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Extended glossary

Extended glossary

This glossary gives brief definitions of all the key terms used in the book.

A | B | C | D | E | F | G | H | I | J | L | M | N | O | P | R | S | T | U | V | W | X | Z


abscission layer The corky layer that forms at the base of the leaf stalk on deciduous trees sealing off the sap flow in the autumn ready for leaf fall.

achene A non-fleshy single seeded indehiscent fruit

activator A nitrogenous substance that is applied to a compost heap to speed up decomposition. They include poultry manure, horse manure, urine and sulphate of ammonia as well as proprietary products.

adenosine triphosphate (ATP) The major source of usable energy in metabolism. During hydrolysis ATP loses one phosphate to become adenosine diphosphate (ADP) which releases usable energy to the plant.

aeration The permeation of soil by air. Cultivation allows air into the soil and when maintaining turf spiking, slitting or aeration is carried out to allow gaseous exchange between the soil air and atmosphere.

after ripening Where metabolic changes must occur in some dormant seeds before germination will happen. Stratification helps this after ripening to take place.

aggregate fruit A fruit composed of many small fruitlets such as a blackberry, Rubus fruticosus, or raspberry, Rubus idaeus. The fruit develops from several separate carpels of the same flower.

air layering A method of propagating certain plants where a portion of the stem is partially cut or twisted to wound it and then wrapped in a growing medum which is covered with an outer sleeve of polythene tied into place with tape. Once rooted the layer is removed and potted up or planted out.

albino Part of a plant or shoot lacking in chlorophyll that appears a white or bright cream in colour. It is unlikely to survive as a pure albino plant as it cannot photosynthesise its own food.

alien A plant that has been introduced to an area by man and has now become naturalised there.

allotment A small portion of rented land where the tenant can grow flowers, fruit and vegetables for home use. Modern allotments tend to be smaller than during the early 20th century.

alluvial soil One that has formed from the silt left behind by rivers or streams.

alpine plant Originally a plant growing at higher altitudes on mountains, but now used more loosely as plants suitable for rock gardens or similar situations.

alternate host Where a pest or pathogen uses two separate species of plant to complete its life cycle. An example being the black bean aphid that overwinters on Euonymus and its summer host is the broad bean, Vicia faba.

alternation of generations The reproductive cycle in which the haploid (n) phase (the gametophyte) produces gametes which after fusion in pairs form a zygote which germinate to produce the diploid (2n) phase (the sporophyte). Spores produced by meiotic division from the sporophyte give rise to the new gametophytes which completes the cycle.

amino acids Organic acids containing nitrogen in a certain configuration and are used in the construction of protein in the plant as well as other functions.

annual ring The ring of wood developed during each growing season in woody plants; it can be used to estimate the age of the plant.

anthocyanin The pigment in plants that gives the pink, red, purple and blue shades.

antipetaly Where the stamens are arranged opposite to the petals.

areole Small swelling on the surface of plants in the Cactaceae family from which spines, hairs, bristles or wool grow. They arise from a leaf axil and are a modified stem.

aril The fleshy covering of some seeds such as yew, Taxus baccata and spindle, Euonymus europaeus. It is usually brightly coloured to attract birds which eat the flesh and spread the seeds.

awn A bristle-like growth usually hairy that grows from certain parts of the plant like the tips of achenes or sepals e.g. Geranium spp.

axil The upper angle between a branch or leaf and the stem from which it grows.



bacillus A rod shaped bacterium. These are likely to become widely used as a form of biological control of many pests and possible some diseases. The bacillus kills the pest and lives off the remains.

back cross When crossing the hybrid with one of its parents to ensure certain characteristics are retained in the next generation.

batter Where the face of a hedge slopes inwards from bottom to top which allows the lower leaves to get sufficient light and gives better stability to the hedge.

blanching A practice used to prevent light getting to part or all of the plant which makes it lose its green colour and become white. It is used when growing leeks, Allium porrum and celery, Apium graveolens, to achieve longer white barrels and also when growing chicory, Cichorium intybus, to reduce the bitter taste of the leaves

bract A specialised leaf that performs another function such as protecting a bud or is colourful to attract pollinating insects as in the case of Euphorbia pulcherrima.

