Gardening Glossary

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offset

A new shoot that forms at the base of a plant or in a leaf axil.

oil

See horticultural oil.

open-pollinated seed

Seed produced from natural, random pollination so that the resulting plants are varied.

organ

A part of a plant, composed of different tissues, that acts as a functional unit.

organelle

A structure within a cell, such as a chloroplast, that performs a specific function.

organic

Referring to substances that contain both carbon and nitrogen.

organic fertilizer

A natural fertilizer material that has undergone little or no processing. Can include plant, animal, or mineral materials.

organic matter

Any material originating from a living organism (peat moss, plant residue, compost, ground bark, manure, etc.).

organism

A living plant or animal.

ornamental plant

A plant grown for beautification, screening, accent, specimen, color, or other aesthetic reasons.

orthoptera

An insect family made up of species having a tough, leathery shell, membranous hindwings, and straight forewings. Includes locusts, crickets, grasshoppers, and katydids.

osmosis

Passage of materials through a membrane from an area of high concentration to an area of lower concentration.

ovary

The part of a flower containing ovules that will develop into seeds upon fertilization. Along with the style and stigma, it makes up the pistil (female sexual organ).

ovule

Within the ovary, a body that will develop into seeds after fertilization.

oxidation

The chemical process by which sugars and starches are converted into energy. In plants, this is also known as respiration.