The Crops in Silico (CiS) framework, yggdrasil, provides support for connecting scientific models written in different programming languages. To connect two models, modelers add communications interfaces to the model code and provide declarative specification files that identfy the models that should be run and the inputs and outputs those models expect. yggdrasil uses this information to launch the models on parallel processes and orchestrate asynchronous communication between them. Although designed for connecting crop models, yggdrasil can be used to connect scientific models from any domain.