Kingdom: Plantae
(Unranked): Angiosperms
(Unranked): Eudicots
(Unranked): Core eudicots
Order: Caryophyllales
Family: Amaranthaceae
Genus: Chenopodium
Species: C. album
Binomial name: Chenopodium album
Common names: Fathen, Lamb's quarters, Melde, White goosefoot, Goosefoot, Fat-hen,

Chenopodium is one of the worst weeds and most widespread synanthropic, plants on the Earth, in its broad circumscription is also among the most polymorphic plant species (occurrence of different forms). It is known as a very competitive weed due to its ability to remove moisture from the soil even in dry conditions. Chenopodium album was the first weed to develop resistance to herbicides within New Zealand.

Chenopodium album is a tall (2 m in height), upright, leafy plant. It grows mainly in spring and summer. It foliage often looks like it has been sprinkled with flour, especially younger leaves and the flowering parts, which are similar in colour to the foliage, i.e. a whitish-green colour. Chenopodium album can vary greatly in size, sometimes flowering when only a few centimetres high, especially in autumn if it established late. Leaf shape can vary quite a bit from having almost no teeth along their margin to having quite jagged margins.  Those that are most jagged along the margins are often actually nettle-leaved Fathen (Chenopodium murale).

It develops during December and May small flowers that are clustered into panicles at tips of branches and upper leaf axils. These flowers are green, inconspicuous, without petals. The fruit is a utricle (a type of dry fruit) with a thin papery covering over the seeds. It is capable of producing thousands of seeds. The seeds are circular, 1 mm in diameter and are a glossy black in colour.
The adult stems are erect, hairless, grooved, branching and light green with a red colouration in varying degrees. Its roots are short and it has a much-branched taproot.

In many parts of the world, this species is cultivated as a grain or vegetable crop (such as in lieu of spinach) and is very palatable and nutritious. It is used as animal feed in Asia and Africa.

Chenopodium album Fathen.JPG

Chenopodium album Fathen-002.JPG

Chenopodium album Fathen-003.JPG 

Chenopodium album Fathen-001.JPG

Another leaf shape.
Chenopodium album Fathen 3 .JPG

The underside of a leaf.
Chenopodium album Fathen 4 .JPG

A stem with red colouration.
Chenopodium album Fathen 1 .JPG 

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/