Abstract Thirty-two rain-garden-engineered filter-bed substrates (EFBS) resulting from combinations of two substrate bases (sand and slate), two organic matter amendments [composted yard waste (CYW) and pine bark (PB)], two combination methods (banding and incorporation), and four combination amounts [2.5 cm/5%, 5.1 cm/10%, 7.6 cm/15%, and 10.2 cm/20% (by vol.)] were evaluated using three plant species (Betula nigra L. ‘Duraheat', Monarda fistulosa L. and Panicum virgatum L. ‘Shenandoah'). The impact of particle size distribution, saturated hydraulic conductivity (Ksat), volume of effluent, evapotranspiration, EFBS composition, and plant growth on water movement within a rain garden was determined. Sand EFBS maintained a numerically lower Ksat compared to slate EFBS regardless of composition. Using CYW and banding reduced effluent volume and increased evapotranspiration. Each EFBS was also evaluated for its ability to support plant growth and nutrient uptake. Shoot dry weight and shoot nutrient content (nitrogen and phosphorus) trends were similar and were highest for all species when grown in sand amended with banded CYW. Higher levels of total soluble nitrogen (TSN) were in the effluent from CYW compared to PB, regardless of substrate base. Sand generally had lower concentrations of TSN and PO4−3-P present in the effluent than slate. Index words: bioretention cell; saturated hydraulic conductivity (Ksat); effluent volume; effluent nutrient concentration; evapotranspiration; particle size distribution; total soluble nitrogen; ortho-phosphate; nitrate; ammonium. Species used in this study: ‘Duraheat' river birch (Betula nigra L.); wild bee balm (Monarda fistulosa L.); and ‘Shenandoah' switch grass (Panicum virgatum L.).

The relationship of specific surface to particle diameter and calcium carbonate (CaCO3) content of limestone was examined. Limestones obtained from 20 North American quarries were wet sieved into eight particle diameter fractions (600 to ?38 mu m). Specific surface of particles was measured in each fraction following the Brunauer-Emmett-Teller theory. The range in specific surface across the 20 sources varied from 74-fold in the coarsest particles (600-300 mu m) to 20-fold in the finest particles (?38 mu m). The pattern of specific surface progressing from the coarsest to the finest particles varied radically between sources. The relationship between specific surface and CaCO3 content was likewise very weak. While particle diameter and CaCO3 equivalent remain the traditional measurements for defining limestone for field production, specific surface provides additional information valuable to define the stricter neutralization capacities of limestone for soilless root substrates.

Twelve rain gardens were constructed to analyze the effectiveness of three different filter bed substrates to support plant growth and remove nutrients from urban stormwater runoff. The filter bed substrates included a sand-based substrate (sand) composed of (v/v/v) of 80% washed sand, 15% clay and silt fines, and 5% pine bark; a soil-based substrate (soil) composed of (v/v) 50% sandy loam soil and 50% pine bark; and a slate-based substrate (slate) composed of (v/v) 80% expanded slate and 20% pine bark. Coarse particles (6.3 to 2.0 mm) in the soil-based substrate created a large-pore network that conducted stormwater more quickly into and through the rain garden than slate or sand as evidenced by the high infiltration and saturated hydraulic conductivity values. Sand had good overall retention of pollutants except nitrogen (N) possibly as a result of the very small percentage (5%) of organic matter and low cation exchange capacity (CEC). Soil had the lowest remediation of phosphorus (P) and highest concentration of P in its effluent and was similar in N removal efficiency to slate. Slate had the best retention of N and P. Overall, all three substrates functioned in reducing the quantity of pollutants in urban stormwater runoff; yet, the impact of substrate on remediation appeared to lessen by Season 2 because there were few differences between substrate in the effluent nutrient concentration. Substrate did not affect shoot or root growth. Eleven of the16 species (B. nigra,B.'Duraheat',M. virginiana,M.'Sweet Thing', I. virginica, I. 'Henry's Garnet', J. effusus, P. 'Shenandoah', H. angustifolius, H. 'First Light', and E. purpureum subsp. maculatum) grew well in the rain gardens and could be used as rain garden plants.