brutting The breaking but not severing of young one-year-old shoots of fruit trees to restrict late growth.

bur A growth usually barbed on a fruit or seed that assists with the dispersal of the seed. The bur catches onto the fur or clothing of passing animals or humans; examples being burdock, Arctium spp. and cleavers Galium aparine.



calcareous and calcicoles Plants that prefer to grow on limey or chalky soils; they have adapted to grow in high pH soils.

calcifuges Plants that prefer to grow in acid soils such as many members of the Ericaceous family.

carotene A yellow or orange pigment in plant tissues which belongs to the carotenoids group and which is found, e.g. in carrots Daucus carota.

catch crop A quick-maturing crop grown on land where a later and usually slower crop is to be planted later in the year.

catkin A spike like inflorescence consisting of unisexual flowers and only found in woody plants such as trees and shrubs.

cellulose The main component of the cell wall of plants which helps to give them some structure and support.

certified stock Plant material (mainly fruit) that has been inspected and is guaranteed to be free from virus infection and other diseases and also true to type.

chipping The damaging of the hard seed coat (testa) before sowing using a knife or file to improve germination. It is used with some cultivars of Sweet pea, Lathyrus spp. and Canna spp.

chitting 1. The sprouting of seed potatoes prior to planting.  The potatoes are placed in trays in a light room with a temperature of approx.10◦C to allow them to sprout ready for planting. 2. Also the partial germination of seed before sowing. This is sometimes carried out with grass seed to get a quicker germination when sowing at the end of a football season to speed up the renovation of the turf. It is done when fluid drilling seeds, again for quicker germination and plant establishment..

chlorosis Where leaves lose all or some of their green colour and usually become yellow or creamish; caused by the loss or reduced development of chlorophyll. It is often caused by nutrient deficiency or diseases and is common in Ericaceous plants growing on soils with a high pH which causes lime induced chlorosis.

cleistogamy Flowers that remain closed in a bud-like state but pollination still takes place within the bud; this can occur in violets. Pollination happens as the anthers and stigmas are close together and the flowers self-pollinate.

cilia Fine hairs on leaves.

coleoptile The outer leaf sheaf of a young grass seedling which protects it as it emerges through the soil.

coleorhiza The protective sheaf around an emerging root of a young grass seedling.

contractile roots Roots that grow down usually from the base of a corm. At the end of the season these roots shrink and pull the new corm that has grown on top of the old one down into the soil. This ensures the corms do not move up to the surface over time.

controlled release A type of fertiliser that releases its nutrients over a set period of time. The time period can vary and is usually indicated on the packet.

cordon A bush or tree trained as a single stem often used in fruit crops. They can be grown upright or at an angle. These types of plants are used in intensive methods of fruit production.

corolla tube Where the petals fuse along their edges to produce a tube like structure as in Narcissi species.

cryptogram A non-flowering plant.

cupule The sheaf of bracts protecting some fruits. Also the cup like structure that holds the nut fruits of the hazel, Corylus avellana and oak, Quercus spp.



dard A lateral shoot no more than 7.5cm in length on an apple or pear tree with a fruit bud at the tip. The cultivar Bramley’s Seedling is known for producing dards.

day neutral plants Plants that flower regardless of the day length.

deficiency This occurs when the plant or growing media are short of essential nutrients which means the plant cannot sustain healthy growth.

denitrification The conversion of nitrate to gaseous nitrogen which is carried out in the soil by certain bacteria.

determinate Where the main stem ends in a terminal flower or truss which stops the further development of the main stem.

disc flowers The flowers in the centre of many inflorescences of the family Asteraceae; the common daisy, Bellis perennis, being a typical example, the outer florets are made up of ray flowers (the white part) and the inner part being the yellow disc florets.

dot plant A plant used in formal bedding schemes that gives height and contrast to the display.  Plants often used include Fuchsia, Pelargonium, heliotrope, Canna and Eucalyptus.

drought A period of dry weather that can have a negative effect on plants. In Britain it is officially a period of 14 days without measurable rainfall.

drupe A type of fleshy fruit derived from a single carpel and usually contains one seed.

drupelet The individual segment of a raspberry, Rubus idaeus, blackberry, Rubus fruticosus,  or related fruit.



emasculation The removal of the anthers of a flower to prevent self-pollination.

