Glossary of Gardening and Horticultural Terms

A

Abiotic –  A non-living occurence that could cause problems. Examples, air pollution and salt.

Abscisic acid – A plant hormone that promotes dormancy in buds and seeds.

Acclimation – The process of adapting plants to a new environment which could be of particular importance to new plants.

Acidic Loving Plants – Plants that require a PH level below 7 to reach their best. Soil ammendments like sulfur might need to be added.

Adaptation – Plant characteristics that allow it to grow in a particular condition. Zonal considerations. Some plants might be adaptable as houseplants i.e. they can grow indoors during winter.

Aeration – Loosening soil mechanically to encourage good air and water flow.

Alkaline – Plants that require a PH above 7. Soil ammendments like lime might need to be added.

Angiosperm – Commonly fruit producing plants where seeds are enclosed within an ovary wall.

Annual – A seed producing plant that grows within a single season and dies.

Anther – Terminal part of the stamen (male) where pollen is produced.

Apex – Tip or terminal. Important to look for especially in tree health.

Apical bud dominance – Healthy terminal apical bud dominance will supress excessive side (lateral) bud growth.

Auxin – An essential plant hormone that controls plant growth.

Axil – Where a leaf stalk or leaf joins the stem.

B

Bacteria – Single cell organisms that often cause plant and animal disease.

Bark – The exterior part of a woody trunk consisting of mostly dead matter. Protects the cambium.

Biennial – These plants complete their life cycle after two years.

Blight – A plant disease that kills leaves, flowers and stems.

Bract – Modified leaf that are colorful. Example, dogwood and poinsettias.

Brambles – Plants with cane shoot growth. Example, raspberries and blackberies.

Broadleaf evergreen – A shrub or tree with green leaves (as opposed to needles) that hold their foliage all year long. Example, Euonymus fortunei (Wintercreeper).

Bud – Embryonic plant tissue.

Bulb – Underground modified leaves that form roots. Examples, onions and tulips.

C

Callus – Corky tissue to protect wounded woody plants.

Calyx – Comprises the sepals, which covers and protects the petals as they develop.

Cambium – A thin tissue layer that provides cells for plant growth. It is found between the xylem and phloem. If it becomes severely damaged the plant will probably die.

Canker – Open wound stem, branch or trunk injury that becomes infected with fungal or bacterial pathogens.

Catkin – Drooping flower clusters. Examples, willow,birch and oak.

Chlorophyll – The pigment that gives plants green coloration.

Chlorosis – A yellowing of leaf tissue due to the lack of chlorophyll. Iron or magnesium additives are used to treat symptoms.

Compaction – Soil pressure that prevents water and air flow.

Companion crops – Two non competitive crops grown at the same time in the same area.

Compost – A mix of soil and decomposing organic matter.

Compound leaf – A leaf blade divided into two or more distinct leaflets. Example, roses.

Conifer – A plant that bears cones.

Cork – Outer bark tissue.

Corm – A swollen underground stem. Example, crocus and gladioli.

Cotyledon – Significant part of the emryo serving as a seed food storage structure.

Cross pollination – The transfer of pollen from one plant to another: from anther to stigma.

Cultivar – Plant species variation developed by human intervention through controlled plant breeding.

Cutting – Production of a new plant from a cutting.

Cytokinin – An essential plant hormone promoting cell division.

D

Damping off – Seedling disease causing decay prior to germination.

Dead heading – The removal of old and dying flowers which can promote new growth.

Deciduous – Plants that shed all their leaves at the end of a growing season usually followed by dormancy.

Desiccation – Drying out and dying of plant tissue.

Dicot – Two cotyledons present in the seed.

Dioecious – Where male and female flowers are found on separate plants. A male and female plant are required for pollination. Example; ginkgo.

Division – A method of propagation by dividing plant roots.

Drip zone -The area around a tree where water drops from the canopy. This is a useful area for root feeding.

Dwarf – A small plant or plant variety as compared to the parent plant.

E

Embryo – Developing plant inside the seed.

