OFFSET: A young plantlet which appears on a mature plant. An offset can generally be detached and used for propagation.

OPEN POLLINATED: Plants pollinated by natural plant movement, wind, or insect activity, not controlled by man.

OPPOSITE: Leaf form, where the leaves are arranged in opposite pairs along the stem. Compare alternate.

ORGANIC: Of plant or animal origin.

ORGANIC GARDENING: The method of gardening utilizing only materials derived from living things.

ORGANIC MATERIAL: Any material which originated as a living organism.

OSMUNDA FIBER: The roots of the fern Osmunda regalis, used for making Orchid Compost.

ORNAMENTAL: A plant that is grown strictly for its foliage or flower rather than for food or any other economic use.

OVER-POTTING: Repotting a plant into a pot which is too large to allow successful establishment.

OVERSEEDING: Planting on top of an existing garden or lawn. Rye grass over lawns for winter. Wildflower seed broadcast in meadows.

OVERWINTER: The process bringing frost-tender plants through the winter by moving them indoors.