Botanical Names
Posted by Phytopath on Jul 4, 2011
To most people, botanical names are considered useless.
“They are too hard to pronounce and too long”, I have heard people say.
So why do we use them?
Because they are universal.
Imagine travelling overseas to a foreign country. A place where English is not commonly spoken and you do not speak the native language. Communication would be difficult.
But if you arranged to meet a botanist or horticulturist and mentioned a few botanical names of plants growing in that region, I am sure that after a few nodding heads you would be taken to the nearest location of those plants that were mentioned.
Now imagine a similar scenario but this time common plant names were used instead of botanical ones.
“I would like to buy some violets” you say. Which are edible (Viola sp.), “to make a violet syrup.” The person you are speaking to nods their head and takes you to a nursery selling African violets. What a disappointment, and they are not even closely related.
What if you had never actually seen the plant you were seeking? The common name that you are using could be a completely different plant in another country or even another state of the same country you live in.
What if the plant with the same common name was poisonous or a skin irritant?
You could find yourself in trouble, health wise, if you intended to ingest it.
So that seems a pretty good reason to use botanical names, especially if you are out of town.
An example of confusing common names exists here in Australia.
We have a tree called a ‘blue gum’, trouble is, there are three different Australian states that have a tree called
‘blue gum’ and they are all different species.
So not to confuse anybody, botanical names are the way to go.
When writing botanical names (correctly), there are just a few things to remember.
The Family name starts with a capital letter e.g. Myrtaceae
The Genus or generic name starts with a capital letter and is underlined or written in italics e.g. Eucalyptus
The species name is written in lower case and also placed in italics or underlined e.g. leucoxylon
Most people use only the genus and species when referring to a particular plant, so an apple tree would be written as Malus domestica
There are other ‘categories’ of plants, like variety, cultivars and hybrids, but let’s start with the basics. 
Bulbous Plants
Posted by Phytopath on May 21, 2011
The tern ‘bulb’ is frequently used to describe plants that have underground storage organs.
The categories used to describe these plants are: – bulbs, corms, tubers, rhizomes or tuberous roots.
Correct identification of the storage organ is important if you are planning to increase the number of plants through propagation.
A true bulb is made up of leaves and petioles (the stalky bit at the end of a leaf) that have been modified and
these leaves are attached to a base plate.
If you cut an onion (true bulb) in half, the concentric rings that can be peeled away are the modified leaves and the solid bit at the bottom is the base plate.
Other examples of true bulbs are: – daffodils and tulips.
Another type of true bulb with a different appearance is a ‘scaly bulb’, sometimes also called a non tunicate bulb.
These bulbs do not have tight concentric rings or a protective tunic (the papery bit of the onion). Two examples of non tunicate bulbs are Lilium and Fritillaria.
Corms are solid inside, unlike the concentric layers of bulbs.
New growth arises at the top of the corm, unlike bulbs where new growth happens at the base plate.
The nodes and internodes occur on the outside or exterior surface of the corm. New cormlets (babies) can develop here and take two or more seasons to flower.
Examples of corms are Gladiolus, Freesia and Watsonia.
When selecting bulbous plants to grow in the garden, the two most influential factors are rainfall and temperature.
There are five broad climatic zones where bulbs are found growing.
- Winter rain and cold winters (-24° to -8°C and 27° to 37°C)
- Winter rain, cool to mild winters (-5° to 4°C and 28° to 38°C)
- Summer rain, cool to mild winters (-1° to 22°C and 30° to 35°C)
- Year round rain, cold winters (-20° to -8°C and 26° to 35°C)
- Year round rain, cool to mild winters (-8° to -3°C and 24° to 34°C)
Some gardeners live in areas that can restrict the selection of bulbous plants that can be grown.
These may be: -
- Lack of winter chilling
- High air and soil temperatures
- Low annual rainfall and high evaporation rates
- Generally poor soils
You are likely to find a bulbous plant to suit most situations or positions in the garden.
Whether it be full sun or dappled shade, sandy soil or heavy clay.
They are a versatile group of plants and can be grown in containers as well as in the garden.
The Colours of Autumn
Posted by Phytopath on Mar 18, 2011
The Southern Hemisphere has moved into autumn. Soon the deciduous trees will start to colour and fall.
Just how and why do they produce such beautiful bonfire colours of yellow, gold, orange, rust and scarlet?
For gardeners who live in temperate regions with four distinct seasons, the beautiful colours of deciduous trees herald the coming of winter.
But the days are still warm and the nights are cooling rapidly: a sure fire recipe for taking successful stem cuttings.
The first six weeks of autumn are a great time to take stem cuttings, while the plant is still manufacturing carbohydrates and storing them for the winter rest.
But then, the leaves will begin to put on a brilliant display of colour before falling like confetti at a wedding.
So why do the leaves fall? Why not stay on the branch just like evergreen trees?
Firstly, the role of the leaves is to supply nourishment to the rest of the tree through the process of photosynthesis.
The leaves do this by using raw materials: carbon dioxide from the air, water from the soil and the energy from sunlight.
The water is taken up by the roots through a network of vessels called ‘xylem’. Think of them as a super highway with many lanes, stretching for many kilometres. The traffic on the highway is traveling in one direction only. One side of the road heading out of the city and the other side of the road the traffic is heading toward the city.
If you have that picture in your mind, you can visualize the xylem vessels traveling from the roots in the soil, all the way up the trunk of the tree and into the veins of the leaves.
It is here in the centre of the leaf tissue called mesophyll, where the water combines with carbon dioxide (which has entered through tiny openings in the leaves, called stomata) through the process of photosynthesis, to form carbohydrates (glucose).
Once the leaves have manufactured their food source, they need to distribute that food to the rest of the plant. So the glucose is now shipped back on the super highway through vessels called ‘phloem’. Think of xylem and phloem as the name of the business trucks that are transporting goods up and down the highway.
I still haven’t explained the process of colour change in the leaves from green to ‘autumn tones’ but I’m getting to that.
Within the chloroplasts (in the leaves) are molecules of colouring agents called chlorophyll, carotenes and xanthophylls. These molecules are in the leaves at other times of the year but the intense green pigment of chlorophyll tends to hide them.
As autumn approaches, a hormone is released within the plant (gee they are clever) to signal the change in temperature and sunlight hours.
The chlorophyll content of the leaves decreases causing leaves to lose their green colour, but reveal the yellow tones that already exist in the leaves.
By the way, carotene is also responsible for the yellow colour of bananas and the orange colour of carrots, pumpkin and sweet potato.
But what about the beautiful red leaf colour of trees like maple?
The red pigment does not already occur in the leaves like the yellow pigment. The red and scarlet colouring of deciduous leaves only occurs during autumn.
The intense red is produced by a pigment called anthocyanin. This pigment is also found in plants like beetroot, radishes (red ones) and hyacinths.
Trapped glucose is responsible for producing the vivid reds of autumn leaves.
When photosynthesis slows down and then ceases, the flow of water from the xylem vessels and glucose from the phloem vessels comes to an end.
The hormone that I mentioned earlier, called abscisic acid, is mobilised and travels to the area where the leaf stem (called a petiole), joins the branch. This area is called the abscission layer. It is here that the flow of water and glucose is blocked. (Kind of like a pile- up on the highway that blocks all traffic movement).
When this happens, some glucose usually remains trapped in the mesophyll cells. A combination of bright sunlight, cool night temperatures and trapped glucose, make a wonderful recipe for scarlet and red autumn leaves.
And what a wonderful sight, unless of course there is an early frost which will turn the leaves dry and brown.
