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Most Phalaenopsis (the moth orchid) species and hybrids start to produce flowering shoots in the fall, bloom in January or February, and become limited in supply by April when market demand is strong. Means to defer the onset of flowering were studied. Starting 15 Sept. 1994, seedlings of 2-year-old hybrid Phalaenopsis TAM Butterfly were exposed to repeated cycles of 1 d darkness/1 d light (natural photoperiod, 1D/1L); 4 d darkness/3 d light (4D/3L); 7 d darkness/7 d light (7D/7L); and the natural photoperiod control (0D/7L). The dark treatments were achieved by covering plants with black fabric or by placing them in a dark cage. Treatments were terminated on 16 Dec., and all plants were exposed to the natural photoperiod. The control plants bloomed on 20 Jan. 1995, whereas the 4D/3L plants did not reach anthesis until 14 Apr., nearly 3 months later. Flowering of the 1D/1L and 7D/7L plants was also deferred until early April. Regardless of treatments, flower count and size were unaffected. In another experiment, beginning 15 Sept. 1995, 3-year-old plants were exposed to repeated weekly cycles of 2D/5L, 3D/4L, 4D/3L, or 5D/2L until 22 Jan. 1996. The nontreated control plants bloomed on 8 Feb. 1996, whereas the 5D/2L did not reach anthesis until 6 May. The 4D/3L treatment was not as effective as it was in 1994 and resulted in anthesis only 4 weeks after the control. In the last experiment, starting on 22 Jan. 1996, plants were removed at 2-week intervals from a 5D/2L treatment that was initiated on 15 Sept. 1995 and exposed to the natural photoperiod. Staggered anthesis was achieved. However, plants that bloomed in May and June had reduced flower count but not flower size.

It was unknown how prolonged periods of cool days and warm nights affect Phalaenopsis Blume hybrids, which perform crassulacean acid metabolism and absorb CO₂ primarily at night. The ‘Lava Glow’ plants vegetatively propagated from a hybrid Doritaenopsis (Phalaenopsis Buddha's Treasure × Doritis pulcherrima Lindley*), 15 cm in leaf span, were grown at day/night (12 hours each daily) temperatures of 30/25, 25/30, 25/20, or 20/25 °C under 170 μmol·m⁻²·s⁻¹ PPF. After 37 weeks, plants at the higher average daily temperature of 27.5 °C (ADT, 30/25 and 25/30 °C) produced more leaves than the lower 22.5 °C ADT. Those grown at 30/25 °C had the largest leaf span and combined length of the new leaves. Plants at 30/25, 25/30, 25/20, or 20/25 °C had 5.0, 4.7, 3.6, and 2.8 new leaves that were 72, 61, 44, and 29 cm in total length, respectively. Warmer nights than days resulted in a small leaf span, reduced leaf growth, and shorter leaves that were particularly noticeable at the 22.5 °C compared with 27.5 °C ADT. Leaves that emerged and grew at the lower ADT had a reduced length to width ratio and a more oval shape. The most striking effect of the 20/25 °C treatment was that 14 of 15 plants bloomed, whereas only five plants at 25/20 °C and none at 30/25 or 25/30 °C produced flowers. Similar results were obtained in a second experiment using 30/20, 20/30, 25/15, or 15/25 °C. After 29 weeks, all plants at 15/25 °C bloomed, whereas none in the other treatments had flowers. Long-term exposure to 15/25 °C resulted in slow leaf production and undesirable small leaves. These results suggest that day and night temperature may both affect growth and flowering of this orchid.

Since Phalaenopsis orchids are CAM plants, learning how they respond to night temperature warmer than the day would help regulate their production. On 1 Apr. 2003, P. amabilis plants were subjected to day/night temperatures at 30/25, 25/30, 25/20, 20/25, 20/15, or 15/20 °C under 140 μmol·m^-2·s^-1 PPF. After 4 months, the total length of new leaves was shorter as a result of fewer and shorter new leaves when nights were cooler than the days and as the average daily temperature declined. More spikes were produced at 25/20 and 20/25 °C than at 20/15 or 15/20 °C. In another experiment, P. amabilis plants were moved to the above conditions on 12 Aug. Plants exposed to 30/25 or 25/30 °C had more leaf growth than at lower temperatures, but no flowering. Plants that were exposed to 25/20 or 20/25 °C spiked in 2 weeks; but plants took 20 and 18 d to spike under 20/15 or 15/20 °C, respectively. Again, as average daily temperature decreased, there was less leaf growth. Cooler day than the night reduced vegetative growth, regardless of temperature. Plants at 25/20 or 20/25 °C had higher flower count (12) than those at 20/15 or 15/20 °C (8). In a third experiment, plants of a large-flowered Doritaenopsis hybrid spiked at 22–24 d when exposed to 25/20 or 20/25 °C, whereas 30-33 d were needed to spike under 20/15 or 15/20 °C. In a fourth experiment, a Doritaenopsis hybrid spiked after 22, 21, or 25 d under 25/25, 25/20, or 20/20 °C. However, 37 d was required to spike under 20/15 °C. These results suggest that the best temperature range for spiking these orchids is 25 to 20 °C and a day/night temperature differential is not needed for spiking when temperature is at or below 25 °C.

