Join thousands of gardeners across the UK who use our free service to buy, sell and swap plants ... and much more.

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.


Means "Spanish" in Latin.

ice age

A period in the Earth's history when large ice sheets and glaciers covered a large proportion of the world's surface. There have been a number of these periods, especially in the Pleistocene period, the most recent being about 10,000 years ago. These ice ages had an important impact on land formations and the evolution of flora and fauna.

ichneumon fly

A parasitic insect which lays its eggs in caterpillars; the larvae of the insect then consume the caterpillar.


These are epidermal cells which secrete gum or slime.


Means "slothful" in Latin.


Means "fiery-red" in Latin.


Means "holly-like" in Latin.


Means "brilliant" in Latin.


A name for an immature insect, and can be a stage between the larva, pupa and the adult insect.


Overlapping (like tiles on a roof).


Means "overlapping" in Latin.


Means "spotless" in Latin.


A term given to a plant which is not killed by specific pests or diseases. (A resistant plant is one that might die eventually if under a bad attack by a pest or disease.)


A pinnate leaf terminating with a single leaflet.


Means "tangled" in Latin.


Means "very noble" in Latin.


Another term for "inserting" or "engrafting".


Sunken (as in the veins of a leaf).


Means "sunken" in Latin.


Means "unequal" in Latin.

inarching graft

A technique of grafting where the stem of either plant is not separated from its own roots until the graft has successfully taken.


Refers to the result of a flower fertilizing itself.


Means "grey" in Latin.


Means "flesh coloured" in Latin.


A measure of length equivalent to 2.54cm (centimetre).


Deeply, sharply and irregularly cut.


Means "incised - cut" in Latin.


Means "unequalled" in Latin.


A term for "thickened", such as an "incrassate epidermis".


Not dehiscent and therefore does not burst open.


Means "of India" in Latin.


This means that the plant originated (native) in the country or region where it is growing.


Dense hair covering.


Folded inwards.


Hardened or weathered.


A small flap or pocket of tissue covering a group of sporangia in many Pteridophytes.


Refers to a plant with no spikes or thorns.


Means "unarmed - spineless" in Latin.


Meaning "lower" or "below""; hence inferior ovary, where the ovary is situated below the calyx.


Refers to a plant that produces no fruit. It can also refers to a soil with few nutrients.


A name given to the field that is nearest to the farmhouse.


Means "puffed up" in Latin.


Bent or flexed.


Bent inwards towards the main axis.


An arrangement of flowers with a common stalk. Some types of inflorescence are: panicle, corymb, cyme, spike, raceme, and umbel.

infra ...

This is a prefix to a word which generally means "below".


A grouping of fruits with a common stalk.

ink disease

A disease affecting bulbous irises where black patches develop on the bulb and on the leaves and flowers in wet weather.


Means "unnamed" in Latin.


Means "without scent" in Latin.

Inonotus hispidus

Bracket-shaped fungal fruiting bodies develop on large limbs or main trunk of trees. These are covered in dense, hair-like growth and are an orangey-rust colour turning dark brown black as they age.


A compound not derived from a biological source. It can mean a chemical not containing carbon. The term non-organic may be used sometimes.


A small arthropod animal with a keratin exoskeleton (hard outer skin) and a body divided up into 3 segments; the head, thorax (with 3 pairs of legs) and abdomen.

insecticidal soap

This is a formulation based on fatty acids from animal or plant sources. They can be used for control of aphids, thrips, red spider mites, scale insects, leaf hoppers, whiteflies, mealy bugs and similar pests. Such soaps last for only a couple of days and are not selective in their action.


A substance used for killing insects, but it may also kill similar creatures such as centipedes, millipedes and symphilids. Insecticides need to be used with care and only when really necessary since they may build up in the environment and insects can become resistant. DDT insecticide is a notable example which was used widely, but which has become generally ineffective now and has accumulated in the food chain such that fish, birds and humans all now have unhealthy quantities in their bodies. Biological control and better cultivation techniques are preferred methods where possible of controlling pests.


Referring to carnivorous plants that trap and digest insects and other small organisms to supplement their nutrient intake.

insect pollination

Refers to the transferring of pollen by insects (or other small animals) from the male anthers to the female stigma of many plants, which are usually those with showy coloured flowers to attract the insect pollinators.


