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Calvin Chong

The first weed disc (Weed Guard) was introduced to Ontario in the early 1980s. They were made of semirigid plastic similar to 45-rpm records. Small holes allow water to penetrate but weeds germinating on the substrate often grow through them. In the 1990s, we obtained 85% reduction of container weeds using discs made from geotextile fabric (Mori Guard) or foam (similar to polyfoam used for container winter protection). The foam disc tended to curl upward at the edges, become easily windblown, and tended to partially expose the surface of the container mix. During the past 15 years, we have annually reused the same fabric discs (now unavailable due to high unit cost), and have tested various other weed discs, including several new-generation types and also the Mori Weed Bag. The new-generation discs are fabricated from materials such as fabric (Tex-R Geodisc), pressed peat moss (Biodisc), corrugated cardboard (Corrudisc), and plastic (Enviro LID). Both Tex-R Geodisc and Enviro LID were as effective or better in controlling weeds than weekly hand-weeding, herbicides, or the Mori Guard fabric disc. The Mori Weed Bag, a patented black polyethylene sleeve with prepunched holes fitted around the container like a florist's plant prepared for market, is used effectively and almost exclusively by one Ontario nursery. We also tested two types of insulated blanket covers, which when placed around the ball of above-ground container-grown trees, prevented weed growth during the summer and also protected the root ball against cold during the winter. We introduced the garbage bag sleeve, the ultimate no-weed method for pot-in-pot tree culture, which also reduces water use and frequency of irrigation. Due to factors such as under-performance, insufficient demand, and/or high costs, only certain discs are currently manufactured: Weed Guard, Tex-R Geodisc, Biodisc, and Enviro LID. The Mori Weed Bag is available but not the insulated blankets.

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Calvin Chong

During the past 20 years, the Ornamental Nursery Research Program at the former Horticultural Research Institute of Ontario (now part of the University of Guelph) has been conducting applied research dealing with environmentally friendly and sustainable nursery production practices with emphasis on container production. The use of farm, industrial, and consumer waste by-products as amendments in nursery substrates has been a major focus. The program has evaluated hundreds of potting mixes derived from individual or combined, raw or composted waste by-products including spent mushroom compost, turkey litter compost, paper mill sludge, municipal waste compost, corrugated cardboard, apple pomace, wood chips from pallets, pulverized glass, and various types of tree barks. With few exceptions, all the above waste by-products tested under our cultural conditions provided acceptable to excellent container-growing media, often in amounts exceeding 50% and sometimes up to 100% by volume in No. 2 containers (6 L), even despite initially elevated and potentially toxic contents of soluble salts [expressed in terms of electrical conductivity measured up to 8.9 dS·m-1 in 1 substrate: 2 water (by volume) extracts] in many of the substrates. A key to these successful results is that salts leach quickly from the containers to benign levels (∼1.0 dS·m-1) with normal irrigation practices. High initial pH in most waste-derived substrates (up to 8.9) has had little or no discernible effect on growth of a wide assortment of deciduous nursery species. By-products such as paper mill sludge and municipal waste compost with soluble salts contents typically ranging from 0.8 to 2.0 dS·m-1, also provide acceptable rooting media provided salts are leached before use to values ≤0.2 dS·m-1. The porosity and aeration characteristics of waste-derived substrates tend to be comparable to, or better than, those of bark.

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Calvin Chong* and Peter Purvis

Silverleaf dogwood (Cornus alba L. `Argenteo-marginata'), forsythia (Forsythia × intermedia Zab. `Lynwood Gold'), and weigela (Weigela florida Bunge A.DC. `Red Prince') were grown in #2 (6-L) containers filled with 100% bark or bark mixed with 20%, 40%, or 60% (by vol.) each of raw paper mill sludge (RB group), composted paper mill sludge (CB group), a proprietory paper mill sludge-derived compost (PB group), and municipal compost (MB group). A fifth substrate group (MH) consisted of 100% hemp chips or hemp chips mixed with the same rates of municipal compost. The containers were trickle-irrigated and fertilized with a controlled-release fertilizer. Among the bark-amended groups, growth was highest for dogwood and forsythia with PB, increasing dramatically and peaking at ca. 40% rate (68 and 94 g/plant top dry weight, respectively). Growth of these species was intermediate with MB and CB and least with RB, increasing to rates ≥ 50% in these groups, except for a nonsignificant response of dogwood to RB. Growth of weigela increased equally with PB and MB substrates up to ca. 40% (117 g/plant), but was unresponsive to rates of RB and CB. With the hemp-amended MH group, growth of all three species increased to rates ≥ 50% (62, 93, and 116 g/plant for dogwood, forsythia, and weigela, respectively). Growth of the three species over most rates of all substrate groups was similar to, or exceeded, that in 80% bark: 15% peat: 5% topsoil, a proven nursery mix. Top dry weight of all three species was positively correlated with soluble salts concentrations in the substrates at planting after first irrigation (0.23-1.72 dS·m-1, range over all substrates) and at various intervals during the season.

