Propagating Chrysanthemums – Increasing Chrysanthemum Plants
The usual way, and indeed the easiest way, of increasing chrysanthemum plants is by cuttings, and the first consideration here is the time to start taking them. Unless the chrysanthemum plants are being grown for exhibition, in which case early growth and flowering is essential, there is not much to be gained from rooting cuttings too early.
Outdoor-flowering chrysanthemum plants are best propagated between mid-February and the end of March. For general purposes cuttings of indoor varieties can be taken between late February and early March. If they are taken any earlier then you will obtain very large plants perhaps too large for the average small greenhouse. Possibly the exceptions to this rule are the large exhibition varieties, the cuttings of which are best taken in November or December to get large enough plants to ‘stop’ in time for earlyto be obtained. Some of the incurved and decorative varieties also have to be taken in December.
Before I go on to discuss the details of taking cuttings for the process of propagating, I think this is a good opportunity to mention that I grow the Favourite and the Loveliness varieties to flower in 6 in. pots, by the following method of propagation. When I have finished taking cuttings for the early batch I put the boxes of stools in a cold frame where they remain until late May or early June. By this time they will have produced shoots about 10 or 12 in. high, I then take the tips off the shoots about 1-1/2 to 2 in. in length – root them, then pot the rooted cuttings in 3-1/2 in. pots, and finally transfer them to the 6 in. size. When the plants are about 5 to 6 in. high, I pinch out the growing tips and let them flower on the first crown buds. They make plants no more than 2 to 2-1/2 ft. high with five or six flowers per plant.
These make first-class pot plants which are ideal for bringing into the living room. They are also good for cutting. Koreans and Pompons are suited to this method of growing, and are also useful as cut flowers. These will flower in September, October and even into November. They will make bushy plants no more than 12 in. high and will produce a mass of flowers.
The Kind of Cuttings
The stools of both the outdoor and greenhouse chrysanthemums which were boxed up, will produce shoots from their bases. These are the best cuttings, far better than those which grow from the stems. However, some of the modern varieties are rather shy in sending up shoots from the base, so to get the number of cuttings required it may be necessary to take a few stem cuttings of these.
The cuttings need not be more than 2 to 3 in. long and should be cut off at the basal end with a sharp knife or razor blade. Cut them straight across just below the lowest leaf joint.
There are a number of rooting mediums which can be used for the successful rooting of cuttings. I prefer to use a mixture of equal parts loam, peat and sand, or even the John Innes Seed Compost. Equal parts of peat and sand may also be used or even sand on its own, but in these instances the cuttings must be potted up as soon as they have formed roots. Vermiculite is popular with many gardeners and cuttings will root rapidly in this material.
Preparing the Cuttings
There is not a great deal of preparation necessary. The main thing is to trim off the lower leaves, so leaving a clear stem for insertion in the compost. Make sure that the base of each cutting has been cut cleanly, without ragged edges. Before inserting the cuttings dip their cut ends into water and then into a suitable hormone rooting powder, to accelerate the formation of roots. I find that a rooting powder makes a difference of 10 days in the time of rooting, and it also encourages a better and stronger root system.
Inserting the Cuttings
I use 3-1/2 in. pots for rooting the chrysanthemum cuttings, placing four or six round the edge. Outdoor varieties are usually rooted in seed boxes in John Innes Seed Compost, about 30 cuttings per box. Make sure that the rooting medium is firm and then, with the aid of a small wooden dibber, insert the cuttings to about half their length, firming them well with the fingers. Make sure that the base of each cutting is in close contact with the bottom of the hole, otherwise they will not root. After they have been inserted give them a good watering with a fine-rosed can. They should not need any more water until they have rooted. If they are given too much water before rooting has taken place they will probably rot off. Make sure that each pot or box has been labelled with the name of the variety; also, the date of taking the cuttings may be useful for future reference.
Where to Root Cuttings
If possible, root them in a closed propagating case, or better still under a mist propagator if this is available. They do not need a high temperature about 10° to 16° C. (50° to 60° F.) is sufficient. A simple propagating case can be made from a reasonably deep bottomless wooden box placed on a layer of moist peat on the greenhouse staging. Place the pots or boxes in this, cover the top of the box with a sheet of glass, and place some newspaper over this to protect the cuttings from the sun.
It will be necessary to turn the glass over each day because water condenses on the underside, and if this drips on to the leaves it will cause them to rot and the chrysanthemum cuttings will almost certainly be lost.
If you have a propagating case with-warming cables, this is ideal for propagating chrysanthemums, as rooting will then be very rapid. The cuttings can be rooted in a layer of pure sand placed over the cables.
If a greenhouse is not available then cuttings of outdoor chrysanthemum varieties may be rooted in a cold frame in mid-March, but ensure that they are well-protected from frost. The base of the frame should be covered with a 2 to 3 in. Layer of fine ashes, followed by a layer of John Innes Seed Compost in which to insert the cuttings. The rooted cuttings can then be planted out straight from the frame.
Hardening-off Chrysanthemum Cuttings
Before the rooted cuttings are potted up they need to be acclimatised to the normal temperature of the greenhouse. If a mist propagator is being used then gradually reduce the amount of mist. The glass on a propagating box can gradually be raised over a period of a few days, so getting the cuttings used to the greenhouse atmosphere. Give the rooted cuttings as much light as possible to prevent them from becoming drawn.
When completely hardened off they should be potted individually in 3-1/2 in. pots, or if you wish to plant the greenhouse varieties in the open ground for the summer they may be placed in seed boxes. Seed boxes can also be used for the outdoor varieties if preferred. The latter can, in fact, be planted out in cold frames once they are well hardened off. Plant them about 3 to 4 in. apart each way in a mixture of equal parts loam, peat and sand placed about 2 to 3 in. thick.
The final hardening-off of both outdoor and greenhouse chrysanthemums consists of placing the plants in a cold frame a few weeks before set-ting them out in the open. Whenever the weather is reasonable prop up the frame lights to allow the free circulation of air. This ventilation can be gradually increased over a few weeks and the lights can be left off completely just before the chrysanthemum plants are removed from the frames.