Ongoing Efforts to Recover Mirabilis macfarlanei, MacFarlane’s Four-O’clock

MacFarlane’s Four-O’clock.
MacFarlane’s Four-O’clock (Mirabilis macfarlanei). Photo by Gene Yates.

three men releasing three-toed stem-boring weevils on Dalmatian toadflax.
Release of the biological control agent, Mecinus janthinus, the three-toed stem-boring weevil, to control the invasive plant Dalmatian toadflax, which degrades habitat for MacFarlane’s Four-O’clock. Photo by Gene Yates.

ripe seeds of MacFarlane’s Four-O’clock.
Ripe seeds of MacFarlane’s Four-O’clock (top) with old withered flowers below. Photo by Gene Yates.

MacFarlane’s four-o’clock is found in only a few patches on the grassy slopes of Hells Canyon of the Snake River and the Imnaha River canyon in northeast Oregon and the adjacent Salmon River canyon of west central Idaho. Although intrinsically rare, this plant has likely experienced a decline in both its historical abundance and range since the advent of large-scale sheep grazing during the homestead era of the late 19th and early 20th centuries. Gentler slopes, where sheep grazed frequently, are now dominated by invasive species, especially annual grasses such as cheatgrass. Consequently, MacFarlane’s four-o’clock is found almost exclusively on steep slopes that were less intensively grazed and where native bunchgrasses are still present.

Invasive plants are present in four MacFarlane’s four-o’clock populations and in proximity to several other populations. A biological control agent, Mecinus janthinus, the three-toed stem-boring weevil, has been released at two MacFarlane’s four-o’clock populations infested with Dalmatian toadflax in partnership with the Oregon Department of Agriculture (ODA). Dan Sharratt, the ODA Northeast Oregon Noxious Weed Management Coordinator, conducted the release. Dan has provided invaluable support to the conservation of the four-o’clock by monitoring other populations for the presence of invasive plants.

Under an earlier partnership, The Oregon Natural Heritage Program produced a model of suitable habitat for MacFarlane’s four-o’clock that reveals abundant suitable habitat still present in Hells Canyon. Much of this habitat has been found to be in relatively good ecological condition. Sheep or cows no longer graze the entire suitable habitat in Hells Canyon and abundant high quality suitable habitat still exists for the four-o’clock. However, the plant does not appear to recolonize suitable habitat effectively. This may be due to the plant’s apparent preference to reproduce by rhizomes versus seedlings or because each flower produces only one relatively large seed that may not disperse far from the plant. Whatever the reason, over the past 20 years, MacFarlane’s four-o’clock has rarely been observed, if at all, to establish new plants by seed. MacFarlane’s four-o’clock may therefore not be able to bridge patches of unsuitable habitat to colonize new ground.

In partnership with the Berry Botanic Garden and the U.S. Fish and Wildlife Service, the Wallowa-Whitman National Forest will reintroduce MacFarlane’s four-o’clock to suitable habitat in Hells Canyon. One objective of this effort is to develop the appropriate technology to produce seedlings under greenhouse conditions and successfully transplant stock to suitable habitat in the wild. Berry Botanic Garden’s Dr. Ed Guerrant is leading the study to germinate seeds and produce transplant stock. In June 2006, the Wallowa-Whitman National Forest botanist collected over 4,000 MacFarlane’s four-o’clock seeds to provide to the Berry Botanic Garden for germination trials. The U.S. Fish and Wildlife Service is providing funding to assist with the reintroduction plan, transplanting, and project monitoring. Dr. Guerrant will also assist with evaluating sites to reintroduce MacFarlane’s four-o’clock.

For More Information

Gene Yates, Forest Botanist
Wallowa-Whitman National Forest
541-523-1390
gyates@fs.fed.us

Partnership Principals

Dr. Ed Guerrant
Berry Botanic Garden
Portland, Oregon

Keith Paul
U.S. Fish and Wildlife Service

Dan Sharratt
Oregon Department of Agriculture