lanceolate or lance-shaped - a leaf having a narrow pointed tip and leaf blade width less than one half the length of the blade. In the shape of a lance.
landscape - a definable, distinct area either arranged by people or by nature. It includes all the plants (softscape) and non-living components (hardscape) found in that area.
landscape horticulture -  the branch of horticulture that deals with the cultivation of plants for their aesthetic value in the landscape. A sub-group of ornamental horticulture.
landscaping - the process of arranging soil, water, plants, and structures to develop a space with a particular tone or appearance.
large size - according to the The American Hosta Society, there are five size categories of hosta including Giant, Large, Medium, Small and Miniature.

Large hostas form a clump that is 18 to 28 inches in height and 81 to 144 square inches in area.

larva - (plural = larvae) the juvenile or immature stage of an insect or nematode. Caterpillars are the larvae of moths and butterflies while grubs are the larvae of beetles. Larvae are often wormlike in appearance.
latent bud - a bud that does not develop (open) in the season in which it was formed. Think of them as buds in waiting. If needed, they can open into new leaves or flowers or stay latent the entire season.
lateral bud - a bud on the side of a stem that grows laterally from that stem.
See apical bud.
lath - a frame or cover made of narrow slats to provide shade for plants.
lath house - a garden structure covered with thin strips of wood and used for growing shade plants or sheltering tender seedlings.
lawn - an area of the landscape that is covered with turfgrass species.
layering - a propagation method in which a part of a stem on a plant is buried or held down in contact with the soil in an effort to make new roots. Many common shrubs with long, weeping canes may be propagated in this manner. Vines and brambles may do this naturally. Once the new roots develop, that part of the stem may be cut off and planted separately.
See air layering.
leaching - water passing through soil or growing media has the ability to "flush out" soluble salts and other mineral elements. This may be a good thing if the soil or container has an excess of soluble salts. However, it can also result in the rapid loss of nitrogen from sandy soils where water moves through quickly.
leader - refers to the tallest, terminal branch on a plant. Ideally, the central leader of the tree will be uniformly straight from the ground to the top of the tree. However, if, during the growth of the tree, the leader is damaged or removed, side branches will turn upward and try to replace it. In a young seedling, this may result in a nearly straight single leader in the mature tree. In older plants, the growth will be distorted and the new leader will have a weak connection to the trunk.
leaf - the primary plant organ which is the site of photosynthesis. It is also key to the water translocation system of the plant since it is the place where evaporation (transpiration) occurs.

Most plants have either simple or compound leaves comprised of a stem (petiole) and one or more blades.

leaflet - compound leaves consist of a stem (petiole) and two or more small blades called leaflets. For example, rose leaves consist of 3 to 7 leaflets on their compound leaves. 
leaf blade - the thin, usually flat part of a leaf that extends from the stem (petiole) and is the main site of photosynthesis. It is what most people call the foliage.
leaf mold - a soil amendment or potting media component composed of partially decayed leaves.
leaf scar - scar left on a cane after a leaf falls off.
legginess or leggy - describes a plant that has grown unnaturally tall with longer than normal distance between the internodes. Usually caused by the plant receiving inadequate light for its proper growth. See etiolation.
legume - member of plant family Fabaceae (formerly Leguminosae) also called the pea or bean family. This is a group of plants noted for having bean like fruit and for having a soil bacteria associated with the roots that is able to fix nitrogen from the air for use by the plant.
lenticel - small usually horizontal openings in the bark of some plant species such as cherry (Prunus). They are involved in gas exchange between the plant and the atmosphere similar to stoma but lenticels do not have the ability to open and close. They are open all the time.
lesion - a wound, discoloration or scar caused by disease or physical injury.
lethal dose 50 or LD50 - the amount of a toxic substance required to kill 50 percent of a test population of animals. The lower the number, the more toxic the material.
liana - this is a general botanical term to describe woody vines similar to the way terms such as tree or shrub are used to indicate a plant's growth habit. These are plants that start in the soil and climb toward the sun usually attached to trees or some other support such as a wall or trellis.

Clematis, wisteria and trumpetvine would be examples that are common found in the home landscape. Of course, there are many other such plants found throughout both the tropical and temperate zones of the world.

light - light, whether from the sun or electric bulbs, is required for all plant growth. It is, of course, a key element of photosynthesis which ultimately supports all life on earth.

Light has three aspects that are important to plant growth including quality (light spectrum), intensity (nearness) and duration (day length). Each plant species has its own minimum requirements for each of these factors in order to grow, flower and reproduce properly.

light soil - a soil composed predominately of sand which means that it may drain well or excessively and may not hold nutrients well.
ligule - a thin, membranous structure found between the stem and the blade of most grasses. It is attached to the blade and may often be used to identify a grass species.
lime - calcium compounds that, when applied to the soil, cause the pH of the soil to become more alkaline i.e. less acid. It should only be applied to beds and borders as the results of a soil test from a reputable university or commercial laboratory.

Unfortunately, lime has become something that people apply for plant problems when they don't know what else to do. It does not get rid of grubs or cure diseases. Lime only acts to reduce the acidity of the soil.

line out - to temporarily plant young seedlings or cuttings in the open ground in a row, fairly close together, for later transplanting, potting, or selling.
liner - a small grafted plant, rooted cutting, or seedling that is ready for transplanting into a pot, transplant bed, or nursery row.
loam - a soil consisting of a mixture of sand, silt and clay. It is usually rich in organic matter, does not compact easily, and drains well after watering. Often an ideal soil for plant growth.
long day (LD) - a plant requiring exposure to long days (12 to 16 hours) to initiate production of flower buds. In fact, it is often the amount of darkness that is important. Many of these plants need to be exposed to less than 8 hours of total darkness to trigger bud formation.

See Long-Day Plant, Short-Day Plant and Day Neutral Plant

lutescent - some hosta cultivars change color as the season progresses.  Lutescent or lutescence refers to those that start the season as a dark color but get lighter and more yellow in late summer. This occurs every growing season and is not the result of bleaching due to poor nutrition or too much sun. Here is a list of lutescent hostas.


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