Willow is one of many genera suitable for field-grown woody floral cut-stem production (Armitage and Laushman, 2003; Greer and Dole, 2008). Selection of ornamental willow species and cultivars for cut stems is based on desirable attributes such as showy catkins and stems that can be harvested in late winter for precocious ornamental catkins, or throughout winter for contorted or colorful stems. Their ornamental attributes combined with off-season flowering timing make willow a desirable crop for floral cut-stem market sales.
Market prices of willow stems are determined by stem length with longer stems commanding higher market prices. When sold by length, stems may be offered as single-stemmed whips or as branched stems (Greer and Dole, 2008). Stem length grading differs slightly depending on market and can be grouped into general categories: tips (1.5 to 3 ft), medium (3 to 5 ft), and large (over 5 ft) (Josiah et al., 2004). Longer stems command higher market prices; therefore, willow species that produce longer stems are more profitable. Currently, the relationship between cultural practices, input and yield is not clearly defined for ornamental willow production (Saska et al., 2010). Efficient management practices are needed to determine cultural requirements that optimize yields without raising input costs of labor or materials. Species that require less input and produce highest yields would be more desirable for cut-stem producers.
Standard recommendations for fertilizing willows for cut-stem production range from 60 to 80 lb/acre nitrogen (N) (Gouin, 1990). However, studies addressing the effects of fertilizer on stem count and length of cuts of ornamental willows have been limited. A 2-year study investigated N fertilization rates on field plantings of giant pussy willow (S. chaenomeloides) and found no significant effect on stem quantity or length at N concentrations of 0.25, 0.5, 1, or 2 oz/plant (20–150 lb/acre N) within 1 year of harvest (Bir and Conner, 2006). Yet, in another study, stem yields of american pussy willow (S. discolor) grown on an unfertilized field buffer were influenced by soil fertility, as plants located next to the fertilized cropland yielded a greater number of stems per plant, whereas yield decreased in plantings located farther away from the cropland (Yoder and Moser, 1993).
Fertilization rates may affect the length and number of stems as well as duration of the growing season subsequently affecting yields. The duration of the stem elongation period is an important consideration for the selection of species suitable for certain hardiness zones. Longer growing seasons, when budbreak takes place earlier in spring and growth continues well into fall, have been recorded as a result of fertilizer treatments for purple osier (S. purpurea) and woolly-stemmed willow (S. dasyclados) (Fuchigami and Weiser, 1981; Sennerby-Forsse and von Fricks, 1987).
The objective of this study was to measure the growth response of five container-grown willows used for cut-stem production based on yield and timing of tip abscission and floral bud burst across five concentrations of controlled-release fertilizer. Yield data were collected on commercially important parameters: total stem length, stem quantity, and stem fresh weight. The effect of fertilizer applications on the timing of growth cessation, signified by tip abscission was evaluated: willows do not form terminal buds, and at the end of the stem elongation, the length of stem apex is reduced in size, followed by the abscission of shoot tips (Lennartson, 2003; Saska and Kuzovkina, 2010). Further, the effect of fertilizer addition on the timing of floral bud burst during the following spring was also evaluated, as this is an important factor for specialty cut-stem growers.
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