endocarp The inner most layer of the ovary wall of a fruit which often becomes hard as in the plum, Prunus spp., stone.

epiphyte Plants that attach themselves to other plants but are only using them for support not food sustenance.

espalier A tree, mainly fruit trees, trained against a wall or along horizontal wires. The tree will have one vertical stem with the lateral branches spaced out horizontally approx. 30 cm apart along the wires to the left and right side of the main stem.



family tree A fruit tree, mainly apples, Malus spp., onto which several cultivars have been grafted.

fan shaped A method of training fruit trees and bushes to keep them restricted and make picking easier. They can be grown against walls or wires supported by stakes.

fasciation Stems become wider and flattened in cross section and sometimes growth is distorted. It is more common in some species than others, Forsythia is fairly commonly affected. It does not appear to do the plant any serious harm and can be pruned out if necessary.

filial generation The hybrid offspring of a cross-bred generation in which the first crossing is denoted as the F1 and the second as the F2 generations.

flocculation Where clay particles come together (flocculate) into crumbs; this happens after an application of lime, calcium sulphate or other soil conditioner. It improves the soil structure of clay soils.

floret A single flower that makes up the composite inflorescence  or the spike of grass flowers. The composite flower is made up of many small florets as in the daisy, Bellis perennis, and dandelion, Taraxacum officinale.

floricane The biennial cane of raspberries and other cane fruits, it will produce flowers and fruits during its second year and then should be pruned out.

foliar feeding Spraying the foliage of plants with a fine spray containing nutrients which are absorbed by the leaf to feed the plant.

fruit setting This occurs when the ovaries have been fertilised which results in seed formation and the swelling of the ovaries. It is the point at which the plant will produce fruit.

fruit thinning The removal of a proportion of the immature fruitlets from the plants to improve the eventual size of the remaining fruits. It also prevents over cropping and biennial bearing in cultivars prone to these problems.

fruiting spur A very short lateral branch that bears a number of fruit buds.



girdle scar The old leaf scars that form the position of last year’s terminal bud.

glabrous Hairless leaves.

glaucous Leaves with a bluish grey tinge usually as a result of a waxy covering over the leaf surface.

glumes Part of the inflorescence in grasses. They are the two bracts at the base of the flower spikelet.

grana Structures within the chloroplasts that are made up of a series of thylakoids stacked up. They contain chlorophyll and carotenoids and are the site of photosynthesis.

gravitropism How the plants shoot and root responds to the Earth’s gravity; also called geotropism.

grex A collective term used mainly with orchids for cultivars from the same hybrid origin.

ground cover plant A plant that is planted to spread and cover the ground and help to prevent weeds growing and look attractive most of the year. They are usually low growing evergreen shrubs but also include herbaceous perennials that retain their leaves over winter.

growing room A windowless room or shed in which light, temperature and humidity are controlled. They are used for raising bedding plants and young vegetable plants that are supplied as plug plants. They are used to start the seedlings off which are then sold or pricked out. As there are no windows and the room is well insulated, heating costs are kept to a minimum.

guttation The exudation of water from the leaves, usually at night caused by root pressure.

guying A system of supporting newly planted trees using guy ropes or wire which are fastened to pegs hammered into the ground and passed through a piece of hosepipe before going around the tree. There are usually 3 or 4 guys for each tree. They are often used on larger trees where a stake would be insufficient or get in the way.

gyres A circle or spiral pattern around a stem.



ha-ha A deep wide ditch that prevents the access of cattle or similar animals into the garden but cannot be seen from the main viewing points such as the house. They form an unobtrusive barrier to animals.

halophyte Plants that have adapted to grow in salty soils such as dunes or marshes in coastal areas.

hardwood cuttings A method of propagating trees and shrubs using material that is one year old and about pencil thickness. The cuttings are made approx. 15 to 20cm (6- 8 inches) long and cut above a node at the top and below a node at the base. They are taken in the autumn / winter, some are rooted outside others put into a frame and evergreens can be put into a mist unit.

heading back The very hard pruning of trees and shrubs by cutting back to near ground level or the base of main branches. It is carried out after budding and grafting (once the scion has taken) and when fruit trees are to be reworked. It can also be used to renovate old or overgrown shrubs and to induce new vigour into plants.

