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AFFECTING THE SPRAY SHAPE OF POMPON CHRYSANTHEMUMS DURING NATURAL SEASON FLOWERING
A general discussion of year-round culture is available (Kofranek, 1980). The chrysanthemum has become the most widely grown cut flower in America surpassing both roses and carnations in quantity and dollar volume.
With the advent of year-round flowering, fewer chrysanthemums are being grown during their natural flowering season.
For the year-round grower, natural flowering may not be convenient to fit into the year-round schedule.
In the future, when fossil fuels become extremely costly and year-round flowering may not be economically feasible, natural season chrysanthemums may again be grown for approximately 3 months per year out-of-doors in mild climates, or in greenhouses which only have limited heat.
Natural flowering of chrysanthemums is possible from early October until early January if the appropriate cultivars are chosen for this succession of flowering.
For commercial cut flower spray types (a corymb inflorescence), rooted cuttings may be planted every week beginning in early July for the 8 week cultivars and ending in mid to late August with the 15 week cultivars.
As a general rule, rooted cuttings of each response group are pinched 2 weeks after planting (Table 1). Cuttings are easily established within 2 weeks of planting during these periods of high light radiation.
Cultivars in the various response groups should be planted on the dates indicated in Table 1 in regions of latitude 42° N and 1 week earlier in more northerly latitudes and 1 week later in more southerly latitudes, but not further south than about 23° N. A soft pinch (Fig. 1) to induce branching is given 2 weeks later for the flowering periods indicated; this is known as the "time pinch." The purpose of the time pinch is to improve the shape of the spray formation of pompon chrysanthemums (Fig. 2B). If the pinch is made too early, a premature crown bud (Fig. 2A) initiates and may cause branching and extreme peduncle elongation; if the pinch is made too late, a terminal bud initiates (Fig. 2C) surrounded by lateral buds borne on short peduncles.
A time pinch given on the proper date for a particular response group results in a flower bud initiated in the center of the spray, which usually develops into an arrangement of inflorescences on peduncles of desirable length (Fig. 2B). Weather conditions that follow may alter the spray development.