Glossary of Gardening Terms

Index P

Palea:
   A floral bract of a grass flower.
Palm:
   Member of the Palmae or Arecaceae family.
Palmate:
   The arrangement of leaf veins or leaflets in such a way that the main divisions arise from a single point.
Pan:
   Shallow dish used for growing alpine plants and sowing seeds; often set into a raised bed.
Panicle:
  An inflorescence type where branches of the inflorescence are themselves branched.
Papillose:
   Covered with little protuberances or vesicles.
Paripinnate:
   Compound leaves with an even number of leaflets.
Parthenocarpy:
   Fruit development without normal fertilisation of the egg cell in the ovule.
Parthenogenesis:
   Development of a new organism from an unfertilised egg.
Parallel-nerved:
   Leaves with unbranched veins.
Parasite:
   Organism living on and drawing nourishment from another.
Parasitic plant:
   A plant which lives on, and acquires it's nutrients from another plant. This often results in declined vigor or death of the host plant.
Parenchyma:
   Undifferentiated tissue of cells present in various parts of plant.
Patens:
   Spreading.
Pathogen:
   Any organism which can cause disease.
Peat:
  

Moisture retentive, humus rich, acid, partially decayed organic matter, with a pH of up to 6.5. Used mainly for potting composts and as a mulch. Derived from sedges (sedge peat) or sphagnum moss (sphagnum peat) and occurring in boggy, waterlogged conditions.

NOTE: Now being phased out in favour of peat substitutes such as coconut fibre (coir), garden compost, mushroom compost, granulated bark and leaf mould.

Peat Bed:
   Area edged with peat blocks and filed with moist, peaty soil, for growing acid loving plants.
Peat moss:
   The partially decomposed remains of various mosses. This is a good, water retentive addition to the soil, but tends to add the acidity of the soil pH.
Pectin:
   Carbohydrate, present in cell-wall of plants.
Pectinate:
   Arrangement of plant organs, usually leaves, in regular, comb-like rows , either single or double ranked.
Pedicel:
   A small stalk attaching a flower or fruit to the main branch of the inflorescence.
Peduncle:
  The main branch of a solitary inflorescence.
Peltate:
   Shield-shaped; of leaves where the stalk arises from the geometric centre of lamina.
Pendant:
   Hanging.
Pepo berry:
  A type of berry with a tough rind that is not easily peeled away. (e.g., pumpkin)
Perennial:
  Any plant that normally lives more than two years.
Perfect flower:
   A flower having both a pistil and stamens.
Perfoliate:
   Leaves with basal lobes uniting round the stem.
Perianth:
   Floral organs which surround the stamens. The collective term for sepals and petals.
Pericarp:
  The fruit wall which develops from the ovary wall. The pericarp may be divided into the endocarp, mesocarp and exocarp.
Perigynous:
   A type of flower structure in which sepals, petals and stamens appear to arise on the side of the ovary.
Perlite:
   Light granules of volcanic minerals added to soil or to potting and seed composts to improve aeration.
Permeable:
   Soil not impeding the diffusion of water.
Perpetual-flowering:
   Describes a plant that bears more or less continuously throughout the year.
Persistent:
   Remaining attached to the plant.
Pesticide:
   Chemical treatment used to control or eradicate pests, diseases or weeds.
Pests:
   Loosely, vermin that feed on plants, and often transmit disease. Any insect or animal which is detrimental to the health and well being of plants or other animals.
Petal:
  The flower parts which are usually showy, and collectively called the corolla.
Petiole:
  The leaf stalk which attaches the leaf blade to the plant stem.
pH:
   pH is a measure of the amount of lime (calcium) contained in your soil. A soil with a pH lower than 7.0 is an acid soil, a soil pH higher than 7.0 is alkaline soil. Soil pH can be tested with an inexpensive test kit. Many garden plants prefer neutral to slightly acid soil with pH 5.5 - 7.5.
Phloem:
  A tissue which transports organic materials such as sugars through the plant.
Photoperiod:
   The number of hours of light in a 24-hour period.
Photosynthate:
   A general term for starch, sugar or any other type of carbohydrate generated as a result of photosynthesis.
Photosynthesis:
  The sequence of chemical reactions performed by green plants in which light energy is used as an energy source to convert carbon dioxide and water into carbohydrates.
Phylloclade:
   Flattened stem resembling a leaf.
Phylogenetic classification:
   Grouping plants according to their genetic relationships, with most closely related plants being most closely grouped.
Phototropism:
  The bending of plants in response to a light source, usually in response to differential auxin concentrations in the stem.
Phytochrome:
  A reversible pigment occurring in green plants that changes form in response to exposure to light and dark, permitting plants to measure the length of the dark period.
Pinch Out:
   (Stop) To remove soft growing points to encourage the bushy growth of sideshoots.
Pinnate:
  The arrangement of leaf veins or leaflets in such a way that the main divisions arise along a central axis, like a feather.
Pinnule:
   Leaflets of a pinnately -compound leaf.
Pistil:
  The unit of the gynoecium composed of stigma, style and ovary.
Pith:
   Central tissue of a stem or root.
Plasma membrane:
   The semi-porous outer membrane of a cell, found between the cytoplasm and the cell wall.
Plunge:
   To sink a container to its rim in ashes, peat, sand, or soil to insulate the roots and prevent the plant from drying out.
Pod:
  

