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Plant Varieties

Plant Knowledge is the cornerstone of all horticulture.
Many people work as gardeners or farm hands in horticulture, without particularly good plant knowledge, and as a result they frequently make mistakes, such as:\
  • Mistaking garden or crop plants for weeds and destroying them mistakingly.
  • Planting inappropriate plants into the wrong place or at the wrong time of year.
  • Pruning, fertilising, watering or spraying plants inappropriately and causing damage.

Anyone who can learn to identify the names, characteristics and requirements of a thousand or more different plant varieties; should not make mistakes like this.

How are Plants Named?
 Linnaeus (1707 1778) was a Swedish botanist largely responsible for stabilising the binomial system (ie. using two names or two words to name one plant). He was also responsible for stabilising some of the other basic principles of nomenclature. However it wasn't until 1867, at the first International Botanical Congress, that the first set of rules were officially adopted by the botanical world. Deficiencies in this code led to the establishment of a number of other sets of rules. A compromise between the existing codes was adopted in 1930 and published as the 3rd edition of the International Rules of Botanical Nomenclature. More recent editions are basically modifications of this code.

The main plant groups in cultivation (ie. phyla) are:
  • ANTHOPHYTA (ie. Angiosperms). This group includes all of the plants which produce flowers (eg. Eucalypts, roses, lettuce, grasses).
  • CONIFEROPHYTA (ie. Conifers). This includes all plants that produce cones (eg. pines, cypress).
  • PTEROPHYTA (eg. Ferns)
Other phyla include mosses, fungi, bacteria and algae.
Anthophyta is divided into two classes:
a) DICOTYLEDONAE. In these plants, the first leaves to appear from a germinating seed are in a pair (two leaves appear at the same time). The veins in the leaves are not parallel in these plants. Examples of dicots are peas and Eucalypts.

b) MONOCOTYLEDONAE. In these plants, the first leaf to appear when a seed germinates is a single leaf. Veins in the leaves are parallel to each other. Examples of monocots are grasses, Iris and orchids.

It can be seen above that you can distinguish between dicotyledons and monocotyledons by a couple of very simple characteristics. In the same way, we can usually distinguish which family a plant belongs to by a few basic characteristics. For example:
•    Lamiaceae family: foliage is perfumed and flowers have two distinct lips, eg. Mint and Lavender.
•    Araceae family: leaves are usually heart-shaped and the plants originate in tropical areas, eg. Philodendron.
•    Asteraceae familiy: have daisy-type flowers, eg. Chrysanthemum.
•    Apiaceae family: flowers occur in an umbrella-like head on a single stalk, eg. Parsley.

You should be able to tell a family name from other types of names by the fact that it will end with "ACEAE". Students have sometimes called the family name a genus. Note that a genus name virtually never ends in the letters "aceae".

For example, Betula pendula   
      Betula is the genus    
      pendula is the species

The genus name begins with a capital letter. The species name is usually written beginning with a small letter.

Sometimes a third word (and perhaps a fourth) is added to follow the species. These words would refer to the variety of that particular species.

For example, Acer palmatum dissectum atropurpurea:
      Acer is the genus
    - palmatum is the species
      dissectum tells us that this is a variety of Acer palmatum with dissected leaves
      purpureum tells us that this variety of Acer palmatum has purple foliage.

You may occasionally be confused by the difference between hybrid and variety.
•    A hybrid plant is one which has resulted from two different species cross breeding. The hybrid is a combination of characteristics from two different species ... something bred or selected out of nature by man.
•    A variety is just a particular type of plant in one species. A variety does not have parents from two different species, but a hybrid does, for example, the hybrid lavender Lavandula x intermedia is a cross between Lavandula angustifolia and Lavandula spica. The ‘x’ indicates that the plant is a hybrid (a ‘cross’ of two species).

Cultivar names are the names used for plants in cultivation. These names may be the hybrid name or even variety name. In most cases cultivar names are to be written in single quotation marks beginning with a capital letter; for example, Grevillea 'Golden Yul-lo'.
 ACS offers a high degree of flexible options for studying courses that will build your plant knowledge.
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