PRESIDIO OF MONTEREY, California -- The "keep out" signs don't display a skull and crossbones, but ignoring them could mean death, or worse, for Yadon's piperia -- an endangered orchid growing in several locations on the Presidio of Monterey."It only grows in this one area," Leanne Obra, a Natural Resources Specialist for the Directorate of Public Works.Yadon's piperia, or Piperia Yadonii, is a ground orchid that grows only in a small expanse of maritime chaparral and coastal woodlands of north Monterey County, and was federally listed as an endangered species in 1998.It keeps a pretty low profile - even for a plant.Yadon's piperia was first discovered in 1925. But it wasn't recognized as a distinct species until 1990. (It was then named for Vern Yadon, a longtime director of the Pacific Grove Natural History Museum).In full bloom, the plant stands more than a foot and a half high, and is topped by a column of tiny white flowers. But you'll rarely see it in that state. Until it flowers, the orchid's asparagus-like stalk is short, green, and easily confused with common weeds.It also goes dormant for six months of the year, dying back to its sturdy, tuberous roots. Some years, the roots stay dormant and don't send shoots to the surface at all.That's a challenge for those working to identify and protect the plants."They are hard to see, and you could be trampling the plants," Obra said. "Even when they're underground, repeated foot traffic can compact the soil above the roots can stop them from growing back."Yadon's piperia isn't an especially delicate flower, but it's finicky about where it will grow. Researchers believe the plant, like other ground orchids, forms a symbiotic relationship with a mycorrhizal fungi that grows in local soils. Without it, seeds from the plant won't germinate and existing plants may struggle to convert nutrients from the soil.Its range is limited to a handful of sites, almost all between Prunedale and Carmel, and all within about six miles of the ocean.But the greatest threat stems from habitat loss and fragmentation caused by development, including some construction projects at PoM.The installation's master plan includes documenting existing Yadon's piperia plants on post, which represent more than five percent of the species' population."Any time we do construction, we consult with the U.S. Fish and Wildlife Service. That's required by Section 7 of the Endangered Species Act," Obra said.In some cases, that means planning new facilities in locations that preserve existing Yadon's piperia populations or habitat.The installation partnered with the Pacific Grove Natural History Museum to conduct an experimental transplant of 52 plants to the museum's garden, where researchers will monitor their response to a variety of soil, water, and sunlight conditions.On the Presidio, cable-wire fencing, signs, and educational displays to warn pedestrians away from established Yadon's piperia populations.Yellow flags mark areas where plants were observed during previous surveys, and where dormant roots could be located or new plants may be growing.One of those areas is located along a foot path just off Rifle Range Road, next to Building 330 -- which is currently under renovation.Obra warns pedestrians to tread carefully, observe all posted signage and stay inside the marked pathway through that area.Violations of the Endangered Species Act are subject to fines of up to $25,000, and criminal penalties of up to $50,000 and one year in prison.