Glossary of horticultural and botanical terms
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Acaricide
A chemical that kills mites and spiders.
Acerose
Narrow with a sharp point. Usually refers to foliage.
Achene
Small dry, one-seeded fruit with an undivided outer wall.
Acid
A term for soil that has a low pH level - hence Acidity. See also pH.
Activator
A chemical added to another chemical to increase its activity.
Active Ingredient
The active chemical in a product as distinct from surfactants, carriers, diluents etc
Acuminate
A leaf that tapers, with slightly concave sides. to a point.
Acute
A leaf with straight sides tapering to a point.
Adpressed
Tightly pressed against. Usually said of foliage that is held close to the stems, as in many conifers.
Adventitious
Occurring away from the usual place - eg., aerial roots on Hedera (ivy) stems. A bud or root that appears on tissue where it would not normally be expected.
Aerial Layering
A propagation process whereby roots are produced on a branch by simulating the subterranean environment.
Aerial Roots
A root appearing above soil level, often from a branch. Used for both support and feeding eg. many orchids and Monstera.
Algicide
A chemical that kills algae.
Alkaline
Said of soil of high pH. Alkalinity is the opposite to acid and acidity. See also pH.
Alpine
A habitat above the snow line and the plants that live there. Often used to refer to any small rockery plant of similar culture.
Alternate
With leaves arranged singly on different sides of the stem, and at different levels.
Angiosperm
A plant that has its seeds enclosed in an ovary. The flowering plants. From Angeion (vessel) and Sperma (seed). See also Gymnosperm.
Annual
A plant that completes its life cycle from seed to maturity in one year.
Anther
The pollen-bearing sac at the tip of a stamen.
Apex
The tip, usually of a leaf - hence apical and apiculate.
Aphicide
A chemical that kills aphids, usually specifically intended for that purpose, as opposed to a general insecticide.
Appendage
An attached secondary part, such as a hanging or projecting bract.
Areole
A raised or sunken spot on the stem in cacti-site of one or more spines or flowers.
Articulate
A stem that is jointed or with nodes where it can be easily separated, ie Zygocactus.
Asexual Propagation
To produce plants without using seeds. Vegetative propagation by methods such as cuttings, layering, tissue culture, etc.
Attenuate
A long, very gradually tapering stem
Avicide
A chemical agent used to destroy or repel birds.
Axil
The upper angle that a leaf-stem makes with the stem from which it appears. Site of many shoots and flower buds, hence axillary.
Bactericide
A chemical that stops or prevents the growth and development of bacteria.
Bare Rooted
Trees and shrubs that are lifted from the open ground and sold with minimal root protection, e.g. roses with their roots wrapped in shredded newspaper.
Bark
The protective hard woody outer layer of a stem.
Basal
At the bottom, e.g. a basal shoot that appears where the stem emerges from the ground.
Base Plate
The flattened or conical stem within a bulb. Usually represented externally by a fleshy plate on the base of a bulb or corm.
Berry
A pulpy fruit, usually small and containing many seeds.
Bicolour or Bicolor
A flower or leaf with two distinct colours borne at the same time.
Biennial
A plant that completes its life cycle over two-years, grows and sets up reserves the first year, flowers, seeds and dies the next year.
Bi-generic
A hybrid between two genera of plants, as opposed to more common hybrids between species or varieties.
Binomial Nomenclature
The system of classification devised by Linnaeus (Carl von Linné) and first introduced in his Systema Naturae (1735) and Genera Plantarum (1737) whereby every living thing is grouped using two names (binomial); genus and species.
Bipinnate
A leaf that is doubly pinnate, i.e. the primary leaflets are divided again into secondary leaflets, as in Jacaranda.
Bisexual
Having organs of both sexes functioning in the same flower.
Bloom
1. A flower. 2. A fine powdery coating found on some leaves and/or fruit.
Bolt
To flower and set seed prematurely. Usually due to planting too late, unfavourable or variable climatic conditions.
Boss
A roundish protuberance on some part of a plant. Generally refers to the compact mass of central stamens projecting above the plane of the petals in some flower types, such as anemone centred camellias or chrysanthemums.
Bottom Heat
Artificially heating the root zone of a cutting bed or pot. Usually by electric heating pads or cables.
Bract
A modified leaf or sepal at the base of a flower, often the most colourful part. e.g. Poinsettia and Bougainvillea.
Brassica
Those members of the Cruciferae normally used as edible vegetables ie cabbage, cauliflower, brussel sprouts, broccoli, kale, turnips, swedes and rape.
Break
A spontaneous change in colour or pattern of a flower as the result of a benign virus.
Bristles
Short stiff hairs.
Broadcast
To scatter seeds by hand.
Bud Break
The period when new growth begins in spring.