This is the first report on how leaf harvest techniques and sulfur may affect leaf initiation and yield of Aloe barbadensis Miller (syn. Aloe vera L.). Two long-term experiments were conducted to determine the effects of supplemental mineral nutrients, severity of harvest, and sulfur application on leaf yield of this species. Plants were each grown in a 38-L pot with or without monthly applications of a 20N–8.6P–16.6K water-soluble fertilizer. In the first experiment, beginning in June 1994 (7 months after initiation), the lower leaves were harvested every 3 months with 12, 15, or 18 leaves remaining per plant. All plants were harvested to 12 leaves at the final harvest in Mar. 1997. Fertilized plants that were harvested to 12 leaves produced 81 leaves each during the 3-year period, whereas those harvested to 15 or 18 leaves each produced 76 leaves. In contrast, each of the nonfertilized plants produced 36 leaves. Fertilization tripled the cumulative weight of harvested leaves over a 3-year period. The initial quarterly and cumulative leaf weights were higher in plants harvested to 12 leaves than those harvested to 15 or 18 leaves. However, this difference diminished and disappeared over time. Fertilized plants harvested to 18 or 15 leaves yielded over 10.8 kg annually, whereas nonfertilized plants with 12 leaves produced an average of 3.5 kg leaves per plant. In the second experiment (with or without fertilizer and micronutrient and 0, 25, 50, or 100 g/pot of powdered sulfur per year), plants responded similarly to fertilization as they did in the first experiment. The added micronutrients (25 g/pot per year) had no effect on plant growth. The highest rate of sulfur resulted in few leaves being harvested and reduced cumulative leaf weight in fertilized plants, but did not affect the number of harvestable leaves or their total weight in nonfertilized plants. Soil pH declined from 7.6 to 4.6 as a result of fertilization regardless of the amount of sulfur being applied. In both experiments, plants that received fertilizer had slight cold injury on the abaxial side of some south-facing leaves. The results suggest the importance of fertilizer application to enhance leaf initiation rate. Plants should be harvested to leave no fewer than 15 leaves, preferably 18, on the plant to maintain high leaf yield.

Cuttings of a thornless mutation of Rosa odorata (RO) and R. multiflora (RM) were rooted in Feb., budded with Rosa `Queen Elizabeth' on 21 Apr. 1987, and planted in 2.6- or 5.2-liter containers. Five weeks after budding, over 50% of the buds on the thornless RO had developed into shoots, while only 4% of the buds on the RM were growing. After an additional 10 weeks, 80% and 60% of the buds on the thornless RO and RM, respectively, had development into shoots. Six months after budding, plants in the 5.2-liter pots produced 1 to 2 folds more flowers than those in 2.6-liter pots. Plants from all four production treatments were planted in a field with alkaline soil on 3 Nov. 1987. During the next four years, plants on RM showed severe chlorosis and had 5% and 45% survival for those produced in 2.6- and 5.2-liter pots, respectively. Those on the thornless RO had 85% and 100% survival when produced in 2.6- and 5.2-liter pots, respectively after four years. Leaves of plants on the thornless RO rootstock had higher concentrations of chlorophyll than those on the RM. However, analyses of leaves did not reveal differences in elemental concentrations among treatments.

Dendrobium Linnapa `No. 3' plants were potted one per 1.75-liter pot with large or small fir bark with or without 30% peatmoss (by volume before mixing). Plants in each medium were fertilized at each or every third irrigation with 1 g·liter⁻¹ of 20N-8.6P-16.6K fertilizer. Neither medium nor fertilization frequency affected flowering date of the first pseudobulb. Adding peatmoss to both types of bark resulted in taller first pseudobulbs. Peatmoss in the large bark promoted the production of more inflorescences and flowers (20) compared to the bark alone (11). Constant fertilization promoted the early emergence and development of the second pseudobulb and resulted in more inflorescences and flowers (21) than intermittent fertilization (12). Vegetatively propagated Phalaenopsis Taisuco Kochdian were planted in 0.5-liter pots with 1) equal volumes of no. 3 perlite, Metro Mix 700, and charcoal (PMC); 2) 100% large fir bark; or 3) 40% medium fir bark, 20% peatmoss, 10% each of no. 3 and no. 2 perlite, 10% vermiculite, and 10% ParGro rockwool (RM). Plants in PMC produced twice the number of new leaves and 1.5 -fold more leaf area than those in the large bark. PMC and RM resulted in similar shoot weights, but the latter enhanced flower count due to more lateral inflorescences. Most (80%) of the roots on plants in the bark were hanging out of the pots, whereas nearly all the roots remained in the pots with PMC. Although medium had no effect on flowering date, flowers on plants produced in PMC and RM were 10% larger than in those on plants produced in bark.

