Horticultural and Botanical Glossary


Annual: a plant completing its life cycle from seed to flower within one year

Damping-off: a decaying disease caused by fungal attack in young seedlings. If some of your seedlings have suddenly collapsed remove those that are affected. This disease is primarily caused by over – watering and planting too many seeds in one area.

Cloning: vegetative reproduction using a single parent and thus offspring are genetically identical to this parent

Coma: a tuft of long hairs growing at either end of a seed to aid distribution using wind or hot air thermals. Dandelion seeds exhibit such structures.

Cotyledons: first leaves to appear from the embryo of a seed plant

Eutrophication: nutrient enrichment [sometimes as a result of human activity] of aquatic environments. Can cause rapid growth of algae [algal blooms]

Florets: Small flowers

Gravitropism (geotropism): A response to gravity, as in roots growing downwards and stems growing upwards

Hybridise: Crossing two species

Hydroponics: Growing plants in a nutrient rich, soil-less medium

Lanceolate: botanical term for leaves that are more oval at the base tapering to a point at the top

Macrophyte:  A plant/alga large enough to be seen with the naked eye

Meristems: actively dividing and growing plant tissues

Misting: using a fine water spray to create humidity around house-plant leaves

Nitrogen-fixing bacteria: Bacteria that convert nitrogen found in the atmosphere into organic compounds that can be taken up by plants. Bacteria can be housed in nodules found on the roots of the pea and bean family

Nodule: small knob-like form extending from the root containing nitrogen-fixing bacteria

Plantlet: small plant formed either on or connected to the parent leaf. Spider plants produce plantlets that can be potted alongside the parent plant either in soil or water (see diagram). Once they have developed roots they may be treated as individual plants and removed from the parent.

Perlite: a broad term for naturally occurring silica-rich rock. Perlite is different from other volcanic glasses as when heated to a suitable point it increases from four to twenty times its original size.  This is due to the rapid expansion of water contained within the perlite itself which creates the light water holding substance that is so valued by gardeners.

Quadrat: a basic grid, traditionally 1m square, to sample vegetation. Charles Darwin is said to be one of the first scientists to use such a tool in his weed plot experiment. A wider range of shapes and sizes are now used in a broader range of habitats

Rhizome: an underground stem. Can be used to vegetatively propagate plants such as Horsetail by dividing small pies and planting horizontally in pots with compost.

Rooting hormones: come in liquid or powder form they can be used to stimulate root growth in fresh cuttings

Root hair: A fine outgrowth of a cell in the outer layer (epidermis) of a root. These hairs increase the surface area of the root and assist in the uptake of water and other nutrients from the soil.

Scape: a leafless flower stalk coming up from the ground supporting one or more single flowers (such as in bluebells) or a head of flowers (such as in dandelions)

Seed or cuttings compost: specialist composts designed for seeds and cuttings, usually based on recipes developed at the John Innes Centre for horticultural research, and so known as ‘John Innes sowing compost’. Unless you are growing carnivorous plants, we advise using peat-free compost, as the use of horticultural peat has severely depleted natural bogs and mires.

Serrated: having a toothed leaf margin

Stem cutting: a technique for propagating plants asexually, by placing a part of the stem of a source plant (containing at least one stem cell) in a suitable medium, such as cuttings compost. The stem will then develop new roots, and become an independent plant. This is a good way to propagate geraniums (Pelargoniums). In propagating geraniums, stem cuttings should be about 10cm in length with two/three leaves at the top of the stem. Any lower leaves on the stem cutting should be removed, as should the small leaf-like stipules as they rot easily and will affect the growth of the cutting. See the advice from the RHS.

Stipules: Outgrowths emerging from the base of the removed leaf stalk

Thigmotropism: A tropic response by a plant part to a touch stimulus. Comes from the Greek ‘Thigma’ for touch

Tissue culture: Growing small pieces of plant tissue in a sterile growing medium that provides the nutrition needed for the selected plant tissue to grow

Transect: A line used in ecological sampling to represent the linear distribution of organisms e.g woodland margin, playing field or investigate an environmental gradient such as moisture levels in heathland. Good for examining the distribution of plant populations when used with a quadrat

Variegated leaves: irregular distribution of colour on leaves- usually 2 colours or more

Vegetative propagation: increasing plant numbers by asexual methods using vegetative parts of the plant. This can occur naturally such as Spider plant plantlets, Strawberry runners, or garlic cormlets  or  artificially through the taking of cuttings and other propagation methods such as cloning by tissue culture

White-fly: a small, white sap-sucking insect with green coloured young that leaves sticky ‘honeydew’ on leaves. Reproduces in large numbers. Excrement attracts mould. The presence of this pest causes leaf distortion and general weakness. Geraniums (Pelargoniums) are particularly susceptible. Be observant and look out for leaves that have been colonised and remove. A liberal wash with dilute soapy water can help control such pests.

Wind-dispersal: a seed distribution method that uses wind or hot-air thermals to move seeds away from the parent plant

Xerophyte: A plant adapted to grow in very dry environments Lithops is a good example

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