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Timothy K. Broschat and Kimberly K. Moore

In two experiments, chinese hibiscus (Hibiscus rosa-sinensis), bamboo palm (Chamaedorea seifrizii), areca palm (Dypsis lutescens), fishtail palm (Caryota mitis), macarthur palm (Ptychosperma macarthurii), shooting star (Pseuderanthemum laxiflorum), downy jasmine (Jasminum multiflorum), plumbago (Plumbago auriculata), alexandra palm (Archontophoenix alexandrae), and foxtail palm (Wodyetia bifurcata) were transplanted into 6.2-L (2-gal) containers. They were fertilized with Osmocote Plus 15N-3.9P-10K (12-to14-month formulation) (Expt. 1) or Nutricote Total 18N-2.6P-6.7K (type 360) (Expt. 2) applied by either top dressing, substrate incorporation, or layering the fertilizer just below the transplanted root ball. Shoot dry weight, plant color, root dry weights in the upper and lower halves of the root ball, and weed shoot dry weight were determined when each species reached marketable size. Optimal fertilizer placement method varied among the species tested. With the exception of areca palm, none of the species tested grew best with incorporated fertilizer. Root dry weights in the lower half of the root ball for chinese hibiscus, bamboo palm, and downy jasmine were greatest when the fertilizer was layered and root dry weights in the upper half of the root ball were greatest for top-dressed chinese hibiscus. Weed growth was lower in pots receiving layered fertilizer for four of the six palm species tested.

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Timothy K. Broschat and Kimberly K. Moore

Zonal geraniums (Pelargonium ×hortorum) from seed and african marigolds (Tagetes erecta), which are known to be highly susceptible to Fe toxicity problems, were grown with I, 2, 4, or 6 mm Fe from ferrous sulfate, ferric citrate, FeEDTA, FeDTPA, FeEDDHA, ferric glucoheptonate, or ferrous ammonium sulfate in the subirrigation solution. FeEDTA and FeDTPA were highly toxic to both species, even at the 1 mm rate. Ferrous sulfate and ferrous ammonium sulfate caused no visible toxicity symptoms on marigolds, but did reduce dry weights with increasing Fe concentrations. Both materials were slightly to moderately toxic on zonal geraniums. FeEDDHA was only mildly toxic at the 1 mm concentration on both species, but was moderately toxic at the 2 and 4 mm concentrations. Substrate pH was generally negatively correlated with geranium dry weight and visible phytotoxicity ratings, with the least toxic materials, ferrous sulfate and ferrous ammonium sulfate, resulting in the lowest substrate pHs and the chelates FeEDTA, FeDTPA, and FeEDDHA the highest pH. The ionic Fe sources, ferrous sulfate and ferrous ammonium sulfate, suppressed P uptake in both species, whereas the Fe chelates did not. Fe EDDHA should be considered as an effective and less toxic alternative for the widely used FeEDTA and FeDTPA in the production of these crops.

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Sven E. Svenson and Timothy K. Broschat

The root distribution of seedlings of Acoelorrhaphe wrightii, Carpentaria acuminata, Chrysalidocarpus lutescens, Livistona chinensis, Phoenix roebellenii, and Washingtonia robusta were grown in nontreated containers or in containers treated on their interior surfaces with 25, 50 or 100 g CU(OH)2/1. Seedlings of all species grown in treated containers had reduced circling or matted roots at the container wall-growing medium interface. The distribution of root dry weight and root length was species specific, and was significantly influenced by the rate of copper hydroxide applied. Copper treatment did not induce visual signs of copper toxicity, nor differences in shoot growth, nor differences in the number of higher-order lateral roots.

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Sven E. Svenson and Timothy K. Broschat

The influence of copper hydroxide [Cu(OH)2] application to interior container surfaces on root growth at the container-medium interface was studied using Carpentaria palm [Carpentaria acuminata (H. Wendl. & Drude) Becc.]. Cu(OH)2 (0, 100, 200, or 400 g) was mixed with one liter of either white latex house paint, or NuFilm-17 surfactant, and applied to all surfaces inside 0.5 liter containers. Plants were grown in untreated containers, in containers treated with paint or NuFilm-17 only, or in containers treated with Cu(OH)2 in paint (100 g rate only) or NuFilm-17 (100, 200 or 400 g per liter). When applied in paint or NuFilm-17, Cu(OH)2 reduced root growth at the container-medium interface, controlling the circular growth pattern commonly observed in container-grown plants. Controlling circling root growth at the soil-container interface did not influence shoot or root dry weight, but did reduce total root length. Application of Cu(OH)2 with paint was unsightly, while application with NuFilm-17 was almost unnoticeable.

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Timothy K. Broschat and Monica L. Elliott

Foxtail palms (Wodyetia bifurcata Irvine) were grown in 6.2-L containers using a 3 calcitic limestone gravel: 2 coir dust (by volume) substrate to induce Fe chlorosis. Plants were treated initially and 2 and 4 months later with soil applications of FeDTPA, FeEDDHA, FeEDTA+FeHEDTA on vermiculite, FeEDTA+FeDTPA on clay, ferric citrate, ferrous ammonium sulfate, ferrous sulfate, ferrous sulfate+sulfur, or iron glucoheptonate at a rate of 0.2 g Fe/container. Similar plants were treated initially and 2 and 4 months later with foliar sprays of FeDTPA, FeEDDHA, ferric citrate, ferrous sulfate, or iron glucoheptonate at a rate of 0.8 g Fe/L. After 6 months, palms receiving soil applications of FeEDDHA, FeEDTA+FeHEDTA on vermiculite, FeDTPA, or FeEDTA+FeDTPA on clay had significantly less chlorosis than plants receiving other soil-applied Fe fertilizers or untreated control plants. Palms treated with foliar Fe fertilizers had chlorosis ratings similar to untreated control plants. Palms with the most severe Fe chlorosis also had the highest levels of leaf spot disease caused by Exserohilum rostratum (Drechs.) K.J. Leonard & E.G. Suggs. Neither chlorosis severity nor leaf spot severity was correlated with total leaf Fe concentration.