Water is one of the planet's most precious non-renewable resources, yet it has become one of the most polluted and neglected. The number one cause of water pollution in many watersheds originates from non-point sources, such as storm water runoff. Rain gardens trap storm water runoff and remove pollutants. To effectively remove pollutants, storm water runoff must be held in the rain garden substrate as long as possible. Since a substrate's water retention characteristics are defined by it particle size distribution, rain garden filter bed substrates are best classified as horticultural substrates. Filter bed substrates sand and slate were tested with composts (biosolids, food, and yard wastes) added. All composts increased course and decreased fine particles when added to sand. Sixty percent amendments of all composts gave the greatest increase in medium particles in sand. For slate, food and yard composts decreased fines, biosolids increased fines, and enzyme had no impact on fines. All composts had no or little impact on medium and coarse particles when added to slate. A 20% addition of all composts resulted in optimal saturated hydraulic flow and greater retention of simulated stormwater runoff in both the sand and slate based substrates. Sand with an initial particle size distribution of 83% fine, 17% medium and 0.25% coarse particles should be amended to achieve a final particle size distribution of 67% fine, 30% medium, and 2% coarse. The coarser textured slate (31% fine, 44% medium, and 24% coarse) should have a final particle size distribution of 30% fine, 48% medium, and 22% coarse particles.

Both water flow through and retention time (Ksat) in filter bed substrates in combination with plants remediate polluted stormwater runoff in rain gardens. Two commonly used rain garden filter bed substrates were evaluated: sand (80% washed sand, 15% clay and silt fines and 5% pine bark v/v/v) and slate (100% expanded D-tank slate). Regression analyses showed that slate banded with increasing amounts of composted yard waste (CYW) resulted in a linear decrease in Ksat while, increasing amounts of pine bark (PB) banded resulted in a linear increase in Ksat. The amount of organic matter added to sand did not alter Ksat. Particle size distribution regression analyses showed that increasing the amount of CYW incorporated in sand caused coarse (>2.0 mm) size particles to increase linearly while, there was a quadratic effect on medium (0.5-2.0 mm) and fine (<0.5 mm) size particles. Amendment amount of CYW or PB with slate had no impact on particle size distributions in the coarse, medium, or fine particles.

The composting of organic waste materials using earthworms yields the value-added product vermicompost (VC). The use of VC as a growing substrate amendment for containerized horticultural crop production is a sustainable nutrient management approach which can benefit crop production by providing plant nutrients and improving crop growth. In order to provide nutrient management guidelines for users of VC amended container substrates, a study was conducted to quantify nutrients supplied to substrates solution and to develop nutrient release kinetic models to predict plant available nutrient based on total initial loading rates. Experimental treatments and results were expressed on a volume basis (4-L container) for easy interpretation and application by growers of crops in containers.

