Most people who take the growing of chrysanthemums seriously will sooner or later gravitate towards exhibiting them, either at their local shows or at national level. Any properly run show in Britain will conduct its chrysanthemum business in accordance with the rules of the National Chrysanthemum Society and the Society’s publications Code of Rules for Judging Chrysanthemums and Exhibiting and Judging should be read by all intending exhibitors.
Ash Base system for earlies
This method has become popular with exhibitors for the housing of rooted cuttings before planting out. It reduces the attention required and may also give better plants in the end. A frame is prepared with a base of 10-15cm (4-6in) of coarse ashes firmed well. On top of this ash base an 8cm (3in) layer of JI No 3 compost is laid, into which the rooted cuttings are planted about 13 x 13cm (5 x 5in) each way. The compost must not be too dry and an initial watering may be given to settle the plants in. Thereafter water is withheld for 10-14 days (a light overhead spray being given if the plants wilt excessively) so that the plants send out roots in search of moisture and a good root system is built up. When they are well established and growing strongly, water may be applied liberally and the goodconditions ensure that no waterlogging occurs. The plants revel in the cool root conditions and growth is rapid. Supplementary liquid feeding may be given as the plants reach the end of their time in the frame, and normal spraying precautions against pests should be taken. In most cases the plants will be stopped in the frame. Air should be admitted progressively and, weather conditions permitting, the frame lights should be removed altogether in the later stages so that the plants are hardened off before planting out. The plants can be lifted with a small hand fork and if the system has been operated correctly it will be found that the massive root systems have used up practically all the compost in the frame.
B-Nine (and other dwarfing agents)
Some chrysanthemum cultivars have a natural habit of growth which makes them rather taller than is desirable, especially when they have to be housed in. Other varieties tend to have a rather long unsightly neck below the bloom, a condition aggravated when grown under frames or covers which draw them up to the light. A chemical known as B-Nine, is of considerable assistance to the exhibiting chrysanthemum grower in alleviating these conditions. It works not by checking the growth of the plant, but by inducing lateral rather than longitudinal expansion of the cells. The result is a stockier, dwarfer plant, with stronger stems and shorter internodes. Normal dilution is 1:40 (1 tablespoon to 0.56 litre/1 pint water) and is applied as a fine spray from a plastic (not metal) sprayer on to the top 15cm (6in) of foliage to run-off point. Two or three applications may be given at any stage considered desirable but it is advisable to make the final application not later than 14 days before the bud is taken. In addition to restricting the height of certain cultivars it is also useful to control the height of plants at certain stages where they are tending to become drawn, eg in poor light conditions or in frames prior to planting out.
Pot chrysanthemums (‘Pot mums’ )
The intensive culture of pot chrysanthemums is practised commercially on a large scale in Britain and Europe generally. It must not be confused with the culture of conventional chrysanthemums in pots since the varieties grown for year-round pot work have been specially bred for this purpose. The categories ‘tall’, ‘medium’ and `short’ are further divided into response groups of 9, 10 and 11 weeks, this referring to the time from bud initiation to flowering under a minimum temperature of 15.6°C (60°F). Under the less precise conditions which frequently exist in small-er greenhouses, temperatures frequently fall below this level, resulting in delays to flowering. Conversely, should the weather be abnormally mild in the autumn or spring, flowering may be advanced. In order to maintain production on a year-round basis, day length manipulation by shading and lighting is necessary. The poor winter light in many northerly areas makes successful winter culture difficult and results in plants of etiolated growth and in of low petal number. In general, few professional or amateur gardeners are much concerned with year-round culture, tending to confine their activities to natural season flowering.
Short-day varieties of pot chrysanthemums initiate their flower buds in day lengths of 12 hours, which means that short-day varieties will not require artificial short days by shading between 21 September and 21 March. Conversely, long days allow vegetative development before the short day period, and this is provided by lighting when the natural day length is less than 12 hours.
As with cut flower chrysanthemums, it is important to remember that for each week the plant is exposed to long days, a week must be added to the time taken to produce the plant in flower, eg an 11 week response plant given 2 weeks of ‘long’ days will not flower for 11 + 2 = 13 weeks.