heeling in The temporary planting of trees and shrubs when they are delivered if they cannot be planted in their permanent position. A trench is dug a spade's depth, 60cm (24 inches) wide and to a length sufficient to hold all the plants. The roots are placed in the trench and covered with soil taken from it. The purpose is to keep the roots moist and protect them from frost until they can be planted properly.

herbicide A chemical used to control weeds

hermetically sealed Many packets of seed are hermetically sealed to exclude moist air and prevent gaseous exchange. This increases the life-span of the seed, thus maintaining its viability for longer. The inside of the packets have very low moisture content and in some cases reduced oxygen levels.

heterophylly Where more than one type of leaf occurs on the same plant, an example being ivy, Hedera helix, with both juvenile and adult foliage on mature plants.

heterosis Also called hybrid vigour where the resulting hybrid is superior to both parents. It often occurs in F1 hybrid plants.

host An organism (plant) in or on which a parasite lives. Weeds can often be hosts for pests and diseases.

hybrid The offspring of two different parents which could be cultivars, varieties or species. The hybrid could be bred from two different cultivars or an inter-specific hybrid from two different species.

hydrophyte A plant that grows wholly or partly submerged in water such as aquatic plants; or that grows in wet conditions like bog plants.

hydroseeding The sowing of imbibed seed in a solution that is sprayed onto steep slopes to give grass cover. Wildflower and other seeds can be included in the mixture if required.

hypertufa A medium made from 1 part cement, 2 parts sand and 2 parts granulated peat that can be shaped into rocks or used to coat containers so they appear to be made from natural materials.



imperfect flower A flower that lacks either stamens or carpels.

inbreeding The breeding of closely related cultivars or species that is usually carried out by repeated self-pollination. It is often carried out prior to producing a F1 hybrid to ensure the characteristics the breeder desires are stable in the parent plants used to produce the F1 hybrid.

incompatible When grafting some scions are incompatible with certain rootstocks and if grafted together the graft will fail, in some case after several years. This can occur with certain cultivars of pears, Pyrus communis, on quince, Cydonia oblonga, rootstocks.

insectivorous plants Plants that have adapted to trap insects to supplement their nutrient uptake. Many of these plants are native to bog areas and have a small root system, owing to this they get most of their nitrogen from insects they trap.

integument The outer layers of tissue enveloping the nucellus of the ovule, which develops into the seed coat (testa).

interfascicular cambium The vascular cambium arising between the fascicles, or vascular bundles. It develops from interfascicular parenchyma.

intermodal cuttings Cuttings taken between the nodes from plants that are capable of rooting using this method. Fuchsia and some Clematis will root by internodal cuttings.

involucre A whorl of bracts surrounding a flower or cluster of flowers. An example being the winter aconite, Eranthis hyemalis.



June drop The shedding of many immature fruits on apple and other top fruit that usually occurs in June. It is the tree's way of reducing the number of fruit that will reach maturity to prevent stress on the tree later in the year.



latent bud A bud that remains dormant and usually concealed until stimulated into growth by the pruning back of adjacent branches.

latex A milky white sap found in some species of plant when they are cut for example Euphorbia spp.

leaching The downward movement through the soil of minerals, or organic ions. These are carried in the percolating water and eventually drain out of the soil and are lost.

leaf bud cutting A cutting which includes a single leaf with a bud in its axil and a small section of stem.

leaflet Compound leaves are made up of a number of leaflets.

leg A short stem from which the branches of a shrub are trained; commonly used on gooseberries, Ribes uva-crispa, and red and white currants, Ribes rubrum, to allow air circulation under the bush which helps to reduce American gooseberry mildew disease.

lenticel Pores that form in the bark of woody stems that allow the passage of air into the stem. This allows the exchange of oxygen and carbon dioxide closer to the area of need rather than the plant having to move it down from the leaves. They appear as small raised areas of a corky nature.

lesion The defined area of diseased tissue that is caused by a canker or leaf spot type disease.

lignified Cells that have become woody by the formation of lignin in the cell walls.

loam soils Soils containing the correct proportions of sand, silt and clay to produce the ideal soil for gardeners.

locule A cavity within an ovary that is made of fused carpels



macronutrients Inorganic elements required in large amounts by the plant for growth. These are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.

