Wednesday, February 13, 2013

Featured Species: The Phantom Orchid

The Phantom Orchid (Cephalanthera austinae) is one of BC's rare orchid species, red-listed in the province and listed as threatened at the federal level under SARA (Canada's species at risk act).  But it's a fun species to search for and is occasionally stumbled upon in the southwestern corner of the province.  You can find it in the Chilliwack area in the Fraser Valley, on Saltspring Island, and around Victoria on Vancouver Island. It is primarily an inhabitant of old-growth forests, but sometimes can persist where old growth once grew. The underground rhizomes and ability to go dormant let it ride out unfavourable conditions and wait for the right ones before sending up new flowering stems.  This ability to persist in unfavourable conditions means that even if you don't find flowering stems, the orchid could still be present.

In British Columbia, we have seen it growing in big-leaf maple stands and beneath western red cedar, primarily shaded habitats that can range from heavily vegetated to sparsely vegetated. It likes limestone and calcareous conditions and has been found on heavily limed compost piles, around limestone quarries, and even on old shell middens.  You wouldn't have known the midden was there until trees were toppled in a storm and the shells exposed.  We have also read about the phantom occurring in the limestone gravel bed of a road in California.

We have even seen the phantom orchid growing inside a horse paddock and a cow pasture, where somehow it survived the trampling and persisted, perhaps benefiting from the nutrient load and lack of competitors. We have encountered other wild orchid species persisting in horse pastures back east so there must be some benefit to the orchids in these situations. Persistence in the face of some disturbances probably depends on the intactness of the underground stems and of the upper soil layers where they occur.

One of the most interesting sites where we found this species was in the midst of a deer bed (black-tailed deer) near Chilliwack.  We flushed two deer that were resting and in the midst of the bed and amongst the deer pellets were scattered flowering stems of phantom orchid.  We frequently encounter it along deer trails, although sometimes the stems have been browsed. 

Although it is a shade-loving plant, there are reports of it growing in sunlight, a population perhaps persisting long after a disturbance or one still struggling to produce flowering stems following changes to its habitat. 

The phantom orchid is an interesting species because it is mycoheterotrophic.  It grows in partnership with a fungus and a tree species.  This means that protecting and managing for this orchid requires protecting and managing the trees and fungus it is dependent upon.

It is also interesting because of the particularly long flowering period here in BC (which is at the northern limits of its range).  We have found it flowering in mid-May, and also found new and emerging flowering stems in mid-July at the same site. As old stems die back, new ones continue to emerge,  probably tied to local microclimate. 

Species like this, occurring at the northern limits of their range in southern BC, contribute to BC's high biodiversity. Our northern populations are the vanguard of the species, ready to spread northward should conditions become favourable.

Phantom orchids in deep shade at Teapot Hill

 Phantom orchid habitat, roadside, Cultus Lake

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