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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.

habit

Refers to the shape in which the plant normally grows; this can be an aid to identifying the plant.

habitat

This is the environment where a plant naturally grows.

haemaleus

Means "blood red" in Latin.

haft

This term can mean a shaft, such as in the narrow base of petals such as irises which are shaft-like.

ha-ha

A term for a raised section of a lawn, field or garden designed so that when viewed from above, the wall is disguised and not easy to see. In this way cattle and other animals are prevented from straying onto the garden and it is a surprise for onlookers; hence 'ha-ha'. An example is the ha-ha in front of the Royal Crescent in Bath.

hair

A fine projection from a surface; one-celled or many-celled, simple or branched, straight or curved, etc. Special kinds of hair include glandular, crisped and star-shaped hairs. Long, soft hairs are described as woolly and those pressed flat to a surface as adpressed.

half hardy

Used to describe plants that require protection during the winter, and can tolerate temperatures down to 0C (32F). Climatic zone of 10.

half hardy annual

These annual plants are able to survive cool conditions but not frost, and are generally sown under glass and planted in their flowering positions when the risk of frost has passed.

half-ripe

Refers to a stem cutting taken when the stems are beginning to turn from the green, soft stage to a woody stage; usually in late summer.

half-standard

Refers to a plant with a shorter main stem (up to 1 metre) than a full standard.

halo blight

A disease that may affect French and runner beans where brown, yellow-edged blotches appear on leaves and soggy blotches on pods.

halophobe

A plant which cannot tolerate salty or seaside conditions.

halophyte

A plant living in a habitat of high salt (sodium chloride) concentration, such as a saltmarsh.

hamate

Meaning "hooked".

hand texturing

This a technique to assess the texture of the soil. A moist sample of soil is rubbed together between the finger and thumb; if a soil is sandy it will feel gritty, a silty soil will feel silky, a clay soil smears. The more clay in the soil sample the stickier the sample will feel.

hanging basket

Refers to any suspended container planted up usually for decoration. Sphagnum moss and other absorbent liners are used. The bottom part of the container is often lined with some polythene to prevent direct loss of moisture from the compost, and water absorbing granules may be added to the compost to reduce the need for frequently watering plants.

hapaxanthic

This means that a plant has only one flowering period.

haploid

Having the basic number of chromosomes. The haploid cells enable the sexual reproduction since they fuse to give the diploid plant, which then later gives rise to the haploid phase. (Diploid cells have twice the haploid number of chromosomes.)

harden off

This is the process of getting a plant which was raised in protected conditions to adapt to the growing conditions outside which might well be colder. A plant may be put outside in late spring in the shelter of a cold frame or wall for increasing periods of time, and kept under cover if there is a danger of frost.

hardiest plants

These can be considered to be those that can survive in extremely cold climates close to the north or south poles. The most northerly plants found at latitudes of 83 degrees North are the Yellow Poppy (Papaver radicatum) and the Arctic Willow (Salix artica). Lichens similar to Rhinodina frigida have been found in Antartica at latitudes of 86 degrees South.

hardiness

Refers to the ability of a plant to survive certain climatic conditions. The primary measure is that of temperature ranges, although other factors such as water needs, humidity, wind etc also affect a plant's hardiness.

hard pruning

Refers to pruning shoots a long way back so that the plant may be only half the original size, or less. Pruning a plant back to within a few buds of the base promotes vigorous growth. Plants which produce buds on old wood near the ground (such as Buddleja) respond to hard pruning.

hardwood cutting

A portion of a plant that is removed and used for vegetative propagation. Hardwood cuttings are taken from mature wood at the end of the growing season. Suitable plants for this method of propagation may be trees, hardy shrubs and soft fruits.

hardy

Description of plants that survive frost in the open and temperatures down to about -10C or 13F. Climatic zone of 8. (However, in hot countries the term hardy may refer to the plant's ability to withstand drought.)

hardy annual

An annual plant which can survive frost and is generally sown directly into the ground where they are to flower. They might be sown in the spring, or possibly in the preceding autumn to flower in the summer.

harrow

Refers to the breaking up of clods of soil into smaller particles on an agricultural scale by using an mechanised implement called a "harrow".

harvest

Generally refers to the gathering in of cultivated crops.

hastate

Shaped like a spearhead.

hastatus

Means "in the shape of a battle-axe" in Latin.

haulm

This refers to the remainder of the plant after harvesting, such as the stubble left after harvesting wheat or barley.

haustorium

An absorptive organ of parasitic plants or animals which penetrates the host tissue.

haw

The berry on the hawthorn plant (Crataegus spp).

