Abstract Biodegradable containers for growing seedlings are environmentally friendly, and are rising in popularity worldwide for this reason. However, the properties of these containers have not been well documented. In this study, three types of biodegradable plug-trays, namely Peat Moss, Wood Fibre, and Cow Manure, were tested to determine their physical and mechanical properties. The water absorption ability of the tray materials was measured over a time period of two hours. The tensile properties of the materials were also measured. Additionally, early seedling growth was observed under a greenhouse condition to investigate the effect of plug-cell size. The weight losses of plug-cells were examined in a field condition to assess the biodegradability. Results showed that the Cow Manure plug-tray samples absorbed the most water (476% of its original weight), Peat Moss absorbed the least (316%), and Wood Fibre was an intermediate between the other two (391%). The Cow Manure plug-tray specimens under air-dry conditions had a tensile strength of 1.82 MPa, which was significantly higher than the others. After absorbing water, the average strength of all the specimens was reduced by approximately 83%. When using the plug-cells to grow beans, longer roots were found in larger plug-cells, as expected. Based on the weight losses data from the field tests, the Cow Manure plug-cells had the best biodegradability, followed by the Wood Fibre, and then Peat Moss. The Cow Manure plug-trays performed the best, in terms of the tensile strength and weight loss.