Every species is adapted to the environment it is native to. Most palms on the Gulf of Mexico coast are either native to the area, or native to an area susceptible to hurricanes, typhoons or other forms of strong storms. Well, at least those that survived Katrina are.

There are other palms adapted to other climates. The windmill palm that is native to China tolerates cold, so can be grown in Portland, Seattle and even Oklahoma City. The California fan palm, or desert fan palm, is native to deserts of Southern California, so likewise tolerates cold, as well as heat and drought.

It is often helpful to know where exotic (non-native) plants originated when determining if they can be accommodated in the garden. For example, knowing that Japanese maples are naturally understory trees (below the canopies of higher trees) helps to select a site in the garden that is partially shaded during the hottest part of the day. Leaves of Japanese maples are easily burned if too exposed to direct sunlight during hot, dry days.

Although the Mediterranean climate of the Santa Clara Valley sustains more plants than almost any other climate in the world, those that do best here are either natives, or exotics that are endemic to an areas with the same sort of climate. Such plants can survive with only minimal watering and enjoy warm but mild summers and cool but mild winters. Unlike some of the exotics, natives also like the local soil types, which may seem too dense (clay) for some plants that prefer better drainage, or too alkaline for those that prefer acid.

However, just because a plant is adapted to life in the Santa Clara Valley does not mean that it necessarily is adapted to the garden. Native plants came here long before any of us did and were perfectly happy without irrigation. Those that wanted more water simply lived near creeks. In the garden, native plants still enjoy the local climate, but many are sensitive to supplemental watering needed by other exotic plants.

This is unfortunately a rather common problem in some modern landscapes that include a few token native plants mixed with other plants that need to be watered. Either the natives get too much water, or the other plants do not get enough. Planting only a few "drought-tolerant" plants to conserve water is ineffective if they are going to get just as much water as everything else anyway.

Many plants from the Mediterranean are just as drought-tolerant as California natives, but are also more adaptable to landscape conditions. For example, oleander, olive and fig are all very tolerant of dry conditions, but will also be quite happy within watered areas and near lawns. Italian stone pines are almost too happy in frequently watered landscapes. They become so densely foliated that they cannot support their own weight and consequently drop large limbs.

Foliage of the Week:
Rex begonia

Begonias are known mostly for their flowers. Tuberous begonias have the largest and most colorful flowers. Fibrous begonias are grown as annuals for their small profuse flowers and glossy foliage. Flowers of rex begonias, however, are rarely seen. They are instead grown for their colorful bold foliage. The thick, glossy dark green leaves are patterned with lighter colors and seem to be made of plastic. These leaves are crisp and succulent with small coarse hairs.

Rex begonia is a type of rhizomatous begonia. Rhizomes that extend outside a pot may be severed and rooted in coarse media, such as perlite mixed with peat moss. Rex begonias can also be propagated by leaf cuttings or by seed. They like humidity, partial shade, regular (but not excessive) watering and rich, well-drained soil. Although not well adapted to exposed areas of the garden, they are happy on sheltered porches or in the home.

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