Duckweed...friend or foe?

Hi!

I have recently built a small wildlife pond in my garden, we've got tadpoles which im super excited about! However the pond surface is completely covered with duckweed, (there are also other pond plants in there) will this hamper the growth of the tadpoles, or harm the wildlife pond in any other way?

Any help would be greatly appreciated as im rather new to all this!

Spuggie

 

Simple answer, no.

 

Hi Spuggie,
For years I have considered duckweed a benefit in the pond ecosystem.
It's pros are that it will export nutrients from the water which otherwise will be used by really undesirables like blanket weed or algae. Duckweed will also block alot of the light through the water which is also required by the menace algaes etc. It's a natural refuge and cover for little critters, it's a food source for some. All I'd be inclined to do is skim off some every now and then, (a small harvest if you like) Regards Justin

 

Ah cool, thats good news cos i quite like the green stuff!!

Thanks peeps!

 

Although duckweed gets frowned upon, and it can be a nuisance, I've never found green water under duckweed.

 

In a small water/pond where it's easily reachable with a net its no problem at all. As said it can be a big advantage in keeping sunlight out of the pond, generally try to keep about 1/4 to 1/3 of the surface clear and you should have a really healthy pond (subsurface weeds/plants will need some sunlight, its all about finding that balance); as the spring and summer progresses you may find yourself removing some almost daily as it spreads at an alarming rate .

As Pete says I've 'never' seen a pond; large or small with green or dirty water beneath duckweed, they are always nice and clear, especially if other pond weeds are present subsurface.

Good Luck

 

It's not allowed in my pond,I have nothing against it,but it is invasive and at onetime it tried to get the better of me and we couldn't see the fish "it lost"....
I'm sure it does no harm.......I wonder why it's called Duckweed?

 

This is a rather dubious benefit, caused mainly by the shade from the duckweed. Clear, shaded water under a duckweed carpet does not support a great deal of life (some around the duckweed itself, detritivores on the bottom, not much in between).

Green water shouldn't be much of a problem anyway especially if you don't have any fish, since in their absence filter-feeding crustaceans such as Daphnia and copepods should quickly multiply and eat the single-celled algae responsible. Submerged plants are also unlikely to do well beneath a lot of duckweed, although some are more shade tolerant than others.

Ideally for wildlife you want a pond with a good mix of different plant types, especially those with a lot of submerged / semi-submerged foliage, and if duckweed's taking over at the expense of other species then that's not so great. It's fine in moderation, as part of a mixed plant community (the same could be said for algae), but not in excess.

Very rapid duckweed (or algal) growth also indicates high levels of nitrates and phosphates, which is a separate problem worth sorting out. This can be especially the case in ponds filled with tapwater, or with topsoil used in planting baskets, or with other sources of nutrient input (e.g. fishfood). Regular removal of duckweed/algae as suggested above should decrease nutrient levels gradually, but it's best to minimise nutrient input in the first place.