Vermicomposting of pig manure is a waste management approach that has been shown to be economically and technologically feasible and yields a value-added end product, vermicompost (VC), that contains plant-available nutrients. The objective of this study was to determine if conventional nursery crop inputs could be replaced by commercially available VC (derived from pig manure) for production of Hibiscus moscheutos ‘Luna Blush’ L. (hibiscus). Hibiscus was grown in 3.8-L containers containing pine bark amended with 11% sand (by vol.), 1.8 kg·m−3 dolomitic limestone, and 0.9 kg·m−3 micronutrient package (PBS) or pine bark amended with 20% VC (by vol.) (20VC). Plants were topdressed with one of three controlled-release fertilizers (CRF) containing only nitrogen (N); N and potassium (K); or N, phosphorus (P), and K. The four treatments included PBS with 17–6–12 (PBS + NPK), 20VC with 17–6–12 (20VC + NPK), 20VC with 17–0–12 (20VC + NK), and 20VC with 17–0–0 (20VC + N). The PBS + NPK treatment, which was supplied with conventional nursery crop nutrient inputs (limestone, sulfated micronutrients, and CRF containing NPK), served as the control treatment to represent the industry standard. All treatments were irrigated to maintain a leaching fraction (LF = volume leached ÷ volume applied) of 0.24. Daily inorganic nitrogen (IN-N) and dissolved reactive phosphorus (DRP) effluent contents were determined. Plants were harvested at 35 and 56 d after potting (DAP). Total plant nutrient contents of P, calcium (Ca), magnesium (Mg), and sulfur (S), iron (Fe), manganese, zinc (Zn), copper (Cu), and boron (B) were equivalent or greater for all three 20VC treatments compared with PBS + NPK. However, total plant K content of 20VC + N was less than 20VC + NPK, 20VC + NK, and PBS + NPK. Regardless of lower K content in the 20VC + N treatment, all three 20VC treatments had equivalent total plant dry weight and number of flowers. Furthermore, all three 20VC treatments averaged 58% and 40% greater plant dry weight than PBS + NPK at 35 and 56 DAP, respectively, and 93% more flowers than PBS + NPK at 56 DAP. All three 20VC treatments had similar IN-N and DRP effluent contents. However, the three 20VC treatments averaged 4.3× more IN-N effluent content and 59× DRP effluent content than PBS + NPK. The nutrient use efficiencies for all treatments were similar, in which nitrogen use efficiency ranged from 9% to 15% and phosphorus use efficiency ranged from 7% to 12%. In conclusion, this source of VC provided equivalent or greater P, Ca, Mg, S, Fe, Zn, and Cu but less K for plant uptake compared with the industry standard (control) treatment and produced larger plants with more flowers than the control. This suggests that dolomitic lime, sulfated micronutrients, and P can be eliminated as substrate additives.

Production of containerized nursery crops requires high inputs of water and mineral nutrients to maximize plant growth to produce a salable plant quickly. However, input efficiencies remain below 50% resulting in major quantities of water and nutrients leached. This study was conducted to determine if production factors could be altered to increase water and phosphorus uptake efficiency (PUE) without sacrificing plant growth. The effects of a pine bark substrate amendment (clay or sand) and a 50% reduction in both P application rate (1.0 g or 0.5 g) and leaching fraction (LF = effluent ÷ influent) (0.1 or 0.2) were investigated. Containerized Skogholm cotoneaster ( Cotoneaster dammeri Schnied. ‘Skogholm’) was grown on gravel floor effluent collection plots that allowed for calculation of water and nutrient budgets. Pine bark amended with 11% (by vol.) Georgiana 0.25 to 0.85 mm calcined palygorksite-bentonite mineral aggregate (clay) increased available water 4% when compared with pine bark amended with 11% (by volume) coarse sand. Decreasing LF from 0.2 to 0.1 reduced cumulative container influent 25% and effluent volume 64%, whereas total plant dry weight was unaffected by LF. Reduction of target LF from 0.2 to 0.1 reduced dissolved reactive P concentration and content by 8% and 64%, respectively. In a sand-amended substrate, total plant dry weight decreased 16% when 1.0× P rate was reduced to 0.5× P, whereas total plant dry weight was unaffected by rate of P when pine bark was amended with clay. Plant content of all macronutrients, with the exception of N, increased when pine bark was amended with clay versus sand. Reducing P rate from 1.0× to 0.5× increased PUE 54% or 11% in a clay or sand-amended substrate, respectively. Amending pine bark with 11% (by volume) 0.25 to 0.85 mm calcined palygorksite-bentonite mineral aggregate produced an equivalent plant with half the P inputs and a 0.1 LF, which reduced water use 25% and P effluent losses 42% when compared with an industry representative substrate [8 pine bark : 1 sand (11% by volume)].