Young, bare-root plants (three leaves, 15 cm in leaf spread) from a vegetatively propagated clone of Phalaenopsis Blume x Taisuco Kochdian were imported in late May and planted in a mix consisting of three parts medium-grade Douglas fir bark and one part each of perlite and coarse peat (by volume) or in pure Chilean sphagnum moss. All plants were given 221 N, 124 P, 515 K, 100 Ca, and 50 Mg (all in mg·L⁻¹) when being irrigated. The total N varied from 0%, 25%, 50%, 75%, to 100% NO₃-N with the balance being NH₄-N. Plants were fertigated when the substrate became dry. For both substrates, as the percentage of NO₃-N increased, plants produced slightly fewer leaves. Regardless of the NO₃-N to NH₄-N ratio, plants grown in moss produced one extra leaf than those planted in the bark mix during an 8-month period. There was a tendency of increasing top leaf length and width as well as the whole-plant leaf spread as NO₃-N increased from 0% to 100% in either substrate. Plants receiving 50% or more NO₃-N in either substrate spiked and flowered 2 weeks earlier than those given 25% or 0% NO3-N. When grown in the bark mix, flower count, flower diameter, and inflorescence length all increased as NO₃-N increased from 0% to 75%. Flower stem (inflorescence, 5 cm from the base) became progressively thicker as NO₃-N increased from 0% to 100%. Only two among the 24 plants grown in moss and receiving 100% NH₄-N bloomed. These results suggest that Phalaenopsis does not grow well with 100% NH₄-N and must be provided with NO3-N at no less than 50%, preferably 75%, of the total N for improved growth and flowering.

Foliar application of 500 or 1000 mg BA or PBA/liter to stock plants of golden pothos [Epipremnum aureum (Linden & Andre) Bunt.] induced axillary bud elongation but did not promote growth of cuttings taken from these stock plants. Cuttings from plants treated with BA + GA₄₊₇, each at 1000 mg·liter^-1, died. Plants grown under 1000 μmol·s^-1·m^-2 had more but smaller leaves than those under 420 μmol·s^-1·m^-2. Cuttings produced under the higher light level grew more rapidly. Leaf area increased while stem length decreased as Osmocote slow-release fertilizer (18N-2.6P-10K) increased from 4 to 16 kg·m^-3. A 24N-3.5P-13.3K water-soluble fertilizer applied at the rate of 0.42 g/500 ml weekly produced the best plants and resulted in the best cutting growth. Cuttings taken from stock plants receiving Osmocote at 4 kg·m^-3 grew slower than those produced at other rates. Placement of cuttings in a mist-propagation bed for 1 or more weeks resulted in an accelerated growth rate relative to nonmisted cuttings. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (1α,2β,4aα,10β) 2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid l,-4a-lactone (GA₄₊₇).

Leaf blades, axillary buds, shoot tips, green bark, suberized bark, or the whole plant of container-grown Hibiscus rosa-sinensis L. cv. Jane Cowl were treated with uniconazole. Applying uniconazole (50 mg·liter^-1) to axillary buds or the green bark below a bud immediately after pruning limited elongation of the first three internodes. Length of the fourth internode was unaffected, regardless of the site of uniconazole application. When used on plants with 24-day-old shoots, uniconazole (40 mg·liter ^-1) applied to the whole plant provided the only satisfactory height control. Leaf size was reduced by nearly 50%, with a concomitant increase (12%) in fresh weight per unit area. GA₃ (50 mg·liter^-1, was more effective in promoting elongation of shoots previously retarded with a drench application of uniconazole (0.1 mg/2.6-liter pot) when applied to the whole shoot, leaf blades, or shoot tip. Application of GA, only to the stein surface, whether old or young, did not effectively encourage the growth of shoots of plants previously treated with uniconazole. Chemical names used: (E)-1-(p-chlorophenyl) -4,4-dimethyl-2-(1,2,4-triazole-1-yl)-1-penton-3-ol (uniconazole); analogue of (1α,2β,4 α,4bβ,10β)-2,4a,7-trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10 dicarboxylic acid 1,4a-lactone (GA₃).

An experiment was initiated to determine the effect of a low N, high P and K fertilizer applied during the flowering season on a hybrid moth orchid (Phalaenopsis TAM Butterfly Blume.). On 1 Sept., plants of flowering size receiving N, P, and K at 100, 44, and 83 mg·L^–1, respectively, from a 20N–8.8P–16.6K soluble fertilizer were given N, P, and K, at 30, 398, and 506 mg·L^–1 (high P), respectively, at each or every fourth irrigation. Control plants continued to receive the 20N–8.8P–16.6K fertilizer. The high P treatments, regardless of the frequency of application, had no effect on the date of emergence of the flowering stem (spiking), anthesis, or flower size. All plants treated with the high P fertilizer had fewer flowers (15 to 19) than the controls (24 flowers). Continuous application of adequate N appears to be more important than low N and increased P for optimal flowering. In a separate experiment using the same hybrid orchid, terminating fertilization completely on 1 Sept., 29 Sept., or 27 Oct. or when the flowering stems were emerging (1 Oct.) reduced flower count (≤19 vs. 24). Flower longevity was reduced by 12 d when fertilization was terminated on 1 Sept. Flower size was unaffected by any treatment in either experiment. Discontinuing fertilization prior to late November reduced flower count. Withholding fertilization for extended periods resulted in red leaves, loss of the lower leaves, and limited production of new leaves.