Hawthorn gall midge

Shoot tips fail to develop, instead rosettes of small leaves grow. Larvae live within.

hay

Long grass which has been sun-dried for use as winter feed for animals.

hay fever

An allergic reaction of some people to high volumes of pollen in the air (from wind pollinating plants). However, dust and pollutants may exacerbate this condition.

hazel-nut gall mite

A pest of hazel-nuts where the larvae and adults suck leaf and flower buds; flowers dry at the same time. The hazels grow irregularly and the number of fruits set is low.

hazel-nut weevil

A pest of hazel-nuts where the larvae chew the kernel and cause 'worminess' of hazel-nuts.

HCH insecticide

Also known as 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.

head

Of flowers or fruits, crowded together at the end of a common stalk.

heart

A term for the centre of vegetables such as cauliflowers and lettuces.

heart rot

A disease of plants such as celery where the centre of the plant goes brown and rotten.

hearts (lack of)

A disorder of cabbages where the plants remain leafy and open with no solid heart being formed. It may be overcome by planting in firm, well manured soil which does not dry out.

heartwood

Refers to the central hard wood of a tree, sometimes called the duramen.

heave

A term given to the action of frost on soil which can uplift poorly rooted plants.

heavy metals

Refers to elements such as lead (symbol Pb), mercury (symbol Hg), cadmium (symbol Cd), vanadium (symbol V) and arsenic (symbol As) which may be pollutants in soil.

heavy soil

Usually refers to soil with a high clay content.

Hebe downy mildew

Discolouration develops on upper leaf surface along with white fungal growth beneath. Infected leaves drop early.

hectare

A measure of land area (ha) equivalent to 10,000 square metres or 2.471 acres.

hedge

Plants used to create a screen. Usually evergreen plants are used such as privet (Ligustrum), and ones which are compact, withstand pruning and are difficult to penetrate such as holly (Ilex), yew (Taxus) and beech (Fagus) are used for hedging.

heel

The small section of older wood that is kept at the base of some cuttings when they are removed from the stem.

heel cutting

This is a type of cutting where a vigorous side shoot is taken from the stem of the parent plant. A small section or heel of older wood is kept at the base of the cutting when they are broken off from the stem. Some plants such as Berberis, Escallonia and Perovskia are better able to produce roots when a heel is retained.

heeling in

This is the technique of placing plant roots in soil before putting them in their final growing positions. This is often done with bare-rooted plants (usually trees) so that the roots are surrounded by moisture and nutrients while they are waiting to be planted.

heliotaxis

This refers to the response or reaction of an organism to the stimulus of the sun's rays.

heliotropism

This is a response to the sun's rays by growth curvature, such as a twining of a plant's stem.

Hellebore leaf blotch

Grey brown lesions develop on leaves causing discolouration. Stems and flowers may also be attacked.

hellenicus

Means "of Greece" in Latin.

helophyte

A plant which grows well in mud, and which may have a medicinal or culinary use such as basil, thyme or feverfew.

helveticus

Means "of Switzerland" in Latin.

Hemerocallis gall midge

Flower buds become abnormally swollen but fail to open before going brown and drying up.

hemispherical scale

Scales develop, immature scales are flat oval and yellow brown. Excrement secreted falls causing sticky leaf surfaces where sooty moulds grow. This sap-feeding insect affects a wide range of ornamental plants.

heptaploid

Having 7 sets of chromosomes.

Heptenophos

An ingredient (often with Permethrin) of insecticides for controlling a range of insects.

herb

A plant that has no woody stem and is soft and leafy (therefore often fairly small in size). For example, a 'herbaceous border' contains medium to small plants which are not woody shrubs or trees. Also refers to a plant used in seasoning or medicine.

herbaceous

Non-woody, soft and leafy. Can refer to a plant organ, having the soft texture and green colour of leaves. Also refers to foliage that dies down at the end of the growing season.

herbaceous perennial

The foliage dies down at the end of the growing season but the plant lives for at least three seasons, whereas a woody-based perennial dies down only partially leaving a woody stem at the base.

herbicide

Generally refers to weedkillers. There are several types including selective, contact, and systemic or translocated. Selective herbicides affect only certain families or species for biochemical reasons or because the herbicide runs off certain leaf types. Contact herbicides usually kill a wide spectrum of plants, usually on a short term basis. Systemic or translocated herbicides are absorbed into all the tissues of the target plants, and are often used to kill perennials.

hermaphrodite

With the stamens and ovaries present on the same flower. Also referred to as bisexual.

hetero ...

