Spergula arvensis is an annual species, and reproduces by seed. Most of the seed produced is through self fertilization, and New (1958) estimated at least 97% of S. arvensis plants reproduce by selfing, with the remainder cross-pollinated by insects.

Highly branched, younger plants produce a higher number of capsules and seeds, and can shed seed over the growing season (New 1961). A large, healthy plant can produce an average of 7500 seeds a year, with an estimated 30.5% of the seed retained and harvested with the crop (New 1961; Bitarafan and Andreasen 2020). It is estimated that cultivated fields in Britain have from 4 – 23 million seeds of S. arvensis in the soil (Holm et al. 1991).

S. arvensis seed is dispersed over short distances by water or in mud stuck to animals or equipment; longer distances in contaminated crop seed (New 1961; Holm et al. 1991). Seeds do not appear to have dormancy, and fresh seed can germinate over the growing season if at or near the soil surface (New 1961; Holm et al. 1991). Natural methods of control include sheep grazing of established plants and repeated cultivation of the soil to remove seedlings (New 1961; Holm et al. 1991).

Spergula arvensis seed is dimorphic with a papillate or a non-papillate surface. The presence of papillae is genetically controlled; each plant can produce only one type of seed (New 1958; Wagner 1988). The 2 types have been considered different varieties by some authors, with the papillate form named Spergula arvensis var. vulgaris (Boenn.) Mert. & Koch, and the non-papillate form S. arvensis var. sativa (Boenn.) Mert. & Koch (New 1961).

The ratio of seed morphs formed a stable pattern across Britain, with papillate seeds more common in the south, and non-papillate in the north (New 1958). Germination experiments showed that papillate seeds germinated better at higher temperatures than non-papillate seeds, reinforcing the observed seed morph pattern (New 1958; Wagner 1988). S. arvensis populations studied along the Pacific coast in the United States did not follow the same climatic pattern as in Britain (Wagner 1986).