Macfarlane's four o'clock occurs on warm, dry, open canyon slopes. Soils are sandy or rocky and often unstable.
This species has a narrow distribution and is currently known only to Hell’s Canyon and northwestern Idaho. Invasive plant invasions are believed to be a primary limiting factor for Macfarlane's four o'clock. Off-highway vehicle use, construction and maintenance of roads and trails, mining, and herbicide drift are additional threats. Historically, uncontrolled livestock grazing degraded habitat but is no longer a major concern. Inbreeding depression may be a limiting factor for Macfarlane's four o'clock.
Develop seed germination, propagation, and transplanting protocols. Conduct pollination studies. Investigate the extent of the seed bank. Determine whether inbreeding depression affects Macfarlane's four o'clock.
Actions implemented through the recovery plan (1985) contributed to improved species status and downlisting from Endangered to Threatened in 1996. Continue implementing actions specified in the recovery plan and monitoring at permanent plots.