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Glossary of plant terms

Search our dictionary of 3,300 botanical and plant-related terms – the largest online.
Or browse the descriptions and definitions using the A-Z.

galactinus

Means "milky" in Latin.

gall

This is an outgrowth from the root, stem, leaf or flower of a plant; this growth of plant tissue can be a response to infestation by a pathogen such as an insect (eg the gall wasp), bacteria or fungi. Such an outgrowth may cause some check to the growth of the plant, especially if the gall is caused by a fungus.

gallicus

Means "French" in Latin.

gall midges

Many types of gall mites affecting plants such as beech and blackcurrants. Larvae feed on plants destroying them.

gallon

A measure of capacity equivalent to 8 pints or 4.54 litre.

gamete

A sex cell (male or female) capable of fusing with another to form a zygote (which will develop into the spore in bryophytes, ferns and other pteridophytes). In flowering plants the male gamete is the pollen grain and the female gamete is the ovum.

gametophyte

The (normally) haploid generation, producing gametes (female egg or male sperm) which fuse to form the diploid sporophyte generation, in bryophytes, ferns and other pteridophytes.

Gamma-BHC

This an insecticide that can be used as a dust to control rootfly, wire-worms, beetles and leatherjackets in the soil. It may be used as a smoke to control pests in the greenhouse. It is also available combined with a fungicide for general treatments. It is also known as just "HCH".

gamopetalous

Refers to a flower in which the petals or corolla are joined up to form a tubular-like structure.

gamosepalous

Refers to a flower in which the sepals are joined up to form a tubular-like structure which may enclose the base of the petals.

gangrene

This is a disease of potatoes where the tubers rot in storage, and is caused by a fungus entering the potato through wounds made when the crop was lifted.

ganoderma

Large, woody, cream-brown brackets develop towards the bottom of trunk weakening tree.

garigue

A type of vegetation composed of low, scattered, often spiny and heath-like shrubs, with usual patches of bare ground between and beneath the clumps of shrubs.

gaseous exchange

Living organisms generally need to absorb oxygen from the air to release energy from food during respiration, and plants need to absorb carbon dioxide to store energy from light during photosynthesis. Gaseous exchange involves the movement of oxygen and carbon dioxide across plant membranes. Small pores (stomata) in the epithelium (especially of the leaves) allows gaseous exchange and transpiration by the plant.

gazebo

This is a small building or structure usually with a seat and often with open sides to enjoy the surrounding garden.

gelidus

Means "of icy regions" in Latin.

gemmatus

Means "jewelled" in Latin.

gemmiferus

Means "bearing buds" in Latin.

gene

A molecular component of the chromosomes which carry the information for inheriting certain characteristics. The total characteristics of an organism is determined by a combination of many thousands of genes held on the chromosomes. (eg a gene for yellow peas as opposed to a gene for green peas.) Genes themselves are composed of DNA molecules.

genera

Plural of genus.

generation

Refers to either the gametophyte (haploid) phase or the sporophyte (diploid) phase of the sexual reproductive cycle. The term also refers to a group of plants or other organisms that are at the same stage of development.

genetically modified plants

In recent years there has been the development of so called 'GM crops' such as some varieties of maize, oil seed rape and soya bean. These varieties contain new genes which have been inserted into the natural genome using laboratory techniques. The new genes may be from other plant species or from non-plant species and act to confer on the target plant characteristics such as increased resistance to certain herbicides or pesticides. This can be of benefit to the grower since it will mean that less chemicals or only certain chemicals may be needed to control weed and pest species, or can otherwise act to increase yields. Certain genes are being experimented with which may act to 'terminate' certain stages of the plants growth which may be of advantage to the agricultural business. However, many people are concerned about the potential environmental and health consequences. 'Genetic pollution' due to cross fertilisation with other plants will most likely occur, resulting in the likely problem of the genes conferring unknown and often undesirable characteristics on these other plants. Considering the many millions of interactions (including vertical and horizontal gene transfer) between life forms, it is very likely that the new genes will affect in some way other plant and even non-plant species including humans. Once this process is underway it will not be possible to contain it.

genetics

Refers to the study of genes and how the various characteristics are inherited through the generations.

genotype

Refers to the genetic make-up of the organism. (The phenotype refers to the outward characteristics of the organism.)

genus

A classification for a group of closely related species: a number of genera form a family. The generic name is the first part of the Latin binomial scientific name, e.g. Primula (genus) vulgaris (species) is the Latin name for the Primrose. There is a botanical convention for nomenclature that the species name is in lower case and that the binomial name is printed in italics.

geological periods

A series of time periods marking out the history of the Earth's development in terms of its geology and natural history. The periods are described separately in this glossary. In order from oldest to most recent they are as follows; Archaeozoic, Proterozoic, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Palaeogene, Neogene, Pleistocene periods.

geophyte

Refers to a perennial plant that overwinters by means of an underground storage organ such as a corm, rhizome, tuber or bulb.

geotropic

The tendency to grow towards the pull of gravity ie roots are positively geotropic, and germinating shoots are negatively geotropic.

