Offshore Flow
Posted June 12th, 2010 by Marc CohenCategories: Growing, Growing Orchids in San Francisco, Problems
When local meteorologists use the phrase “offshore flow,” it’s going to heat up here in the San Francisco Bay Area. Orchid growers on the coast, like me, normally take advantage of the cool fog flowing off the Northern Pacific to maintain good humidity. Those moderate conditions allow many orchid varieties to grow outdoors all year. But when conditions change to offshore flow, the typical marine influence disappears. Instead of cool, moist breezes blowing from the ocean, hot, dry air flows from inland. For example, today it’s 83F (28C) in the shade, 92F (33C) on the back deck, and a desert-like 13% humidity.
Since I don’t have any automatic watering systems, that means I have my work cut out for me. With my mister bottle for indoor orchids and a hose for outdoor orchids, I spray down the plants numerous times during the day. It’s more about wetting the leaves and roots than watering the potting material. In addition, I wet down any surfaces, like the wood surface of our deck, so the evaporating water can supplement the meager humidity.
Even some delicate orchid varieties, like this Masdevallia which likes to stay below 75F (24C) all year, can handle the heat as long as there’s good humidity. Fortunately, this hot spell is only forecast to last for the weekend, so the fog can take over again soon. But for now, I have to grab my mister bottle and go…



































