They are best-known for their lawn-like appearance, or as a food for ducks and swans.

There are three different species clearly visible in the accompanying photo, with another very tiny dot-like one also present.

The denser, smaller one in the photo is a true duckweed, but the two larger sorts are not. One is a type of aquatic fern, while the other is an aquatic liverwort.

True duckweeds are flowering plants, but their flowers are rarely seen. Even then, a good lens or a microscope is necessary.

The tiniest duckweed in the photo is probably not visible to most people - it is the very tiny green oval dot in between the larger species. It is only the size of a dot from a pen.

This is appropriately called the tiny duckweed, or Wolffia, and is the world's smallest flowering plant.

Under a lens, it can be seen to resemble a miniature iceberg, with most of its tiny bulk below the surface. It has no roots.

A close look at a patch of duckweed will reveal a range of small creatures on its surface, many of them tiny bugs known as pond-skaters that suck the juices from insects and similar small creatures that fall onto the water.

Below the surface, often sheltering amongst the roots, are other tiny animals - mainly crustaceans.

All sorts of other small creatures shelter beneath the cover of duckweed.

Duckweed of most species is readily eaten by ducks and swans in particular, but other waterbirds, and some fish, feed on it, too.

Wallabies have been seen scooping it up to eat.

Most "duckweeds" reproduce quickly in high-nutrient water, especially when the water is warm.

They reproduce by simply growing and dividing into separate plants.

Flowering of the true duckweeds is rare, occurring mainly when water-levels drop, leaving the plants drying in the mud. The petal-less flowers are minute, far too small to discern with the naked eye.

The absence of many species of waterbirds was a noticeable feature of 2022. Now some are returning.

Small grebes - the Australasian and the hoary-headed - have reappeared in small numbers, and coots have returned to Lake Wendouree, along with grey and chestnut teals.

Nankeen night-heron and darter have been sighted again, too, but only one of each.

The larger wading birds, such as herons, egrets, ibises and spoonbills continue to be almost absent, apart from the white ibis and the white-faced heron, which never left.

I am wondering what this plant is, growing in my neighbour's place at Haddon where there was a vegetable garden.

Apparently it is very fast growing so we are thinking some type of weed.

It has some round prickly things and white tube like flowers.

M.F., Haddon

Your fast-growing plant is common thornapple.

It is an annual, likely to die before winter.

It is native to Central America, and in Victoria is found mostly in milder areas, rather than here in the Ballarat district.

It is not uncommon in northern Victorian irrigation areas.

You might remember around Christmas-time, there was a food scare with a poisonous weed in packaged salad mix. The culprit was this plant or a close relative.

Although its leaves, flowers and fruits are interesting, I suggest getting rid of it and not letting any seeds escape from the prickly fruits.

Email questions and photos to rthomas@vic.australis.com.au, or send to Roger Thomas at The Courier, PO Box 21, Ballarat, 3353.

Have you tried The Courier's app? It can be downloaded here.