Malus sieversii modern apple cultivars. Unlike domesticated varieties its leaves go red in autumn: 62.2% of the trees in the wild do this compared to only 2.8% of the regular apple plant or the 2,170 English cultivated varieties. The species is now considered vulnerable to extinction. "Malus sieversii" has previously been identified as the main contributor to the genome of the cultivated apple ("Malus pumila"), on the basis of morphological, molecular, and historical evidence. A DNA analysis in 2010 confirmed "M. sieversii" as the progenitor of the cultivated apple. A third species that has been thought to have made contributions to the
Malus are borne in corymbs, and have five petals, which may be white, pink or red, and are perfect, with usually red stamens that produce copious pollen, and a half-inferior ovary; flowering occurs in the spring after 50–80 growing degree days (varying greatly according to subspecies and cultivar). Apples require cross-pollination between individuals by insects (typically bees, which freely visit the flowers for both nectar and pollen); all are self-sterile, and (with the exception of a few specially developed cultivars) self-pollination is impossible, making pollinating insects essential. Several "Malus" species, including domestic apples, hybridize freely. They are used as food plants