The Orange-tip is single brooded though there is some debate about whether or not there is a second brood in the south of England. The adults are on the wing April to June but it can be as early as March. Males generally emerge about one or two weeks before females during the first warm spell.
The female lays bright orange cone-shaped eggs singly on cruciferous plants in May and June. The female is able to apply a chemical test via her feet to ensure the plant she chooses contains mustard oils, which make the butterflies taste nasty to birds. The male's orange tips serve as a warning of that taste.
Eggs hatch after about two weeks into pale orange larvae, which feed on the developing seed heads of the plant. By the second instar the larvae are pale green and by the last instar they have pale green stripes down each side and are almost identical in size and colour to the seed pods they feed on. You have to look very hard to spot them. Each larva needs the benefit of a whole plant and in the event of additional eggs having been laid on the same plant, the strongest larva will often eat any opposition. However the writer has seen two larvae of different instars survive on the same plant. Larvae are subject to attacks from other insects, birds and a parasitic fly Phryxe vulgaris.
After three to four weeks they leave their foodplants and travel for up to 30 hours to pupate. Pupae are bright green initially then turn a buff green and are buried deep in protective vegetation, possibly quite high up. They do not pupate on their food plants, probably because the foodplants wither over winter and would not be a stable perch. Winter is passed in the pupal stage. Emmet & Heath (1989) suggested that occasionally this may last through a second winter and that might explain adults being occasionally seen in later summer, perhaps because something has triggered an interruption to a second winter hibernation.