Pine bark is the most common container substrate in the Southeastern United States nursery industry. Pine bark based substrates provide excellent aeration and a moderate amount of available water (AW), however, they have little water buffering capacity. Thus, frequent irrigation events are required to maintain adequate water. This often leads to low water use efficiency. Current studies have shown reduced water application needs and increased plant stomatal conductance and carbon assimilation when plants were grown in a mineral aggregate amended pine bark substrate compared to pine bark alone. An increase in water buffering capacity was reported which may explain the plant response. Our objective was to determine if increased substrate water buffering capacity could be explained as a function of substrate physical properties. To accomplish this objective, pine bark was amended with a calcined Georgiana palygorksite-bentonite aggregate (0.85–0.25 mm) at 0%, 4%, 8%, 12%, 16%, 20% and 24% (by vol.). Physical properties consisting of total porosity, container capacity, air space (AS), bulk density, AW, and unavailable water (UW) were determined. Soil moisture characteristic curves were determined for amendment rates of 0%, 8%, 12%, 16% and 20% (by vol.). Container capacity and AW increased linearly with increasing amendment rate, whereas UW and AS decreased linearly with increasing rate of mineral aggregate. Substrate moisture characteristic curves showed that more water was retained at greater substrate moisture tensions with increasing mineral aggregate rate, thereby increasing readily available water. Volumetric water content was initially greater at the 0% rate, however it quickly decreased at approximately 2 cm substrate moisture tension below those substrates amended with the mineral. The physical properties of the substrate in association with the inherent zeolitic and absorbed water of the mineral increased water content, resulting in increased buffering capacity which could reduce plant water stress. INTRODUCTION The United States nursery industry is a leading crop sector of U.S. agriculture with 3.97 billion dollars in gross sales in 2003 (USDA, 2004). Nursery inventory consisted of 73% containerized plants, with the Southeastern United States accounting for 41% of the over 7,000 national operations and 34% of the 186,000 ha in production area (USDA, 2004). Pine bark is the standard component of soilless substrate in containerized nursery production in the Southeastern United States. Pine bark was chosen due to its availability, favorable physical properties, and lack of detrimental chemical constituents. A salable Proc. IS on Growing Media Ed.: J.-C. Michel Acta Hort. 779, ISHS 2008 132 plant can be produced quickly in a pine bark substrate associated with high nutrient and water inputs. Pine bark is a relatively inert media with less water holding capacity than a mineral soil. Therefore, water use efficiency is a concern for growers due to increasing local, state, and federal intervention with water use and water availability. Best management practices for containerized plant production introduced in 1997 (Yeager et al., 1997) are becoming implemented widely in the United States, resulting in increased water use efficiency. Increased water use efficiency has been achieved by reducing water volume applied, adjusting water application timing, increasing water application efficiency, and amending soilless substrates. While many of these practices have been adopted by the nursery industry, there has been little change in substrate composition since the introduction of pine bark media due to cost, acceptance, and availability. Calcined or expanded clay and zeolite are alternatives to sand or other inorganic components used in peator pine bark-based soilless substrate (Handreck and Black, 2002; Reed, 1996). Clay mineral aggregate amendments have been studied primarily in peat-based substrates with little research being conducted with pine bark-based media. Warren and Bilderback (1992) compared rates (0, 27, 54, 67 and 81 kg m) of arcillite in a pine bark substrate, reporting curvilinear increases in available water (AW) and growth of Rhododendron sp. ‘Sunglow’ with increasing rates of arcillite. Cotoneaster dammeri C.K. Schneid. ‘Skogholm’ grown in a 14 L container with pine bark amended with 8% (by vol.) of calcined 0.85 to 0.25 mm Georgiana palygorksite-bentonite mineral aggregate required 0.4 liters day less water to grow an equivalent plant (Owen et al., 2003). In addition, stomatal conductance and net photosynthesis were significantly greater in the clay amended substrate compared to an unameded pine bark (Owen et al., 2006). This decrease in water use and increase in stomatal conductance without affecting plant growth was attributed to an increase in water buffering capacity. Clay offers the water buffering capacity found in soil, which is not typically present in soilless substrates due to their relatively inert components. Clays of interest as a soilless substrate amendment are the 2:1 layer phyllosillicate minerals: smectite, palygorskite, and illite. These phyllosillicate minerals are formed in layers composed of one octahedral sheet between two parallel tetrahedral sheets. Clays used in our research are a composite of the minerals: montmorillonite and palygorskite. Montmorillonite, a smectite, is a 2:1 layer mineral with a plate like surface or structure. The water associated with smectite is surface adsorbed or tightly bound interlayer water (Velde, 1992). Palygorskite (syn. attapulgite, Fuller’s Earth, hormite clay) ores occur in the Fuller’s Earth District in southern Georgia and northern Florida. Palygorskite is a silicon (Si) rich mineral that occurs as a 2:1 dioctahedral fibrous or chain-like aluminosilicate that appear as rods. This unique structure allows for the presence of zeolitic water (Velde, 1992). Adsorbed and crystalline water are also associated with this mineral. Crystalline water is a part of the mineral structure and zeolitic water occurs within the minerals capillary pores. The surface of the mineral can also adsorb water through electrostatic forces or hydrogen bonding, creating a hydration shell around an industrial mineral aggregate. Industrial clay minerals require processing before being used in industrial applications such as chemical carrier or barrier clay. The mineral is screened into various particle sizes for use with the most popular size for the agriculture industry falling between 0.85 and 0.25 mm (Moll and Goss, 1997). Industrial clay minerals are dried at approximately 121°C and described as regular volatile material (RVM) (Moll and Goss, 1997). RVM products are soft and have 8 to 12% water by weight. This dried product can be subjected to further heating (≤ 800°C) and classified as a low volatile material (LVM) which is calcined, or fixed, containing 0 to 1% water by weight (personal communication, Robert Goss, Oil-Dri RD Velde, 1992). At the completion of Ca-montmorillonite

