Euphorbia pulcherrima Willd. `V-14 Glory Red', `V-17 Marble', and `Jingle Bells 3' were grown in various peat-based potting media amended with ground, non-composted woody stem core of kenaf (Hibiscus cannabinus L.) and fertilized at every irrigation with a 17N–2.2P–13.8K fertilizer at 300 ppm N. Kenaf is an annual tropical species grown in several Gulf Coast states as a fiber crop. Growth and overall quality of all cultivars was best in media containing 50% to 70% coarse grind of kenaf (by volume) and was similar to a commercial soilless control medium (Sunshine #1, SunGro Horticulture, Inc.). Media containing greater than 70% fine grind kenaf resulted in significantly smaller plants with chlorosis of both lower and upper leaves, and also resulted in undesirable shrinkage of media in the containers. Addition of 19N–2.6P–10K Osmocote to kenaf-amended media at a rate of 3.5 kg·m–3 resulted in significantly better plants with less chlorosis than similar media without Osmocote. Media containing kenaf also resulted in significantly less water-holding capacity than Sunshine #1 and required morefrequent irrigation to sustain the growth of plants.
Lisa Chen Cushman, H. Brent Pemberton, J. Creighton Miller Jr., and John W. Kelly
Simulated shipping (storage) experiments were conducted to determine the effects of shipping temperature and duration on flower longevity and leaf abscission of pot rose Rosa L. `Meijikatar' (= Orange Sunblaze) and `Meirutral' (= Red Sunblaze). In addition, three flower stages (1 = tight bud, calyx not reflexing; 2 = showing color, calyx reflexing, no petals reflexed; 3 = full color, petals beginning to reflex, traditional bud stage) were selected immediately prior to storing plants at 4, 16, or 28 °C for 2, 4, or 6 days. The experiment was conducted during the summer and repeated during the winter. Evaluations were made in an interior environment at 21 °C for both experiments. `Meirutral' exhibited longer poststorage longevity and less leaf abscission than `Meijikatar' in both experiments. Flowers of both cultivars advanced by about one stage during storage at temperatures greater than 4 °C in summer, but developed more slowly in winter. Results from both experiments showed that plants stored at 4 °C had the longest poststorage floral longevity, the best flower quality, and the least leaf abscission, regardless of cultivar, storage duration, or flower stage at the beginning of storage. For plants stored at 16 °C, floral longevity decreased and leaf abscission increased when the duration was longer than 4 days. At 28 °C, flower longevity decreased and leaf abscission increased, especially at durations longer than 2 days. In the winter experiment, there was no leaf abscission on plants placed in the dark at 21 °C and watered during storage treatments lasting up to 6 days. In the summer experiment, the younger the flower, the more it was negatively affected by high storage temperature. Overall, poststorage floral longevity was longer in the summer than the winter experiment.
Oswaldo Macz, Ellen T. Paparozzi, Walter W. Stroup, Terril A. Nell, and Ria Leonard
Research on hydroponically grown mums showed that nitrogen (N) levels applied can be reduced when adequate sulfur (S) is also applied. However, changes in stem length, leaf area, and time-to-fl ower can be affected. Our goal was to evaluate whether reduced N levels in combination with S would affect commercial production and post-harvest longevity of pot mums. `White Diamond' was grown in a peat:perlite:vermiculite medium following a commercial production schedule. N levels applied were 50, 100, 150 and 200 mg/L. S levels were 0, 5, 10, 20, and 80 mg/L. The treatment design was a complete factorial 4 × 5 with 20 treatment combinations. The experimental design was a split-plot with N levels as the whole-plot and S levels as the split-plot factor. Variables measured were plant height, leaf area, days to bud set, days to first color, and days to flower opening. Plants were ship to the Univ. of Florida for postharvest evaluation. Data were analyzed using SAS PROC MIXED AND PROC REG. N and S interactions were significant for all variables measured except flower longevity. Plants receiving 0 mg/L S did not produce inflorescences, had shorter stems, and less leaf area regardless of N levels. Plants receiving 50 mg/L N and some S produced inflorescences, but were of inferior quality to plants receiving 100, 150, and 200 mg/L N. Plants receiving 200 mg/L N and 80 mg/L S showed breakdown of plant architecture. Plants of commercial quality were obtained at 100, 150, and 200 mg/L N in combination with either 5, 10, or 20 mg/L S.
