Azolla in Tiny City Pond

[motnworb]

We have a tiny wildlife pond in our back garden with common duckweed and I've just identified Azolla.

Should I try and remove the Azolla? Will it be beneficial to wildlife to get rid of it as a non-native?

We've stocked the pond only with native plants, we have common frog tadpoles and various inverts (snails/ mayfly/ damselfly/ etc), we built it solely for wildlife.

I don't mind the duckweed, the other plants are growing fine, but we did have a problem in the spring with blanketweed (very fine string algae) and I have heard that Azolla will keep that in check. Or will the duckweed and other plants do that with or without the Azolla?

There isn't really anywhere the Azolla could escape to from our pond into the wild, we live right in the center of London, the nearest wild place is 5 miles or more away.

To sum up: Should I bother to try and remove it or just accept its there and leave it be.

Thanks in advance

[healfdan]

Azolla is a small water fern that looks pretty, turns from green to red and sits delightfully on the surface of any small water body. Unfortunately it will take a lot of work keeping it in check, as isolated groups will double in size in a week, eventually covering the pond surface. This leads to reduced light penetration in the pond, possible loss of submerged aquatic plants and ultimately low oxygen levels.
The fern like leaves can be carried on the feet or bodies of many creatures that visit the pond and this includes song birds drinking and bathing.

You say you live in the city with no wildlife corridoor close by, just a thought: how did Azolla get into your pond? The choice is yours but most conservation minded people would advise getting rid of it.
Healfdan

[Tiggrx]

I too would advise getting rid of it. Not an easy task though, my pond has had plenty of it for several years. It could easily spread from your pond into wild habitats, small fragments stick to birds, aquatic insects etc. which can carry it from waterbody to waterbody.

I hope your duckweed is Common Duckweed and not the increasingly common alien invader Least Duckweed, which is now a common species in many areas (again including my pond). Another nearly impossible species to eradicate.

[Kayleigh]

Originally Posted by Tiggrx

I too would advise getting rid of it. Not an easy task though, my pond has had plenty of it for several years. It could easily spread from your pond into wild habitats, small fragments stick to birds, aquatic insects etc. which can carry it from waterbody to waterbody.

I hope your duckweed is Common Duckweed and not the increasingly common alien invader Least Duckweed, which is now a common species in many areas (again including my pond). Another nearly impossible species to eradicate.

How can you tell the difference between common duck weed and Least as a search on the web just throws up common duck weed.
I cant get rid of the stuff it dont like moving water but neither does wildlife.

[JennyS]

If you've both species of Duckweed in the pond the size difference is clear as Least Duckweed is tiny:



Photo taken yesterday showing both species but unfortunately I wasn't listening well enough to remember the critical ID details

[Kayleigh]

Originally Posted by JennyS

If you've both species of Duckweed in the pond the size difference is clear as Least Duckweed is tiny:



Photo taken yesterday showing both species but unfortunately I wasn't listening well enough to remember the critical ID details

Cheers Jenny,
mine all look the same size and I think its the native one..its still a pain to get rid of though.

[Malcolm Banks]

Ahh you must try the fabulously versatile high tech gizzmo called a pea stick.
After twizzling blanket weed out with said device, I found they are also very useful for scooping (or twizzling) out large numbers of duckweed, using the roots to counterbalance the leaves (scooping technique) or to wind around the stick (twizzling). It will not eradicate the duckweed, but 5 mins every day or so should keep it to acceptable density, and the satisfaction of getting a really big clump in just one go is another reward.

Glad I haven't got any azolla though, sounds like the pond plant equivalent of FMD according to healfdan
M

[dampflippers]

When I once returned from holiday to find the few fronds of azolla had completely blanketed my pond about an inch thick, it took ages to remove it. I was skimming it off daily for ages.
Then each spring I would try to remove as much as I could see.
Thankfully because of the hard winter, I think I have finally got rid of it.

So now your tadpoles are bigger I would suggest skimming off as much as you can as often as you can. Put it on the edge of the pond and try to help pond creatures back in. If you find you are scooping up tadpoles still, wait a bit longer. Similarly, if you have newts they may have been laying eggs on it, so I would delay until late summer.
Then start again as soon as you see it and continue until next year's tadpoles hatch.

You say there is nowhere for it to spread to- what about other garden ponds, canals, urban rivers or streams, park ponds etc.

It composts well!

[motnworb]

Thanks for all the advice on this one, we have been taking bits off by hand and just dumping them nearby whenever we sit by the pond. It really is a pond that is too small for nets and things (think large puddle).

dampflippers - No I wasn't kidding, there are no water features nearby (except the Thames, but I would hazard a guess that Azolla won't get a foot hold on this part of that river, we're still tidal here). I live about as close to the center of London as you can get and am surrounded by a lot of concrete and tarmac. Our row of houses is just 12 houses and then its concrete school playgrounds and more concrete. Nobody else on our row has a pond, in fact our neighbours on one side have even complained about bird noise from our feeders... Much nicer to hear police sirens and screaming I assume.

The frogs only got there because a friend who lives in another part of town, for some reason felt she had too many tadpoles and was going to just throw some out of her pond. So we conducted a rescue mission. We're so urban and the pond is so small that a year on we haven't had any pond skaters or water beetles find it.

I don't think you can get more urban. :O)