perennials: Any plant with a life cycle of three or more years. Herbaceous (non-woody) perennials include flowering plants and herbs, mainly. Woody perennials include trees and shrubs. Longevity depends on the plant and growing conditions.

pH: The measure of soil's acidity. Soil with low pH means it's too acidic; soil with high pH means it's alkaline. Most plants grow best in soil with a pH value between 6.5 and 7.2. Neutral soils measure 7.

photosynthesis: The process through which plants take nutrients from the air and from the water in the soil to produce sugars that fuels the plant's growth.

primary nutrients: Nitrogen, phosphorous, and potassium are the three nutrients plants need in the largest quantities.