-free" in the autumn.
is it a good idea?


opinions/advice welcome.

thanks, ben

Things were going well in my pond until duckweed arrived. I now can't get rid of it and it gets into starwort and pondweed as well as covering the surface. I tried to establish frogbit without success but I got another lot late last autumn and chucked it in and lo and behold it is all over the pond - tangled up in the above plants! I am very tempted to put in another pond and have the frogbit and no potted plants at all. If the soil of them is enriching the water and feeding the duckweed then I am better off without them.
I have got plenty of wildlife in the pond but if I want to sit and watch it I have to brush the surface to clear a bit of free water and then the taddies and newts move into view.

Yep the duckweed forms a dense mat and even scooping as much out as poss (not in taddie season) is no good as within days it's back as bad as ever. I did used to have a good coverage of pondweed (Potamogetonaceae family) but that struggles with the duckweed. 

i bet that was a chore lal. i applaud your hardwork and dedication.

here's another approach if you havent tried/fancy it;

the chap i referred to DOES keep one area (approx 2ft sq) pretty free of duckweed though.

by employing a barrier strategy in open water.

hes got a wooden frame (like a picture frame but with thicker framework and no glass) floating freely in the pond.
inevitably its not completely devoid of Lemna inside but its not that far off. it does a really good job of offering a "viewing hatch" to whats below and the clear water it enframes is certainly in amazingly sharp contrast to the density of the duckweed coating that lies beyond its confines. its the only place where you can see below the surface and for a garden, this is a large pond.

i see scores tadpoles and helvs (inc egg-layers) in it every day when i visit. it certainly looks like the animals are exploiting its light-offering properties by coming up within it when in need of air although obviously its hard to tell if theyre surfacing just as much elsewhere owing to the mat's obscuring "qualities".

ALWAYS loads of taddies/newts in it anyway. (along with great clouds of Daphnia- great watching the newts snap at these!)

however,

the sight of the device floating there detracts from the overall aesthetic "natural" beauty of the pool somewhat though. a small price to pay perhaps. depending how "pond proud" you are i suppose.

just to move on a little...

if left unchecked would duckweed become be a major disaster for amphibian colonies?


ive never bothered looking for them much at sites where Lemna is particularily bad. at the very sight of duckweed i often lose the will to bother and just go elsewhere!

ben