[elkhornsloughctp.org] Habitat: Habitat Confined to three habitats: 1) maritime chaparral, with Hookers manzanita (Arctostaphylos hookeri ssp. hookeri); 2) Monterey pine (Pinus radiata) forest, sometimes with Gowen cypress (Hesperocyparis goveniana); 3) Monterey cypress (Hesperocyparis macrocarpa) forest. The populations in woodland communities occur under partial canopy cover in an open mostly herbaceous understory (Morgan and Ackerman 1990). Associated soils are sandstone outcrops or shallow soils above granitic bedrock. On ancient marine terraces above decomposed granitic bedrock in forested communities, in highly leached and acidic soils, typically with a clay hardpan at variable depths. (contributed by Mary Ann Machi)

[Wikipedia] Description: Along with most other orchids P. yadonii: (a) is a bisexual perennial green plant that grows from buried tubers; manifests a fruit capsule bearing numerous minute seeds; (b) exhibits pollen that is sticky, and which is removed as sessile anther sacs; and (c) has a stigma fused with its style into a column. Yadon's piperia exhibits a basal rosette leaf formation. The subsurface architecture of this terrestrial wild orchid consists of a rhizome structure, from which emanate tubers. The rhizome extracts nutrients from fungal intermediates and may also store some of these nutrients. A basal rosette of leaves develops from the tuber at the surface of the soil, each of the two or three leaves being lanceolate in shape.[3] Each leaf ranges from 10 to 15 centimeters in length and 20 to 35 millimeters in width. Leaves of younger plants are often more diminutive in size. The dense inflorescence is borne on a single erect vertical spike varying from 12 to 55 centimeters in height.[4] Each flower has a spur of length 1.5 to 5 millimeters, short compared to other members of the genus. Yadon's Piperia typically presents three upper tepals, each of which contains both green and white pigmentation; moreover, there are three lower tepals that are white only. The earliest blooming time is June. When P. yadonii blooms, as late as August, all of its sepals and petals may be purely white. Another key identification feature is the characteristically abbreviated spur, which typically measures 1.5 to 6.0 millimeters in length. P. yadonii's leaves usually wither by blooming time, except for a small percentage of very large individuals. The geographic range of P. yadonii overlaps that of P. elegans, P. elongata, P. michaelii, and P. transversa; consequently, P. yadonii is clearly distinguished from them only in the flowering stage. Sympatric occurrences in mixed populations with P. elongata and P. elegans are noted in the literature. (contributed by Mary Ann Machi)