Budding
Grafting by inserting a stem-bud of one plant into the cambium layer of another similar plant.
Bulb
An underground storage organ composed of fleshy scales.
Bulblets
Small seedling bulbs or the small immature bulbs that often form around a larger parent bulb during the growing season. Also known as bulbils.
Bullate
A puckered surface. A seersucker effect seen on some leaves, e.g. Myrtus bullata.
Calcareous
Chalky, containing unusually high levels of calcium carbonate (lime).
Calcifuge
Plants that are intolerant of alkalinity. e.g. Rhododendron, Camellia and Protea.
Callus
1. The protective tissue that forms over a wound. 2. The white tissue that forms on the subterranean part of a cutting prior to root formation.
Calyx
The outer covering, often decorative, of a flower bud, usually consisting of united sepals. Plural, calyces.
Cambium
Basic growth cells. May be found in leaves, roots or stems but best known as the layer of growing cells immediately beneath the bark or skin of a stem. Hence cambium layer.
Campanulate
Shaped like a bell. Usually referring to a flower, implies not only shape but also a somewhat pendulous habit.
Canaliculate
With upturned edges.
Cane
1. The jointed stem of large grassy plants, eg., bamboo. 2. The long arching growths of many plant genera, e.g. orchids, raspberries, roses.
Capsule
A dry, divisible fruit composed of two or more sections.
Capillary Action or Capillarity
The process whereby water is drawn up or down a narrow tube (or soil surface) by the interaction of the forces of cohesion, adhesion and surface tension.
Carpel
One of the units comprising a pistil or ovary.
Catkin
A scaly-bracted, usually hanging inflorescence, such as those of Garrya elliptica. Also known informally as a tassel.
Chilling Requirement
Some plants, particularly fruit trees, require a period of cold to grow and perform properly. The degree of cold required is known as the chilling requirement. Little used term among gardeners but important to orchardists.
Chimaera
A mutation that produces two clearly distinct tissue types. Such plants often show features of two distinct species, e.g. Cantua buxifolia often develops branches that appear to be identical to the closely related species Cantua bicolor.
Chlorophyll
The green present in leaves and plants, necessary for the process of photosynthesis, which uses solar energy to produce essential plant growth products. See also photosynthesis.
Chlorosis
An abnormal yellowing of a plant, most commonly due to a lack of iron in the soil, or the inability of a plant to absorb iron from soil.
Ciliate
Having a fringe of small hairs.
Cladode
A flattened stem having the form and function of a leaf. Also known as a cladophyll or phylloclade.
Cladophyll
See Cladode.
Clone
An exact replica of the parent plant. Any plant propagated by vegetative means, such as division, budding, cuttings, layers. These methods are widely used for plants that do not grow true from seed.
Column
The structure formed by the union of style and stamens, as in the Orchid family.
Companioning or Companion Planting
A horticultural theory (by no means universally accepted) which proposes that certain plant genera grow better in proximity to certain others, each genus conferring some benefit on the other. For instance, garlic supposedly protects roses from aphids.
Compatible
1. When two or more chemicals can be mixed together without affecting the properties or activity of either. 2. A rootstock and scion that may be successfully joined by grafting or budding.
Compost
1. A mixture of decomposed organic material used as a soil conditioner, mulch and to stimulate plant growth. 2. Sometimes, loosely, a potting mix.
Composite
Like a daisy. That is, a dense grouping of tiny single flowers surrounded by a single row of petals.
Compound
1. A leaf composed of two or more leaflets. 2. A flower composed of many small flowers or florets.
Cone
A dense construction of seed-bearing scales on a central axis, often woody and elongated (pine-cones). Some cones, such as those of yew (Taxus) resemble berries. Hence conifer.
Conifer
A plant that bears its seeds in cones.
Container Grown
Plants raised entirely in containers (pots), as opposed to open ground or field grown.
Cordate
A heart-shaped leaf.
Corm
An underground storage organ similar to a bulb but lacking scales, e.g. Gladiolus.
Cormlets
Small seedling corms or the small immature corms that often form around a larger parent corm during the growing season. Also known as cormels.
Corolla
The petals of a flower. The array of petals immediately within the calyces.
Corona
The crown or circle of appendages around the centre of a flower, usually between the petals and stamens but may be part of the corolla. e.g. the outer circle of stamens, as in Hymenocallis, or an outgrowth of the perianth, as in Narcissus.
Corymb
A more or less flat-topped inflorescence, the outer flowers opening first.
Costapalmate
A specialised form of palmate leaf where the petiole extends into the leaf thereby dividing it at the base, e.g. Sabal palms.
Cotyledon
The first leaf to emerge from a germinating seed. The fleshy seed leaves of a dicotyledon or the initial leaf of a monocotyledon.
