Gardening Glossary, Terms & Phrases Explained | LTG

Gardening Terms & Phrases Explained

Not sure what 'Companion Planting' is? Confused about 'heading back' and 'heeling in'? Here are some common gardening terms explained.

The world of Horticulture can often be a confusing and over technical one, many terms have been used for hundreds of years passed down from generations without their meaning actually being understood. The following is an A-Z listing of some of the most commonly used terms, and a few not so common ones, with a simple explanation of their meaning. 

Click a letter to skip to that section - A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z


Acaricide - A pesticide used to control mites.

Acid Soil - Soil with a pH lower than 7, 7 is neutral and soils over 7 are alkaline. Most plants prefer soils of around 6 - 7. Basic testing kits can be bought at most garden retailers.

Active Ingredient - The ingredient in pesticide products which is toxic to the target.

Aerate - Turning, loosening or driving holes into the ground to aid water and air circulation in the soil. This improves the structure of the soil and makes it easier for roots to grow, breath and get moisture.

Algicide - Chemical used to control algae.

Alkaline Soil- Soil with a pH greater than 7. 7 is neutral, soils with a pH under 7 are acidic. Most plants prefer soils with a pH of 6-7. Basic testing kits are available at garden retailers. 

Annuals - A plants whose life cycle takes a year to complete, from seed germination, to flowering, to setting seed and dying. 

Aphids  - Small sap-feeding insects. Maturing into Greenfly and Blackfly.


Bacterial Blight - A bacterial disease causing widespread blackening of leaves and shoots

Bacterial Canker - A bacterial disease causing sunken lesions of dead cells in the stem tissue. 

Bareroot - Plants that are supplied without soil around their roots. Usually they are dug up during their dormant period, rinsed of soil and sold for replanting.

Bedding Plants - Usually annual plants, sold for providing a quick, colourful display. 

Biennial - A Plant whose life cycles takes 2 years to complete, in most cases it will only flower in the second year. 

Black Spot - One of te most common diseases of Roses, caused by the fungus Diplocarpon rosae.

Bleeding canker - A bark disease of deciduous trees usually caused by Phytophthora cactorum. Gunny liquid oozes from lesions in the bark. 

Blossom-end rot - A non-parasitic disease of tomatoes and peppers. Seen as water-soaked patches on the fruit, caused by calcium deficiency usually linked to irregular watering.

Bolting - Usually referring to vegetables, bolting is when the plant produces flowers too quickly, rather than producing a food crop. In most cases related to excessive temperatures.

Bonsai - A Skillful art of growing miniature plants in small containers.

Bract - A group of leaves grown just below a flower or group of flowers. Often mistaken for flowers/petals as with the Poinsettias red bracts. 


Catkin - A slim, drooping group of flowers

Chlorophyll - The green pigment in leaves, usually the dominating pigment in a healthy plant. 

Companion Planting - Growing plants close to each other for beneficial purposes, such as growing flowering plants near your crops to encourage pollinating insects. 

Compost - A blend of decomposed and decomposing organic materials used for soil improving, mulching, planting and fertilising. 

Corm - An underground stem which becomes enlarged and produces roots and top growth during the growing season.

Crown - The join between the roots and the base of the plant top growth. 

Cultivate - Turning over and breaking up the surface of the soil, removing large stones, lumps and weeds ready for planting.

Cuttings - A propagation method where a new plant is grown from a root, stem or leaf.


Damping Off - a fungal disease affecting mainly seedlings and causing the stems to rot at soil level. Usual causes are over-watering, over-crowding and poor air circulation.

Dead heading - The act of pinching, pruning or snapping off dead heads of flowers. This will prevent the plant setting to seed and encourage more blooms. 

Dibber - A tool for making holes in the soil/compost for seeds, seedlings or bulbs.

Dividing -  Usually done to mature perennials, dividing is the act of splitting the plants roots making multiple plants out of one plant.

Double digging - Preparing the soil to the depth of two spade heads, about 10 inches. 

Double flower - A flower with loads of petals, overlapping and making the flower look big and full.


Evergreen - A plant which does not lose its leaves all at one time.


Family - A group used to classify plants. A family will be made up of several similar genera. 

Fertiliser - Plant foods used to produce more flowers, fruits, root growth and healthier plants. Also used to improve the fertility of soils.

Forcing - Speeding up the plants growth to maturity. Usually to see flowers earlier.

Frond - Usually referring to 'ferns' or 'palms', the frond is the leaf structure and branches.

Fungicide - A pesticide used to kill or control fungi.


Genera (Genus) - A group of closely related plants. In the plant name the genera sits above 'Species' and below 'Family'.

Germination - The start of growth in a seed.

Grafting - Attaching part of one plant onto another plant, so it grows from the host plants root stock. Usually done to create hardier plants.


Hardiness- A means of measuring how tolerant a plant is to cold and frost, without protection. 

Heading back - Pruning a mature branch back to a stub. 

Heeling in  - Placing the plant in a shallow trench and covering the roots with soil, used as temporary placement until ready to plant up in permanent place.

Herbaceous - Used to describe plants which tend to have soft fleshy stems rather than tough woody ones. 

Herbicide - A type of pesticide use to control weeds. 

Horticulture - The science of cultivating plants. 