Nonpoint source effluent containing nitrate N (NO 3 -N) and phosphorus (P) from containerized nursery production has garnered local, regional, and national concern. Industrial minerals have long been used as absorbents, agrochemical carriers, and barriers to retain heavy metals. Our objective was to determine the effects of a palygorskite–bentonite industrial mineral aggregate on the physical and chemical properties of a soilless substrate and the resulting impact on water and nutrient efficiency. The mineral aggregate had two particle size ranges (0.25 to 0.85 mm or 0.85 to 4.75 mm) in combination with two temperature pretreatments [low volatile material (LVM) or regular volatile material (RVM)]. A representative substrate (8 pine bark:1 coarse sand) of the southeastern United States nursery industry was also included in the study as a control. Cotoneaster dammeri C.K. Schneid. ‘Skogholm’ was grown in all substrates on collection pads that allowed for the quantification of daily influent and effluent volumes to calculate cumulative NO 3 -N, ammonium N (NH 4 -N), and dissolved reactive phosphorus (DRP) loss for 112 days. There was a 13% to 15% decrease in daily water application volume with no effect on Skogholm cotoneaster growth, which equated into a savings of 22 to 26 L per 14-L container in mineral aggregate-amended substrates compared with a sand-amended substrate (control). Mineral aggregate-amended substrates decreased NH 4 -N and DRP effluent 39% and 34%, respectively, compared with the control. In addition, LVM and particle size 0.25 to 0.85 mm reduced effluent DRP compared with the 0.85 to 4.75-mm RVM aggregate. Plant dry weight was unaffected by any of the treatments. Substantial nutrient content reduction in effluent and reductions in water application were achieved with amending pine bark with 0.25 to 0.85 mm LVM industrial mineral aggregate. A 0.25 to 0.85-mm LVM industrial mineral aggregate pine bark-amended substrate reduced effluent DRP and NH 4 -N greater than 40% and reduced water application 15% or 26 L when compared with the industry representative substrate.

Problems of inconsistent initial pH in peat moss-based substrates that are created using standard formulas for limestone additions, and pH drift from the target in those substrates may be due to variations in the CEC and BS of peat moss. This study was conducted to determine whether such variation exists. Sixty-four peat moss samples were obtained from several bogs across Alberta, Canada. Adsorbed cations on each peat moss sample were displaced with hydrochloric acid (HCl), and flushed out with three deionized water washes. The displacing/flushing solution was collected and later analyzed for concentration of bases (Ca, Mg, K, and Na) using atomic absorption spectrometry. After cations were removed, the peat moss exchange sites were saturated with barium acetate [Ba(OAc) 2 ] to displace the H + , which were then collected by a second flushing with deionized water. This second displacing/flushing solution was titrated with measured amounts of NaOH to a phenolphthalein end point. Base saturation and CEC were calculated. There were significant variations in CEC (ranging from 108.12 to 162.25 cmol·kg -1 ) and BS (ranging from 13.52% to 63.97% of CEC) among the peat moss samples. Ca accounted for 78.08% of the BS. For a given peat moss, the higher the BS, the lower the neutralization requirement to achieve a target pH. Also, high CEC peat mosses may have greater buffering capacity than those with low CEC, which may result in less pH drift.