maiden A plant, usually a tree or shrub, in its first year of growth. They are often sold as 1 year old maidens and can then be trained to the type of tree required.

meristem The embryonic tissue regions mainly concerned with the production of new cells.

micronutrients Inorganic elements required in very small or trace amounts (also called trace elements) for plant growth and which include iron, manganese, boron, copper, zinc, chlorine, molybdenum and nickel.

monocarpic Plants which flower once and then die. These can be annuals and biennials, but also include some perennials that grow for a number of years before flowering once and then dying.

monogerm seed A seed that contains one embryo and is produced by the seed companies to save the thinning of seedlings. It is used in the beet family, Amaranthaceae, where each seed is a cluster of embryos and will produce a number of seedlings that require thinning.

mucilage A thick sticky substance produced by some plants. The substance on many carnivorous plants that traps insects is a type of mucilage.



necrosis Brown or blackish areas where cell tissue has died usually as a result of pest or disease attack or nutrient deficiency.

net venation The arrangement of the veins in leaf blades when they resemble a net, typical of many dicotyledonous plants. It is also called reticulate venation.

nitrification The oxidation of ammonium compounds or ammonia to nitrate in the soil; which is carried out by certain soil bacteria.

nitrogen fixing bacteria Soil bacteria that convert atmospheric nitrogen into nitrogen compounds.

nuclear stock Plants propagated from a mother plant that has been tested for trueness to type and is free of pests, diseases and viruses; and is used for the basis of producing certified stock for sale to growers.



obligate parasite A parasite that is entirely dependent on its host for its nutrition and survival.

offset A lateral that grows low down on the plant and developing its own roots while still attached to the parent. If removed carefully and inserted into growing media, it will grow into a new plant.

open-centre The training of a fruit tree to have a goblet shaped crown but leaving the centre open to allow good access for sunlight allowing increased photosynthesis and better ripening of the fruit.

organic 1.Refers to living organisms in general and to compounds formed by living organisms such as organic matter. 2. In chemistry it refers to compounds that contain carbon.

organism An individual living creature which can be unicellular as in some bacteria or multicellular as in many insects and animals.

outbreeder A plant that reproduces mainly by cross-pollination.



pappus The fan of hairs on some seeds that is used to aid their dispersal.

parallel venation The pattern of the veins in the leaf in which the main veins run parallel as in many monocotyledons like grasses.

parasite An organism that lives on or in another organism (host)and derives its nutrition from it. It is detrimental to the host and often results in the host's death.

perfect flower A flower having both stamens and carpels, a hermaphroditic flower.

pericarp The fruit wall which has developed from the ovary wall.

phylloclade Stems that are short and flattened and that carry out the function of the leaves. An example being butchers broom, Ruscus aculeatus.

phyllotaxy The arrangement of plant parts on an axis; commonly used to describe the arrangement of leaves on the stem.

phylogenetic The evolutionary relationship between various species and plant populations. This has become more common now DNA can be sequenced and relationships more accurately determined.

physiological disorder A condition that is harmful to plant growth that is not caused by a pathogen such as a pest or disease. These disorders are caused by factors including weather, particular extreme weather conditions, nutrient deficiency, and other abiotic factors.

piping A cutting taken from Carnations and pinks by pulling it from the parent plant at a joint and inserting it into the growing media without any trimming.

pneumatophores Growths on the roots of trees that grow in swampy conditions, they come up to the surface of the water and are believed to assist in the intake of oxygen for respiration in the roots.

polyploidy A plant having more than twice the usual haploid number of chromosomes; triploids and tetraploids are polyploids.

pome A simple fleshy fruit in which the outer portion is formed from the tissues that surround the ovary, that expand with the growing fruit. It is only found in the family Rosaceae.

pricking out The transferring of very young seedlings from the seedbed or container they were sown in to a new container or permanent position.

primocane The current seasons cane of raspberries that will fruit in the autumn and grown as autumn fruiting raspberries.

prop roots Roots that arise from the stem above soil level and grow down into the soil, which help to support the plant. They are common in some monocots such as maize, Zea mays.

protein A complex organic compound composed of many amino acids joined by peptide bonds.

protoplasm A general term used to refer to the living substances of all cells.