This is a prefix to a word which generally means "different" or "more than one".

heterogamous

A plant which bears 2 types of flower, such as the disc florets and ray florets of the daisy. It may also refer to a plant with male and female flowers on the same plant, or it may also refer to indirect pollination.

heteromorphic

Having more than one growth form.

heterophyllous

Having more than one leaf form.

heterosporous

This refers to the asexual production of spores of both sexes (the male microspore and the female megaspore), which then develop into haploid male and female gametophytes.The gametophyte generation then produce egg and sperm which will fuse to form the diploid zygote which will develop into the sporophyte generation, which in turn will form microsporangia (giving rise to microspores) and megasporangia (giving rise to megaspores).

heterostylous

Refers to flowers on a plant which have different types of style, or where they differ in number or length. An example is Primula vulgaris (primrose) which has 2 types of style to give "pin-eyed" and "thrum-eyed" primroses.

heterotrophic

Unable to manufacture food from inorganic raw materials.

hexaploid

Having 6 sets of chromosomes.

hibernaculum

This is a winter bud or bulb from which the plant will grow in the spring.

hibernicus

Means "Irish" in Latin.

hibernus

Means "winter flowering" in Latin.

hiemalis

Means "of the winter" in Latin.

high temperature injury

Injury may be temporary or result in tissue death and permanent damage. Scorching or scalding of leaves, fruits and flowers is common. Wilting may occur if plant is losing more water than it can take up.

hilum

The light coloured scar visible on a seed which was where it was attached to the parent plant by the funicle (stalk).

himalaicus

Means "of the Himalayas" in Latin.

hip

Fruit of the rose.

hippocrepian

Horse-shoe shaped.

hirsute

With rather coarse or stiff hairs.

hirsutus

Means "hairy" in Latin.

hirtellous

Slightly hirsute or downy.

hispanicus

Means "Spanish" in Latin.

hispid

Having rigid hairs or bristles.

hispidus

Means "with bristles" in Latin.

hoar frost

A layer of frozen, crystallised water on the ground and other surfaces where dew has been frozen.

hoary

Covered with close white hairs.

hoe

An implement for cultivating the soil and removing weeds.

holdfast

Referring primarily to seaweeds and other algae, it is the organ which anchors the plant to the substratum.

hollow heart

A disorder in potatoes where the tubers are hollow in the centre, possibly caused by soil conditions.

hollyhock rust

Raised round browny-yellow spots develop on lower leaf surfaces. Large area of leaves may be killed and fall away.

Holly leaf miner

Leaves develop pale-green or purple-brown blotches where internal tissue has been eaten out by larvae of a small fly maggot.

Holm oak leaf miner

Leaves develop elongated brown white blotches on upper leaf surface, lower surface have blistered appearance. Caused by caterpillars of a tiny moth.

homogamous

A plant with hermaphrodite flowers, or flowers of the same sex.

homomorphic

Having the same shape.

homosporous

Having spores all of one sort, as in most Pteridophytes. The haploid spores have been produced following meiosis from the diploid sporophyte generation. The spores develop into the "hermaphrodite" gametophyte generation which then produce egg or sperm, which will fuse to form the diploid zygote which then develops into the sporophyte.

honeydew

This a name given to a sticky substance which is secreted by aphids. The honeydew falls onto leaves below, and can encourage the growth of sooty mould.

honey fungus

This is a soil-borne fungal disease (caused by Armillaria mellea) which affects the roots of trees and some herbaceous plants. Infection may be noticed by the appearance of fungal fruiting bodies (like mushrooms) at the tree base in autumn, and lace-like, black strips under the bark. The fungal mycelium travels beneath the soil surface and can infect plants nearby. No easy cure is available and the plant and affected soil should be removed.

honeysuckle aphid

Aphids form colonies on shoot tips and buds which can result in buds aborting and shoot tips drying up.

hoof and horn

A fertilizer made from ground up hoofs and horns, which is rich in nitrogen. It is a slow acting fertilizer since it is broken down gradually by micro-organisms in the soil to release the locked up nitrogen compounds.

hop manure

This is spent hops from a brewery, which can be used to make heavy soils more workable.

horizontalis

Means "flat growing" in Latin.

hormone

This is a compound produced in plants (and other organisms) which acts to regulate growth and other reactions in the tissues.

hormone rooting powder

This contains growth promoting hormones, into which cuttings may be dipped to enable roots to develop more quickly. The powder usually includes synthetic plant hormones and a fungicide. The rooting powder may also be available in a liquid form.

hornbeam witches brooms

Branched twigs develop. A whiteish layer of fungal spores may develop on leaf surface from late spring.

horridus

Means "very thorny" in Latin.

