Types and Classification. There areand which are dealt with elsewhere. Here we are only concerned with the florist chrysanthemums developed over many centuries from plants of Chinese and Japanese origin. For garden purposes these are broadly divided into three main , Early Flowering or Border which normally flower in the open before October 1st, October Flowering or Mid-season and Late Flowering or Indoor which normally flower under glass between November and January. The controlling body for classification in Britain is the National Society.
Within each division the varieties are classified according to flower characteristics. Singles have up to five rows of petals and a button-like disk.-centred varieties are similar except that a low, soft cushion of very short petals replaces the button-like centre. Doubles have so many petals that no central disk is visible until the flower fades.
Doubles are split into three groups according to the form of the petals. In Incurved varieties these all curl inwards making a ball-like flower. Reflexed varieties have outward or downward-curling petals. Intermediate varieties have the inner petals curling inwards and the outer petals curling outwards. For exhibition purposes there are further subdivisions of each group according to the normal size of the flower.
There are also some other special classes. Pompons have very small fully doubleproduced freely in clusters. Thread petalled or Rayonante are doubles with petals rolled lengthwise like thin quills. In Spoon-petalled varieties petals are partly rolled but open out at the end like little spoons. Cascade varieties have lax growth and can be trained as hanging plants. Charm varieties are very branching, compact and have numerous small single flowers. Korean and Rubellum varieties have very numerous single or semi-double flowers but are relatively hardy and may be grown outdoors all the year in mild places and on light soils. All other chrysanthemums, even the Early Flowering or Border varieties, are likely to need winter protection in most parts of Britain.
Propagation. Though chrysanthemums can be raised quite easily from, are very variable in quality and this method is therefore hardly ever adopted, except with Cascade and Charm (small single-flowered) varieties. is sown in February in a warm and subsequent treatment of is similar to that of half-hardy (405 to ).
Cuttings are almost invariably employed for other chrysanthemums and selected Cascades. These are taken from November until May; the earliestfor exhibition varieties and especially those to be flowered on second crown buds, and the latest cuttings for dwarf plants. With the exception of late cuttings, which are often prepared from the tops of plants rooted earlier in the year, all cuttings are made from sucker growths, i.e. shoots coming direct from the through the soil. Shoots growing from the old, woody flower will not make good cuttings. Cuttings are 2-3 in. in length, trimmed below a joint and the lower are removed. They are inserted 4 in. deep in sandy soil, usually in or boxes, and are rooted on the cool staging or in a propagating frame. Great ‘heat is undesirable as it encourages disease.
. As soon as cuttings are rooted and growing, they are potted singly in 3-in. pots and ordinary . Pot rather firmly and shade for a day or so until established. Subsequently, grow on in full sun and average temperature of 55°-60°. Pot on as smaller pots become moderately full of roots, using similar throughout but coarser in texture as plants get bigger. For final in late May or June into 8-9 in. pots loam may be in lumps as large as a small hen’s egg. To this final compost, basic fertilizer should be added instead of the general potting fertilizer. Pot firmly throughout. Early-flowering and Korean chrysanthemums are not usually potted beyond 3-in. pots, in which they are hardened off in a frame and planted outdoors 1 ft. apart in rows 2 ft. apart in early May.
Stopping. This meansthe growing tips of the plants. It is practised for two distinct reasons: (i) to make the plants more bushy, and (ii) to obtain buds and flowers at the right time. The first purpose is necessary only for decorative varieties, singles grown for decoration, late-flowering varieties grown as large specimen plants, early-flowering types grown for garden decoration or small flowers in sprays, and Koreans. As a rule two stoppings are then given, the first when the young plants are 6 or 7 in. in height and the second when the side growths produced as a result of the first stopping are about 8 in. long. For exhibition purposes, early-flowering chrysanthemums are usually grown with one stopping only during the first half of May.
When stopping to time blooms for exhibition, each variety must be treated according to its peculiarities. Catalogues issued by trade specialists usually give instructions which may need to be modified to suit the locality. Left to itself thewill, after a few weeks, produce a flower bud at the tip of the . This bud prevents further extension of the main stem and forces the plant to produce side growths. It is, in consequence, known as a BREAK BUD. Some time later the side growths will produce flower buds, known as FIRST CROWN BUDS. Further shoots appear below them, themselves terminating in flower buds some weeks later. These are SECOND CROWN BUDS. Again, the process is repeated, but the third batch of side growths will end in clusters of flower buds, not in one flower bud surrounded by further shoots. The plant has reached the end of its development and these buds are in consequence known as TERMINAL BUDS. By the tips of shoots a little before each stage in this sequence would occur naturally, the next stage can also be advanced by a few days. Since the sequence of growth and bud formation is controlled by the interaction of warmth and day length it is subject to modification according to the time at which cuttings are taken. It can also be modified by artificial control of temperature and by the use of blackouts or lighting to shorten or lengthen the days, and it is by these means that commercial growers are able to produce chrysanthemum cut flowers throughout the year. However, not all varieties respond equally well or in a similar manner and for good results it is essential to be able to control the lighting and heating very accurately.
A special system of stopping and training is necessary for Cascade chrysanthemums. After the first stopping of the rooted, the uppermost new shoot is tied to a bamboo cane sloping downwards at an angle of 45° towards the north, and is not stopped again. The plant must be stood on a shelf or raised bench both in the greenhouse and when outdoors from June to September. All other growths are stopped after the fourth . If they form secondary growths, these are stopped in turn at the fourth . No growths are stopped after the middle of September. When the plants are brought into the greenhouse the main stems are lowered so that they hang perpendicularly.
Bud Taking. This signifies the gardener’s decision that the particular flower bud just formed will develop into a bloom at the right time and so must be kept. All other buds or side growths surrounding or immediately beneath it are rubbed out. Usually buds of intermediate or reflexed varieties required for exhibition about the second week in November should be taken between the middle and end of August, while incurves may be a week or fortnight later. Buds that appear a little too soon can be retarded by leaving side growths round them for a week or fortnight.
Bud selection is also sometimes determined by the type of flower required since first crown buds tend to produce flowers with more petals than second crown buds which, in time, have more petals than do flowers from terminal buds.
Cultural Routine.are almost hardy but the flowers and flower buds of all kinds except the very hardy Korean varieties may be damaged severely by frost. They require cool greenhouse protection from early October until the end of May. During the remaining months they are best outdoors in a sunny . Old roots are discarded and only the rooted cuttings retained. These are watered moderately at first, but more freely as weather becomes warmer. In summer, water is supplied freely. Feed with chrysanthemum summer fertilizer from mid-July till flower buds show colour.
When plants are stood outdoors, pots should be placed on boards, slates, or a gravel or ash base to assistand to keep out worms. Stake and tie each plant securely.
Alternatively, decorative varieties may be planted out in late May in ordinary well-dug soil, 18 in. apart in rows 21 ft. apart. They are then lifted with good balls of soil in the autumn and replanted in the greenhouse either in beds or boxes. These may be left in the open all the winter in well-drained soil, but a few plants should be lifted in October into a frame with old potting soil to give cuttings. After flowering, cut down all plants to within about 4 in. of soil level.can be grown successfully by the ring culture method.
Chrysanthemums are frequently attacked in summer byand capsid bugs and flowers may be damaged by earwigs. All can be kept under control by occasional spraying with suitable insecticides. Diseases include rust and , also grey mould (botrytis) which is particularly likely to damage expanding flowers, causing them to decay. This disease thrives in a cold, damp atmosphere and is best controlled by good ventilation coupled with some artificial heat to dry the air and keep it on the move. Other diseases can be controlled by occasional spraying or dusting with fungicide.