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.
