This paper presents a theoretical analysis of using shallow solar ponds in greenhouses in cold climatic conditions. A shallow solar pond, which can be built as an integral part of a greenhouse, can be used for both collection and storage of solar energy. The heat given our by the shallow solar pond is used for heating the greenhouse during the day. In addition, the collected heat during the day can also be used efficiently for heating the greenhouse at night. The performance of the shallow solar pond is investigated under different weather conditions for different solar pond areas. The results show, particularly, that using a shallow solar pond in a greenhouse can provide great saving of energy needed to heat the greenhouses in the months between March and October. There is no need to use any auxiliary heat between May and September, as the solar heat alone is sufficient to provide all the necessary heating; the energy stored by the pond during the day is enough to provide the night time heating or the necessary heat under cloudy conditions. The results suggest that there is a huge potential in using shallow solar ponds in greenhouses to save energy. Another obvious attraction is that it would be relatively cheap to implement the novel idea of such application.