Arctostaphylos uva-ursi has been a source of taxonomic uncertainty. The most recent treatment recognized four subspecies and two varieties in North America, differing in pubescence of young stems and petioles and greatly overlapping in ranges. In Michigan the non-glandular var. coactilis, the most common of the entities in the state (63.6% of all randomly collected specimens), prefers the most exposed habitats with the least water-retentive substrates; the reverse is true of the glandular subsp. adenotricha (29.5% of specimens); and the glandular subsp. longipilosa (6.8% of specimens) was found only in jack pine woods. Var. coactilis may be insensitive to pH; subsp. adenotricha may prefer more basic substrates; and subsp. longipilosa may prefer more acidic ones. The study suggests that introgression may be the source of much of the morphological intermediacy and that the species as a whole occurs in Michigan on substrates that are more commonly neutral to basic than is widely believed.