Many factors influence the success or failure of a plant in the landscape. To be successful, it is important to analyze the site and select a plant that will thrive in those specific conditions. Some of the factors to be evaluated are: how much light the plant will receive, soil type, the amount of moisture in the immediate area and exposure to air pollution or salt. Sometimes it is easy to see that a location gets full sun, but often there are trees and buildings in the area that create shade. To determine how much light a plant will receive, check the area at several times of day on sunny days, several times in the growing season. If a site gets direct sunlight most of the afternoon, it is considered to be in full sun. If the site gets only morning sun or the area is light but doesn't receive any direct sun, it is considered to be shaded. An area that doesn't get any direct sun and the light is limited by overhanging trees or structures is said to be in deep shade. All soils are made up of particles of clay, silt and sand. There should also be some organic materials such as decomposing leaves, twigs and plant material. To determine how much of each ingredient there is in your soil, fill a glass jar one third to one half full with a representative soil sample. Then fill it with water, cap it and shake it until everything is stirred up. Set the jar down and watch. The sand will settle out first within a few minutes. In a few hours, the silt will settle and by the next day the clay will have settled. On top of all that, you should see the organic matter, though some may still be floating. Since your soil will now be clearly layered, you can easily determine what predominant type of soil you have so you can select the appropriate plants.

Although you can control the amount of moisture you provide to a plant, you can't control what nature will provide. Because of the contours of the land and the soil types, some areas will hold more moisture. Checking on a site occasionally during the year is the best way to determine if it is going to be particularly dry or wet.
Exposure to salt comes from de-icers used on sidewalks, driveways and roads. Whether it is in the soil or splashed up onto the foliage, salts can harm plants. Another potential problem is air pollution. While this is usually an urban problem, rural areas with nearby industrial sites may also be exposed to air pollutants that have an adverse effect on plants.