Creeper
A trailing or climbing plant.
Crenate
A leaf with shallow, rounded teeth, or scalloped edges.
Crenulate
Finely crenate.
Crown
1. The corona. 2. The base of a plant where stem and root meet. 3. Part of a rhizome with a bud, suitable for propagation by dividing, e.g. rhubarb
Cucurbit
A plant belonging to the gourd family, such as pumpkins, marrows, cucumbers, squash, zucchini and buttercup.
Cultivar
A botanical term for a variety that has arisen or is maintained in cultivation as distinct from a variety that occurs naturally in the wild. A contraction of cultivated variety.
Cuneate
Wedge shaped with a gradual even taper to the base.
Cupressoid
A type of conifer foliage that resembles that of Cupressus, ie green stems with small protuberances but no obvious leaves, needles or cladodes.
Cuspidate
With a sharp pointed tip.
Cutting
An amputated section of a plant or tree that will develop new roots and become self-sufficient. These may be taken from stems, branches, sometimes roots and leaves.
Cyme
A type of broad, flat-topped inflorescence in which the centre flowers open first.
Damping Off
A disease causing abrupt death of apparently healthy seedlings caused by fungi in the soil.
Deadhead
A term used to describe the removal of faded flower-heads to prevent the production of seed. This prevents the plant expending energy producing unwanted seeds and enables it to make new growth. It may also lead to heavier flowering.
Deciduous
A plant or tree that sheds all its leaves for a period of the year. In temperate climates this is usually in winter but in the tropics it may be during the dry season and in arid areas plants are frequently dormant during summer to avoid the desiccating heat.
Defoliant
A chemical used to remove the leaves of a plant.
Defoliate
To strip a plant of its leaves.
Dentate
A leaf with a serrated or toothed edge.
Denticle
A small tooth, as in one section of a dentate leaf.
Denticulate
Very finely toothed.
Desiccate
To wilt and dry out.
Dicotyledons
Plants that produce two seed leaves. Usually the offspring of angiosperms.
Dieback
A variety of fungal diseases that kill part or all of a plant by causing the tissues to die back from a tip or cut branch. Often due to faulty pruning techniques.
Differentiation
The point at which the type of growth is determined, ie when the basic meristem or cambium tissue becomes root, leaf, stem or flower tissue.
Digitate
A leaf shape that resembles the arrangement of the fingers on a hand. e.g. Schefflera.
Dimorphic or Dimorphous
Occurring in two distinct but usually similar forms, often at the same time or within one growing season. Usually distinct from juvenile and adult forms that change over a long period.
Dioecious
With unisexual flowers, male and female blossoms borne on separate plants.
Diploid
A plant with two complete sets of chromosomes.
Disbudding
Removing side flower buds to concentrate growth in a single flower to enlarge it.
Disc
The central area of the flower head, being mostly composed of florets. Used mainly to refer to members of the Asteraceae or other daisy-like flowers.
Dissected
Deeply cut into numerous segments, e.g. weeping maple (Acer palmatum 'Dissectum')
Divaricate
Spreading widely.
Divide
To separate a clump of perennial plants into smaller clumps, hence division.
Divided
Describes a leaf that is separated nearly to the base or the midrib.
Dolomite
The mineral calcium magnesium carbonate, CaMg(CO3)2; a form of lime used to add calcium without greatly altering the soil's pH.
Dominance
A growth characteristic that assumes primary importance. Apical buds are dominant over those lower down the stem. Some plants have dominant flower colour pigments, e.g. purplish pink in evergreen azaleas.
Dormancy
The time when a plant makes minimum growth, Usually but not always occurring during winter. Often when a plant is bare of foliage. Hence dormant.
Drift
1. A term used to describe an informal planting of bulbs. 2. The movement of air borne particles of spray or dust away from the target area.
Drip Line
The circle around the outermost branch tips of a shrub or tree. The limit to which rainwater drips fall from the plant. Used when referring to watering and feeding.
Drupe
A pulpy fruit containing one (rarely two) seeds enclosed in a woody case (stone). e.g. peach and plum.
Dust
1. A chemical applied as a fine powder. 2. Apply a fine coating.
Elepidote
1. Lacking scales, the opposite of lepidote. 2. One of the major divisions of the genus Rhododendron.
Elliptical
A leaf that is longer than it is wide and tapers continually towards the tip and the base from the centre.
Embryo
The young plant within the seed.
Endosperm
The food storage tissue within a seed. Absorbed by the embryo during germination.
Endemic
Native to a particular, often very restricted area.
Entire
A leaf with a continuous, unbroken margin.
Epiphyte
A plant growing on another tree or plant, using roots for support only and feeding from nutrients in water and decaying plant or insect tissue, not from its host, e.g. many orchids.