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Calvin Chong* and Adam Dale

Terminal stem cuttings of seven woody nursery species [boxwood (Buxus sempervirens L. `Green Mountain'), coralberry (Symphoricarpus × chenaultii Rehd. `Hancock'), lilac (Syringa velutina Kom.), Peegee hydrangea (Hydrangea paniculata Siebold. `Grandiflora'), purple-leaf sandcherry (Prunus × cistena N.E. Hansen), Rose-of-Sharon (Hibiscus syriacus L. `Lucy'), and winged spindle-tree (Euonymus alata Thunb.) Siebold. `Compacta')] were rooted under outdoor lath (50% shade) and mist in leached rooting media consisting of 0, 20, 40, 60 and 80% by volume of 2-year-old grape pomace amended in binary mixtures with sphagnum peat, perlite or composted bark. Rooting performance, expressed in terms of percent rooting, mean root number per rooted cutting, and length of the longest root per cutting, was regressed on level of pomace. When there were differences due to amendments, most species rooted better with perlite than with bark and peat, to a lesser degree, due in part to more favourable air-filled porosities with perlite (33% to 42%) than with bark (29% to 37%) or peat (24% to 35%). With boxwood, increasing level of pomace up to ≈60%, especially when mixed with perlite or peat, resulted in substantial increases in rooting percentage, root number and length. All three rooting parameters of winged spindle-tree decreased linearly with increasing level of pomace with perlite or bark. The effect of pomace level on other species varied between these extremes with little or no negative effect on rooting.

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Calvin Chong and Peter Purvis

Plug-rooted liners of deutzia (Deutzia gracilis), dogwood (Cornus alba `Argenteo-marginata'), forsythia (Forsythia×intermedia `Lynwood Gold'), and ninebark (Physocarpus opulifolius) were grown in 6-L containers. There were 36 different treatment substrates formulated in factorial combinations: two types of paper mill sludge (raw or composted) each at three rates (25%, 33%, or 50%, by volume) mixed with one of three sources of municipal waste compost (cities of Guelph, Toronto, or Waterloo; 25%, 33%, or 50%), and the remainder consisting of one of two base supplements (pine bark or 1-year-old wood chips; 50%, 33%, or 0%). The containers were trickle-irrigated and fertilized with a controlled-release fertilizer. Dogwood (no treatment interaction and responding only to the main effect of compost sources) grew equally well with Toronto and Waterloo composts, but less well with the Guelph compost. Ninebark tended to grow better with Toronto compost, intermediate or similar with Waterloo compost, and least with Guelph compost. Forsythia grew equally well in all bark-based substrates, regardless of sludge type and rate or compost source. With wood-chip-based substrates, however, forsythia grew better with Waterloo than with Guelph compost, and better with raw than with composted sludge when mixed with Toronto compost. Deutzia responded similarly to most substrates, but grew marginally better with raw than with composted paper sludge when Waterloo or Toronto compost was present. Despite these differences in species responses, all plants were of marketable size at the end of the season. There was no sign of nutrient toxicity or deficiency due to any of the substrates.

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Calvin Chong and Bob Hamersma

Stem cuttings of seven deciduous landscape shrubs {silky dogwood (Cornus amomum Mill.), coralberry (Symphoricarpos orbiculatus Moench), Peegee hydrangea (Hydrangea paniculata Siebold. `Grandiflora'), Bridal-wreath spirea [Spiraea ×vanhoutteii (C. Briot) Zab.], spirea (Spiraea ×bumalda Burv. `Goldmound'), fragrant viburnum (Viburnum farreri Stearn), and weigela [Weigela florida (Bunge) A. DC. `Variegata Nana']} were rooted under mist in 100% perlite (no sludge) medium or in mixtures of 10%, 20%, 30%, 40%, 50%, or 60% (v/v) of raw paper mill sludge and perlite. There was a large linear reduction in percent rooting of viburnum (from 80% to 21% with 0% and 60% sludge, respectively) in response to increasing level of sludge. The mean root count per cutting also was significantly decreased, from 14 to 5. However, the length of longest root was unaffected. In contrast, all the other species ranked good to excellent in rooting, regardless of the level of sludge. Differences, if any, in rooting performance were not of practical significance.

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Calvin Chong and Bob Hamersma

Terminal stem cuttings of four evergreens [arborvitae (Thuja occidentalis L.), `Calgary Carpet' juniper (Juniperus sabina L.), `Hetzii' juniper (Juniperus virginiana L.), and Tamarix juniper (Juniperus sabina L.)] and four deciduous {Amur maple (Acer ginnala Maxim.), common lilac (Syringa vulgaris L.), ninebark [Physocarpus opulifolius (L.) Maxim.], and viburnum (Viburnum farreri Stearn)} woody landscape shrubs were treated with 0%, 0.1%, 0.3%, or 0.8% IBA mixed in talc or with 0%, 0.25%, 0.5%, 1.0%, or 1.5% IBA dissolved in 95% ethanol, radiator antifreeze (95% ethylene glycol), or windshield washer fluid (47.5% methanol). None of the carriers were phytotoxic to the cuttings. Cuttings treated with IBA in radiator antifreeze or windshield washer fluid produced rooting in most taxa similar to those treated with IBA in ethanol. Cuttings of the evergreen taxa produced more roots with liquid than with talc IBA at similar concentration ranges. There were some differences in rooting performance (expressed in terms of percent rooting, mean root count per rooted cutting, and length of the longest root per cutting) of taxa to solvents and IBA concentrations. However, such differences, if any, were generally small or commercially insignificant, except for ninebark, which rooted optimally with no IBA and exhibited a large reduction in percent rooting with increasing IBA concentrations in windshield washer fluid. Chemical name used: indolebutyric acid (IBA).