The physical and chemical properties of pine bark yield low water and nutrient efficiency; consequently, an engineered substrate altering the substrate properties may allow greater water and nutrient retention. Past research has focused on controlling the quantity and rate of water and nutrient inputs. In this study, pine bark was amended at 8% (by volume) with a Georgiana palygorksite-bentonite blended industrial mineral aggregate with a particle size of 850 μm-4.75 mm or 300 μm-710 μm to improve water and nutrient efficiency. Each particle size was pretreated at temperatures of ≈140 °C (pasteurized) or ≈390 °C (calcined). The study was a 2 (particle size) × 2 (heat pretreatment) factorial in a randomized complete-block design with four replications. The control was a pine bark substrate amended with 11% sand (by volume). Containers (14 L) were topdressed with 17–5–12 controlled release fertilizer. A 0.2 leaching fraction was maintained by biweekly monitoring container influent from spray stakes and effluent volume measured daily. An aliquot of the daily collected effluent was analyzed for phosphorus (P). After 112 days, tops and roots were harvested, dried, and weighed for dry weight comparisons. Compared to pine bark amended with sand the 300 μm-710 μm particle size mineral decreased mean daily water application by ≈0.4 L/day per container. The calcined mineral reduced P leaching by ≈10 mg of P per container or 60% over the course of the study compared to pine bark: sand. Top and root dry weights were unaffected. These results suggest 300 μm–710 μm calcined mineral provided the most significant decreases in water use and P leaching while growing an equivalent plant.

Abstract Rooted stem cuttings of ‘Skogholm’ cotoneaster (Cotoneaster dammeri ‘Skogholm’) potted into 14.2 liter (#5) containers in a pine bark: sand substrate were used to determine the effects of the nursery floor on plant growth, water use efficiency, substrate and plant canopy temperature, winter protection, and mineral nutrient efficacy. Four nursery floors were evaluated: black plastic, black ground fabric over black plastic, white plastic, and gravel from May 10, 2001, to April 23, 2002. Plants grown on gravel or ground fabric/black plastic had greater top and root dry weights compared to plants grown on white plastic. Water use efficiency was similar across all nursery floors, requiring an average 391 ml (13.2 oz) of water to produce a gram (0.04 oz) of plant material. Net photosynthetic rates of plants grown on black plastic, gravel, or ground fabric/black plastic were significantly greater than cotoneaster grown on white plastic. Plants grown on white plastic had significantly higher plant canopy [1 to 2C (1.8 to 3.6F)] and substrate temperatures [1 to 4C (1.8 to 7.2F)] daily from 1000 HR to 2000 HR throughout the summer months compared to all other nursery floors. Plant canopy and substrate temperatures were unaffected by the nursery floor during the winter months. Nitrogen efficiency was 42% on ground fabric/black plastic, 40% on gravel, 37% on black plastic and 33% on white plastic. Phosphorus efficiency was 53% on gravel, 52% on ground fabric/black plastic, 49% on black plastic and 43% on white plastic.