Humus - Dark organic matter in soils, derived from decomposed plant matter.

Hybrid - When a new plant is created by cross-pollinating two different species or varieties.


Inflorescence - The part of the plant that carries the flower.

Insecticide  - Type of pesticide use to control insect pests.


Japonica - Used in plant names to highlight plants native to Japan (e.g. Fatsia japonica, Skimmia japonica)


K - The K in N-P-K formula stands for Potassium (from Kalium - plant ashes)


Leaf Mold - Decomposing leaf matter used to improve soils.

Leatherjackets - The larvae of crane flies or daddy long-legs. Adult female lay eggs just below the soil surface usually in grassy areas, the larvae then feed on the roots of the grass causing dead and damaged  areas.

Loam - A mixture of clay, sand and silt making a rich soil.


Manure - Organic matter excreted by animals

Micro nutrients  - Mineral elements that plants require in very small quantities, micro-nutrients or trace elements can be found in most good garden fertilisers.

Molluscicide - A pesticide used to control molluscs. (slugs and snails)

Mulch - A layer placed over the soil to prevent weeds and lock in soil moisture. Usually organic material, but plastic sheeting is often also used.


Node - The part of the plant where more leaves, stems or flowers start to grow.


Organic - Any material which was once a living organism. 


Palmate - Mostly used in horticulture to describe the shape of a leaf, palmate means 'like a hand'. A central point will have segments growing out like fingers. (e.g Acer palmatum)

Parasitic plant - A plant that lives on another plant, drawing its nutrients from the host plant. (e.g Mistletoe)

Perennial - A plant that lives for multiple growing seasons. 

Pest - Any living organism causing harm to cultivated plants.

Pesticide - Any substance used to kill, control or diminish a pest.

Pinching out - Removing fresh growth usually at the top of the plant to promote a fuller, bushier plant.

Pinnate - A feather-like leaf structure, with pairs of leaflets either opposite or alternate growing along the main leaf stem. (e.g Robinia)

Pollination - The transfer of pollen from the male part of the flower (stamen) to the female part of the flower (pistil) resulting in the formation of a seed.

Propagation - The method of starting a new plant. (e.g. seeds and cuttings)


Quercus - The latin name for 'Oak'. Latin names often help us understand what a plant looks like. Ilex is the latin name for 'Holly'. So the 'Quercus ilex' is an Oak tree with holly like leaves. 


Raised bed - A bed raised up higher than ground level, this can provide better drainage, aeration and warmer soils.

Rhizome - A plant stem that grows horizontally, usually under the surface of the soil. New plants will grow from various points of the rhizome. (e.g. Iris)

Root ball - The mass of roots under the plant with soil attached.

Runner - A thin stem growing from the base of a plant, ending with the growing of a new plant. (e.g. Strawberry)


Scarifying - Raking over the top of a lawn to remove thatch and loosen the surface to aid fresh growth.

Spores - The reproductive cells of mosses, fungi and ferns. Found in plants that do not produce seeds or flowers.

Sucker - New growth coming from the rootstock of a grafted plant. Should be removed as they 'suck' or draw energy from the desired plant.

Systemic - The mode of action of a chemical applied to control the pest from within. The chemical is absorbed into the plant and circulated via the sap system, common in fungicides (disease control), insecticides (bug, insect control) and herbicides (weed killers).


Tap root - The main thick root of a plant, usually growing straight down.

Tendril - The thin, twisting and clinging growth of many vines. Used by the plant to attach itself to a surface and climb. 

Thatch - The layer of dead organic matter on a lawn, this should be removed to aid water, nutrient and light penetration. 

Thinning - Removing some seedlings to avoid over-crowding and allowing other seedlings to grow with sufficient space. Trees and shrubs can also be thinned by removing older branches.

Top-Dress - Spreading soil amendments, fertilisers etc in a thin layer over the soil surface. 

Topsoil - The top layer of native soil, also referring to soil purchased in bags from garden centres. 

Transplanting - Taking a plant from its current growing position, and placing it in a new one. Can be in the garden flower beds, or from one pot to another.

Tuber -  An enlarged underground stem which stores food from which a  new plant will grow. ( e.g Dahlia, Begonia) 


Umbel - A flower cluster that forms a bit like an umbrellas spokes. Flower stems all come from a central point. (e.g. Sambucus - Elderberry)


Variegated - Leaves which have multiple colours. 

Vermiculite - When the mineral 'mica' is heated to the point of expansion it creates small spong-like granules. Used to improve aeration and water retention when planting in pots and containers.


Waterlogged - ground that is saturated and cannot absorb any more water. 

Weeds - Any plant growing in a place where it is not wanted.


Xanthos - The Greek for 'Yellow'. Plants with names starting 'Xanth' will have yellow features. (e.g. Xanthorhiza - Xanthos = Yellow, rhiza = root, so this plant has yellow roots.)


Yarrow - Achillea millefolium, commonly found growing in lawns and tough to control. Achillea comes from the Greek for Achilles who is said to have discovered its medicinal properties.

Yield - The measure of a crop obtained in a harvest.  


Zantedeshia - Also known as Arum lily and Calla lily. Named after Giovanni Zantedeschi (1773-1846) an Italian botanist and physician. 

Zinc - A trace element used by plants.


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