Epiphyte – A non parasitic plant that draws  nutrients from the air and usually grows on another plant. Example, orchids.

Espalier – Training to grow on a trellis or wall.

Etiolation – Where lack of sufficient light induces weak growth; elongated pale stems with under-developed leaves.

Eukaryotic organism – The earliest formed microfossils that posses a clearly defined nucleus.

Evergreen – Leaf retention and functionality is maintained throughout the year.

Exotic – A plant not native to a particular region.

F

Fertilizer – Materials that add nutrients to plants. The most common being nitrogen (N), phosphorus (P), and potassium (K).

Fibrous roots – Heavily branched roots with no taproot development.

Filament – a thread like structure. or slender stalk the bears the anther (where pollen develops).

Floret – A small flower that is part of a larger flower. Example, sunflower – the florets develop individually. Broccoli is another example.

Flower – The seed bearing part of a plant.

Foliar feeding – Applying, usually by spray, fertilizer to plant leaves.

Frass – Termite droppings. A sign that termites are present.

Frond – Leaf of a palm or fern.

Frost line – The depth at which soil groundwater freezes.

Fruit – The ripened plant ovary which contains seeds.

Fruiting habit – Describes the way in which fruit forms and grows on woody plants.

Fungicide – Pestcides that kill and prevent fungi and their spores.

Fungus – Eukaryotic organisms that lack chlorophyll – often a cause of plant disease.

G

Gall – Pathogen or pest induced swelling and outgrowth.

Genus – Taxonomic rank used in biological classification.

Germinate – The sprouting process.

Gibberellin – An important plant hormone that promotes internode elongation and cell enlargement.

Girdling – The removing of woody material inward to the cambium. Also known as ring-barking. It can ultimately kill the plant.

Grafting – Joining plants together to form one growing structure. Example, most commercially available roses are grafted onto rootstock.

Graft union – The point where grafted plants join together. Also called a bud union.

Gymnosperm – Seed producing plants frequently in the form of cones. The seeds are exposed. Examples include; conifers, cycads and Ginkgo.

H

Hardpan – A hard, impervious layer (like clay) that prevents water drainage.

Hardy – The adaptation of plants to harsh climates.

Harden off – Acclimating indoor seedling in preparation before transplanting them outdoors.

Heading back – Cutting back the terminal portion of a branch to a bud.

Heartwood – Older, dead, central wood of trees that no longer transports water and nutrients. It is commonly darker in color.

Healing in – A process to temporarily store plants before permanent planting. Usually by digging a shallow trench and covering the roots with soil.

Herbaceous – Plants that do not develop a permanent woody structure. We often refer to the many herbaceous perennials species which die back to soil level after each season. Examples, coneflower, day lillies, coreopsis.

Herbicide – A chemical, usually in spray form, that kills weeds.

Hormone – Essential chemicals produced by plants that regulate most life cycle aspects – growth, development, reproduction, and longevity.

Horticulture – The art, science, technology, and business of plant cultivation.

Humidity – The concentration of water vapor in the air.

Humus – The organic material that forms in the soil when plant and animal matter decay. Also called compost.

Hybrid – The result of cross pollinating and producing seed of two different plant varieties.

Hydroponics – A horticultural practice that grows plants without using soil.

I

Imperfect flower – A flower containing only the male or female reproductive organs, but never both. Example, most grasses, squash,sweet corn, cucumber.

Incomplete flower – A flower missing any of it’s natural form parts, which could be, the petals, sepals, stamen or pistils.

Indigenous – Native to a particular region or area.

Infectious – Spreading and transmitted, such as infectious disease by bacteria, virus, fungi or parasite.

Inflorescence – Describes the various arrangement of flowers on a plant.

Insecticide – Substances (either chemical or organic) used to kill and repel unwanted insects.

Integrated Pest Management (IPM) – Effective and environmentally sensitive pest management practice.

Internode – The portion of a stem between nodes.

Invasive – A species that is not native to a particular area and can cause harm to the native environment.

