a

active
Active features are those with moving parts and/or controls such as fans, pumps and automated blinds or louvres. For example, a solar hot water system which uses a pump to circulate water through the collector is classified as active while one relying on natural the thermosiphon effect is classified as a passive system.

aerobic
Refers to processes which occur in the presence of oxygen (because the process needs oxygen). Usually used for describing a characteristic of compost heaps. Describes organisms living or occurring only in the presence of oxygen.

This contrasts with anaerobic processes.

afforestation
Creating a forest(s) where there was not one before. This can be used to act as a greenhouse gas sink, and to provide timber as an alternative to destroying existing forests.

albedo
The reflection of solar radiation (falling on the earth) back into space.

anaerobic
Refers to processes which are caused by the action of anaerobes which are micro-organisms which require or can survive in an oxygen-free environment. Usually term used when talking about compost heaps.

Methane is created by the anaerobic decomposition of organic material.

Anaerobic is the opposite of aerobic processes.

b

bacterium
Microscopic, one-celled organisms lacking chlorophyll, and causing disease in tomato; such as bacterial canker, bacterial wilt, bacterial stem rot, pith necrosis, and bacterial soft rot.

ballast
An electrical device in a fluorescent or other discharge light fitting which acts to limit the electrical current in the lamp.

biological control
Using one or more living organisms to help control a pest or limit its population.

biodegradable
The ability of a substance to be broken down physically and/or chemically by microorganisms. For example, many chemicals, food scraps, cotton, wool, and paper are bio-degradable; plastics and polyester generally are not.

biomass / energy
Term to describe the resource of energy stored in plants and animals or released during their use or processing including as a by-product or "waste".

biosphere
(A) The system comprising the earth and its atmosphere, which supports life.

botany
Botany is the scientific study of plant life. As a branch of biology, it is also sometimes referred to as plant science(s) or plant biology. Botany covers a wide range of scientific disciplines that study the growth, reproduction, metabolism, development, diseases, and evolution of plants. Vegetation: all the plant life in a particular region or period; "Pleistocene vegetation"; "the flora of southern California"; "the botany of China."

blossom-end rot
A sunken, leathery brown or black spot on the bottom or near the bottom of a tomato fruit; not from a disease; usually from lack of water or not enough calcium in the fruit.

broom

1. Any of various Mediterranean shrubs of the genus Cytisus in the pea family, especially C. scoparius, having mostly compound leaves with three leaflets and showy, usually bright yellow flowers.
2. Any of several similar or related shrubs, especially in the genera Genista and Spartium.

BTU (British Thermal Unit)
A common unit of measure to rate performance of heaters and cooking systems.

Derivation and definition: the amount of heat necessary to raise one (1) pound of water, one (1) degree Fahrenheit. Imperial unit of energy equal to 1.055 kJ (kiloJoules).

bullish
A plant with thick, leathery, darkgreen leaves, little or no fruit, and very vegetative; may be caused by overfertilization with nitrogen or genetic off-type.

bumblebee (bumble bee)
Like the common honeybee, the bumblebee feeds on nectar and gathers pollen to feed its young. They tend to be larger than other members of the bee family. Most, but not all, bumblebee species are gentle. Queen and worker bumblebees can sting, which is not barbed like that of the honeybee, so they can sting more than once.

Bumblebees are characterized by a larger black body with white, yellow, orange, or even red stripes, while some species may be entirely black. Another distinguishing characteristic is the nature of the soft long pile that covers their entire body, making them appear and feel fuzzy.

Bumblebees are incredibly important pollinators of both crops and wildflowers, and are increasingly cultured for agricultural use as pollinators. Bumblebees can pollinate plant species that other pollinators cannot by using a technique known as buzz pollination. For example, bumblebee colonies are often emplaced in greenhouse tomato production, because the frequency of "buzzing" that a bumblebee exhibits, effectively pollinates tomatoes.

c

canker
A sunken, discolored area of diseased plant tissue that is usually dry and corky in texture.

canopy
The uppermost layer in a forest, formed by the crowns of the trees. Also called crown canopy.

carbon dioxide
The main greenhouse gas and the gas to which other greenhouse gases are compared. Most of the increase in CO2 concentration in the atmosphere is attributable to:

1. Increasing the source of CO2 by burning fossil fuels and so releasing carbon which has been previously stored out of the atmosphere, and
2. Reducing the capacity of the earth to remove CO2 from the atmosphere by destroying forests (see carbon sinks).

