In South Africa Chrysantheums are almost the most popular indoor flowering potplant. While I have been very successful with many other plants, I have never been able propagate Mums satisfactorily. The 2nd set of flowers are trivial.
My gardening book says the following "To produce the compact plants often bearing 20 or more blooms requires special production techniques involving artificial shortening and lengthening days"
'Mums bloom in response to day-length. As the days grow shorter relative to the nights, flower buds are formed and then open. Growing 'mums under artificial light can thus be used to make them bloom out of season. This is why you can buy flowering 'mums when they are not flowering in your garden.
Making them compact with many blooms is something else. From spring through about two weeks after the summer solstice, keep pinching them back. (I even use pruning shears and cut back to only 2-4 leaves per stem. In the northern hemisphere, I do this until about the end of the first week of July.) This makes them bushy with many stems. When flower buds start to form, disbud; leave only the main center bud on each stem. This results in fewer but larger flowers. The effect is better than many smaller flowers.
At least every other year (better every year), new plants should be started from the old plants. Merely dividing the old clumps -- keeping newer portions and discarding the rest -- is the most reliable. However, the most vigorous results are obtained by rooting cuttings, of which 1/2 to 2/3 will survive. When you replant from either divisions or cuttings, put a small amount of bone meal in the planting hole about 3-4 inches (7-10 cm) below the roots. The phosphorous will promote both root growth and flowers.
Your advice is great, but It appears to me that Michael is trying to take cuttings and raise the mums as a house plant without benefit of a greenhouse.(Maybe I'm reading too much into his question?) If one purchases mums as an out-of-season blooming plant for a holiday before spring arrives, cut off the spent blossoms and keep them alive until they can safely be planted outside. Once it's warm enough to support growth, plant them in the ground in a sunny location. Before planting, loosen the roots if root bound and then follow David's instructions. I have often been given mums in pots that were bloomed out in the fall and had them survive and bloom the following year. In fact, our garden club has a number of mums planted in a project area that a local merchant donated after they failed to sell in the fall. This is their third year of blooming.
".......In South Africa Chrysanthemums are almost the most popular indoor flowering potplant. While I have been very successful with many other plants, I have never been able propagate Mums satisfactorily. The 2nd set of flowers are trivial. My gardening book says the following "To produce the compact plants often bearing 20 or more blooms requires special production techniques involving artificial shortening and lengthening days" ..........."
Pot mums are grown using daylight regulation, either giving extra light to prevent bud imitation to early or by blacking out the benches with black polythene to shorten the day length to initiate the bud set, but the thing that you wont be able to do is to treat the young plants with a growth regulator to make compact plants suited to pot culture. This is why when you plant out a pot mum and its roots get into fresh soil the plant grows to 3 or 4 ft before flowering, it's got away from the retardant chemicals. You could get some of the more recently introduced "Garden Mums" that are compact, self stopping and have small flowers, these will give good bushy plants in season without to much trouble, but not if you are trying to grow them for all their life in the house. They all need good light.
For the most valuable information on creating mums. I have a large atrium in my house and there is clear perspex in the overhead roof. It gets very bright in there.
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