Horse chestnut leaf blotch

Leaf blotches that are brown and yellow develop from mid summer onwards. Black fungal fruiting develop on upper leaf surface, if badly affected leaves drop off.

Horse chestnut marginal leaf scorch

Leaf browning or scorching occurs in early to mid summer.

Horse chestnut scale

A grey-brown, flat scale (approx 4mm) appear on trunks and larger branches. Scale rest on a white, waxy egg mass. When they fall away they leave white patches on bark.

hortensis

Means "of gardens" in Latin.

horticulture

The culture of plants for food, ornamentation and other uses. Generally regarded as being on a smaller, but more intensive scale than in agriculture (which is primarily for food production by growing plants and animals).

host

The organism from which a parasite obtains its food.

hostile

This term may be used to describe an environment which is hostile to the successful growing of a plant. An example might be that ericaceous (acid-loving or lime-hating) plants such as Rhododendron would find an alkaline soil hostile.

hot bed

Under-soil heating may be used to help raise plants such as early lettuces.

hot water treatment

Bulbs may be immersed in water of a certain temperature for a certain length of time in an attempt to kill pests. However this needs to be done carefully since the bulbs may be destroyed and the pests may not be killed.

hoverflies

Is sometimes called the Narcissus bulb fly, laying eggs on the bulbs.

hull

This term may be given to the pods holding peas, beans or nuts.

humidity

Refers to the amount of water vapour present in the air. Many tropical plants such as most bird nest ferns generally thrive in humid or semi-humid conditions, whereas cacti generally prefer a drier atmosphere.

humifusus

Means "ground spreading" in Latin.

humilis

Means "dwarf" in Latin.

humus

The black, organic, crumbly substance remaining when dead plant matter has broken down. Leaf-mould is one source of humus which releases its nutrients gradually and is a good soil conditioner.

hyacinthus

Means "deep blue" in Latin.

hyaline

Thin and more or less transparent.

hybrid

A plant created through the cross-fertilization of two species. Such cross-breeding between two different species, results in a hybrid plant with some characteristics of each parent plant. In many botanical books a hybrid is indicated by a x (x symbol) before the species name.

hybrid tea

This name is given to a group of roses which are derived from a hybrid between "hybrid perpetuals" (large, vigorous, fragrant) and "tea roses" (recurring flowers, glossy petals).

hybridus

Means "intermediate" in Latin.

hybrid vigour

Often a hybrid plant will display more vigorous growth than either of the parent plants.

hydathode

A water-secreting gland or pore found in the leaves of many plants; sometimes called a lime dot.

Hydrangea leaf spot

Grey, brown or purple spot become apparent on older foliage and fungal fruiting bodies may develop.

Hydrangea powdery mildew

Dense white deposits form on upper leaf surfaces, occasionally on petioles and new stem growth. Affected leaves become distorted, especially when young.

Hydrangea scale

Scale visible on underside of leaves.

hydrogen

This is a chemical element (symbol H) which together with oxygen makes up water molecules. It is essential for organic life processes, and as water is absorbed by both plants and animals for respiration. Hydrogen is incorporated (synthesised) during metabolism by biochemical processes into compounds such as carbohydrates and proteins.

hydrophilus

Means "water-loving" in Latin.

hydrophyte

A term for a plant growing in water.

hydroponics

This is cultivation of plants in a nutrient solution rather than in the soil; sometimes soil-less cultivation. The plants need to be supported in some way since their roots are growing in flowing water with dissolved nutrients; for example tomatoes may be supported by twine around their stems. There are various hydroponic techniques including the nutrient film technique, aggregate culture and rockwool.

hydroscopic

Expanding in contact with water, and contracting when there is no water.

hygroscopic

Water absorbing.

hylophilus

Means "wood-loving" in Latin.

hypanthium

The extension of the receptacle above the base of the ovary, in perigynous and epigynous flowers.

hyphae

Fine thread-like growths made by fungi.

hypnoides

Means "moss-like" in Latin.

hypocotyl

The stem of a seedling between the root and the cotyledons.

hypogeal germination

In hypogeal germination where the cotyledons are left below in the soil, the epicotyl (a stem-like structure bearing the first true leaves) is the first visible sign above soil of germination. In epigeal germination the cotyledons appear above the soil on the hypocotyl, and then the epicotyl develops.

hypogeus

Means "underground" in Latin.

hypogynous

Referring to a flower with a superior ovary, where the calyx, corolla and stamens are inserted at the base of the ovary.

hypophyllus

Means "whiteish beneath" in Latin.

hysteranthous

Referring to leaves which develop after the flowers.

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