J

Juglone – A chemical primarily produced in the roots of black walnut trees which is toxic to many plants. Juglone is often the cause of surrounding perennial plant death.

L

Landscaping – The practice and art of designing and implementing outdoor spaces.  The process usually starts with a landscape plan.

Larva – The active immature stage of insect development.

Latent bud – An inactive bud ready to grow if stimulated by the right conditions.

Lateral meristem – The vascular and cork cambium. Cell division in the vascular meristem results in increased plant girth.

Layering – An asexual plant propogation technique. The new plant is temporarily attached to a mother plant while it forms roots. Natural layering is where a branch touches the soil and forms new adventitious roots.

Leaching – The draining away of nutrients in the soil. This is applicable to potted plants as well, requiring the need for regular fertilizing to achieve optimim plant growth.

Leaf mold – Produced by decomposing leaves as they break down into organic compost.

Leggy – Long spindly growth often as a result of insufficient light.

Legume – Seed pod. Examples, beans, peas, lentils.

Lenticel – Pores in a woody stem that allow for the exchange of gas between the plant and atmosphere.

Loam – Loamy soil has more-or-less an equal proporation of sand, silt, and cay.

M

Macro-nutrient – The most important required for good plant growth are; nitrogen, phosphorus, and potasium.

Manure – Animal dung. An organic soil fertilizer and enhancer.

Meristem – Plant tissue where cells actively divide.

Metamorphosis – The process of insect transformation from immature to adult form.

Microbe – A microorganism.

Microclimate – A climate of a small area within a larger area. Particularly significant in an urban environment that can affect plant growth and performance. Example, barrier walls affecting sunlight and/or channeling wind.

Micro-nutrient – While these are essential they are only required in minute amounts; boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), chlorine (Cl).

Monocot – A single cotyledon present in the seed. Example, grass.

Monoecious – Has both male and female flowers on the same plant.

Mosaic – A viral infection characterized by leaves mottled with yellow, white and green spots. Being a plant virus, there is no cure and best practise would be to remove and destroy infected plants.

Mulch – A protective covering (most commonly organic, but can be inorganic) spread over the soil. Generally used to contain weed growth and help retain moisture.

Mycelium – Mass of branching thread-like hyphae that make up the vegetative body of fungi.

Mycorrhiza – Fungi that has a symbiotic (mutually beneficial) relationship with plant roots.

N

Native – A plant that grows naturally and is indigenous to a region.

Naturalizing – Bulbs, once planted, that are left and return year-after-year.

Necrosis – Death of plant tissue.

Nematode – Microscopic wormlike organisms that could cause plant disease.

Node – Location on a stem to which a leaf or branch is attached. Most pruning should be done just above a node.

Nose – Bulb tip.

Nymph – Immature stage of insects.

O

Offset – Sometimes called a pup. Many plants produce offsets which will grow to be virtually identical to the mother plant. Example, bromeliads, cacti.

Open center pruning – Eliminates the central trunk to encourage lateral growth. Particularly used on fruit bearing trees.

Organic – Substances produced by plants and animals.

Ovary – Enlarged basal part of the pistil (female organ of a flower) that becomes the fruit.

Overwinter – Caring for plants in a condition that will let them survive winter and dormancy.

Ovule – The organ forming the seeds of flowering plants.

P

Panicle – A branched raceme bearing more than one flower. Example, astilbe.

Parasite – A pest living off the host plant to the detriment of the plant.

Parthenocarpic – Production of fruit without pollination. Examples, pineapple, banana, watermelon. Seedless varieties are developed by parthenocarpy.

Pathogen – A broad term of the organism that causes plant disease. Examples, fungi, bacteria, nematodes.

Peat moss – The production of a growing medium from sphagnum moss. It’s low PH (acidic) level makes it a suitable ammendment for plants like blueberries and azaleas. Peat has virtually zero organic fertilizer value. The sale of peat moss to gardeners will be banned in 2024 in the UK to help alleviate the further destruction of peatland.

Pedicel – Stalk bearing an individual flower.

