Types of Chrysanthemum
Types of chrysanthemum
1. Incurved — where the majority of the petals turn inwards to form a ball-shaped flower
2. Incurving — the same, butare of a looser habit
3. Reflexing — where petals turn outwards or have a dropping habit
4. Singles — which have a ring of petals; up to five rings for exhibition
5. Large exhibition—which have enormous flowers of incurving, incurved or reflexing habit
6. Other types, including Spiders, Rayonnante, Anemone, in the early, mid and late-flowering groups
7. Sprays — for cut flower production or in pots (frequently called American sprays) Further groupings
For indoor culture, natural season, spot cropping or year-round culture, varieties are categorized as tall, medium or short. Still further grouping relates to temperature requirements during bud initiation periods, requiring reference to specialist catalogues. For direct planting and year-round culture chrysanthemums are categorized in response groups, according to the number of weeks from bud initiation to flowering under inside conditions.
The photoperiodic nature of chrysanthemums
Most chrystanthemums (apart from non-photoperiodic earlies and some ‘mids’ which successfully initiate their flower buds in long days) will only initiate their flower buds when the day length is less than about 12-14 hours. Equal day and night length occurs at equinox. It follows therefore that for natural season cropping it is necessary to plant sufficiently in advance of bud initiation to ensure sufficient vegetative development beforehand. Because of this photoperiodicity, chrysanthemums react very positively to the artificial stimulus of shading to make artificially short days, or lengthening with low intensity light to give artificially long days. Response groups indicate when the chrysanthemum will flower from bud initiation, and cropping can be organized accordingly.
This involves the use of 100W tungsten clear filament lamps. For beds 1.2m (4ft) wide tungsten rubber sheathed or polychloroprene cables are suspended 1.2 — 1.5m (4-5ft) above the centre of the bed. The 100W lamps are spaced l.8m (6ft) apart (or 60W 1.2m/4ft apart) in special lamp-holders made of neoprene with waterproof connection to the cable. The importance of this cannot be over-emphasized. Very careful wiring is required; preferably the system should be professionally installed. It may be necessary to increase the amount of light in winter in very poor light areas.
The period of light necessary will be 2 hours in mid- to late spring, late summer and early autumn, 3-4 hours in mid- to late autumn, late winter and early spring, and 5 hours in early and mid-winter. It is usual (and also cheapest) to give light in the middle of the night to ensure that the dark periods do not exceed 7 hours. Cyclic lighting (3 minutes on, 9 minutes off)has been found effective, although it is not a technique which appears to have been widely developed. It is obvious that a time clock is an advantage for the operation of the lights. From early spring to early autumn shading with dense black polythene sheeting or other dense material is necessary to simulate short days, usually from 18.00 hours until 07.00 hours. This is achieved by putting the polythene over metal hoops or by block arrangement. Support both in beds out of doors and in greenhouse borders is by means of strained nylon netting.
This requires exact programming on a week-by-week basis by specialist cutting suppliers, following the necessary shading and lighting pattern and basically the same cultural, spot cropping or direct planting procedures. Difficulty can be experienced in poorer light areas if considering year-round cropping, especially during the dullest months of the year.
IMPORTANT NOTE :A technique which is finding favour is to root cuttings in 6-7cm (2in) peat pots or small pots and take them to the 12 leaf stage under glass, giving supplementary lighting if necessary during poor light periods and ‘short days’ immediately on planting out in the greenhouse border. This technique obviously has application not only in year-round cropping and direct planting.