Plant systems biologists have developed many mathematical models at the organ, cell and molecular scales. There is now a need to be able to incorporate these models into existing plant/crop models in order to access their effects at the plant, crop and landscape levels and under different climatic conditions. However, many of the plant/crop models are not readily available and the definitive model descriptions exist only as computer code often in legacy formats and so there is a real danger of thembeing lost altogether. This poster describes the PlaSMo project which is converting a set of the existing models into a standardised open XML format that will provide full and unambiguous descriptions of the models that users could implement in their own computational environments or use in packages designed to read the XML. To facilitate the conversion the models are being reimplemented in the graphical format used by the declarative modelling package Simile which can use the XML format. The XML versions of the models will then be made available from a specially designed web-portal which will also provide documentation, datasets and example output.