Peduncle – Flower stalk.

Perennials – Plants that live for more than two years (longer than biennials).

Perfect flower – Both male and female reproductive structures are present.

Perlite – Organic volcanic material that improves aeration, water retention and drainage when used as a soil additive.

Pesticide – Substances used to control pests.

Petal – Parts of the flower that are often prominently colored.

Petiole – Stalk that joins to a leaf stem.

PH – The measure of acidity or alkalinity. On a scale of 1 to 14, 7 is neutral, below 7 is acidic, above 7 is alkaline.

Phloem – Vascular tissue that carries food to the leaves and roots. Located on the outer side of the cambium.

Photoperiodism – The response of plants to light exposure. Long day plants require more light exposure than short day plants. Day neutral plants require equal light and dark exposure.

Photosynthesis – The process by which green plants use sunlight to synthesize foods from carbon dioxide and water.

Phototropism – Plant movement in response to light.

Phytoplasma – A bacteria that infects many plants and crops.

Pinching – The removal of a growing stem, usually the terminal bud, to promote bushy growth and side branching. Commonly used in growing bonsai.

Pistil – Female reproductive parts of a flower comprising the ovary, stigma and style.

Pith – The oldest part of a tree located at the center of the trunk.

Pollen – Minute grains produced by the male part of the flower that causes the female part to produce seeds.

Pollination – The tranfer of pollen grains from the male anther to the female stigma.

Pome – A type of fruit. Example, apple, pear.

Post-emergent herbicide – Applied directly to green tissue to kill or inhibit plant growth.

Pre-emergent herbicide – applied to the soil before green tissue is present to kill or inhibit plant growth.

Prickle – A sharp thorn like growth which developes on the bark. Example, roses, cacti, blackberry, raspberry.

Primary growth – Growth from the apical meristem.

Propagation – Producing plants using a variety of methods. Can be sexually (from seed) and asexually, example, cuttings.

R

Raceme – A flower cluster with the seperate flowers attached by short equal stems.

Radicle – First part of the seedling to emerge from the seed.

Resistance – The ability of plants to combat pathogens. Developing disease resistant plants is a prominent part of modern horticulture.

Respiration – The absorption of oxygene molecules to produce water, carbon dioxide and energy.

Rhizome – A modified stem that send out shoots and roots from its nodes. Examples, canna lillies, bearded iris, ginger.

Roguing – Removal of inferior and diseased plants.

Root – Underground part of a plant. Anchors, absorbs minerals and sometimes stores food.

Root hairs – Cylindrical root extensions used to absorb food and water.

Root rot – Tissue decay mostly due to excessive water.

Rootstock – The root system and part of a tree where another tree (the scion) is grafted on. Very common on fruit trees and roses.

Runner – A long, thin stem that produces roots from where the nodes touch the soil. Example, strawberries.

S

Sapwood – Outer, living layers of secondary wood delivering water through the xylem.

Scaffold branching – The primary branches emerging from the trunk.

Scape – A long, leafless flower stalk emerging directly from the roots. Example, daffodil.

Scarification – Weaking the seed coat to encourage germination. Most common method is mechanical.

Scion – The detached shoot that is propogated onto rootstock by grafting.

Scorch – Browing and drying out of leaf tips and margins.

Scoring -Making a shallow cut around the trunk or branches of fruit trees to increase yield.

Secondary growth – Is characterized by the increase in thickness (girth) as a result of cell division in lateral meristems (cambium).

Secondary mineral nutrients – Boron, copper, iron, chlorine, manganese, zinc and molybdenum. These are used in much smaller amounts by plants and are largely and readily available in most soils.

Self-pollination – Pollination from the anther to the stigma takes place on the same plant.

Sepal – Sepals protect the flower buds and often support the petals when in bloom.

Short day plants –  A plant that requires a long period of darkness (day length is less than 12 hours) to flower. Examples, chrysanthemums, nicotiana, cosmos…Many spring and fall plants fall into this category.

