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Peat moss is the main component used in soilless greenhouse substrates and is thus in high demand commercially. Due to both perceived environmental and economic concerns associated with peat harvest and production, an increased search for alternative substrates has occurred. A majority of the viable alternatives available to growers are wood-based substrates. These substrates are readily available and could be considered more sustainable, depending on geographic location, than peat moss. One example of these wood-based substrates is eastern redcedar (Juniperus virginiana L.). The objectives of these experiments were to evaluate post-distilled, milled eastern redcedar shavings, in varying volumetric concentrations, as a substrate component, and to compare its effectiveness to a grower's standard peat-lite mix. Petunia ×hybrida Vilm. ‘Celebrity Blue’ and Impatiens walleriana Hook.f. ‘Extreme Violet’ grown in substrates containing up to 40% eastern redcedar product had equal or greater growth index than in the standard peat-lite mix, although bloom count was reduced in one experiment. Therefore, growers could amend their substrates with up to 40% eastern redcedar shavings and see little to no change in marketable plant growth for these two annual species.

Steel slag (SS) is a fertilizer amendment with a high concentration of calcium oxide, and thus capable of raising substrate pH similar to dolomitic lime (DL). Steel slag, however, contains higher concentrations of some nutrients, such as iron, manganese, and silicon, compared to DL. The objective of this research was to determine the effect of SS rate on pH in a substrate composed of 80 pine bark:20 sphagnum peatmoss (v:v), as well as growth and nutrient concentration of butterfly bush (Buddleja davidii ‘Pink Delight’ Franch.). The base substrate was amended with either DL or SS at rates of 0, 0.6, 2.4, 4.8, 9.5, or 14.3 kg·m−3. Substrates were placed into 12-L nursery containers and potted with a single butterfly bush per container. Dolomitic lime amendment resulted in higher substrate pH at rates from 0.6 to 4.8 kg·m−3 while the SS amendment caused a greater increase in pH at rates higher than 4.8 kg·m−3. Butterfly bush responded well to all but the highest SS rate applied. As the rate of SS increased to 14.3 kg·m−3, decreased Mg availability may have reduced shoot growth. Based on the results of this experiment, SS could be used as an alternative to DL. However, incorporation rates would need to be adjusted slightly higher for SS compared to DL to achieve a desired pH in the range of 6 to 6.5.

In an effort to compare yield and time required to remove substrate from roots of liners, Ophiopogon japonicus and Ophiopogon japonicus ‘Nana’ (lilyturf) bare root bibs were potted into 100% aged pine bark, 8: 2 (v: v) pine bark: peat moss, 100% perlite, 100% fine grade Profile™ porous ceramic (Profile™ products LLC, Buffalo Grove, IL), or 100% course grade Profile™ porous ceramic. In a second study Ophiopogon japonicus was potted into 100% aged pine bark, 100% 3/16-inch HydRocks® (Big River Industries Alpharetta, GA), fine grade 100% Profile™, 100% perlite, 100% sand, 8: 2 (v: v) pine bark: peat moss, and 3: 1 (v: v) 3/16 HydRocks®: sand. In the second study, fine grade Profile™ produced the highest number of total bibs per container and bib production was similar to 8: 2 pine bark: peat moss. HydRocks® was similar to pine bark in total bibs per container but was more efficiently removed from roots. Removal of the HydRocks® substrate from plant roots required 50% less time than removal of pine bark: peat moss substrate and 51% less time than removal of pine bark substrate. HydRocks® took 23% less time to remove from roots than fine grade Profile™. Results indicate that clay materials such as HydRocks® and Profile™, when compared to conventional substrates can provide suitable yields while also decreasing labor cost by decreasing time to bare-root.

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.

Water-holding capacity of substrates increased as the proportion of sphagnum peat and coir increased, and coir-based substrates had greater water-holding capacities than comparable peat-based substrates. There were no significant differences between coir and peat-based substrates with respect to bulk density, percent pore space and percent solids. Air-filled pore space and water-filled pore space decreased and increased, respectively, as the proportion of peat and coir increased. ‘Pink Elite’ geranium plants grown in coir-based substrates had greater root fresh weights than those grown in sphagnum-peat based substrates. Greatest root fresh weight occurred in an 80% coir and 20% perlite substrate. Days to flower, height, shoot fresh weight and number of axillary shoots were not significantly different between substrates. ‘Janie Bright Yellow’ marigold and ‘Blue Lace Carpet’ petunia plants had increased heights and shoot fresh weights when grown in coir-based substrates as compared with sphagnum peat-based substrates. Greatest heights and shoot fresh weights of petunia and marigold occurred in an 80% coir and 20% perlite substrate. Days to flower were reduced for marigold plants grown in coir-based substrates.

This study was designed to determine whether differences existed in the amount of Derby (metolachlor and simazine) leached through four substrates used in container production. Substrate compositions (by vol) used in this study were 3:1 redwood bark:sand, 2:1:1 redwood bark:Yolo loam:sand, 3:1 pine bark:sand, and 1:1 composted hardwood bark:pine bark. Substrates were packed into #3 containers, and 4.5 kg ai/ha (4 lb ai/A) of metolachlor and 1.1 kg ai/ha (1 lb ai/A) of simazine were applied to the containers as a granular formulation. Containers were leached with 2.7 cm (1.06 in) of water per day, and leachate samples were collected 0, 1, 2, 4, 8, and 16 days after herbicide application. Both herbicides were detected in the redwood bark:sand leachate on the day of herbicide application, and concentrations increased over time but appeared to level off between day 8 and day 16. Metolachlor and simazine were detected in the redwood bark:Yolo loam:sand leachate 4 days after application, and concentrations of both herbicides increased over time. Metolachlor and simazine were detected in a few leachate samples from the hardwood bark:pine bark and pine bark:sand substrates. Substrate ranking based on the amount of herbicide lost was 3:1 redwood bark:sand >2:1:1 redwood bark:Yolo loam:sand >1:1 hardwood bark:pine bark >3:1 pine bark:sand.