Ericaceous
Belonging to the Erica family, e.g. Calluna, Erica, Pieris and Rhododendron.
Espalier
A shrub, tree or vine trained formally in two dimensions only - generally against a wall or fence.
Evergreen
Having foliage that remains green and growing throughout the year.
Exotic
A plant that is foreign to the country in which it is growing, as opposed to native or endemic.
Exserted
Protruding, as in the style or stamens of a flower.
Eye
1. An undeveloped growth bud of a storage organ such as a bulb, corm or tuber. 2. A contrasting colour spot in the centre of a flower.
F1, F2 hybrid
Respectively, the first and second generation offspring from a given parent plant or cross.
Falcate
Sickle-shaped or with a pronounced curve. Usually refers to foliage.
Fall
One of the outer petals of Iris and related plants, often drooping.
Family
A group of related botanical genera.
Fasciation
An abnormal growth in which normally cylindrical stems become flattened, or a condition in which several stems become fused together. Quite often seen in delphiniums, lilies and cucumbers.
Fastigiate
Narrow and upright with branches or stems erect and more or less parallel.
Fertilise or Fertilize
1. Apply nutrients, either to the soil or directly to the foliage of a plant. 2. To successfully pollinate.
Filament
A thread-like organ, especially of a stamen supporting an anther.
Floccose
Covered in small woolly or hairy tufts.
Floret
One of many small flowers in a compound head, such as that of broccoli.
Forcing
To artificially speed up maturation or flowering.
Friable
Soil that is easily crumbled or reduced to a fine texture without being dry and dusty.
Frond
The foliage of ferns. Also used to describe leaves of a similar appearance such as the foliage of feather palms.
Fruticose
Having a dense shrubby growth habit.
Fungicide
A group of chemicals that are specifically designed to prevent or destroy any types of fungus.
Generic Name
A plant's first scientific name, indicating the genus to which it belongs, e.g. Pinus.
Genus
A grouping of closely related species. Plural, Genera
Gesneriad
A member of the botanical family Gesneriaceae, which includes African Violets (Saintpaulia), Cape Primrose (Streptocarpus) and Gloxinia (Sinningia).
Glabrous
Smooth, without hairs of any kind.
Glaucous
Leaves with a distinct blue or grey tint, often due to being covered with a waxy bloom that is easily rubbed or marked.
Globose
Globe-shaped or nearly so.
Glochid
A minute barbed spine, often occurring in tufts on Cacti.
Grafting
A propagation method whereby a bud or shoot is severed from its parent plant and joined to a rooted section of another. Used for rapid multiplication of woody plants but generally restricted to those that do not readily strike from cuttings or perform poorly on their own roots.
Grex
A group of seedlings from the same cross. Sister seedlings. A term most commonly used when referring to Rhododendron cultivars.
Growing-On Line
A newly propagated plant ready for potting on or planting out. Also known as a liner.
Gymnosperm
A plant bearing its seeds naked, not enclosed in an ovary. e.g. conifers. Gymnosperms are always wind pollinated. From Gumnus (naked) and Sperma (seed). See also Angiosperm.
Half-Hardy
Able to withstand normal winter conditions but subject to damage in particularly sever or prolonged winters. Rather a vague term.
Halophyte
A plant tolerant of salt in the soil or atmosphere, e.g. Atriplex spp.
Harden Off
To acclimatise or prepare for colder weather.
Hardwood Cutting
A cutting taken from wood of the previous season's growth.
Hardy
Degree of frost tolerance. The minimum temperature a particular plant can be expected to survive, perhaps with some damage. Should be used in conjunction with a rating, e.g. hardy to -10°C. Does not mean tough or disease resistant. Hence hardiness.
Haulm
Stems and leaves of peas, beans, potatoes or grasses.
Heel
A small strip of material from the main stem that is left on a side-shoot cutting. Usually obtained by tearing the side-shoot from the branch rather than cutting it. Meant to improve the chances of a strike, particularly with conifers, but of dubious merit.
Heeling In
Temporarily covering a plant's roots with soil or other moisture retentive material before final planting.
Herbaceous Perennial
A non-woody plant that dies back to the roots in winter, sending up new growth in spring.
Herbicide
A chemical that will destroy growing plants or weeds.
Hermaphrodite
Having functioning male and female organs in the same flower.
Hirsute
Covered with hair.
Honeydew
The sticky secretion of many sap sucking insects. Can lead to fungus problems, especially sooty mould.
Hormone
An imprecise term used for many synthetically produced growth promoting or modifying agents, especially indolebutyric acid, a root forming hormone.
Hose in Hose
A flower with two similar corollas, one within the other.
Humus
The rich debris resulting from the rotting of vegetable and other organic material.
