Dear LASN: Native species should be promoted to compensate for past over-use of exotics. Many natives with high landscape values are not known to designers or the nursery trade. One of the many problems with exotics is that while they are tested for "adaptability," they are not tested for "weed potential," leading to ecological disasters. Michael Parkey, ASLA, Dallas, TX

Dear LASN: In addition to adaptability of the exotic, a thorough consideration of the potential imbalance or disruption the exotic could cause to the existing site needs to be examined. It is more reasonable to promote native species planting due to the lack of study of exotic's side-effects. Columbus, OH

Dear LASN: First the professionals should agree to define what is a "native." I've found many eco-people and industry people do not always agree and that is a problem. LA's should select plants for many differing purposes and ought to consider use of "natives" primarily, but not all natives can fulfill the aesthetics required. Exotics, if not needing much special IPM or chemicals are satisfactory for those few instances. Trenton, NJ

Dear LASN: It is very reasonable to promote native species only plantings. I believe that the competitive nature of the nursery business (i.e., speeding up growing these exotics to landscape sizes) is resulting in plantings that lack vigorous, striving characteristics. Hardiness is being bred out of most of these hybrids. Fortunately interest in, use of, and availability of native plants are increasing by LA's like myself. There really are quite an adequate range of native plants that will do the job superbly. Ed Petcavage, RLA, Weston, MA

Dear LASN: I am a landscape architect not a zealot. Native is defined by a romantic notion of how things were. Many Asian species are now naturally adapted throughout the U.S. and can be thought of as native. Right plant - right place. Native species have a proper place, not everywhere, especially in urban conditions. Boston, MA

Dear LASN: I (and other foresters, horticulturists and LAs) always recommend indigenous species native to the site, region or environment. Exotics can be invasive, can carry problem insect or disease pests, and some cannot withstand our extreme in hot and cold. If I use them at all it would be indoors or in greenhouse operations.