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Michael P. Harvey and Mark H. Brand

Studies initiated in Spring 1998 analyzed the influence of division size, shade, and temperature on the growth rate of the ornamental grass Hakonechloa macra `Aureola' in nursery-container production. To determine the optimum division size for production, container-grown stock plants were used to make early spring divisions of four sizes (1-2, 4-6, 8-10, and 12-15 buds). Divisions were established in 325-ml pots for 1 month before being transplanted to 3.7-L nursery containers. Plants were grown outdoors and received topdressed 17-6-10 slow-release fertilizer (containing micronutrients) and drip irrigation from June through September. Average leaf area, shoot number and bud count increased linearly as division size increased, but average height remained the same between each treatment. Plants of all division sizes exhibited healthy growth, with 50% of the plants in the 4-6 buds/division treatment growing to marketable size compared to 45%, 35% and 15% in the 8-10, 12-15, and 1-2 buds/division treatments, respectively. Four shade densities (0%, 30%, 50%, and 70%) were tested to determine which promoted optimum growth. As shading increased, average shoot number per plant decreased, average height and shoot length increased and bud count remained the same. To determine the optimum growing temperature for Hakonechloa, divisions were grown in 325-ml pots under four different day/night temperatures (15/10, 21/16, 27/22, and 33/28 °C) for 12 weeks in growth chambers. Plants were fertigated daily with a 5-25-5 liquid fertilizer. Average bud count, leaf area, plant height, plant width, shoot length, and shoot number increased as temperature increased to 27/22 °C, then decreased significantly beyond this temperature optimum.

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Michael P. Harvey and Mark H. Brand

Studies conducted in 1998 and 1999 analyzed the influence of division size, nutrition, and potting medium pH on the growth rate of Hakonechloa macra `Aureola' in nursery-container production. For each study, divisions were made from container-grown nursery stock in late March, then established in 325-mL pots in a greenhouse prior to being transplanted to 3.7-L nursery containers in late May. Grass plants were grown outdoors, under 30% shade density cloth, with drip irrigation from June through September, and, excluding plants in the nutrition study, received top-dressed 17-6-10 slow-release fertilizer containing micronutrients. To determine the optimum division size for production, divisions of four sizes were made (based on one to two, four to six, eight to 10, or 12 to 15 buds per plant). There was a significant division size effect on bud count, leaf area, plant weight, width, and shoot count only when comparing the two lowest division sizes with the two highest. Treatment effects were insignificant among divisions containing one to two and four to six buds, or between eight to 10 and 12-15 buds. Both the larger two sizes produced marketable plants; therefore, divisions with eight to 10 buds are recommended for a schedule aimed at producing salable Hakonechloa over one growing season. The smallest division class is believed to be the more efficient size when one merely wishes to increase plant stock. In a separate study, a factorial trial testing ppm fertilizer (28, 56, 112, 224, and 448 ppm N) and N-P-K formulation (1-1-1, 2-1-2 and 4-1-4) did not generate significant differences between formulations. Plants were fertigated once a week, and EC levels were monitored bi-weekly from leachate collected in drainage saucers. Plant responses to N rates suggest that electrical conductivity levels be kept around 2.5 mS·cm-1 from a 112 ppm N fertilizer (EC can go as high as 4.0 mS·cm-1 with 224 ppm N). It was evident H. macra `Aureola' prefers acidic soil in production. When lime was not included in the potting mixture (a control treatment equating to a pH of about 4.5), leaf area, bud count, and shoot number doubled relative to the three lime treatments (2, 6, and 16 g lime/L of media, or 3.4, 10.1, and 26.9 lb/yard3).