Hybrid
The result of cross-fertilisation of different kinds of parent plants.
Hypocotyl
The stem of a seedling between the shoots and the roots. This area of very soft, easily damaged tissue is of vital importance in seedling development.
Imbricate
Made up of or covered with overlapping tile-like scales.
Incompatible
1. A chemical that is not capable of being mixed or used in combination with certain other chemicals. 2. A rootstock and scion that cannot be successfully joined by budding or grafting.
Indigenous
Native to a particular country or area. See also endemic and exotic.
Indumentum
See Tomentum.
Inflorescence
1. The flowering part of a plant, irrespective of arrangement. 2. The arrangement of blooms in a flower head.
Insecticide
A chemical intended to kill insects.
Integrated Mite Control (IMC)
The use of predatory mites to control plant feeding mites with the strategic use of miticides where necessary.
Integrated Pest Management (IPC)
An ecologically based pest control strategy that includes the judicious use of chemicals and other control measures.
Internode
The length of stem between two nodes, hence internodal and internodal distance.
Invasive
Said of a plant that grows quickly and spreads to occupy more than its allotted space, usually to the detriment of surrounding plants. e.g. couch grass, kikuyu grass, convolvulus, Oxalis, etc.
Juvenile
A young or immature plant. Many plants display distinct differences between juvenile and adult foliage and growth habit.
Keel
1. In a pea-type flower the joined, lowermost petals. 2. A central ridge on the top part of a flower.
Labellum
The lip of an orchid, differing strongly from the other petals.
Laciniate
A leaf with fine lobes giving the impression of being cut by hand.
Lanceolate
A lance-shaped leaf, long and gradually tapering.
Latent Bud
A normal bud that for some reason has not developed. Latent buds will often begin to grow when other, more dominant, growth is removed.
Lateral
On or at the side, e.g. a side-branch produced from a main stalk or trunk.
Layering
Propagation by pinning a partly cut branch down to the ground until it produces roots. See also Aerial Layering.
Lax
Loose, often semi-pendulous or trailing growth.
Leaching
Movement sideways, downwards or outwards of any chemical or fertiliser in the soil as a result of rain or watering.
Leader
The plant's dominant shoot.
Leaflet
One of the smaller leaf-like parts of a compound leaf.
Leaf Axil
The acute angle produced at the junction of a leaf with its stem.
Leaf-Cutting
A method of propagating many tropical plants from portions of their leaves, e.g. African violets, peperomia and Rex begonias.
Leaf Mould or Leaf Mold
The fine compost created by the decomposition of fallen leaves, usually natural.
Leaf Scar
The mark left when a leaf falls. Very noticeable on some plants such as palms.
Leaf Stage
Growth stage of a crop or weed, usually expressed in number of leaves, e.g. second leaf stage.
Legume
A plant that produces pea-type seeds attached alternately to both sides of the pod, e.g. peas, beans and lupins. Hence leguminous.
Lepidote
1. Covered in small scales, the opposite of elepidote. 2. One of the major divisions of the genus Rhododendron.
Lignotuber
A subterranean bulb-like storage chamber of many Eucalypts and some members of the protea family that enables them to regenerate after fire.
Liner
A newly propagated plant ready for potting on or planting out. Also known as a growing-on line.
Linear
A long narrow leaf, with sides almost parallel, as in a blade of grass or our native flax Phormium.
Loam
A friable topsoil containing sand, clay and silt particles, with the addition of organic matter. Hence Loamy.
Lobulate
Having small lobes. Usually refers to leaves or flowers.
Mature
1. A plant that has reached flowering age and is able to reproduce sexually. 2. A fully ripe fruit or seed.
Membranous
Thin and flexible.
Miticide
A chemical compound formulated to destroy mites as opposed to insects.
Monoecious
Having male and female reproductive organs in separate flowers on the one plant.
Monopodial
A plant with a main stem that continues to grow indefinitely without branching, as in orchid genera Vanda.
Monotypic
A single species genus.
Molluscicide
A chemical used to kill or control snails and slugs, e.g. snail baits.
Monocarpic
A plant that dies after flowering. Usually refers to those plants that take longer than two years to reach maturity as opposed to annual and perennials, which are not expected to live beyond flowering.
Monocotyledon
Plants that produce a single seedling leaf and includes grasses and cereals.
Mucronate
With a sharp point at the tip. Usually refers to foliage.
Mulch
A soil-covering used to conserve moisture or prevent root damage by heat or frost. May be of organic matter (compost or peat) pebbles, even plastic.
Mutant
The result of a mutation. A variant, differing genetically and often visibly from its parent or parents and arising spontaneously.
