The letters Jan Brueghel (1568-1625) wrote to his Italian patron Federico, cardinal Borromeo, between 1605 and 1625, provide some information about his flower paintings. The first significant item occurs in a letter of April 14, 16o6, in which he mentions having started on a flower piece with beautiful and rare species, all painted from life. He had seen and `portrayed' some of them in Brussels (note 16). In a letter of almost the same date to Borromeo's fellow-citizen, the collector Bianchi, Brueghel writes that the piece was to consist of m<>re than a hundred different flowers, and that he had never made such a picture before (note 17). The painting, which is still in the Ambrosiana in Milan, was thus Brueghel's very first flower piece (fig. 3). This is even more obvious when it is compared to a second version (fig. 4), probably painted soon afterwards, in which the flowers are distributcd more evenly over the surface. An arrangement of this kind of bouquet was not possiblc in Brueghel's day. Such flowers were too costly to be placed in vases (note 21); even in gardens they were displayed as single specimens (figs. 5 and 6). They were exotic rarities like the sunflower, which was thought to have been imported from Peru (note 25; fig. 7). Brueghel's native city, Antwerp, was the centre of botanical knowledge in the early 17th century in Europe because of the books published by Plantijn on herbs and plants, written by the leading botanists: Dodonacus, Lobelius and Clusius. In Brueghcl's day plants were fashionable collector's items, not only in the gardens of the aristocracy but also in those of the wealthy bourgeoisie. In this context a picture by a Brueghel imitator featuring Pictura painting a large flower piece (fig. 9) seems quite understandable. Illustrations of plants in books show little or no shadow on their forms, and the light is often diffuse (figs. 7 and 11). Brueghel's flower pieces have the same diffuse light and ignore the effect of light and shade. He may have becn influenced by these illustrations, and he adhered to the same principle: the recognizability of his flowers was all important. Brueghel's bouquet for Borromco (fig.3) consists of flowers which were rare, and therefore valuable. As he wrote to his pastron: 'Underneath the flowers I have made an ornament, with some coins (..). Your Excellency must judge for himself whether flowers do not deserve to take precedence above gold and ornaments' (note 18). Cardinal Borromeo was delighted (notes 47 - 5 1) and wrote that he had paid the value of the ornament as the price of the painting (note 48). However, painted flowers were merc substitues for the real ones to the Cardinal, who docs not seem to have reacted to the next flower piece Brueghel sent him, at the end of 1609 (fig. 15). It was the last flower piece Brueghel painted for him. It is interesting to note that the correspondence gives the impression that this piece was painted partly out of doors (notes 5 4 and 56). Remarks in a letter to Bianchi give some impression of how Brueghel painted his flower pieces. According to him he made no drawing or sketch, he painted alleprinle and arranged he flowers on the surface of the painting while working on it. The combination of spring and summer flowers is understandable when one realizes that it took him about four months to make such a picture. One wonders, however, whether he and his assistants (note 61) did not work on several near identical paintings at the same time. His remark that he painted several bouquets every spring (note 64) suggests the possibility and so does the fact that only about twelve different compositions of flower pieces by him are known, all in more than one version (cf. e.g. figs. 18 and 19). Only very few paintings - the ones for Borromeo, possibly those for the Vienna and/or Brussels court - have no known repeats. Brueghel was boasting when he wrote that he worked exclusively from life. Examination of a flower piece in Cambridge revealed a complete underdrawing (fig. 23); moreover, the iris is copied from a print by Pierre Vallet (fig. 25; note 68). He borrowed some day lilies from a woodcut in Dodonaeus' Stirpium Historiae Pemptades Sex (figs. 26 and 27). One flower - the red Anemone coccinaea on its twisted stem which often appears in his pictures - may be artificial, made from cloth or silk. Nevertheless, his flowers pieces were portraits of betanical rarities, as was probably the case in similar situations at the time (note 79). Any other meaning - for example as a vanitas - is highly unlikely. Neither Brueghel nor Borromco ever mention a religious morality in connection with these flower paintings. Therefore, the endeavour to 'Immorta]17.e' the ephemeral beauty of these flowers must often have been the chief motivation. On the basis of this appreciation for rare flowers, their occurrence in bouquets, and the assumption that Brueghel painted several near-identical flower pieces during a number of years a chronology of (most of) Brueghel's flower pieces has been added as appendix.