pseudobulb A swollen growth that looks like a bulb but is not; they are common in some orchid species.



replant disease This occurs when plants of the same species are replanted on the same site. This can happen if fruit or roses are replanted on the same site. It is believed to be caused by soil borne fungus.

revert Where variegated plants revert back to their original green form. If this occurs all plain green shoots should be removed back to variegated growth.

reworking The changing of the cultivar of a fruit tree by grafting a new cultivar onto the existing one. The tree is usually hard pruned back and the scions grafted onto the remaining branches.

root pressure The pressure developed in roots caused by osmosis. It is this that causes sap to exude from cut surfaces when a branch is removed or a tree felled.

rosulate A plant with a rosette habit of growth during part of its life cycle. Often seen in biennials when they over-winter, they have a rosette. During spring the centre of the rosette grows up to form the flower spike.

runner A horizontal stem growing at ground level that can root at the tips to produce a new plant, as in strawberry, Fragaria spp.



saprophyte A plant (usually a fungus) that feeds on decaying organic matter.

sapwood The outer wood of a stem or trunk which is usually distinguished from the heartwood by its lighter colour.

self-pollination The transfer of pollen from the anthers to the stigma of the same flower or flowers on the same plant.

self-sterile Plants incapable of producing viable seed after self-fertilisation, this helps to prevent in-breeding.

side-dressing An application of fertiliser applied alongside a row of crops.

silt Fine soil particles between 0.06mm to 0.002mm in diameter.

slip A small cutting often with a heel. It is a term used for the supply of unrooted cuttings of sweet potato, Ipomoea spp. 

slow release fertiliser A fertilisers formulated to release its nutrients  slowly over a period of time which can be nine months or more.

soakaway A large pit filled with clean hard-core or reject stone which collects the water from a drainage system where no other outlet is available. The water slowly drains out over a period of time.

soil moisture deficit The amount of water required to return the soil to field capacity, usually measured in millimetres.

spadix A fleshy flower spike which is usually partially enclosed by a spathe, as in the family Araceae.

spathe A bract enclosing one or many flowers. They are often brightly coloured as in Spathiphyllum spp. which have large fleshy spathes. Narcissi spp. have a brown membranous spathe that protects the flower bud.

spikelet Part of the inflorescence of grass flowers.

spit A spade or forks depth of soil measured as approximately 30cm (12 inches).

sporangium An organ that produces spores.

sport A mutation which can be natural or induced by chemicals. The plant will vary in some way from the normal parent. Many of the Chrysanthemums grown for cut flowers and pot plants are sports.

spur A short lateral twig on a fruit tree or bush on which the flowers and fruits will be produced.

stele The central core inside the cortex of roots and stems of vascular plants.

stipules A small leaf-like growth at the base of the petiole, usually occurring in pairs as in pea, Pisum sativum, but can be single as in Pelargonium zonale. In some plants like oak, Quercus spp. and beech, Fagus sylvatica, they are scale-like and drop off once the young leaves have fully opened.

straw bale culture The growing of plants on straw bales, mainly used in greenhouses or polytunnels for crops like tomatoes, cucumber and peppers.

strig A short stem that bears a number of currants as in black, Ribes nigrum, and red currants, Ribes rubrum.

subsoil The soil under the topsoil layer approximately 30cm to 45cm (12 – 18 inches) depth. It is usually a lighter colour than the topsoil and is mainly infertile.

succession The orderly progression of changes in the plant community composition that occurs during the development of any area from initial colonisation to the climax vegetation.

succulent A plant with thick fleshy water storing leaves or stems, for example, cacti.

sucker A shoot produced by the roots or base of the stem that gives rise to a new plant.

sulphur-shy Certain cultivars of fruit trees and bushes can be damaged by the use of lime sulphur; so should not be sprayed with this material.

summer pruning Pruning carried out mainly between July and early September especially on trained apple and pear trees to restrict growth and encourage fruit bud production.

surfactant A type of detergent that is added to water when spraying to reduce its surface tension and help it to “stick” to leaves. They are often used on plants with waxy leaves such as crops in the Brassica family, Brassicaceae.