The selection of varieties for pot culture is particularly important, as techniques require modification accordingly.
These grow too tall for pots if allowed to develop naturally and require treatment with dwarfing chemicals. As stem length is unduly increased by long day treatment, they are therefore given short day treatment immediately after potting.
Normally speaking, one week of long day treatment is given to these varieties after potting, although in good conditions this week of long days is generally unnecessary in spring and autumn.
Three weeks of long days in winter, two weeks in autumn and spring and one week in summer is the normal treatment, with the exception of vigorous varieties which do not need any long day treatment in summer and can be given short days immediately after potting. When these varieties are grown at a time of year when day length is longer than 12 hours they are usually allowed to grow naturally for one or two weeks before being given short days but, on the other hand, if the day length is less than 12 hours artificial light can be used to give artificial long days.
Cuttings from specialist raisers are again desirable, having a special advantage in their uniformity of size for pot work. Amateur gardeners will once again find it difficult to obtain small quantities of cuttings and will need to contact a commercial grower or an amateur chrysanthemum specialist. On a limited scale, plants can be kept as a source of cuttings provided they are kept vegetative by long days.
Pot size and compost
Pot chrysanthemums are commercially grown five or six rooted cuttings to a 14cm (5-1/2in) deep pan. Alternatively three cuttings can be put in an 11-12cm (4-1/2in) deep pan, and one cutting in a 8-10cm (3-1/2in) pot. Plastic pans or pots are invariably used.
Either a compost of JIP2 standard or a soilless equivalent can be used. Standard composts often give rise to trouble as their nitrogen level may be too high for the poor light conditions in northerly latitidues during the autumn and winter months, giving rise to lanky, unproductive growth. Many growers and gardeners could achieve much greater success by selecting a compost of lower nutrient level and liquid feeding from the outset, modifying the feed according to the growth exhibited. In general terms, higher nitrogen feeds are given in the summer than in the winter, irrespective of region, reducing the nitrogen level in winter commensurate with light levels.
Pots are loosely filled to within 0.6-1.2cm (¼-1/2in) of the rim and firmed by dumping on a hard surface. Plants are then set into dibber holes at equal depth and equal spacing around the edge of the pots, with the base of the plant just below the surface of the compost. Cuttings with larger roots may require larger planting holes to allow entry of the root without damage. Cuttings should be watered in and the pots kept close together for a week or two, spacing the pots at 30 x 30cm (12 x 12in) thereafter to allow sufficient room for uninhibited growth.
The soft tip of the growing plant is generally removed two weeks after planting, except pinching (7-10 days) is advisable to encourage a lower break. Single stem plants of certain varieties can be grown, being later disbudded so that only the terminal bud remains on each stem, extra plants being required in the centre of each pot in this case.
While many varieties will make good plants with no disbudding, there are exceptions. Plants grown single in 8-10cm (Min) pots are not disbudded at all, it obviously being an advantage to have as large a number of flowers as possible. It is essential to take specialist advice on this matter.
Phosfon is a dwarfing agent which is mixed in powder form with the compost for all tall varieties, generally speaking about 21-42g (4— l-1/2oz) per bushel according to variety, although makers’ recommendations must be closely followed in respect of quantities for different varieties. Delays to flowering have been induced following the use of Phosphon. B-Nine, a liquid form of growth retardant, can be sprayed on the plants 2-4 weeks after pinching when the resultant break shoots are 1.25cm (1/2in) or so in length and it is used at the rate of 50m per 1/litre (8fl oz) per gallon of water, the same distribution rate for all varieties. B-Nine may not be sufficiently dwarfing for some very tall varieties.
Natural season culture
Many gardeners will be interested mainly in natural season culture, in which case either medium or short varieties are potted in the first week of September to allow two weeks or so of long days before 21 September when bud initiation is naturally induced. Assuming bud initiation in late September / early October, varieties will flower during early winter, although much will depend on temperature and other factors such as the application of Phosfon, etc.
If you are really keen to learn more about chrysanthemum growing, and meet others of similar enthusiasm, it is a good idea to join the National Chrysanthemum Society.