Allelopathy

The phenomenon in which one plant directly harms another (to reduce competition), particularly when young through the production of chemical compounds released into the environment.

Arboriculture

The selection, planting and care of individual trees, shrubs, vines, and other perennial, woody plants, and the study of how they grow and respond to cultural practices and the environment. The purpose is generally to manage woody landscape plants, often in a garden or urban setting, for plant health and longevity, pest and pathogen resistance, risk management, maximum return on investment, and ornamental or aesthetic reasons. In this, it needs to be distinguished from forestry, which is the commercial production and use of timber and other forest products from plantations and forests.

Bi-Generic Hybrid

The resultant hybridism is between two (2) species from different (yet related) genera. In terms of botanical nomenclature plants of this nature should be written with the 'x' indicating the hybridism before the genus name. For example: x Cupressocyparis leylandii 'Naylor's Blue'.

Cambium

Layer of actively dividing cells between the bark and the wood.

Chlorophyll: The green photosynthetic pigment found in plants, algae, and cyanobacteria. Its name is derived from ancient Greek; chloros = green and phyllon = leaf. Chlorophyll absorbs mostly in the blue and to a lesser extent red portions of the electromagnetic spectrum, thus its intense green color.

Chlorosis: An unhealthy condition shown by yellowing of foliage or shoot tips. Occurs when chlorophyll is destroyed or its formation is inhibited by nutrient deficiencies, drought, disease or other environmental factors.

Dioecious

Having unisexual flowers; male and female on different plants.

Epicormic Growth/Branches

Formed when dormant foliage buds on the trunk and branches are activated as a result of environmental stress or injury to the original crown. Best examples seen on the genus Eucalyptus.

Family

A genus or genera of plants having a number of taxonomic features in common. For example: Myrtaceae (Myrtle Family) or Araucariaceae (Araucaria Family).

Girdling

Trees are girdled when the flow of food material in the inner bark and phloem is stopped, usually as a result of continuous incision or damage around the trunk of the tree, through the bark and cambium. The effect is usually fatal within two to six months.

Haustorium

A special branch of a hypha of a parasitic (or partly parasitic) fungus or plant, adapted to absorb water and mineral nutrients from the host, particularly from living cells; for example Amyema pendula (Weeping Mistletoe).

Heartwood

The dense and often dark-coloured wood that lies in the inner part of the trunk or branch that is devoid of living cells. Toxic waste materials are usually deposited in the heartwood giving it durable qualities.

Hybrid

The progeny resulting from the crossing of two related parents of different species, usually of the same genera, and occasionally different genera. The name of such a plant should be written as such Acer x freemanii.

Indigenous

Originating in and characterising a particular region, area or country.

Kino

A viscous, reddish, black liquid developed in the cambial zone, notably of Eucalyptus and Angophora, as a result of injury. They are rich in tannons (polyphenols) which can be phytotoxic to fungi.

Lignotuber

A woody swelling, partly or wholly underground at the base of the stem of certain plant species, notably many Eucalypts. It is composed of energy reserves and dormant buds which can emerge as a survival response to an externally applied stress eg: fire, drought or soil compaction.

Longicorn Beetles

There are hundreds of species of Longicorn Beetles that attack both trees and shrubs. Fortunately, most are confined to dead limbs and fallen trees. However, some are serious pests of weakened and/or injured trees, causing their death by ring barking. The eggs of these beetles are laid in the bark, usually in injuries or fire scars. The young larvae hatch and feed initially in the phloem/cambium region. Larva move into the sapwood and/or heartwood and may travel for 1-3m where it will make the characteristic hole in the sapwood just beneath the bark. Trees may live for several years under attack from this pest, however the tree often becomes unsafe as the trunk(s) may snap at a weakened point where larva may have concentrated their activities.

Meristem

A group of localised, dividing cells, which produce active growth; this could occur either at the root and shoot tips or in the trunk (lateral growth).

Monoecious

With unisexual male and female flowers on the one plant.

Mulch

An organic or sometimes inorganic product that is placed on top of the existing soil surface around plants to perform a number of functions such as weed suppression, aid in the regulation of soil temperature and moisture levels and to improve landscape aesthetics. Mulches can be made from a variety of materials however organic products such as wood chips and straws are useful as they decompose over time adding organic matter to the soil and improve soil structure.

Mycorrhiza

A symbiotic association between a fungus and a higher plant, most often consisting of an intimate relation between the plant's roots and the fungal mycelium.

Nitrogen

Essential for healthy vegetative growth and is also used on the formation of chlorophyll and protein.

Palm

The word Palm should be used as opposed to the commonly used phrase 'Palm Tree' as Palms are not trees by definition as they do not form wood as a tree does, nor do they form bark. Palms have a hard stem that contains bundles of conductive vessels scattered throughout softer tissue. Secondary thickening of the stem is absent, or slight, and even then it is not cambial but from divisions in the ground parenchyma. This type of structure not only provides the Palm trunk with strength but also stability. Palm root systems are also not woody like a tree and they invariably do not 'branch'. Therefore the phrase 'Palm Tree' is a contradiction in terms and we should more correctly just say 'Palm'.

Pathogen

A parasite capable of producing disease in its host.

Phloem

Specialised tissue for transporting materials around a plant; usually situated between the bark and the wood.

Radicle

The first formed root of a seedling, from which the primary plant root develops.

Root Collar

The region of the plant where the major roots arise; the transition zone between the stem and the root, sometimes recognisable by a slight swelling.

Saprophyte

A fungus or plant that lives exclusively on dead plant or animal matter, commonly assisting its decay.

Sapwood

Newly formed wood; characterised by the presence of living tissue, which store energy and an absence of plant waste products. Usually light coloured.

Symbiosis

The term first used by Anton de Bary in 1879 to describe two unlike organisms living together beneficially (symbionts), eg; lichens and mycorrhiza.

Symptoms

Visible evidence of disturbances in the normal growth development of a plant.

Taxonomy

The system and procedure of biological description, classification and nomenclature.

Tree

A woody plant growing to a height of 5 metres or more, often displaying a main trunk and somewhat symmetrical canopy. The lower part of the trunk can be free of branches for some distance.

Weed

A generic word for a plant growing in a location where it is not wanted. Weeds become of environmental and economic significance in connection with natural bushland and agriculture, where they may displace and/or out compete the native flora or damage crops when growing in fields and may poison domesticated and/or native. Many weeds are short-lived annual plants that can produce copious numbers of fertile seed that are easily dispersed. Many weed species take advantage of temporarily bare soil (or mostly so) to produce another generation of seeds that in many cases can be stored in the soil for long periods of time and can be activated into growth when environmental conditions are conducive to their growth.