Mycorrhiza
Fungi that form a beneficial association with plant roots and undertake some of the functions of the roots. They may in return be provided with carbohydrates from the plant. Some plants, such as Telopea rely on mycorrhiza for proper development.
Native
A plant that occurs naturally in the area in which it is growing.
Natural Cross
A hybrid that occurs between two distinct but usually related plant species, without human help.
Necrosis
Death of living plant tissue, hence necrotic.
Nectary
The nectar producing part of a flower.
Node
A point on a stem from which leaves develop.
NPK
A measure of the percentages of nitrogen (N), phosphorus (P) and potassium (K) in a fertiliser. A fertiliser with an NPK of 12-10-15 has 12 percent total nitrogen, 10 percent phosphoric acid and 15 percent water soluble potash. NPK is also known as the guaranteed analysis.
Nutrient Deficiency
A deficiency of any substance required for tissue maintenance or growth.
Oblong
A leaf that is longer than it is wide with more or less parallel sides and bluntly rounded ends.
Obovate
Egg shaped, with the broadest end at the top. Usually refers to fruit. See also ovate.
Offset
A small division from the side of a mature clump-forming plant. Usually able to be broken off without lifting the parent plant unlike division.
Open Ground
Plants raised in fields and lifted prior to sale, as opposed to container grown.
Opposite
Leaves on both sides of the stem at the same point on the stem.
Orbicular
A leaf that is almost circular and very flat.
Osmosis
The process whereby the sap is transported around a plant. The diffusion of a liquid through a semipermeable membrane from an area of higher concentration to an area of lower concentration. This continues until there is an equal concentration of fluid on both sides of the membrane. By varying the pressure on the plant cells the rate of osmosis can be varied. A plant can do this itself to some degree but it is also affected by temperature and air pressure.
Ovary
The structure at the base of the pistil in which the seeds of angiosperms develop.
Ovate
Egg shaped, with the broadest end at the base. Usually refers to fruit. See also obovate.
Ovicide
A chemical that destroys eggs.
Palmate
Roughly hand-shaped, with three or more lobes radiating fanwise from the petiole, e.g. most fan palms.
Panicle
A branching cluster of flowers.
Parasite
A plant that lives off another plant and which is usually unable to survive without the host plant until mature.
Pathogen
An organism capable of causing disease. Especially a bacterium or fungus.
Pedicel
The stalk of an individual flower or that of a floret within a compound head.
Peduncle
The main flower stalk, which may support many flowers.
Peltate
Shield shaped. Usually refers to leaves with the petiole attached well away from the edge of the leaf, e.g. Pelargonium peltata.
Perennial
A plant that lives for more than two years and regrows from the same stem or root system each year.
Perianth
A collective term for the entire floral envelope consisting of calyx, corolla, petals and sepals or the calyx and corolla separately.
Pericarp
The outside layer or skin of a fruit.
Petaloid
Resembling a petal. Usually a reference to modified stamens that have taken on a petal-like form.
Petiole
The stalk of a leaf.
pH
The degree of acidity or alkalinity in soil measured on a scale of from 0 (acid) -14 (alkaline) with 7 as the neutral point. A logarithmic measure of the potential of Hydrogen ions. The scientific definition is; the negative common logarithm of the hydrogen-ion concentration in a solution, expressed in moles per litre of solution. Where a neutral solution has a concentration of 10-7 moles per litre.
Pheromone
A substance, often a scent, produced by animals and insects to communicate with others of the same species. Insect sex pheromones are used in IPM programmes to disrupt the breeding of some insect pests, such as moths and beetles.
Photosynthesis
The process whereby plants use solar energy, through the catalytic action of chlorophyll, to convert water and carbon dioxide into carbohydrates.
Phylloclade
See Cladode.
Phytotoxic
Harmful to plants.
Picotee
Edged with a contrasting colour. Usually refers to white flowers with a brightly coloured border. originally a term used to describe carnations but now used for many plants.
Pilose
Covered in a dense layer of soft hairs. Felted.
Pinna
The individual leaflets of a pinnate leaf, plural pinnae.
Pinnate
A leaf form with leaflets arranged on both sides of the stalk (rhachis) in the manner of a feather.
Pistil
The prominent female organ of a flower, including the stigma, style, and ovary and generally surrounded by male stamens and projecting beyond them.
Pollen
The spores or grains borne by an anther, containing the fertilising male gametes.
Pollination
Applying pollen to the stigma.
Polymorphic
Occurring is several forms, ie species with varying leaf forms such Pseudopanax lessonii.
Pricking Out
The initial transplanting of young seedlings or freshly struck cuttings.
Procumbent
Said of a plant which trails without rooting at intervals.
Protectant
A fungicide applied to the plant surface before disease attack to prevent disease penetration and subsequent infection.
