Ivydene Gardens Glossary: P

Packs Compartmented trays in which individual seeds or seedlings are grown.

Pan 1) A shallow, earthenware or plastic pot that is much wider than it is deep. 2) A layer of soil that is impermeable to water and oxygen and impedes root growth and drainage. Some pans (hardpans) occur naturally on clay or iron-rich soils. Soils capped (see Capping) by heavy rain or excess watering, or by continuous use of cultivation machinery are also known as pans or hardpans.

Panicle An indeterminate, branched inflorescence often consisting of several racemose branches. The term is also loosely used to describe any type of inflorescence.

Parterre A level area containing ornamental beds, often with low-growing plants and enclosed in dwarf hedges (see knot garden).

Parthenocarpic The production of fruit without fertilisation having taken place.

Pathogens Micro-organisms that cause disease.

Patio Today meaning a paved area in a garden, attached to a house, the word derives from a Spanish word meaning paved courtyard.

Peat Partially decayed, humus-rich vegetation formed on the surface of waterlogged soils. Moss or sphagnum peat is largely derived from partially decayed sphagnum moss and is used in potting composts. Sedge peat is derived from sedges, mosses and heathers; it is coarser than moss peat and is less suitable for potting composts.

Peat bed Beds usually constructed from peat blocks and filled with very peaty soil; used to grow acid-loving plants, particularly in soils with a high pH.

Peat blocks Blocks of peat cut from natural peat deposits.

Peat substitute A term applied to a number of different organic materials — such as coconut fibre — used in place of peat for potting composts and soil improvers.

Peduncle The stalk of a flower.

Peltate (of leaves) A leaf with the stalk usually attached centrally beneath the leaf blade: sometimes the stalk may be off-centre within the leaf margin.

Perennial Strictly, any plant living for at least three seasons; commonly applied to herbaceous plants and woody perennials (i.e. trees and shrubs). (See also Annual, Biennial.)

Perianth The collective term for the calyx and the corolla, particularly when they are very similar in form, as in many bulb flowers.

Perianth segment One portion of a perianth, usually resembling a petal and sometimes known as a tepal.

Perlite Small granules of expanded, volcanic minerals added to growing media to improve aeration.

Perpetual Of plants that bloom more or less continuously throughout the growing season or over long periods of time.

Pesticide A chemical substance, usually manufactured, that is used to kill pests including insects (insecticide), mites (acaricide) and nematodes (nematicide).

Petal A modified leaf, often brightly coloured; one part of the corolla usually of a dicotyledonous flower.

Petiole The stalk of a leaf.

pH A measure of alkalinity or acidity, used horticulturally to refer to soils. The scale measures from 1 to 14; pH 7 is neutral, above 7 is alkaline, and below 7 acid (see also Acid, Alkaline and Neutral).

Photosynthesis The production of organic compounds required for growth in plants by a complex process involving chlorophyll, light energy, carbon dioxide, and water.

Picotee A term describing petals with a narrow margin of a contrasting colour.

Pinching out The removal of the growing tip of a plant (by finger and thumb) to induce the production of sideshoots or the formation of flower buds. Also known as “stopping”.

Pistil See Carpel.

Pith (of stems) The soft plant tissue in the central part of a stem.

Pleaching A technique whereby branches from a row of trees are woven together and trained to form a wall or canopy of foliage.

Plunge To sink a pot up to its rim in a bed of ashes, peat, sand, or soil to protect the roots of the plant or plants in the pot from extremes of temperature.

Pod An ill-defined term generally applied to any dry dehiscent fruit; it is particularly used for peas and beans.

Pollarding The regular pruning back of the main branches of a tree to the main stem or trunk, or to a short branch framework, usually to a height of about 2m (6ft) (see Coppicing).

Pollen The male cells of a plant, formed in the anther.

Pollination The transfer of pollen from anthers to stigmas. (See also Crosspollination, Open-pollination, and Self pollination.)

Pollinator 1) The agent or means by which pollination is carried out (e.g. insects, wind). 2) Used in fruit growing to describe a cultivar required to ensure fruit set on another self- or partially self-sterile cultivar.

Ponderisms

What disease did cured ham actually have?

If a deaf person has to go to court, is it still called a hearing?

Why do people pay to go up tall buildings and then put money in binoculars to look at things on the ground?

If electricity comes from electrons, does morality come from morons?

Pollution

"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it." - Quotation from President George W. Bush

Polyembryonic Containing more than one embryo in an ovule or seed.

Pome fruit A firm, fleshy fruit formed by the fusion of the ovary and the hypanthium (the fused base of calyx and corolla); for example an apple or pear.

Pompon Usually small, almost globular flowerheads made up of numerous florets.

Potting compost (also potting mix or potting medium) A mixture of loam, peat substitute (or peat), sand, and nutrients in varying proportions. Soil-less composts contain no loam and mainly comprise peat with nutrients added.

Potting on Transferring a plant from one pot to a larger one.

Potting up Transferring seedlings into individual pots of compost.

Pricking out The transferring of young seedlings from where they have germinated in beds or pots to positions where they have room to grow on.

Propagation The increase of plants by seed (usually sexual) or vegetative (asexual) means.

Propagator A structure that provides a humid atmosphere for raising seedlings, rooting cuttings, or other plants being propagated.

Proximal end (of cuttings) The end that was originally nearest to the crown of the parent plant.

Pruning Removing dead or unwanted shoots or branches from a plant. Pruning can encourage more vigorous growth in the plant.

Pseudobulb The thickened, bulb-like stem of a sympodial orchid arising from a (sometimes very short) rhizome.