carbon sink
A way of removing carbon from the atmosphere, including natural mechanisms such as photosynthesis in trees (CO2 to wood) and calcium carbonate (CaCO3) formation by marine molluscs.

chlorosis
Yellowing of normally green tissue caused by the lack of chlorophyll; can be caused by disease, lack of nutrients, shading, age, or other factors.

climate
The long-term average weather of a region including typical weather patterns, the frequency and intensity of storms, cold spells, and heat waves. Climate is not the same as weather.

cold greenhouse (cool house)
Naturally heated by the sun, a "cold greenhouse" uses no internal electrical or other artificial heat source. A cold greenhouse usually has a minimum temperature of 28 degrees F maintained through the winter. During these tempratures no growth occurs in this type of house, but you can over winter plants that are not frost sensitive.

Good for growing carrots and root vegetables into fall months. (night temp: 35-45F)

See also cool greenhouse, moderate greenhouse, and warm greenhouse

compost
Decomposed organic material that is produced when bacteria in soil break down garbage and biodegradable trash, making organic fertilizer. Making compost requires turning and mixing and exposing the materials to air. Gardeners and farmers use compost for soil enrichment. The relatively stable humus material that is produced from a composting process in which bacteria in soil mixed with garbage and degradable trash break down the mixture into organic fertilizer.

condensation
Accumulation of water droplets on the inside of plastic covering the greenhouse that can then drip onto plants, resulting in artificial rain on the crop; can also form on leaf and fruit surfaces, promoting disease.

conservatory
A conservatory is a greenhouse (usually) attached to a house. In the 18th and 19th centuries, the collecting of exotic plants and the production under glass of out-of-season flowers and fruits were popular pastimes among those who could afford this kind of luxury. Grapes and oranges, as well as orchids and other tropical flowers, were among the products of upper-class conservatories. The most elaborate conservatories were warmed by wood- or coal-heated air introduced through under-floor ducts.

convection
Heat transfer by the movement of fluids (liquids and gases) containing heat energy.

cool greenhouse (cool house)
"Cool greenhouses" are heated during the cooler months (with electricity, gas, oil or propane) to a minimum temperature of 45 degrees F. This is just warm enough for a little plant growth and frost sensitive plants (like tomatoes) can be over wintered in this envrionment.

Good for growing lettuce, cabbage, beets, and leafy vegetables. (night temp: 45-50F)

See also cold greenhouse, moderate greenhouse, and warm greenhouse

cool pad
See wet wall

corolla
All of the flower petals considered together make up the corolla.

d

decompose
To break down into component parts or basic elements; decomposition of organic materials by bacteria is an essential life process because it makes essential nutrients available for use by plants and animals.

deforestation
Loss of forest, usually as the result of clearing for agricultural (especially for cattle grazing) or other land uses such as roads and buildings. Deforestation destroys what may be an important sink for excess CO2 in the atmosphere.

Although afforestation is promoted as a way of taking CO2 from the atmosphere, reducing or stopping deforestation is a much cheaper and achievable strategy, which also has the advantage of preserving a greater diversity of plant and animal species.

degree days
A measure of the demand for heating ("heating degree-days") or cooling heating ("cooling degree-days") in a geographical location, expressed as degree-days per year to a base temperature. One degree-day means that the temperature needed to be changed by an average of 24 degree-hours during the year.

e

ecologically sustainable development
Development that does not degrade (often improves) the quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends.

electroconductivity (EC)
A measurement of how much electrical current a solution can conduct; corresponds to amount of fertilizer dissolved in solution.

f

fertigation
Mixing or puting fertilizer into the irrigation water so fertilizer is delivered with irrigation water.

floriculture
A discipline of horticulture concerned with the cultivation of flowering and ornamental plants. Flowering plants are cultivated all over the world both indoors and out. The development plant breeding of new varieties is a major occupation of floriculturists.

fluorescent lighting
Fluorescent lamps (also called tubes) use electricity to excite a gas in the glass tube. This causes ultraviolet light to be emitted and to strike the inside surface of the tube, which is coated with a special coating which fluoresces (the radiation causes it to emit visible light).

