Plants with flower heads arranged in this way are classed botanically in the family Composite. The plants has a fibrous root system which under suitable conditions, may penetrate to a depth of 12-16 in. The stem which becomes considerably hardened and woody, bears numerous alternate foliage leaves, the outline of which is divided into a terminal lobe and 4 or 6 lateral lobes, the depth of the segmentation and shape of the lobes differing with varieties. In addition to shape variations the leaves vary in size, colour, glossiness and in susceptibility to rust diseases. The shoots produce a strong smell.
Most chrysanthemums have big flowers and attractive colours.
There are two categories of flower formation. Chrysanthemums are short day plants which need a short day to flower. Nevertheless, the flowering period can be delayed by lengthening the day period through the use of artificial lighting. Lighting should be given for four hours every night, starting from propagating till about 8 - 10 weeks before flowering.