Prothallus
The sexual regeneration stage of a fern.
Pseudobulb
The thickened bulb-like storage organ found in many orchids.
Pubescent
Covered, often sparsely, in short hairs.
Raceme
A stalk with flowers along its length, the individual blossoms with short stems, e.g. Delphinium.
Radicle
The root of the embryo seedling, often covered in fine root hairs.
Ray
1. A stem of an umbel. 2. One of the outer flowers of a compound head, e.g. the florets to which the petals are attached in a daisy-like head.
Recurved
Bent backwards and/or downwards. Often refers to petals or sepal, e.g. many Fuchsia flowers.
Reflexed
Sharply recurved.
Reniform
Kidney shaped.
Residual
A chemical designed that remains active for a period in the soil or on the plant.
Respiration
A process similar to breathing whereby plants combine oxygen with carbohydrate molecule and releasing carbon as carbon dioxide and water.
Reticulate
1. A net-like structure. 2. Net-like markings.
Rhachis
The central vein or axis of a leaf or inflorescence.
Rhizome
An underground or surface creeping stem or root that enables plants to spread. May also act as a storage organ.
Rhomboidal
Diamond shaped.
Root-Cutting
A method of propagating Wisteria and other plants from small sections of root.
Root Hair
The very fine hair-like growths at the tip of a root. The most active feeding and growing part of the root.
Rootstock
A rooted section of plant used as the base onto which a scion from another plant is grafted.
Rosette
An arrangement of leaves radiating from a crown or centre, usually close to the ground, e.g. Iceland poppies, lettuce and dandelion.
Run-Off
The excess of a spray solution that runs off a surface after it has been thoroughly wetted.
Russet
A rough brownish marking on leaves, fruits or tubers.
Sac
A pouch-like structure, e.g. a pollen sac.
Sagittate
A leaf shaped like an arrowhead.
Scale
1. The protective covering of many so-called scale insects that suck vital fluids out of plant tissue. 2. A segment of bulb that may in some cases, e.g. lilies, be detached for propagation.
Scandent
Having a climbing habit, also semi-scandent.
Scarify
To weaken the covering of some hard-cased seeds to hasten germination. Large seeds can be nicked with a knife, smaller seeds rubbed between coarse sandpaper.
Scion
A bud or shoot that is grafted onto the stock of another plant.
Sepal
The individual segment of a calyx, an outer petal.
Serrate
A leaf with a saw-toothed, or serrated, edge, with the teeth pointing away from the stem.
Sessile
Without a stalk. Usually refers to leaves or flowers.
Softwood
Unripened, immature tissue of any woody plant. Used for propagation in some species.
Soil Fumigant
A chemical applied to the soil either by injection, mixing or under an impermeable sheet (plastic) for the control of soil pests, diseases and weeds.
Spadix
A fleshy spike or a small flower head.
Spatulate
A oblong leaf that gradually broadens towards the tip.
Species
The basic or minor unit in binomial nomenclature.
Specific Name
A plant’s second name. The name that describes the species, e.g. Pinus radiata.
Spike
A series of stalkless flowers on a single stem. The lower flowers are the first to open.
Sporangia
Spore clusters, usually found on the underside of a sporophyll.
Spore
The reproductive cell of ferns, mosses and fungi, Although distributed like seed a spore differs from a flower’s seed in that it is an asexual reproductive organ rather than the result of sexual reproduction.
Sporophyll
Modified leaves or fronds that bear sporangia. The ‘fertile fronds’ of ferns.
Sport
A mutation showing distinct variations from the norm, e.g. a different foliage form or flower colour.
Spreader
A substance that increases the area that a given volume of liquid will cover, usually by reducing surface tension.
Spur
1. A specialised flowering and fruiting side shoot found in many fruit trees. 2. The tubular structure seen on some flowers, e.g. larkspur and Aquilegia.
Stamen
The pollen-bearing or male organ of a flower. Usually composed of a filament and an anther.
Staminoides
Sterile stamen-like structures without pollen.
Standard
1. A plant grafted onto a tall straight stock stem or trained to a bushy head at the top of a tall stem. 2. A more or less erect petal of a flower, e.g. Iris.
Stellate
Starlike or star shaped, e.g. the flowers of Magnolia stellata.
Sticker
A material added to a chemical to increase its adherence to a leaf surface.
Stigma
A sticky pad at the end of the style that receives the pollen.
Stipe
The petiole of a fern frond.
Stock
The parent plant onto which the scion or cutting is grafted. Also a term for the parent plant from which cuttings are collected.
Stolon
A shoot that runs along the ground, taking root at intervals and giving rise to new plants, e.g. couch or kikuyu grass. An often misused term.