Fluorescent lighting is typically five times as efficient as incandescent lighting in converting electricity to light, and the lamps last about 8 times as long (8,000 hours compared with 1,000 hours). Tri-phosphor fluorescent lamps which produce about 20% more light for the same electricity consumption, have gained popularity in the early 1990s. In 1996 tri phosphor lamps were introduced with double the life (now 16,000 hours) and a much better performance maintenance over their life.

foliar spray
A pesticide that is sprayed on the leaves of plants.

fruit
In botany, a fruit is the ripened ovary—together with seeds—of a flowering plant. In many species, the fruit incorporates the ripened ovary and surrounding tissues. Fruits are the means by which flowering plants disseminate seeds.

In cuisine, when discussing fruit as food, the term usually refers to just those plant fruits that are sweet and fleshy, examples of which include plum, apple and orange. However, a great many common vegetables, as well as nuts and grains, are the fruit of the plant species they come from.

Technically classified as a species of fruit, the tomato is popularly considered a vegetable.

fruiting bodies
Complex fungal structures containing spores.

fungicide
A chemical or biological product applied to plants to prevent infection by disease-causing organisms.

fungus
A microscopic organism lacking chlorophyll and the ability to manufacture its own food, with a body of spider web-like filaments.

g

geothermal (energy)
Natural heat occuring and rising from the earth's core.

Energy obtained from the heat below the Earth's surface.

glasshouse
See greenhouse.

glazing
The covering over a greenhouse; this can be polyethylene, polycarbonate, glass, or other transparent materials.

gorse
Any of several spiny shrubs of the genus Ulex, especially U. europaeus, native to Europe and having fragrant yellow flowers and black pods. Also called furze, whin.

green electricity
electricity which is generated from sources which are judged to harm the environment less than conventional methods. Green electricity sources could include:

• wind
• solar
• small and existing large dams (not new large dams)
• some biomass

greenhouse (building)
A greenhouse, also called a "glasshouse" or "hothouse", is a clear building structure created for the protection, cultivation and exhibition of plants under controlled conditions. A greenhouse is built almost entirely from glass or translucent plastic; it heats up because the sun's incoming solar (electromagnetic) radiation warms plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces, along with humidity from the existing moisture in plant soil, is retained in the building by the roof and walls — creating an optimum growing environment for many plant species.

See also conservatory.

greenhouse effect (natural)
The effect of water vapour, CO2, and other gases which allow heat radiated from the sun to pass through to the earth, but restrict the heat radiated from the earth. This imbalance in heat flows is a natural phenomenon which causes the earth to be warmer than it would otherwise be, and so makes life possible. This effect, known as the greenhouse effect, was discovered late in the 1800s.

growhouse
See greenhouse.

h

habitat
The natural environment in which a plant grows.

heat pump
A mechanical device for moving heat energy from one place to another, cooling the former and heating the latter. Examples include refrigerators, chillers, air-conditioners and heat-pump water heaters.

heat transfer
The movement of heat energy from one place to another by one or a combination of conduction, convection, and radiation..

horticulture
The science and art of growing fruit, flowers, ornamental plants, and vegetables in small gardens. Horticulture derives from the Latin hortus. It meant a 'garden' space, in contrast to an 'agricultural' space. Mode of production based on growing domesticated crops in gardens using simple hand tools.

host
A plant that is attacked by a pathogen. The place that the pathogen dwells.

hothouse
See greenhouse.

humidity
Humidity is the concentration of water vapor in the air (not the total amount of vapor and liquid).

See also Hygrometer.

humus
A dark colored, stable form of organic matter that remains after most of plant or animal residues have decomposed.

hydroponic
Using water to grow plants without soil; soil-less culture.

hygrometer
An instrument that measures the water vapor content of the atmosphere ¯ humidity.

i

incandescent
Lighting which uses a filament which is heated to white hot by the electric current it carries (and so incandesces). This is the least efficient form of electric lighting and so is appropriate only for lights with low burning hours or very low light output requirements.

indigenous
Originating and living or occurring — naturally — in an area or environment.

infra-red radiation
Electromagnetic radiation lying in the wavelength interval from 0.7 µ to 1000 µ . Its lower limit is bounded by visible radiation, and its upper limit by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at infra-red wavelength.

Water vapour, carbon dioxide, and ozone, absorb infra-red radiation and play important roles in the propagation of infra-red radiation in the atmosphere. .

internode
The part of the stem between leaves.

inversion (temperature)
A layer of cold air sitting over a warmer layer of air which acts as a blanket trapping pollutants and preventing their dispersion.