One-celled fruit of the Leguminosae family that splits along 2 sides to disperse ripe seeds.

Loosely, any dry fruit that splits to disperse seed.
Pollard:
   To cut branches back hard to the main trunk of a tree in order to restrict growth.
Pollen:
   Grains released from anthers containing the male element necessary for fertilisation.
Pollinate:
   To transfer pollen from the anther to the stigma.
Pollination:
   The transfer of pollen from the anther of a stamen to the stigma of a pistil.
Pollinator:
   The vector such as wind, insects or birds which carries pollen from one flower to another.
Polliniser:
   A plant which serves as a source of pollen.
Ponpom:
   A roughly spherical flower with tightly packed florets that are often curved inwards.
Pome fruit:
   A fleshy fruit in which the succulent tissues are derived from a greatly enlarged receptacle. (e.g., apple or a pear)
Pot bound:
   A condition which exists when a potted plant has outgrown its container. The roots become entangled and matted together, and the growth of the plant becomes stunted. When repotting, loosen the roots on the outer edges of the root ball, to induce them to once again grow outward.
Pot on:
   To remove a plant (usually a cutting or seedling) from an outgrown container, and place it with fresh compost in a larger container, with room for further growth.
Potting Compost:
   Well-drained but moisture retentive growing medium used mainly for container-grown plants. Loam-based potting compost is based on loam mixed with peat (or substitute), and Perlite, vermiculite, or sharp sand. Loamless potting composts are based on peat (or substitute), mixed with sphagnum moss and Perlite or vermiculite.
Pre-Chill:
   Stratify.
Pre-soak:
   To soak the seed in recently boiled water for between 10 minutes and 72 hours, depending on the seed species, to soften the seed coating prior to sowing.
Prickle:
   A sharp structure arising as a modification of the epidermis found randomly on bark or other plant parts.
Prick Out:
   To transfer seedlings or small cuttings from where they have propagated into appropriate containers to grow on.
Procumbent:
   Lying flat or trailing.
Propagate:
   To increase plants by seed or cuttings etc.
Propagator:
   Small closed case with a transparent lid, used to provide a humid atmosphere under glass, usually with bottom heat, for rooting cuttings, germinating seed, or raising other plants.
Prostrate:
   Describes a plant with a spreading habit or trailing stems lying flat on the ground.
Pruinose:
   White-frosted.
Prune:
   To cut or lop superfluous branches etc. in order to induce regular growth.
Pseudobulb:
   Swelling of the lowest node of a stem, (applied to orchids).
Psuedocephalium:
   Woody, flower-bearing, densely spined area near the apex of some cacti.
Ptisan:
   A nourishing concoction (as in herbal tea). (Also called a Tisane)
Pubescent:
   Covered in downy hairs.
Purgative:
   Aperient.

Last updated 10 March, 2002
© copyright 1999, P. A. Owen