Stomata
The pores, on the underside of the leaves, through which a plant transpires. Plants are able to regulate the flow of moisture through the stomata to help cope with water stress. Singular, stoma.
Stratify
To treat dormant seeds by chilling under moist conditions to simulate winter conditions and effect germination - hence stratified.
Strike
To cause a cutting to take root.
Strobilus
A fruiting body with overlapping scales. Most commonly used in reference to conifers. Plural strobili.
Style
The tubular part of the pistil between the ovary and stigma, often elongated.
Subshrub
A permanently wooded plant with soft pliable stems. Often green barked but woody at the base.
Succulent
Leaves or stems that are juicy, fleshy and often thick.
Sucker
An adventitious stem arising from the roots of a woody plant, often from the stock rather than the scion of a grafted plant.
Symbiosis
Two plants or other organisms lining together to their mutual benefit.
Sympodial
Having the growth of the stem or rhizome periodically terminated, with growth continuing from a lateral branch, as seen in some orchid genera such as Cattleya.
Systemic
Any substance capable of permeating through the entire plant. Often said of insecticides and fungicides that destroy pests and diseases by circulating through the sap system.
Taxonomy
The science of plant classification, hence Taxonomist.
Tender
Intolerant of freezing conditions or prolonged exposure to low temperatures above freezing.
Tendril
A twisting, threadlike extension by which a plant clings to a support. It may be a part of a leaf or stem.
Tepal
A name used to describe the petal-like structures of a flower that does not have clearly defined sepals and petals, e.g. Magnolia.
Terminal Bud
The bud at the tip of the stem. Usually the first to burst into growth at bud break.
Ternate
Arranged in threes.
Tetraploid
A plant with four complete sets of chromosomes.
Thinning Out
1. Pruning to reduce foliage density. 2. Removing some seedlings to allow more room for the remainder to grow.
Tip-Cutting
A cutting of new growth, used for the propagating many plants but difficult to keep from wilting without some control over humidity, such as a misting unit.
Tomentum
The furry coating found on some leaves and stems, e.g. ‘Pohutukawa’ and many rhododendrons. Hence tomentose. Also known as indumentum.
Topiary
Trimming shrubs and trees to predetermined shapes for aesthetic appeal rather than growth restriction or function.
Transpiration
Loss of moisture through the surface cells of the plant, primarily through the stomata.
Trifoliate
A leaf that is divided into three leaflets, e.g. clover.
Triploid
A plant with three complete sets of chromosomes.
Truncate
Ending or cut off abruptly or unexpectedly, at right angles.
Truss
A compound terminal cluster of flowers borne on one stalk.
Tuber
A modified root that acts as a storage organ. Similar to a rhizome but usually shorter and thicker and does not elongate greatly as it grows, e.g. potatoes.
Tuberous Root
An underground storage organ that resembles a tuber but is actually a root. Growth buds form from the point where the previous year’s growth stems were rather than from eyes, e.g. Dahlia.
Turgid
Plant material at its normal moisture level. As opposed to wilted.
Umbel
A group of flower heads growing from a common point in a stem, hence umbellate.
Undulate
Having a wavy edge.
Union
The join between a rootstock and scion.
Unisexual
Flowers with either functioning male or female organs but not both.
Varietal Name
A name used to describe a selected form as opposed to a hybrid. eg., Podocarpus totara ‘aurea’ (‘Golden Totara’)
Variety (officially Varietas)
1. A subdivision of a species. 2. A recognisably different member of a plant species capable of cultivation.
Vegetative
1.Those parts of the plant that are not flowering or involved with flowering. 2. A condition of growth in which flowering has not and is not about to occur.
Viability
1. The number of seeds in a group that are alive at any particular time. 2. The period of time after ripening in which a seed remains able to germinate. Proper storage can greatly extend viability but some plants, e.g. Delphinium, have a naturally short viability period.
Virus
A minute organism, only able to replicate within a living cell, that causes discolouration, malformation or death. Few plant viruses have practical cures.
Verrucose
Warty. Usually a reference to a leaf, stem or fruit surface. Hence verrucosis, a disease that causes warty growths on the surface of fruit, especially citrus.
Voluble
Twining, especially climbing by twining.
Water Shoot
Very vigorous soft wooded shoot that grow very rapidly. Usually non-productive and best removed.
Water Stress
When a plant is using more moisture than it can take in. Usually leads to wilting.
Whorl
A circle of three or more flowers or branches appearing around the a stem, branch or trunk at the same level.
Wilt
A virus disease characterised by wilted foliage, more properly known as verticillium wilt.
Xerophyte
A plant adapted to growing in dry regions. Hence xerophytic.
Zygomorphic
Bilaterally symmetrical, capable of being divided into two equal halves in one plane only, as in many flowers.
Copyright Geoff Bryant
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