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Michael P. Harvey and Mark H. Brand

Hakonechloa macra Makino 'Aureola' is an ornamental, shade tolerant landscape grass that grows slowly and commands high prices. Hakonechloa plants grown from four initial division sizes, of 1-2, 4-6, 8-10, or 12-15 tiller buds, were evaluated following a complete growing season (105 days). Based on visual observation, we rated 100% of plants grown from the two larger division sizes to be salable compared with only 30% of those from divisions containing 4-6 growing points, and none from the smallest division size. However, divisions of 1-2 tiller buds produced twice as many new shoots and tiller buds per initial tiller bud as did larger division sizes. To produce salable plants in one growing season, results suggest the use of 8-10 tiller bud divisions, but for propagation and increase of stock material, where it is important to obtain the greatest number of new growing points per initial growing point, use of the smaller division sizes is indicated. Hakonechloa plants were grown under shading densities of 0%, 30%, 50%, or 70% provided by polypropylene shade cloth. Shading increased overall growth and improved the appearance and leaf color of Hakonechloa, but at 70% shade density, plants appeared languid and open. For this reason, 50% shading is recommended for nursery production of Hakonechloa macra 'Aureola'.

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Michael P. Harvey and Mark H. Brand

Optimum growing temperatures were determined for Hakonechloa macra Makino 'Aureola' and Chasmanthium latifolium (Michx.) Yates, two shade-tolerant ornamental grasses found naturally in regions differing in temperature conditions. Plants were grown in four growth chambers at average daily temperatures of 13, 19, 25, and 31 °C for 12 weeks. After the treatment period, plants were destructively harvested to quantify growth and shoot tissue concentrations of N, P, K, Ca, and Mg. Optimal growth occurred at an average daily temperature of 25 °C for both grasses, but Hakonechloa was better able to tolerate lower temperatures. Hakonechloa died at 31 °C, while Chasmanthium growth was only slightly reduced at this temperature. Nutrient concentrations in shoot tissue for both species increased with increasing temperatures up to the temperature supporting optimal growth. At 13 and 19 °C, the concentrations of most nutrients were higher for Hakonechloa than for Chasmanthium, possibly reflecting the greater growth (higher nutrient demand) of Hakonechloa at lower temperatures. When compared on a per plant basis at each grasses' optimum temperature for growth, Chasmanthium has a much greater demand for nutrients than Hakonechloa, reflecting the greater growth potential of Chasmanthium.

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Michael P. Harvey, George C. Elliott, and Mark H. Brand

The shade-tolerant, variegated grass Hakonechloa macra `Aureola' is a valuable ornamental. In an experiment replicated in two growing seasons, Hakonechloa plants were fertilized at each irrigation (fertigation) with factorial combinations of three fertilizer formulations (N:P molar ratios 5:1, 10:1, and 20:1) at five N concentrations (2, 4, 8, 16, and 32 mmol·L-1), along with an unfertilized control, to determine the effect of N:P ratio and N concentration on vegetative growth and to establish fertility guidelines for production. Root dry weight and tiller bud growth increased slightly as N:P ratio increased. Fertilizer N concentration of 16 mmol·L-1 promoted the most shoot growth, whereas the number of tiller buds and root growth were greatest at 2 and 4 mmol·L-1 N. No interaction occurred between N:P ratio and fertilizer concentration. Results indicate that an N concentration of 8 mmol·L-1, with an N:P ratio of 10:1 or 20:1 is optimal for production of Hakonechloa. At this fertilizer concentration, the mean electrical conductivity of extracts obtained by a solution displacement extraction (pour-through) procedure was 2.3 ± 0.45 dS·m-1 (mean ± standard deviation). Tissue nutrient concentrations of N, P, K, Ca, and Mg were (in mg·g-1): 24.0, 2.8, 14.3, 2.1, and 2.1, respectively. In a concurrent study, Hakonechloa plants were grown in pine bark: peat: sand mix with dolomitic lime added at 0, 1.2, 3.6, and 9.5 kg·m-3 producing pH ranging from ≈4.5 to 7.2. Growth of Hakonechloa was greatest with no lime (pH 4.5) and declined markedly as the rate of lime increased. Concentrations of N, P, and K in shoot tissue were greatest at a pH between 4.5 and 5.6 (0 and 1.2 kg·m-3 dolomitic lime). These findings clearly support recommending production of Hakonechloa in soilless potting mix with pH ≈4.5 and constant fertigation with N at 8 mmol·L-1.