symbiosis The association of one plant with another to the mutual benefit of both of them as seen  in the relationship between plants in the Papilionaceae family and Rhizobium bacterium, and also between mychorrhizal fungi and some woody plants.

systemic Pesticides that are systemic are absorbed by the plant and then translocated within the leaves, stems and roots. This gives the plant greater protection against pests and diseases than contact pesticides which can wash off during rain.



tetraploid A plant containing twice the usual (diploid) number of chromosomes.

thigmomorphogenesis The alteration of plant growth in response to mechanical stimulus. The brushing of seedlings with paper or card is reported to give more compact plants with a better habit of growth.

thigmotropism The response of some plant organs to physical touch. An example being the tendrils of climbing plants which twine around the support when in contact with it.

thong A root cutting taken from a fleshy rooted plant like, bear’s breeches,  Acanthus spp.

tip-bearer A type of fruit tree that produces fruit buds at the tips of young shoots; and which are unsuitable for training as cordons, espaliers and other intensive production systems. The apple, Malus domestica ‘Worcester Pearmain’, is an example of a tip-bearer.

tiller A shoot arising from the base of a plant, used frequently to describe the basal side growths on grasses.

tissue A group of similar cells organised into a structural and functional unit that will have a similar purpose.

topsoil The top 30cm to 45cm ( 12 – 18 inches) of soil which is the most fertile and usually a darker colour than lower layers of soil.

torus   The flattened receptacle of a flower.

translocated When used in relation to pesticides, it means they are capable of moving around the plant. They can be applied to the leaf and will be translocated around the plant including down to the roots. Glyphosate® is a typical translocated herbicide that will control most perennial weeds.

transplant To move a seedling or plant from one position to another.

trichomes Epidermal growths such as hairs of leaves or stems but can also include some scale like growths as well as some spines. The stinging & annual nettles, Urtica spp. have glandular trichomes on their leaves and it is these that break when touched and sting.

tricolpates Another name for the Eudicots as their pollen grains have three grooves (called colpi) on them.

truss A short stem that bears a number of flowers and fruits as in the tomato, Lycopersicon esculentu.

turion The overwintering bud in some aquatic plants.



urine Liquid waste from animals which can be used as a liquid fertiliser containing nitrogen and potassium or as a compost activator.



vector  A pathogen that carries a disease or virus from one organism to another.

velamen A thick layer of epidermal cells covering the aerial roots of some orchids and aroids; it can also occur on some other plant roots.

vermicompost The casts from worms (usually from a wormery) that are collected together and used as a growing media or for topdressing. 

vermiculite An aluminosilicate mineral that has been heat treated to form expanded granules that has a laminated structure. This gives the growing media good aeration and water retention but is also light in weight.

viable Able to live as in viable seed, which is able to germinate.

viroid A very small pathogen similar to a virus that cause a number of diseases such as Chrysanthemum stunt.

virus An agent causing damage to plants. They are of microscopic size and are transmitted by vectors such as aphids and nematodes, and also grafting.

vista A view usually through a narrow opening or along an avenue of trees.

viticulture The cultivation of grape vines.



waterlogging When the growing media is saturated in water. It can be as a result of overwatering in pot plants or caused by compaction or low-lying ground outdoors.

water shoot A soft quick growing shoot that grows vertically usually after pruning has been carried out on trees or shrubs.

weed wiper A tool that contains some herbicide solution and has a wick that is wiped over the foliage of weeds and deposits some of the chemical that will kill the weed.

wetting agent 1. A chemical added to sprayer tanks that assists the pesticide in sticking to waxy of hairy leaves, it can also help the pesticide spread over the leaf surface.2. A chemical used in turf culture to help water penetrate the soil to improve the movement of irrigation water both into and through the soil. They are especially useful if the soil (root zone) is hydrophobic.

whip A young tree usually one year old consisting of a single stem and no side branches.

winter garden A garden area that has been designed and planted to look its best during the winter period; making full use of winter flowering plants, coloured barks and other winter features.

witches' broom The development of a large number of shoots from one point that forma mass of growth. It is caused by the plant reacting to some form of attack by fungi or insects. It is mainly seen on woody plants



xanthophyll A yellow carotenoid pigment found in the chloroplasts of some plants.



zeatin A natural cytokinin that has been found in maize, Zea mays, and is a plant hormone.

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