Larry J. Kuhns and Tracey L. Harpster
A study was initiated to determine how well plants would grow in potting media available to consumers through garden centers and national chain stores. Nine media were evaluated. The chemical and physical characteristics were determined, and six geraniums (Pelargonium sp) and six marigolds (Tagetes patula) were grown in each of the media. Three of each six were fertilized, three were not. The plants that were fertilized received 100 ppm N and K and 50 ppm P once a week. Three months after seeding the flowers, flowers and buds on the marigolds were counted and the plants were harvested. Dry weights were determined. Nitrate-N ranged from 6 to 627 ppm, pH from 4.9 to 7.1, phosphorus from 88 to 502 pounds/A, potassium from 1.0 to 6.9 meq/100 g, magnesium from 1.4 to 10.8 meq/100 g, calcium from 5.2 to 30.0 meq/100 g, soluble salts from 20 to 151 mmhos, and CEC from 13.0 to 43.8 meq/100cc. Bulk density ranged from 21 to 53 g/100cc, water holding capacity from 32 to 53 ml/100cc, percent air-pore space from 2.7 to 15.7, and total porosity ranged from 65% to 78%. Unfertilized marigolds weighed between 0.1 and 9.6 g; fertilized marigolds weighed 1.4 to 17.2 g. Unfertilized geraniums weighed between 1.4 and 23.3 g; fertilized geraniums weighed 4.4 to 56 g. There were 1.3 to 16 flowers on unfertilized and 7 to 24.3 flowers on fertilized marigolds.
Timothy S. Prather, James J. Stapleton, Susan B. Mallek, Tarcisio S. Ruiz, and Clyde L. Elmore
A double-tent solarization technique, which accumulates higher soil temperatures than solarization of open fields, was recently approved by the California Department of Food and Agriculture (CDFA) as a nematicidal treatment for container nurseries. Due to the need for broad-spectrum pest control in container nursery settings, this technique was tested to determine its usefulness as an herbicidal treatment. Laboratory-derived thermal death dosages (temperatur × time) for several weed species important in California, including common purslane (Portulaca oleracea), tumble pigweed (Amaranthus albus), and black nightshade (Solanum nigrum), were previously determined and the data were used as guidelines for devising treatment duration in this study. In two field experiments conducted in 1999 and 2000 to validate the laboratory data, moist soil was placed in black polyethylene planting bags [3.8 L (1 gal) volume], artificially infested with seeds of the three test species, and subjected to 0 to 24 hours of double-tent solarization after reaching a threshold temperature of 60 °C (140 °F) (about 1.5 to 2.0 h after initiation of the experiment). In 1999, samples were removed at 2, 4, 20, and 24 hours after reaching the 60 °C threshold, then incubated to ameliorate possible secondary dormancy effects. Seeds failed to germinate in any of the solarized treatments. In 2000, samples were removed at 0, 1, 2, and 6 h after reaching 60 °C. Again, apart from the nonsolarized control treatment, all weed seeds failed to germinate at any of the sampling periods, in accordance with prior laboratory thermal death results. Reference tests to estimate effects of container size on soil heating showed that soil in smaller container sizes (soil volume) reached higher temperatures, and were maintained at high temperature [above 60 °C (140 °F)] for a longer period of time, than larger container sizes. The double-tent solarization technique can be used by commercial growers and household gardeners to effectively and inexpensively produce weed-free soil and potting mixes in warmer climatic areas.
Thomas M. Rathier
Two year-long, factorial experiments were conducted on Rhododendron catawbienses (cv. Roseum elegans) grown in 2.3-liter plastic pots. I) Annual N rates of 0, 0.4, 0.8, 1.6, and 3.2 g/pot were applied as NH4NO3 (SBL) or sulfur-coated urea (SR) to plants potted in a composted hardwood bark (CHB)/peatmoss (P)/sand (S) medium. Plant growth and quality was best at 0.8 g N/pot for SBL and 1.6 and 3.2 g N/pot for SR. II) Annual N rates of 0.8 (SBL) and 2.4 (SR) g/pot were chosen as optimum rates and applied to plants potted in the following media: pine bark (PB)/P/S; CHB/P/S; P/S; and PB/CHB/P/S. Plant growth and N uptake was best in PB/PS. Plant quality was best in P/S. NO3 in leachate did not differ among media, but was greater in SBL. Total N immobilized in media was greater in PB/CHB/P/S. N recovered from SR-treated pots as unused fertilizer did not differ among media. Total applied N recovered was 90% for SBL and 51% for SR.