IPM (Integrated Pest Management)
Using various methods of insect and disease control rather than only chemicals.

j

k

l

land fill gas
a mixture of gases (mainly methane and carbon dioxide, both greenhouse gases) generated as the result of anaerobic decomposition of organic matter in land-fill rubbish dumps. This gas can be used in spark ignition gas engines (usually about 1 MW generation capacity) to produce electricity. This has a double greenhouse benefit of burning the greenhouse gas methane which would otherwise escape to the atmosphere, and the electricity generated reduces the amount which needs to be produces using coal or natural gas.

In some cases, the waste heat from the engines can be used (combined heat and power), e.g. for nearby horticulture. Another benefit is the prevention of damage to grass cover and other vegetation on closed land-fill sites.

leaflet
The subdivisions of a leaf; as in the tomato leaf is compound, so it is made up of many leaflets.

lean & lower
Leaning plants over and dropping them when they are taller than the support wire; it is important to lean when lowering to avoid stem breakage; this needs to be repeated every 2 weeks or so in mature plants.

lean to (GlassHut Lean2)
A style of greenhouse. Lean to greenhouse are typified by the rectangular-shaped plan view and slanted roof braced on one side by the wall of the attaching house.

m

media
(plural) material in which plants are grown, such as perlite, pine bark, and peat moss.

medium
Singular form of media.

methane
A gaseous, colourless, explosive, hydrocarbon and the main component of natural gas, and a powerful greenhouse gas. Also called "swamp gas" because it is produced by bacteria when organic matter decomposes without oxygen (eg. in land-fills and swamps). Also produced in the gut of animals (especially ruminants such as cattle) and found in coal beds. Methane is the only greenhouse gas which is produced in greater quantities in developing countries than in developed countries.

See also anarobic and greenhouse gases.

moderate greenhouse (moderate house)
A balanced and yet active greenhouse, a "moderate greenhouse" is heated at night during many months with a minimum temperature of 50 degrees F maintained. A wide assortment of plants can be kept active during the winter, including some exotic varieties and many vegetables.

Good for growing beans, cucumbers, herbs, strawberries, some tomatoes. Some plants can be propagated. (night temp: 55-60F)

See also cold greenhouse, cool greenhouse, and warm greenhouse

n

nitrogen oxides
Compounds containing nitrogen and oxygen and no other elements.

NOx gases are precursor gases which react with sunlight to form ground-level ozone and contributes to other adverse effects including aggravation of respiratory disease, fading of some fabrics, contribution of nitric acid to acid rain and the formation of smog.

node
The point on the stem where a leaf is attached.

NFT (Nutrient Film Technique)
Using plastic sheeting and water to grow plants hydroponically.

o

ozone
A molecule made up of three atoms of oxygen. In the stratosphere, it occurs naturally and it provides a protective layer shielding the Earth from ultraviolet radiation and subsequent harmful health effects on humans and the environment. In the troposphere, it is a chemical oxidant and major component of photochemical smog.

p

particulates
Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols. The physical characteristics of particles, and how they combine with other particles, are part of the feedback mechanisms of the atmosphere.

passive (systems)
Passive features are those which reduce energy needs without having moving parts and/or controls. Passive features include shading using fixed eaves, trees, etc, appropriate building orientation, insulation and thermal mass, thermo-siphon hot water systems, etc).

This contrasts with Active systems.

pathogen
A living organism that can infect a plant; in the context of biological control, a disease organism that attacks a pest species and helps control the pest.

pedicel
The "flower stalk" that holds a single flower.

peduncle
The "fruit stalk" that holds a cluster of fruit.

petiole
The "stem" of a leaf; attaches the plant stem to the leaf blade.

pH
The measure of the activity of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The pH is a measure of the acidity or basicity (alkalinity) of a material when dissolved in water. It is expressed on a scale from 0 to 14. Roughly, pH can be divided into the following ranges:

	pH 0 - 2	Strongly acidic
	pH 3 - 5	Weakly acidic
	pH 6 - 8	Neutral
	pH 9 - 11	Weakly basic
	pH 12 - 14	Strongly basic

photovoltaic (PV)
Materials or devices which convert light energy into electrical energy. The electricity produced is direct current (DC) and so can be used for appliances which use DC (eg calculators, instruments, radios, battery chargers), or converted to Alternating Current (AC) for use in standard appliances. Because of the intermittent availability and variability of the energy source, battery storage is normally included in PV systems.