Means "striking" in Latin.


Refers to the 2 coats covering the ovule which develop into the seed coat.

inter ...

This is a prefix to a word which generally means "between" or "among".


This is the planting of fast growing vegetables between slower crops to maximise the use of the land. An example might be the planting of lettuces or radishes (fast growing) in alternate rows between sweetcorn or parsnips (slow growing).


Meaning "between the leaves", such as interfoliar flowers.

internodal cuttings

Part of the stem between the nodes are taken for the cuttings.


The portion of a stem between 2 nodes.


Not continuous.

interspecific hybrid

This is a hybrid of 2 different species within the same genus, and is indicated in some botanical books by the generic name followed by an x (x symbol) and then the specific name. In this package such a hybrid is indicated by the generic name followed by the species name followed by the word "hybrid" eg Abelia grandiflora hybrid.


The inner part of the wall of a pollen grain.

intra ...

This is a prefix to a word which generally means "within" or "inside".


Not native; a plant brought into a country or region from elsewhere.


The acquiring of characteristics by one species from another by hybridisation (the act of creating a hybrid), following by back-crossing (where the offspring are crossed with the parent plant).


This means "upside down".


Covered or enclosed.


A collection of bracts or leafy structures surrounding a flower head, groups of flowers, or a single flower.


Meaning that the organ is "rolled inwards at the margin".


Means "rolled inwards" in Latin.

Irishmans cuttings

This term refers to shoots which develop around the base of some plants such as chrysanthemums, with roots already attached; these shoots can be taken off and used for growing on.

Iris ink disease

Blue-black streaking appears on outer surface of bulb, if left will turn black and rot.

Iris leaf spot

Water soaked spots develop on foliage later turning brown with grey centres. Affected irises grow less vigorous and flower poorly.

Iris rhizome rot

Foliage turns yellow and withers from leaf tips and margins. A soft, smelly rot develops at base of affected leaves and rapidly spreads down the rhizome. In extreme cases, leaves may yellow and topple over.

Iris rust

Orange-yellow pustules develop on leaves which erupt to produce masses of spores. Infected leaves discolour turning yellow, brown then they drop off.

Iris sawfly

Notches are eaten from leaf margin which cause extensive defoliation.

Iris scorch

Upper part of affected leaves wilt, bend over and become red-brown. Roots die back, some rot and others disintegrate internally.


An element (symbol Fe) which is a micronutrient, needed by plants but only in small quantities. It is usually available in the soil, but if deficient then the plant will suffer chlorosis of young rapidly expanding leaves. To correct an iron deficiency, manure or a balanced fertilizer can be used which contains proportions of nitrogen, phosphate and potash (NPK) plus other minor nutrients. Sequestrene is a formulation of chelated iron and other minerals which may be applied to the soil to correct certain mineral deficiencies.

iron deficiency

Generally causes young leaves at the tip of shoots to turn yellow with yellow spreading to the rest of foliage but remaining firm and not falling.

iron sequestrene

This is a formulation of chelated iron and other mineral nutrients which may be applied to the soil to correct certain mineral deficiencies.

iron sulphate

This name may be used as an alternative to ferrous sulphate.

irregular watering

Fruits are unusually small and may be thick-skinned. Surface may be ruptured with splits when fruits swell in response to sudden water availability.


This refers to any type of watering done by humans to promote plant growth. Some irrigation systems can be highly mechanised such as the "centre pivot" systems used in large scale agriculture where a central water source feeds a rotating pipe and spraying arm supported on motorised wheels; such systems can irrigate a circle of land which can be hundreds of metres in radius. Drip irrigation and trickle irrigation methods are common techniques for horticultural scale irrigation.


Means "Icelandic" in Latin.

iso ...

This is a prefix to a word which generally means "the same as" or "equal".


Having the same number of parts.


Of similar form


Means "Italian" in Latin.

ivy leaf spot

Brown or dark grey spots develop on ivy foliage, may be surrounded by band of reddish discolouration. Fungal bodies may develop.

ivy on tree trunks

Growth of trees may be constricted. In windy areas it increases the possibility of the tree being blown over.

Production v5.9.2 (d960957)