Many more unusual orchids can be seen at the Orchid Luau, a show and sale by the Peninsula Orchid Society. Hourly lectures will address cultivation of the various orchid genera. The Orchid Luau will be from 10 a.m. to 5 p.m. on Jan. 8 and 9 at 2600 Middlefield Road in Redwood City. Admission is $5. More information may be obtained at www.penorchidsoc.org or by emailing meg570@comcast.net.

The most popular orchids are grown in pots of very light and coarse organic medium, such as bark, so they are unable to exploit the excellent soil of the Santa Clara Valley. Those of us who enjoy growing fruit trees do not need to be reminded of the local soil quality. The USDA Natural Resources Conservation Service does not need to be reminded either, but is currently conducting a soil survey to assess the affects of urbanization since the previous soil survey of 1942.

Obtaining data from public space is easy, but the USDA needs help to get information from less accessible areas, such as residential neighborhoods. Anyone who would like to help with this survey by allowing inspection within a respective garden or landscape will receive the results of the corresponding inspection, which evaluates texture, pH, salt content and depth to restrictive strata. Inspection of soil only requires a three-inch wide hole to be manually augered into the soil.

It will be several years before the survey is completed and becomes available to the public, but preliminary data will be available as the survey progresses and as each inspection is completed. The Natural Resources Conservation Service may be contacted at 925.672.4577, ext. 111, or at william.reed@ca.usda.gov to arrange for a soil examination.

Flower of the Week: Orchid

This little gardening column cannot possibly do justice to the topic of orchids, which not only involves a seemingly limitless range of cultivars and varieties, and a vast range of species, but also an extensive range of genera. Bletilla, Cattleya, Cymbidium, Dendrobium, Epidendrum, Oncidium, Phalaenopsis and Vanda are some of the more familiar genera. Brassavola, Calypso, Coelogyne, Epipactis, Laelia, Lycaste, Odontoglossum, Paphiopedilum and Pleione are somewhat more obscure, but are nonetheless popular among orchid enthusiasts, who can probably pronounce these names better than you can.

Many orchids are terrestrial, which means they grow in soil. However, the most popular are epiphytic, which means they naturally grow in organic debris that collects in the branches of tropical and subtropical trees. Some epiphytic orchids grow in rock outcroppings or can actually grip onto tree bark, but all epiphytes are sustained by air, rain and accumulation of organic litter.

Rain and a regular supply of organic litter can be irregular and unreliable, so epiphytic orchids store resources in distended stems known as "pseudobulbs." Some are slender and stem-like and others are plump and bulb-like. Foliage may emerge from the distal tips or along the length of pseudobulbs.

Terrestrial orchids (such as Bletilla striata) can be grown in pots of standard potting soil or even in the garden, but epiphytic orchids must be grown in a coarse and well-aerated organic medium, such as ground bark. This medium does not hold moisture well, so it should be watered about weekly and fertilized with a soluble fertilizer as often as twice a month. Some epiphytic orchids can be grown on slabs of coarse bark known as "bars" or "rafts."

Many orchids grow well outside of the home and some even require seasonal chilling; but most prefer to grow as houseplants in bright locations. Most appreciate humidity. To learn more, you will simply need to attend the Orchid Luau.

Horticulturist Tony Tomeo can be contacted at 408.358.2574 or at LGHORTICULTURE@aol.com.