It means that the fruit tree has undergone several tests to check that it does not have any diseases and that all those tests have given negative results for viruses. These tests are made by the Plant Health Service of each Autonomous Community in Spain through daily visits to the production site as well as by taking samples. A certified plant is the best guarantee of its health status. Every certified fruit tree wears a blue label on its trunk indicating the name of the rootstock and its variety, the name of the producer as well as its phytosanitary registration number.