Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Caryophyllales
Family: Caryophyllaceae
Genus: Polycarpon
Species: P. tetraphyllum
Binomial name: Polycarpon tetraphyllum
Synonym: Mollugo tetraphylla
Common names: Allseed, Four leaved allseed, Fourleaf allseed, Fourleaf many seeds, Four leaf allseed, Four-leaved all-seed, Four-leaved allseed, Polycarpon.

Polycarpon tetraphyllum is an invasive herb originally from Central and Western Europe, Mediterranean and the Middle East. It is now naturalised in many countries including New Zealand.
Polycarpon tetraphyllum is a small, spreading, glabrous, hairless, annual herb. It grows up to 15 cm in height and is found growing from cracks or crevices or hidden beneath other plants. Its habitat is sandy soils, in coastal areas and on wasteland. 
The leaves are spoon-shaped and have a short slender stem and are opposite and appear to be in whorls of four.
Polycarpon tetraphyllum tiny flowers are white and numerous and are in loose bunches at the end of most stems. The flowers are said to be homogamous, self-pollinating and often cleistogamous (propagating by using non-opening, self-pollinating flowers). Fruit is a rounded capsule.
This plant can be removed by grabbing it firmly near the roots and pulling. Since it is a prolific seeder, plants that are removed should be placed in a bag for disposal.

Polycarpon tetraphyllum Allseed 1 .JPG  

Allseed Polycarpon tetraphyllum -001.JPG

Allseed Polycarpon tetraphyllum -002.JPG  

The leaves are in a whorl of four.
Allseed Polycarpon tetraphyllum -003.JPG


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