| larva | The immature form of an insect that undergoes complete metamorphosis. Different from the adult in form. Also called a caterpillar. |
| latent bud | A bud that does not break during the season after it is formed. Usually found on the lower portion of a shoot, it does not expand under normal growth stimuli, but will break if the growth above it is damaged or pruned away. |
| lateral | A branch attached to and subordinate to another branch or trunk. |
| lateral bud | A bud on the side, rather than the tip, of a stem. |
| lateral meristem | A region where cells divide, located along the length of a stem or root. |
| latex | A thick, white, fluid secretion of many plant species. |
| laticifer | A cell producing latex. |
| layering | A method of stimulating adventitious roots to form on a stem. There are two primary methods of layering. In ground layering, a low-growing branch is bent to the ground and covered with soil. In air layering, moist rooting medium is wrapped around a node on an aboveground stem. |
| leaching | Movement of water and soluble nutrients down through the soil profile. |
| leader | A developing stem or trunk that is longer and more vigorous than laterals. See central leader. |
| leaf | An outgrowth of a stem, usually the principal organ of photosynthesis. |
| leaf primordium | An immature leaf, located at a stem tip. |
| leaf rosette | A group of leaves radiating from a short stem. |
| leaf scar | A visible, thickened crescent or line on a stem where a leaf was attached. |
| leaf tendril | A modified leaf or leaf part used as a grasping organ. |
| leaflet | A single division of a compound leaf. |
| lenticel | A small opening on the surface of fruits, stems, and roots that allows exchange of gases between internal tissues and the atmosphere. |
| lepidoptera | An insect family made up of species having four wings covered with minute scales. Members undergo complete metamorphosis through the egg, larva, pupa, and adult stages. Includes butterflies and moths. |
| lignin | A tough, durable plant substance deposited in cell walls, especially in wood. |
| lime | A rock powder consisting primarily of calcium carbonate. Used to raise soil pH (decrease acidity). |
| loam | A soil with roughly equal influence from sand, silt, and clay particles. |
| lodge | To fall over, usually due to rain or wind. Corn and tall grasses are examples of plants susceptible to lodging. |
| long-day plant | A plant requiring more than 12 hours of continuous daylight to stimulate a change in growth, e.g., a shift from the vegetative to reproductive phase. See short-day plant, day-neutral plant. |
