# [Wet Thumb Forum]-Plant identification surprise!



## Miss Fishy (May 13, 2006)

When I was about ten, I started my first planted pond and quickly became interested in aquatic plants. One day I found some tiny green floating plants which I thought might be Duckweed. I took them along to a LFS, and the owner said that they were indeed Duckweed, _Lemna minor_ to be exact, and that the plant was a useless nuisance. I kept it anyway, and it became one of my favourite plants.

Yesterday, I was reading through two books on native Australian aquatic plants that I just borrowed from the library, when I came across a key to the Lemnaceae family. To my great surprise, I discovered that the little plant that has been floating around my tanks and ponds for the last 11 years is not _Lemna minor_ at all! It is in fact _Landoltia punctata_! It was originally known as _Spirodela punctata_, but the name was changed in 1999. Unlike _Lemna minor_ this plant has more than one root (usually 2-8), a dorsal and ventral scale, and is purple on the underside. It is native to Australia, India, China, South East Asia, Polynesia, New Zealand and introduced in the USA.

I was so excited by my discovery that I scanned some plants and drew a diagram:










From Alex.


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## MyraVan (Feb 13, 2005)

I like duckweed too. My apple snails also like it. What I like about it is that it efficiently uses up extra nutrients in the water, and it's easy to keep under control by simply removing bits of it. With submerged plants you have to uproot them, which makes a bit of a mess. (I have almost exclusively rosette plants, not stem plants, maybe stem plants are easier to trim?)

In my apple snail tank I also have floating salvinia and water lettuce (pista stratois or something like that) but the snails don't eat those!


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## Miss Fishy (May 13, 2006)

Hehehe, I think the submerged plants are easier to keep pruned! I do have mainly stem plants and tiny plants with runners, 'though. When I want to thin out the floating plants, my whole arm gets covered in them. I even found some in my bath the other day!

From Alex.


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## dwalstad (Apr 14, 2006)

Miss Fishy,

Thanks for the nice photos and drawing of your plant. 

Floating plants are great if you can get them to grow. Far better to have thriving duckweed than ammonia accumulation or algae.


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## rgrycki (Jun 13, 2005)

Sorry to Hi-jack this thread but.... I have a problem growing duckweed in any number. I got some from hitchhikers on other plants and love the stuff but it only grows in limited numbers in my el-natural 10 gal guppy tank (~2 w/gal) w/ a HOB filter. Any suggestions?


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## Miss Fishy (May 13, 2006)

Dear RobertG,

I've read here and elsewhere that floating plants can suffer from iron deficiency in tanks without water column fertilisation. Since they can't get nutrients from the substrate they suffer when the iron in the water is used up. If your water has plenty of other nutrients, perhaps this could be the problem? Is it only Duckweed that doesn't grow in you tank, or can you not get other floating plants to grow either? Do the Duckweed plants you have look healthy? My _Landoltia punctata_ ("Thin Duckweed") changes its size and appearance quite a bit depending on nutrient levels.










The left plant is from a bucket that I grow Daphnia in, where Thin Duckweed is the only plant. There is soil and mixed cow and chicken manure in the bucket to encourage algae, and the Thin Duckweed grows large, is dark green, and has short, thick roots. The middle plant is what it looks like when growing in an older pond without the manure and with a couple of rooted plant species; it is smaller and paler green. The right plant is growing in a densely planted tank with many fast-growing rooted plants, and as you can see it is very small, pale green, and has very long, thin roots.

From Alex.


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## rgrycki (Jun 13, 2005)

They look fairly healthy, but what you say makes sense, some of the other plants in the tank (egeria najans/ludwigia) are showing minor signs of micro-nutrient deficiencies. I'll start dosing a little flourish and see what happens.


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## dwalstad (Apr 14, 2006)

I also can't get duckweed to grow in my tanks. I'm almost sure its iron deficiency.

My Water Sprite won't grow as a floating plant in my tanks. However, it does fine if I give the roots access to soil where it can find plentiful iron.


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