There can be little doubt that a great number of ardent growers dream that one day they will produce the ultimate, a really outstanding bloom or plant, just a little bit different from the rest - a change of colour - maybe a larger size of bloom or improvement in the quality of the foliage or growing habits. One way to try and do this in the home garden is by chemical mutation which may sound rather fearsome, but could provide a pleasant surprise.
Colchicine has been used on African Violets to create improved plants for many years and has great possibilities for doing the same for chrysanthemums. Colchicine is a chemical derived from the bulb of the Colchicum, Meadow Saffron, more commonly known as the Autumn Crocus. This is a plant which produces its flowers before the foliage appears, hence the common name, Naked Ladies. However every part of the plant is toxic and needs to be handled with great care.
In this article I describe how colchicine can be used to produce new cultivars.
Like radioactive isotopes, colchicine, when applied to actively growing and dividing cells, acts on the chromosome numbers. The best place to find these cells is in the terminal branch buds, at the tips. Different types of plants require different dilutions of Colchicine to be successful, and unfortunately the correct dilutions to use for each plant has never been accurately determined. Even different cultivars within a species will react best with differing solutions.
The best way I have found to overcome this problem is to use 3 different dilutions for different periods of time on the same plant. In this way the chance of a doubling of the chromosomes is enhanced. Colchicine may be acquired from the chemist. The product I use is called Calgout which is used in the treatment of gout. It comes in tablet form, 0.5mg. The tablets are relatively inexpensive but are generally available only on prescription. I recommend initially using the Colchicine in 3 strengths by mixing a 0.5mg tablet with 50ml, 100ml and 150ml of water. As you become more interested in this area of plant experimentation you can try much weaker and stronger solutions and vary the time of application. The important thing is to keep accurate records. I usually apply the colchicine for 12, 24 and 48 hrs but this also can be infinately varied. Hopefully one of your trials will result in the doubling of chromosomes in the plant cells and the production of a wondrous new chrysanthemum.
It is possible that plant injury will occur should the solution be too strong or the exposure too long, or a combination of both, for any particular variety. Therefore it will be necessary to record each individual operation.
Procedure
Wrap cotton wool or a strip of cloth around the bud area and saturate with the necessary solution. It will be found to be easier if side leaves are first pulled off. It is a good idea to make minute slits at the base of the bud thus enabling a quicker penetration of the solution. Remove cloth at the end of the desired duration time. If using on outdoor plants, cover the impregnated cotton wool or cloth with adhesive or plastic tape. After Colchicine treatment the plant will often try to send out side shoots. Keep these pinched out thus forcing top growth. At first growth is slowed down, then it will become distorted and uneven, as affected, and unaffected, cells battle to take over. Later if the procedure has been successful, stems should grow thicker and leaves greener, whilst the flowers should be different. Doubling up of the chromosomes, by this specialised Colchicine treatment, not only creates a new plant but sets up new breeding possibilities. Colchicine can be applied to any part of the plant. If you do not have success with the bud area try the roots. In this case wrap the roots in sphagnum moss or cotton wool, wet it thoroughly in water and wrap in aluminum foil to prevent drying out. Then suspend the plant in the desired concentration of Colchicine. It may be necessary to curtail or extend period of immersion depending on the plant's reaction. After exposure wash thoroughly and repot. Always remember that the treatment is a shock to the plant. Baby it afterwards and keep it warm and out of direct sun.
In conclusion, remember to take care when handling Colchicine.