Salinas, CA, United States
Salinas, CA, United States

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Lin M.,Texas A&M University | Starman T.W.,Texas A&M University | Wang Y.-T.,Matsui Nursery | Niu G.,Texas AgriLife Research Center | Cothren J.T.,Texas A&M University
Scientia Horticulturae | Year: 2011

Orchids are currently the most valuable potted crop in the United States. To date, no studies focused on making possible the year-round greenhouse production of flowering nobile dendrobium orchids. This experiment was aimed at developing a strategy to defer flowering of nobile dendrobium orchids by holding them under low temperature. Mature Den. Red Emperor 'Prince' and Den. Sea Mary 'Snow King' were held at 10 °C for various durations (0, 4, 8, 12 or 16 weeks) after vernalization (4 weeks at 10 °C). Plants were forced in a greenhouse after holding. Time to flower, flower differentiation (flowering node percentage, number of aerial shoot and aborted bud) and flower quality (total flower number, flower diameter, flower number per flowering node and flower longevity) were determined. Increase of low temperature holding duration from 0 to 16 weeks extended time to flower up to 3 months and did not affect parameters of flower except producing larger flowers and reducing flower number per flowering node for Den. Red Emperor 'Prince'. Notably, the flower longevity was not adversely affected. Defoliation was aggravated in Den. Red Emperor 'Prince' by longer duration of cooling and was considered a detrimental effect of low temperature holding. © 2011 Elsevier B.V.

Lin M.,Texas A&M University | Starman T.W.,Matsui Nursery | Wang Y.-T.,Texas AgriLife Research Center | Niu G.,Matsui Nursery
HortScience | Year: 2011

The flowering time and flower quality of three hybrid Dendrobium nobile cultivars in relation to light intensity during cooling and duration of vernalization were studied in the first experiment. Mature Dendrobium Red Emperor 'Prince', Den. Sea Mary 'Snow King', and Den. Love Memory 'Fizz' plants were vernalized at 10 °C under 300 to 350 μmol m -2 s -1 photosynthetic photon flux (PPF) (12-h photoperiod) or darkness, each with four cooling durations (2, 4, 6, or 8 weeks). Plants were forced in a greenhouse after vernalization. At least 4 weeks of 10 °C cooling in light was needed for complete flower initiation of Den. Red Emperor 'Prince', whereas Den. Sea Mary 'Snow King' and Den. Love Memory 'Fizz' only needed 2 weeks of 10 °C cooling regardless of light. For all three cultivars, darkness during vernalization slightly delayed flowering and resulted in fewer but larger flowers. Longer cooling duration delayed flowering, decreased flower longevity, and produced more and larger flowers. In a second experiment, Den. Love Memory 'Fizz' plants were vernalized at 15 °C for 4 weeks under a 12-h photoperiod and PPF of 0, 50, 100, or 200 μmol m -2 s -1. Compared with 200 μmol m -2 s -1, low PPF at 50 or 100 μmol m -2 s -1 did not affect flowering time or flower qualities; however, darkness delayed flowering and reduced flower qualities except flower diameter.

Wang Y.-T.,Matsui Nursery | Wang Y.-T.,Texas A&M University
Acta Horticulturae | Year: 2010

Phalaenopsis is the most important potted orchid around the world. It has a long juvenile period. High fertilizer concentrations in general accelerate vegetative growth and fast accumulation of the total leaf area to have plants mature quickly. In most bark mixes, fertilizers providing 200 mg/L nitrogen (N) promote growth over lower concentrations. High fertilizer concentrations ensure high flower count but do not always increase flower size. Phalaenopsis needs at least 50% of the N in the nitrate form for improved growth and flowering, regardless of being planted in a bark mix or in sphagnum moss. N concentration close to 300 mg/L, particularly in the ammonium form, has been reported to delay spiking and flowering to a certain extent. Phosphorus (P) at 25 to 50 mg/L is adequate for optimum growth. P concentration in the nutrient solution does not affect flower size. Starting to apply high levels of P one month before spiking does not further enhance flowering. Fertilization may be terminated completely when the inflorescence has reached 10 cm in length or at first flower opening without affecting flower count. Fast-growing larger plants in a bark/peat mix have lower P concentration in their leaves than the slow-growing smaller plants in pure bark, but the entire plants in both media have similar total amounts of P. When using high N levels (200 mg/L or higher), potassium (K) must be at 200 mg/L or higher for obtaining healthy foliage, increased flower count, and larger flowers than lower concentrations. Plants under low K (0 to 100 mg/L) appear healthy when vegetative; but, as soon as being induced to enter the reproductive phase, yellowing and abscission of the lower leaves occur. Foliar feed alone does not provide adequate amounts of nutrients for Phalaenopsis. Moisture tension of the tightly packed sphagnum moss remains at or higher than-20 kPa until 90% of the water is lost, compare with 55% water loss in a peat/diatomite mix; thereby, providing higher amount of available water to roots. The pH of the sphagnum moss in growing containers is often between 3.0 and 3.5. Yet, this low pH does not seem to negatively affect plant growth or cause apparent toxicity from the accumulation of certain micronutrients in plants.

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