Zhanao Deng, Brent K. Harbaugh, and Natalia A. Peres
pot-plant producers, homeowners, and landscapers ( Evans et al., 1992 ; Harbaugh and Tjia, 1985 ). The majority of caladiums commercially produced in the world belong to the fancy leaf type, and the most popular color has been white (white center with
Harvey J. Lang
Analysts of potting media for pH and electrical conductivity (EC) can be a useful tool for monitoring the nutritional status of greenhouse grown plants. This research examined the variability associated with procedures involved in the determination of pH and EC in greenhouse potting media. Three commonly used methods, the 1:5 dilution, the 1:2 dilution and the saturated media extract, were examined on several different commercial potting media. Because of the different dilution volumes used, there were significant differences in pH and EC between the three methods for all media tested. Within each method, results varied baaed on whether readings were taken in the slurry, solution phase, or extract, with extracts resulting in consistently higher pH, but lower EC values. There was a significant effect of medium-solution equilibration time on both pH and EC, with variability decreasing after 30 minutes of equilibration. Samples taken from the upper half of pots had higher EC readings than those collected from the bottom half of pots only on plants fertilized with N concentrations greater than 200 ppm. There was also slight variability between the different calibrated instruments used in determining pH and EC. Details of each study along with grower recommendations will be discussed.
Anne K. Carter
In the northeastern United States, vegetable crop classes and growers' meetings are often held during winter months when field demonstrations are impossible. A pot-sized demonstration was set up in the greenhouse in May and Nov. 2002 as a student laboratory to show the effects of season extension materials on the early growth of winter squash. The treatments were black plastic mulch and rowcover, alone and in combination. The treatments were also placed on either a heated [18.3 °C (65 °F)] or unheated germination mat to simulate warmer and cooler spring soils. Butternut squash (Cucurbita moschata) was sown in 10.2 × 10.2 × 11.43-cm (4 × 4 × 4.5 inches) pots in soilless medium. The plants were grown and observed for 30 days, then harvested and weighed. The plants in the greenhouse grew as expected of plants grown under similar conditions in the field. Bottom heat, mulch, and rowcover had an increasingly greater effect on the growth of subsequent leaves as shown by comparisons of leaves 1, 2, and 3. Warmer soils tended to have the greatest effect on all measured parameters, but this was not as obvious in the May experiment as it was in the November experiment. Thus, this pot demonstration can be used in a student laboratory. The pots and plants are small enough to transport to and set up at winter growers' meetings as well.
Eduardo Olate, Doris Ly, George Elliott, and Mark Bridgen
Two butterfly-type cultivars of Alstroemeria were used to evaluate the effect of different dates of propagation and cold storage techniques on the growth and flowering of potted plants. The cultivars used were `Patricia Lynn' and FL-101. Plants were propagated during four different dates of 1997 (weeks 39, 41, 43, and 47) in large nursery pots (3.8 L) or in small nursery pots (1.4 L). Following division, all plants were grown for 4 weeks. After this period of establishment, plants in the large nursery pots were transferred directly to the final growing greenhouse (16 °C nights) and plants in the small pots were refrigerated at 4 °C for 8, 6, 4, or 0 weeks with either complete light or complete dark conditions. Once the cold treatment was accomplished, all plants were transferred on the same date to large nursery pots for finishing with those plants that had been initially propagated in large pots. All plants were cut back on week 3 of 1998. Plants were evaluated for date of harvest, visual evaluation, fresh aerial weight, number and length of flowering stems, and number of florets per flowering stem. Refrigerated treatments delayed the time of flowering when compared to plants that were grown with no refrigeration. Fresh weight and stem length values of plants that were not refrigerated were less than or equal to those of plants that were refrigerated, with the exception of plants that was propagated on week 47. In addition, the number of flowering stems that were produced from plants that were refrigerated was either greater than or the same as plants that were not refrigerated. The presence or absence of light during refrigeration had no effect on subsequent plant growth and development. There were no differences observed among treatments for visual evaluation and number of florets produced per inflorescence. This research demonstrated that potted Alstroemeria plants can be propagated early and stored under cold conditions without these procedures affecting final plant performance, but the process will affect the scheduling of the crop.