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Kimberly A. Klock-Moore and Timothy K. Broschat

Growth of hand-watered and subirrigated `Ultra Red' petunia (Petunia ×hybrida Hort.) and `Super Elfin Violet' impatiens (Impatiens wallerana Hook.f.) plants were compared when grown using four controlled-release fertilizer rates and four fertilizer placements in the pot. Furthermore, the amount of NO3-N leached from hand-watered plants was compared to amount captured by subirrigation system. Before planting, Osmocote (14N-6.2P-11.6K) (4 month release) was either topdressed (TD), layered in the middle of the pot (M), layered at the bottom of the pot (B), or incorporated throughout (I) the substrate at 1.25, 2.5, 5.0, or 7.5 kg·m-3 (oz/ft3). Shoot dry mass of petunia plants was similar between both irrigation systems and among the four fertilizer placements. Subirrigated petunias fertilized with 2.5 kg·m-3 had similar shoot dry mass as hand-watered petunias fertilized with 7.5 kg·m-3. Hand-watered impatiens had greater shoot dry mass than subirrigated impatiens. Hand-watered impatiens also had greater shoot dry mass in pots with fertilizer at TD, M, or I than with fertilizer at B, but no difference in growth was observed in subirrigated impatiens among the different fertilizer placements. Finally, significantly more NO3-N was leached from hand-watered plants than was captured with the subirrigation systems.

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Timothy K. Broschat and Sven E. Svenson

Heliconia stricta Huber `Dwarf Jamaican' were grown in 10-liter containers under full sun or 50% shade for 1 year, and H. caribaea Lamarck `Purpurea' were grown in an open field for 2.5 years. Rhizomes were soaked for 1 hour before planting or plants were sprayed with 30 μm DCPTA after two leaves had emerged. Heliconia stricta grown under full sun produced more inflorescences than those grown under 50% shade, and DCPTA-treated plants grown under shade produced more pseudostems and were taller than control plants. DCPTA-treated H. caribaea produced more pseudostems per plant than control plants during their first year, but differences in the number of pseudostems and inflorescences during subsequent years were not significant. Chemical name used: 2-(3,4-dichlorophenoxy)triethylamine (DCPTA).

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Timothy K. Broschat and Monica L. Elliott

Container-grown mexican fan palm (Washingtonia robusta) and queen palm (Syagrus romanzoffiana) transplanted into a field nursery having phosphorus (P)-sufficient and P-deficient soils were treated at the time of planting with four commercial microbial inoculants (each containing arbuscular mycorrhizal fungi, alone or with other microbial components or fertilizers), two fertilizers, or nothing (control). All but the control palms received applications of an 8N–0.9P–10K palm fertilizer every 3 months for 2 years. None of the treatments improved growth over the control in the P-deficient soil. In the P-sufficient soil, none of the microbial inoculants improved growth over that of similarly fertilized noninoculated palms. Discrepancies were observed regarding nonmycorrhizal fungi and bacteria present in the microbial inoculant products. The type and quantity of these microbes listed on the labels of the microbial inoculant products did not necessarily match the type and quantity actually detected in the products.

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Monica L. Elliott and Timothy K. Broschat

A commercially available microbial inoculant (Plant Growth Activator Plus) that contains 50 microorganisms, primarily bacteria, was evaluated in a soilless container substrate to determine its effects on root bacterial populations and growth response of container-grown plants at three fertilizer rates. The tropical ornamental plants included hibiscus (Hibiscus rosa-sinensis `Double Red'), spathiphyllum (Spathiphyllum `Green Velvet') and areca palm (Dypsis lutescens). The bacterial groups enumerated were fluorescent pseudomonads, actinomycetes, heat-tolerant bacteria, and total aerobic bacteria. Analysis of the inoculant before its use determined that fluorescent pseudomonads claimed to be in the inoculant were not viable. The plant variables measured were plant color rating, shoot dry weight and root dry weight. Only hibiscus shoot dry weight and color rating increased in response to the addition of the inoculant to the substrate. Hibiscus roots also had a significant increase in the populations of fluores-cent pseudomonads and heat-tolerant bacteria. From a commercial production point of view, increasing fertilizer rates in the substrate provided a stronger response in hibiscus than did addition of the microbial inoculant. Furthermore, use of the inoculant in this substrate did not compensate for reduced fertilizer inputs.

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Alan W. Meerow and Timothy K. Broschat

Growth of Hibiscus rosasinensis L. `President' under daily irrigation and decreasing irrigation frequency was compared in a 5 pine bark : 4 sedge peat : 1 sand (by volume) medium amended further with 0%, 10%, 20%, or 30% (by volume) Axis, a kiln-fired diatomaceous earth granule. Half of each substrate treatment also was drenched three times with Agroroots, a kelp extract. Shoot and root dry weights were compared after 4.5 months of growth. Container media amended with Axis at 10% volume yielded hibiscus plants with higher shoot dry weights than nonamended media. Root-zone drenches with Agroroots increased shoot dry weights of plants subjected to decreasing irrigation frequency and grown without Axis, but did not significantly affect plants receiving daily irrigation. Shelf-life effects of Axis treatment revealed that all plants reached the permanent wilting point 5 days after cessation of daily irrigation. Both products may allow container plant production with less irrigation. Further tests should be conducted with a broader range of species.