Root growth of Mugho pine seedlings was studied in Southern Ontario using a recently constructed rhizotron at the University of Guelph. The investigations have indicated that root growth of this pine in the season following transplanting extends from April to late November. During the summer, average daily root elongation was found to be 6.5 mm in sandy loam and 5.4 mm in organic soils, while during the autumn it was 2.9 and 3.7 mm respectively. Correlations were found to exist between root diameter and rates of root elongation, and suberization. The latter phenomenon began 5 to 7 days after new root growth. In late autumn metacutization occurred. A resinous type of exudate has been observed from the fully suberized roots. Qualitative thin-layer chromatographic studies have shown that the root exudates differed from exudates obtained by wounding pine shoots.