Cleistocactus strausii
The cactus prefers free draining soils, strong sunlight, but not high temperatures — in fact it can withstand hard frosts down to -10 °C. In its natural habitat it receives plenty of water during the summer, but almost none over the winter. In cultivation, watering too much in winter often leads to root rot.
San Andreas Creek
Fog drip may play a key role in the precipitation in the upper watershed. On Cahill Ridge (just west of San Mateo Creek and east of Pilarcitos Creek, at an elevation of , Oberlander measured fog drip beneath tanoak ("Lithocarpus densiflorus"), Coast redwood and three Douglas fir trees, the latter tall. He found that the trees most exposed produced the most precipitation and in five weeks of measurement (July 20 – August 28, 1951) fog drip below the tanoak produced of precipitation, more than the total annual precipitation on nearby grasslands and chaparral. The Douglas fir produced of fog drip and appeared to provide unique conditions supporting the orchids giant helleborine ("Epipactis gigantea") and phantom orchid ("Cephalanthera austiniae"), since these plants were found exclusively in these moist ridge tops.