Geranium downy mildew

Discolouration and fungal patches develop on leaves, if badly affected will die.

Geranium sawfly

Round holes appear in foliage caused by larvae of a sawfly.

germanicus

Means "of Germany" in Latin.

germination

The first stage in the development of a plant from a seed, starting when water is taken into the seed, growth begins using stored food energy and ending with the emergence of the first true leaves which are photosynthetic.

Geum sawflies

Leaves are eaten up by leaf-mining sawfly.

ghost spot

Fungal disease of tomatoes where the fruits develop white, circular spots centred with brown.

gibberellins

These are complex plant hormones which act to control cells and their elongation during germination and growth.

gibbous

Swollen, usually at the base.

gibbus

Means "swollen on one side" in Latin.

giganteus

Means "very large" in Latin.

girdling

This refers to the damage or removal of the bark by an animal or by physical damage. This will inhibit the flow of sugars from the shoot to the root causing the death of the roots and then the plant.

glaber

Means "smooth skinned" in Latin.

glabrous

Not hairy, and hence generally smooth.

glacial

These exist in the polar regions and consist of ice and compacted snow which has accumulated over thousands of years. A body of ice that covers a large land surface or continent, for example Greenland or Antarctica, and flows outward in all directions is called an ice sheet. The ice sheets appear to expand and contract over periods of hundreds of years as the planet's climatic conditions vary. In recent years the ice sheets have been contracting noticeably and this has been linked to global warming caused in large part by human activity. Glaciers themselves are tongues of ice, originating in the snowfields of mountains above the snowline, which move slowly downhill and are constantly replenished from its source. Apart from some extremely hardy plants that may grow amongst the moraines at the edges of glaciers, no vegetation (other than some algae) can exist in the glacial regions.

Gladiolus core rot

Corm rots from inwards out and becomes brownish-black.

Gladiolus corm rot

Brown markings develop on corm, usually on base whilst in storage. Discolouration spreads downwards and the leaves turn brown and die. Roots of affected corms blacken and may die back.

Gladiolus dry rot

Corms develop slightly sunken lesions. Rotting occurs and cause blackish areas.

Gladiolus hard rot

Small, purple-brown spots develop on leaves. At base of corms, dark, red-brown areas appear.

Gladiolus thrips

Foliage develops a fine, pale mottling and flowers have pale flecking. Small dark insects may be visible, damage is usually worse in late summer.

gland

Organs of secretion usually on the tips of hairs; hence glandular hairs.

glandular

With secreting organs.

glandulosus

Means "with glands" in Latin.

glasshouse

Some form of glazed structure to protect plants from the extremes of climate. The general term of 'greenhouse' includes glasshouses and those covered with polythene etc.

glasshouse leafhopper

A pale motling appears on upper leaf surface of many indoor plants. Caused by sap-feeding insects which been breeding continuously throughout the year.

glasshouse red spider mite (2-spotted mite)

Leaves develop a pale mottling, turns green then yellow-white. Afterwards they dry up and fall prematurely.

glasshouse whitefly

Whiteflies live on undersides of leaves causing upside to become sticky. Sooty moulds then form. Affects many houseplants, greenhouse plants, ornamentals and vegetables.

glaucous

Covered with a bloom which is often waxy, thus giving the organ a bluish or greyish colour.

glaucus

Means "with waxy bloom" in Latin.

Gleditsia gall midge

In early summer leaves fail to expand into normal shape and form. Leaves appear folded as galls appear.

Gleosporium rot

Sunken lesions on surface. Affects apples, quinces and pears.

gleying

A term given to the blue-grey colour of the waterlogged level in clay soils.

global greenhouse effect

Refers to an overall warming of the planet's atmosphere due to release of pollutants such as chlorofluorocarbon gases. Increased carbon dioxide production by traffic, industry etc also contributes to this affect. Loss of plant life, notably loss of rainforests, by human activity means that natural control of the atmospheric conditions is being severely damaged.

globose

Spherical in shape.

globosus

Means "globular" in Latin.

glochid

Barbed hair or bristle, especially on cacti.

glucose

A sugar that is produced by plants through photosynthesis. It is a basic molecular component of cellulose and starch.