Abstract Pine bark based substrates, commonly used in the southeastern United States for container nursery crop protection, have low moisture retention properties; therefore, daily irrigation during the growing season is required to maximize plant growth. Current guidelines state that irrigation should occur during the early morning hours (before 1000 HR). However, limited research indicated that multiple application of water each day resulted in significantly more growth compared to early morning application. The objective of these studies was to evaluate the effects of irrigation timing on plant growth, photosynthesis, water utilization efficiency, and substrate temperature. In experiment 1, the daily total volume of irrigation required to maintain 0.4 leaching fraction (LF) in the early morning application (0300, 0500, and 0700 HR) was divided into three equal parts and applied at the following times: 0300, 0500, and 0700 HR; 1200, 1500, and 1800 HR; 0900, 1200, and 1500 HR; and 0500, 1200, and 1900 HR. In experiment 2, the daily total volume of irrigation to maintain 0.15 LF within each timing was divided into three equal parts and applied at the following times: 0200, 0400, and 0600 HR; 0600, 0900, and 1200 HR; 1200, 1500, and 1800 HR; and 0600, 1200, and 1800 HR. Irrigation applied at 1200, 1500, and 1800 HR produced 57% and 69% greater total plant dry weight in experiments 1 and 2, respectively, compared to plants irrigated during early morning hours. Root: top ratio was unaffected by irrigation timing. In both experiments, irrigation applied at 1200, 1500, and 1800 HR had higher water utilization efficiency compare to irrigation applied at 0300, 0500, and 0700 HR or 0600, 0900, and 1200 HR. In experiment 2, plants irrigated at 1200, 1500, and 1800 HR maintained higher rates of net CO2 assimilation and stomatal conductance, and lower substrate temperatures from 1800 to 2200 HR compared to plants irrigated at 0300, 0500, and 0700 HR or 0600, 0900, and 1200 HR.

Abstract The landscape industry uses containerized plant material throughout the year. Thus, traditional spring potting at many nurseries has changed to potting throughout the year. The objective of this study was to determine the effect of potting date and rate of fertilization on plant growth and mineral nutrient content, substrate electrical conductivity (EC) and pH, and winter injury. To complete this objective, rooted stem cuttings of Ilex crenata Thunb. ‘Compacta’ and Viburnum awabuki K. Koch. ‘Chindo’ were potted in Raleigh, NC, July 17, 1998; September 7, 1998; October 29, 1998; March 25, 1999; and May 13, 1999. Two controlled-release fertilizers [Wilbro/Polyon 15N–1.8P–7.5K (15N–4P2O5–9K2O) and Scotts 23N–1.8P–6.6K (23N–4P2O5–8K2O)] were applied at four rates: a split application with 0.5X incorporated at potting and surface application of the remaining 0.5X six months after potting date [X = manufacturers' recommended rate per 3.8 liter (4 qt) container], and 1X, 1.5X, and 2X incorporated at potting. Plant growth and mineral nutrient content were determined one year after initial potting date. Substrate EC and pH were measured monthly. ‘Compacta’ holly and ‘Chindo’ viburnum potted in September or October were larger than plants potted in March regardless of fertilizer and rates of fertilization. In general, holly and viburnum were smaller when fertilized with 0.5/0.5X compared to 1X regardless of fertilizer and date of potting. Within each rate of fertilization, viburnum potted in September had significantly greater N and P content compared to viburnum potted in March or May. Nitrogen and P content were highly correlated to plant dry weight (r > 0.79, P = 0.0001). Mineral nutrient content of holly responded similarly. No plants were injured by winter temperatures regardless of potting date or rate of fertilization throughout the study period. Plants potted in July, September, or October had the highest substrate EC values in March, whereas plants potted in March or May had highest EC values in August regardless of species, fertilizer or rate of fertilization. Substrate pH was unaffected by date of potting, but pH decreased with increasing rates of fertilization.

Japanese cedar, Cryptomeria japonica (Thunb. ex L.f.) D. Don [Cupressaceae Bartling, formerly assigned to Taxodiaceae Warm.] is increasing in popularity as a landscape plant in the eastern United States. A taxonomic study of cultivars grown in the eastern United States was conducted. Forty-five cultivars were recognized. Each cultivar bears synonymy, a quantitative morphological description newly described from field data, herbarium vouchers, references to original literature and observational notes. A glossary of taxonomic terms relevant to Cryptomeria is presented. A taxonomic key is presented for segregation of cultivars that should assist professional plantsmen in identification of taxa cultivated in the eastern United States.