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There has been recent speculation in trade journals that landscape fabrics, while doing a excellent job of weed control, may have a detrimental effect upon ornamental plant growth. A study is in progress to investigate the manner in which applied landscape fabric affects soil aeration, soil temperature, and water infiltration rate over a period of 18 months. The experimental design is a split-plot with main plots identified as composted or non-composted areas. Within each main plot, the design is a randomized complete block with four blocks and three treatments per block (control, organic mulch, landscape fabric + organic mulch). Each plot has been planted with herbaceous perennials so as to allow analysis of treatment effects upon plant growth. Re-dox potential is measured on a weekly and infiltration rate is measured on a biweekly basis. Soil temperature within plots is monitored on a continuous basis. Preliminary results suggest that landscape fabrics have a detrimental effect on soil aeration and that this likely has a adverse effect upon plant growth. An attempt will be made in this study to contrast any adverse effects of landscape fabric use with the obvious benefits offered by increased weed control.
Two experiments investigated the relationship of light and temperature in seed germination of Fraser fir [Abies fraseri (Pursh) Poir.]. Irradiation during the warm portion of 9/15 hr thermoperiod of 20/10C and 30/20C increased germination percentages after 42 days, and the degree of stimulation depended on the timing of the light exposures. A 1-hr exposure was most effective during the latter part of the warm portion of the thermoperiods, and varying the time of irradiation had the greatest effect at 20/10C. The involvement of phytochrome in this photomorphogenic response was ascertained by demonstration of red/far-red reversibility.
Vegetative shoots were forced in the greenhouse from excised stem (branch) sections of dormant Japanese maple (Acer palmatum Thunb.), red maple (Acer rubrum L.), and sugar maple (Acer saccharum Marsh.). Softwood shoots generated in this way were used as stem cuttings in a subsequent adventitious rooting study. Data indicate that maple shoots can be forced using this technique, but that both the percentage of stem sections forming shoots and the number of shoots produced are highly variable among both species and clones. Whereas Japanese and red maple formed shoots on >50% of stem sections, shoots were generated on only 20% of sugar maple stem sections. Significant variability was also observed in rooting response, with red maple shoots rooting at much higher percentages (60%) than either Japanese maple (26%) or sugar maple (15%).
Development of this software was initiated after receipt of a USDA Higher Education Challenge Grant. The visually realistic software, which uses digital photography as a software base, will serve as an effective and cost-efficient means through which students in landscape horticulture programs can improve their skills in estimating job costs prior to entering the job market. The software will allow students, while in a classroom setting, to visualize a job site from various perspectives, determine the tasks (landscape installation/landscape maintenance) that must be accomplished, and calculate an estimate taking into account direct costs (materials, labor, equipment), indirect costs (overhead), and profit. The interactive nature of the software will allow students to compare their estimates with one of known accuracy generated simultaneously by the computer. Incorporation of this software into academic curricula should increase prospects of long-term success for the many students who plan to start their own landscape horticulture businesses soon after graduating from college and university programs.
Studies were conducted to investigate the effects of season (timing), IBA application, genotype, crown position, type of cutting (straight vs. heel), cutting length, and stock plant age upon adventitious rooting of stem cuttings of eastern redcedar (Juniperus virginiana L.). Genotype had a strong influence on percent rooting, root count, and root length of 4-year-old trees. With trees of this age, percent rooting was maximized (87%) with hardwood cuttings taken in January and treated with 5000 ppm IBA. Crown position from which cuttings were collected did not influence rooting. Straight cuttings, with or without a light wound, rooted at a significantly higher percentage (78%) than heel cuttings (52%). With 30-year-old trees, cuttings from the lower third of the crown rooted at a significantly higher percentage (67%) than cuttings from the middle third (43%). Better rooting was obtained with straight (68%) than heel (47%) cuttings. Cutting length affected rooting, with root count and length highest in longer cuttings. Increased tree age reduced rooting, although cuttings from 40-year-old trees retained substantial rooting capacity. Chemical name used: 1 H-indole-3-butyric acid (IBA).
Hardwood stem cuttings of eastern redcedar (Juniperus virginiana L.), taken from containerized stock plants fertilized weekly with 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N, were treated with 7500 ppm IBA and placed under intermittent mist for 12 weeks. Foliar starch and sucrose concentrations within cuttings at time of excision were significantly correlated with percent rooting and root length, respectively. Of the mineral nutrients analyzed (N, P, K, Ca, Mg, Mn, and B), only B and K were significantly correlated with rooting response. A threshold N level (20 ppm), applied weekly, maximized rooting; higher concentrations decreased response. Although N fertilization of stock plants affected adventitious rooting, there were no significant correlations between foliar N levels and measures of rooting response. Chemical name used: 1 H- indole-3-butyric acid (IBA).
Seeds of `Dawn Carpet' and `Little Bright Eye' annual vinca [Catharanthus roseus (L.) G. Don] were subjected to 32 treatments, arranged as a four × four × two factorial. For each cultivar, seeds were exposed to one of four temperatures (15, 20, 25, or 30C) during the 8-hour (day) and 16-hour (night) portions of the cycle. Within each temperature regime, half the seeds of each cultivar were irradiated for 1 hour daily, and the other half remained in constant darkness. Final germination percentages were suppressed at 15C day or night temperatures; at temperatures ≥20C, there were no significant differences between treatments. Heat input (daily degree hours) was a controlling factor in germination; different temperature cycles with equivalent numbers of daily degree hours had similar effects on germination response. There was a strong interaction between temperature and irradiation regime for both cultivars. Irradiating seeds for 1 hour/day reduced final germination percentages under cool (15C) conditions; response was not adversely affected when seeds at 15C were germinated in darkness. In a second experiment, seeds at 25C were exposed to daily photoperiods of 0, 1, 2, 4, 8, 12, or 24 hours. Germination percentages obtained in darkness and at photoperiods ≤12 hours were equivalent. Twenty-four-hour photoperiods suppressed germination compared to all other irradiation treatments.
Containerized seedlings of eastern redcedar (Juniperus virginiana L.) were fertilized weekly for 175 days with a solution containing 50 ppm P, 150 ppm K, and either 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N. Plant height, stem diameter, and shoot and root dry weights increased asymptotically with applied N; 640 ppm N diminished response. Growth after 175 (height, stem diameter) and 180 (shoot and root dry weights) days was optimal (90% of maximum) at N concentrations of 115, 155, 230, and 105 ppm, respectively, 1.5% foliar N optimized height growth. Foliar concentrations of N, P, and K increased in treated plants over the duration of the experiment, while Ca, Mg, and Mn decreased or remained constant. Starch concentration of fertilized plants decreased sharply after initiation of the experiment, but controls showed little change during the first 120 days. Sucrose concentration remained constant over the summer but increased sharply in late fall. At 180 days, foliar concentrations of starch, sucrose, hexose, N, P, K, and B increased asymptotically with applied N; concentrations of Ca, Mg, and Mn decreased.