Glufosinate ammonium

Herbicide often used for general weed killing purposes.

glume

A chaff-like bract; in particular the bracts at the base of the spikelets of grasses. The glume protects the grass flower before it opens.

glutinosus

Means "gluey" in Latin.

glutinous

Meaning "sticky".

glyphosate

A chemical general purpose weedkiller which is absorbed by the shoot tissues, the soil tending to neutralise its activity.

gooseberry dieback

Stems die back, occasionally whole bush is affected. During damp weather a fungal growth can be seen.

gooseberry leaf spot

Small brown angular spots which may be followed by a shedding of the leaves. Caused by various disease agents; some produce little damage.

gooseberry mildew

This is a common and serious disease of gooseberries. The disease starts as a white powdery coating on young leaves, as season progresses the fungus becomes brown and felty. Distortion of shoots and fruits may occur. Mould of fruits can easily be wiped off making them still edible.

gooseberry rust

In spring red-orange pustules develop on older lower fruit and stems. Fungus causes curling of leaves.

gooseberry sawfly

From mid to late spring bushes become severely defoliated in a matter of just days; the larvae of sawflies can be extremely voracious feeders. Leaves are holed or eaten back to veins. Although fruit is not damaged, the vigour of the bush can be greatly affected. Eggs are laid in the centre of the bushes and can go unnoticed during initial stage of infestation. They pupate in the soil over winter.

gracilis

Means "slender" in Latin.

graecus

Means "Grecian" in Latin.

graft hybrid

A plant produced by grafting in which the tissue of the scion mingles with that of the stock. (It is a type of chimaera.) An example of a graft hybrid plant is Laburnocytisus (formed by growth from the union of Laburnum and Cytisus). In some botanical books a graft hybrid is represented by a + (+ symbol).

grafting

Insertion of the tissue of one plant (species or variety) into the tissue of another plant, so that the tissues mingle together and both plants grow together, callus growth covering the graft union. The 'scion' is inserted into the 'stock' or 'rootstock'. The tissues mix and continue to function for mutual benefit such as where the stock has strong roots and the scion has favoured characteristics.

graft union

The position where the scion was inserted into the rootstock, and it is often noticeable by the swelling caused by the callus growth which healed the wound. Also known simply as the 'union'.

grain

Refers generally to mature seed, especially of the Graminae (grass) family such as wheat, oats, barley etc.

grain-alien

An alien plant introduced as a contaminant of grain.

gram

A measure of weight (gm) equivalent to 0.035 ounces.

gramineus

Means "grasslike" in Latin.

grandis

Means "large" in Latin.

granular

Covered with very small grains; minutely or finely mealy.

granulose

With a fine sand-like surface texture.

grape berry moth, vine moth

A pest attacking grapes and vines where the first generation caterpillars gnaw buds and inflorescences. The second-generation caterpillars feed in the berries.

grass

A large group of monocotyledon flowering plants. They generally have hollow round stems with solid nodes at regular intervals. The leaves are narrow, strap-like with parallel venation and are borne on a sheath which surrounds the stem. The flowers are borne in loose panicles, spikes or racemes.

grass; thinning or yellowing

Thinning grass is cause by shading, if area not shaded suspect growing conditions. Yellowing grass can be caused by either leatherjackets, fusarium patch or lack of nitrogen.

gravel bed

Used in aggregate culture, which is a form of hydroponics.

grazing

Refers to the eating by animals such as cattle of grasses and other growing plants. Because grasses grow from the bottom of the stems (tiller) near the soil, the shoots are regenerated after grazing.

grease band

This is a band of a sticky, oil-based substance which is put around the trunk of some trees to trap pests such as winter moths which climb up the trunks to lay their eggs.

greenback of tomatoes

This is a disorder of tomatoes where the fruits fail to ripen at the top, and is caused by poor cultivation.

greenfly

This is the common name for a form of aphid which is a pest of a number of plants. The insect feeds by a pointed mouthpart called a stylet which is inserted into the plant tissues to suck up sap. They cause damage by reducing the health and vigour of the plant, transmitting viral diseases and by producing honeydew which stimulates the spread of the sooty mould fungus.

greenhouse

The general term of greenhouse includes glasshouses and those covered with polythene etc. to protect plants from the extremes of climate.

