A system and apparatus for growing plants is disclosed. The system includes a first thermal panel with multiple flow channels, the thermal panel being located between a growing space and a light source. A cooling fluid is circulated in a countercurrent flow pattern (i.e. in at least two different directions). The channels may be connected to one or more headers, which serve as a fluid manifold to deliver fluid and collect fluid from the flow channels. Growing closely spaced plants from seed or cuttings to transplants for the field or a greenhouse is one application of this system.