I have broccoli plants that have blossomed after the winter. gathering the flowers I get the seeds for the next sowing, and the plant must be uprooted or left to plant again?
broccoli, like most cruciferae, are biennial plants; in spring or summer they begin to develop, producing inflorescences, the ones we collect and eat for several weeks; after the winter frost the plant begins to develop a tall stem, which bears yellow or white flowers, very different from those of the inflorescences that we have collected and consumed; from these particular flowers the seeds are also produced, the ones you keep to sow them in the following months, and start the cycle again. After the production of the seeds, the plant perishes and dies, because it has already implemented its entire life cycle. If you were to cut the stem that bears the seeds, perhaps the plant could live longer, but it will hardly continue to constantly produce inflorescences to cut and eat, because over time it will tend to have no more resources to be able to produce the inflorescences edible; besides this, plants, like all living things, have a very precise life cycle, this cycle in many plants is completely aimed at propagation, to perpetuate the species; when a broccoli plant begins to prepare for flowering, it stops producing the large and fleshy lateral inflorescences, because it is trying to keep reserves of water and nutrients, which will be used to produce flowers, fruits and seeds, to go to conclude its life cycle. For this reason, even if your plant were to survive for a few more weeks, it would still not produce interesting broccoli for consumption in the kitchen.
Crucifers of the brassica genus have been cultivated by man for several millennia, this long cultivation period has allowed the development of numerous hybrids and natural cultivars, some of which produce inflorescences ready for consumption in autumn, others in spring, others in summer. For this reason it is possible to have broccoli almost all year round. So if you are particularly greedy for broccoli, and you want to get them in your garden for a longer period of time, try to plant plants of different varieties than the one you usually use, with a staggered development period over the months, in so as to prolong the harvest.