My home garden is landscaped mostly with concrete pavement with some additional asphalt. These two groundcovers have absolutely no problems with disease or pests and require very minimal maintenance. Unfortunately, much of the pavement is south of a two-story-high, lightly colored stucco wall. The reflective glare during warm summer days is unbearable, even for yuccas and dracaenas. I don't mind limiting my selections to species that are resilient to severe exposure, but have never found anything that will survive on the south side of the home.

Melissa's Mondo Condo is a residence in Santa Clara recently occupied by a friend from high school (named Melissa) that has the opposite problem. The fenced garden is close to the north side of the two-story residence. During winter, much of the garden is always shaded. Just as many species are more tolerant of extreme exposure, many others are more tolerant of shade than others, but limiting selection to these species is not necessarily easy.

Exposure to sunlight is most direct from the south. Walls on the north side of a building are, of course, the most shaded. East- and west-facing walls are exposed to sunlight for perhaps the same amount of time, but eastern exposures are cooler than potentially harsh western exposures because the exposure is in the morning when the air is still cool, but western exposure is during the warmer afternoon. This is why some rhododendrons that require substantial sun exposure to bloom prefer an eastern exposure, but might be damaged if exposed in the afternoon. Of course, sun exposure is diminished all the way around during winter when days are shorter, the sun is lower on the horizon and sunlight must penetrate more of the atmosphere.

Exposure may change through the seasons, as sources of shade are more or less able to provide shade. During winter, when sunlight is received from a lower angle, it may be obstructed by buildings or trees that will not provide shade during summer when sunlight is received at a more vertical angle. Deciduous trees that may provide shade during summer defoliate during winter, so that exposure to warming sunlight is actually enhanced during winter instead of summer. This is how deciduous shade trees south of the home help conserve energy otherwise used for winter heating and summer cooling.

Flower of the Week:
Fairy primrose

I really dislike primroses. I tried growing some several years ago, but found that handling them causes a severe rash resembling that caused by poison oak. Because this allergy is somewhat rare, it is not often discussed, so garden enthusiasts who enjoy primroses but are allergic to them may not be aware of what is causing their symptoms. Primroses are otherwise exceptional perennials that are used primarily as cool-season annuals.

Fairy primrose, Primula malacoides, if planted early in autumn, will bloom through late winter and into spring. Small flowers are suspended in several distinct circular whorls arranged evenly along vertical stems that can be a foot high. Floral color may be white, pink, lavender and "pinkish" red and rosy red. The rounded and lobed leaves emerge from basal rosettes on proportionately long petioles (foliar stalks) but only extend a few inches. Fairy primrose is a reliable source of annual color for winter, but is somewhat delicately textured, so is more effective if planted closer together than more spreading annuals would be, or if planted in conjunction with other winter annuals.

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