Simple layering – When a flexible branch bends and touches the soil, roots are formed, and a new plant grows. Asexual propagation.

Soil conditioner – Soil amendments to improve soil structure. Example, gypsum.

Sphagnum moss / sphagnum peat – Sphagnum peat is dried, processed, and compacted sphagnum moss taken from swamp bogs.

Spore – Particles that allow fungi to reproduce.

Stamen – Pollen producing reproductive organ (male) of a flower.

Stem – Bears the leaves and flowers.

Stigma – The apex of the flower pistil (female) where pollen is deposited.

Stipule – A small outgrowth found on the base of a leafstalk. Example, roses.

Stolon – Horizontal growing stems on or just below the soil surface which root at the nodes. Example, strawberries.

Stomata – Tiny openings found on the underside of leaves through which gases and water vapor pass. They are critical and are considered the pores that give us life.

Stratification – Exposing seeds to moist cool conditions which aide germination.

Succulents – Have thick fleshy leaves for sustained water retention. They thrive in arid climates.

Sucker – Shoots emerging and growing from the roots of trees and shrubs.

Systemic – Substances moving through the plant vascular system. Example, systemic herbicides move through the vascular system killing the entire plant.

T

Taproot – A deeply penetrating vertical root.

Tendril – A modified stem or leaf used to support climbing plants.

Tepal – Where there is no differntiation between petals and sepals. Example, magnolia, tulip.

Terminal bud – The bud at the tip of a stem.

Thatch – Mostly dead, tightly intermingled material that develops on neglected lawns. Removing this material is called dethatching.

Thinning – A broad term to remove plant and plant material to avoid overcrowding.

Thorn – Sharp modifed stems that grow from buds and are connected to the vascular system. Example, hawthorn.

Tilth – The physical condition of soil and suitability for planting and growing crops.

Tissue culture – The cultivation of plants from cell level in a sterile environment. Also called micropropagation.

Top working – Grafting established trees into another variety by inserting grafts into its branches.

Training – Pruning and staking plants to adapt to a particular area or shape.

Translocation – Movement of substances through the plant vascular system.

Transpiration – The process of water movement and evaporation from plants. Most of the water intake, between 97 and 99.5%, is lost by transpiration thrrough the stomata.

Tropism – The growth response of a plant to its environment. The response is dependent on the direction of the stimulus. Example, growth towards the light source.

Truss – A stem the carries flowers directly. Example, tomatoes.

Tuber – Short, fleshy, mostly underground stems. Example, potatoes and beetroot.

Turgid – Pressure from water inside the cell and against the cell wall.

U

Umbel – A flat topped or ball shaped flower cluster. The flower stalks all grow from the same point on the main stem. Example, carrots, parsely, dill, onion (Allium).

V

Variegated – Leaves that have two or more colors.

Variety – A subgroup of a species that has similar characteristics.

Vascular cambium – A layer of meristem cells between the primary phloem and xylem.

Vascular system – Cells that distribute nutrients and water throughout the plant.

Vector – Usually insects that tranfer the spread of pathogens to plants.

Vegetative reproduction – The asexual reproduction of plants. Example, cuttings and grafting.

Vermiculite – A mineral that has undergone heat treated expansion and is used as a soil ammendment and rooting agent for plants.

Viruses – Intracellular parasites that grow and multiply in living cells. Symptoms are virtually impossible to treat other than by destroying infected plants.

W

Warm season grasses –  They grow best with temperatures between 80F – 95F. Example, zoysia grass.

Waterlogged – Soil saturated with water that lacks oxygen.

Water sprout – Shoots arising from the trunk of a tree or branches. This is often due to severe pruning – there is a tendency for these shoots to be weak.

Weed – An unwanted plant.

Whorl – Consists of at least three elements from a single point. Can be leaves, petals, sepals, carpels or stamens.

X

Xeriscaping – Gardening and landscaping with drought resistant plants that do not require much water. Examples in our zone, lavender, Russian sage.

Xylem – Vascular tissue located on the inside of the cambium used for transporting water and dissolved nutrients upwards.