Plants are medium in size, growing slowly at first, then developing rapidly with a somewhat open canopy. Stems, leaves, and petioles are dark green with slight purple pigmentation in the stems and petioles. Flowers are lilac with white tips. Pollen is abundant and fertile. For this reason and for its desirable characteristic, Katahdin appears in the pedigrees of many North American varieties.
Tubers are round to oblong with buff, smooth skin and creamy white flesh.
Lateral eyes are shallow and apical eyes are moderately deep. Specific gravity and cooking quality are medium. Dormancy is medium. Katahdin is susceptible to scab and resistant to mild mosaic, net necrosis and brown rot. It does not have a high degree of resistance to other major diseases, but neither is it especially susceptible to them.