In connection with the recent emergence of a new discipline, conservation biology, a new conservation tool has been explored by the scientific community: reintroductions of rare or threatened taxa into nature. This article, which is based on two examples of reintroductions of plant species carried out in France, illustrates how the rationality of such projects, often presented by their promoters as falling within the scope of taxa retained as ‘protected species’, is more socially constructed on technical, strategic and communicational criteria. In this sense, they are either a negotiation or the crystallisation of a variety of objectives. Observation of the construction of the reintroduced flower then makes it possible to observe the reciprocal influences between local networks, rooted in the territories, and global networks.