greenhouse effect

This is the process of the heating of a greenhouse caused by the absorption of infra-red and other thermal wavelengths onto surfaces inside the greenhouse. This is also caused by the increased levels of carbon dioxide and water vapour trapped inside the greenhouse. The term global greenhouse effect refers to an overall warming of the planet's atmosphere due to release of pollutants such as chlorofluorocarbon gases.

green manure

Green manure is a crop such as clover which is ploughed into the soil while still green, which then rots to provide organic matter and nutrients to the soil. Green manure crops are rapidly maturing which are often grown over winter to take up and store nitrogen which would otherwise be washed from the soil; these nutrients are released for other plants when the ploughed in crop rots down.

green peach aphid

A pest that in spring damages leaves and shoots by sucking sap; the leaves turn yellow and are shed and the pest spreads virus diseases.

green petal

Petals are green and strawberry fruits fail to fatten. Plants appear to be stunted and distorted, and may die.

green potato tubers

A disorder of potatoes where the tubers are green both inside and outside.

green spruce aphid

The foliage develops a white-yellow mottling, turns brown and drops off during late winter.

green top of carrots

Carrots are green not orange; roots exposed to sunlight turn green.

greenwood cutting

A portion of a plant that is removed and used for vegetative propagation: greenwood cuttings are made from the tip of young growth.

grex

This term refers to a group of plants which are very similar, yet there may be a number of species or varieties.

grey bulb rot

Fungal disease affecting particularly Hyacinths where the top of the bulb becomes dry and grey; black fungal resting bodies found.

grey mould

Fungal disease affecting a wide range of plants where the brown rotting stems become covered with grey furry mould.

Grifola frondosa

Grey tan brackets develop around base of a tree. Infected wood becomes soft and pulpy.

griseus

Means "grey" in Latin.

ground cover

Plants used to cover the soil, smothering weeds with attractive foliage.

grower

Refers generally to any person who grows plants, although more specifically it may be used for commercial growers such as horticulturists.

growing bag

Bags of compost with nutrients, which are used for planting crops such as tomatoes. The bags are usually made of polythene to retain moisture and the plants are grown and watered through holes in the upper surface.

growing lamp

An electric light that produces a particular spectrum suitable for the growth of plants. Different wavelengths of light promote different growth responses, and can induce flower formation in certain species.

growing medium

A non-specific term which could be the soil, agar, a compost of some type etc.

growing on

The process of taking a plantlet and cultivating it so that it develops further.

growing point

The apex of a shoot or root where the rapidly dividing cells elongate the tissues.

growth

The life process of "growing" or development where a organism may add new cells and tissues to itself, and also reproduce by various methods.

growth regulators

Plant hormones which may be naturally occurring or synthetic, and which may be applied to plants to promote growth.

growth rings

These are annual rings found in woody tissue which indicate the yearly growth of the plant. The woody tissue is laid down by the cambium as the stem or trunk increases in girth. In spring there is generally rapid growth and the wood vessel cells have a large diameter, and hence this part of the ring is light coloured. Slower growth in the summer is shown by the darker part of the ring.

grub

General term for the larval stage of an insect. Also this term refers to the digging up of plants from the soil.

guano

This is a term for bird droppings. Fertilizer from sea bird droppings is high in phosphate, which promotes good root growth.

guard cells

These are a pair of cells which surround the stomatal openings, controlling the opening and closing of the stomata, and hence help to regulate gaseous exchange.

gumming

This is the production of a sticky substance by some plant species. Gums may be exuded from eucalyptus trees (a method of protection against pests and fire). The exudation may occur naturally or it may occur as a result of infection with a pathogen.

gummosis

This is a fungal disease of melons, cucumbers and marrows. It may be caused by poor ventilation and high temperatures.

guttation

This refers to the production of water at the ends of veins in the leaf, or the forcing out of water from the surface of the leaf veins. This helps the plant evaporate water from the leaf surface, especially during high humidity atmospheric conditions.

guttatus

Means "covered with dots" in Latin.

guying

This may refer to the supporting of newly planted shrubs and trees by ropes etc which are staked into the ground.

gymnosperm

A member of the Gymnospermae class, which includes conifers and other plants where the seeds are not enclosed within an ovary.

gynaecium

A collective term for the female reproductive structures of an angiosperm plant, which include the ova, carpels, stigma and style.

gynodioecious

Having female and bisexual plants.

gypsum

This is a soft rock which is hydrated calcium sulphate, which can be used to incorporate calcium into the soil.

gypsy moth

Defoliation of plants in early summer caused by caterpillars of a moth. They are very distinctive in colour due to blue warts on each front segment of their bodies. The other segments have reddish warts.

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