Duckweed or Lemna minor is considered to be the smallest flowering plant on earth. This plant belongs to a whole group of plants called floaters. These plants do not grow in earth, they just float on the surface of the water and absorb all the nutrients they need right out of that water. They help with the bio-load of your water garden and shade the water. To me these little plants are very attractive, but if they are happy they can be very invasive and in many parts of the country they have become a pest, clocking water ways. Duckweed has spread all over the world, mainly brought in by water birds in their feathers. I have never been able to keep this plant for long in my ponds because my fish like to eat it or my filters are sucking it in. Now I keep it in my tub gardens where it is a nice addition. You can find Duckweed also here in Arizona in the rivers like the San Pedro and the creeks like in Ramsey Canyon. I do not advise to harvest it from there. Ponds attract their own pests and you do not need to add them from other waters and you can bring in all sorts of nasty insects. Duckweed is a perennial and flourishes in the cooler temperatures of spring and fall. In summer it is better kept in a shady spot.

Another similar plant, just somewhat with bigger leaves is Frog bit - Hydrocharis morsus ranae. This plant is native to Europe and western Asia. Shiny leaves grow in rosettes on top of the water. The undersides are puffed with spongy, air holding tissue. This plant does not grow as vigorously as other floating plants, it does bloom white occasionally.

Fairy moss - Azolla caroliniana, bright green fonds that turn reddish in full sun and in fall. This plant can quickly cover a ponds surface and needs to be controlled, but is very attractive.

Water fern - Salvinia auriculata is a rapid growing aquatic fern with heavily textured, delicate foliage. It grows fast in warm weather and is also invasive. All these little plants are very nice in container water gardens where they can be controlled and give a finishing touch.