Similar to Narrow-leaved Flax (Linum bienne, see above). However, it has darker blue and larger flowers, with petals 10–15 mm long. Sepals may be minutely hairy on the margins, and the style is elongated, linear to club-shaped. The 5 stamens have conspicuous blue anthers, and meet at the tips. This plant could be mistaken for the native Western Blue Flax (Linum lewisii, not shown), but it has sepals that are not hairy, and a stigma that is head-like rather than elongated.