podocarps
Podocarps are seed-producing plants, or gymnosperms, and have evolved a method of reproduction that is much less water-dependent than the pteridophytes. The word podocarp actually means 'foot root', since the part that produces fruit was the stalk, and was supposedly foot-shaped. They are also hardy to drought.

pollination
An important step in the reproduction of seed plants: the transfer of pollen grains (male gametes) to the plant carpel, the structure that contains the ovule (female gamete). The receptive part of the carpel is called a stigma in the flowers of angiosperms and a micropyle in gymnosperms. The study of pollination brings together many disciplines, such as botany, horticulture, entomology, and ecology. Pollination is important in horticulture because most plant fruits will not develop if the ovules are not fertilized.

pollinators
The agent (usually bees) that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. Though the terms are sometimes confused, a pollinator is different from a pollenizer, which is a plant that is a source of pollen for the pollination process.

Bumblebees (specifically) are the pollinators of choice for most greenhouse pollination, although other types of bees have been used, as well as artificial pollination.

PPM (Parts Per Million)
The concentration of a fertilizer or any other material in water. Note: 10,000 parts per million = 1%.

r

radiation (solar)
Heat transfer across a space without the use of convection or conduction. Radiation can be in the visible part of the spectrum or the infra-red part.

see also infra-red radiation reforestation
Regrowth of forest on land that was previously forested by indigenous species..

relative humidity
The amount of water in the air divided by the amount of water the air could hold if saturated, at a particular temperature; expressed as a percentage.

renewable
Energy sources which are continually renewed at the same rate as their use, by natural means alone (eg. solar, wind, wave, hydro).

s

seedling
A very young plant.

solubility limit
The most fertilizer that can be dissolved in water at a given temperature; the solubility limit increases as water warms.

stem (tomoato)
The main trunk of the plant; has roots attached at the base and leaves, flowers, and fruit attached to above-ground portion; tomatoes are usually pruned to one main stem.

sustainable
Meeting present needs without compromising the ability of future generations to meet their needs. This includes managing finite resources (such as fossil fuels which are being exhausted at over 1000 times the rate of regeneration) and protecting the natural environment.

see also ecologically sustainable development

systemic
A pesticide that is absorbed by the plant, either through the roots or leaves, and translocated to other plant parts, where it controls insect or disease pests; also refers to a a href="#pathogen" title="pathogen">pathogen, such as a virus, that spreads inside the plant.

t

toxicity
A compound’s ability to injure a plant, such as too much of a nutrient or chemical.

terrestrial
Pertaining to the land; not aquatic: a terrestrial plant or animal.

transpiration
The flow of water from the plant to the atmosphere, such as evaporation of moisture from the plant through the leaf surfaces.

turgid
The stiffness of a plant because of internal water pressure; opposite of wilted; it is best to remove shoots (suckers) or leaves when plants are turgid so you can easily snap off shoots or leaves.

u

v

vegetable
A culinary term somewhat arbitrary and subjective... Any part of a herbaceous plant that humans eat whole or in part is a vegetable, except for culinary fruits, grains, nuts, herbs, and spices. Also, mushrooms are commonly considered vegetables, despite belonging to a different biological kingdom.

Vegetables include leaf vegetables (for example lettuce), stem vegetables (asparagus), root vegetables (carrot), flower vegetables (broccoli), bulbs (garlic) and botanical fruits such as cucumbers, squashes, pumpkins, avocados, capsicums, green beans, and fleshy, immature seeds such as those of peas or beans.

Technically classified as a species of fruit, the tomato is popularly considered a vegetable.

w

warm greenhouse (warm house)
A "warm greenhouse" is where all the action is. This house is heated at night during most months and a minimum temperature of 55 degrees F is maintained. A wide assortment of plants can be grown during the winter, including exotic varieties and most vegetables.

Good for growing peppers, varieties of tomatoes, melons, most vegetables, tropical plants. It may be necessary to provide extra lighting in winter. (night temp: 65-70F)

See also cold greenhouse, cool greenhouse, and moderate greenhouse

water soluble
A formulation (of pesticide) sold in "water soluble packages" that have a premeasured amount of dry, water soluble insecticide. The package dissolves when you put it in water, thus releasing the pesticide it contains.

wet wall
An evaporative cooling system, also called cool pad system; cools by pulling water-saturated air into the greenhouse that vaporizes, absorbing heat in the process; the exhaust fans then remove the warmed vapor.

wilt
The loss of turgidity in plant tissue associated with the lack of water.

x

y

z