Popular press articles report that consumers often experience inconsistent results with retail potting media; however, few reports in the popular or scientific literature have quantified the variability in media properties. The purpose of this study was to assess the variability in physical and chemical properties among different brands of retail potting media and within certain brands. Twenty-four different packages of branded media, and multiple packages of five brands, were acquired from nine regional and national retail chain stores located in the Salt Lake City, Utah, area. Samples were analyzed for five physical and nine chemical properties. The coefficients of variation (cvs) among brands for initial gravimetric water content, bulk density, porosity, water retention, and air space were 85%, 74%, 21%, 59%, and 44%, respectively. The cvs among brands for saturated media (SM) pH, SM extract electrical conductivity (EC), nitrate-nitrogen (NO3-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), total carbon (C), total nitrogen (N), and C:N ratio were 18%, 81%, 132%, 153%, 96%, 78%, 71%, 36%, 45%, and 49%, respectively. Only one of the 24 brands met all published standards for chemical properties of premium media. Thirteen of the brands did not meet standards for NO3-N; 12 did not meet standards for pH; and six did not meet standards for EC. There was more variation in physical and chemical properties among brands than within a brand of media. Label information describing media composition was not consistent with certain physical and chemical properties. No recommendations can be made which would allow consumers to select media that meets published standards. These results indicate better awareness of and/or adherence to standards is needed by the retail media industry to improve product quality and consistency.
There is extensive variability in physical and chemical properties among brands of retail potting media. The purpose of this study was to assess variability in seed germination and plant growth responses among and within brands. Twenty-four different brands of media, and multiple bags of five brands, were purchased at nine retail stores. Tomato (Lycopersicon esculentum) seeds were germinated in 11 different brands of media and in media from different bags of four of the same brands. Marigold (Tagetes erecta) and petunia (Petunia×hybrida) were grown to flowering in 10 brands of media. Germination varied significantly among media brands and among bags of one of the brands. Plant performance also varied significantly, with several of the brands producing plants with few flowers, long times to flowering, and low shoot and root dry weights even though all treatments received uniform applications of a complete fertilizer solution three times per week. Few relationships could be discerned between individual physical and chemical properties of the media and plant performance. Results indicate improvements in quality among brands and quality control within brands are needed in the retail potting media industry. Quality assessment tools emphasizing plant performance could improve overall media quality.
The authors investigated salinity tolerance of four intermountain western United States native (Penstemon palmeri, Mirabilis multiflora, Geranium viscosissimum, and Eriogonum jamesii) and four common (Echinacea purpurea, Lavandula angustifolia, Leucanthemum ×superbum ‘Alaska’, and ×Penstemon mexicali ‘Red Rocks’) ornamental herbaceous perennials. Each was irrigated with a solution containing 2 CaCl2 : 1 NaCl (m ratio) at salinity levels of 0 (control), 1000, 3000, and 5000 mg·L−1 during two 8-week experiments. They measured weekly visual quality and gas exchange and final shoot and root dry weights. Mirabilis multiflora, L. ×superbum, and L. angustifolia maintained high visual quality and 100% survival across salinity levels. However, dry weights for L. ×superbum decreased at salt levels ≥ 3000 mg·L−1 in both experiments and for L. angustifolia in one experiment. Mortality rates of 12% to 100% were observed for the remaining five species irrigated with 3000 and 5000-mg·L−1 solutions. Visual quality of P. palmeri, G. viscosissimum, and E. purpurea varied with time of year the experiment was conducted, with low visual quality associated with high temperatures and light intensities, whereas dry matter and gas exchange responses to salinity were similar between the two experiments. Penstemon ×mexicali and E. jamesii exhibited high mortality, low visual quality, and low gas exchange in the case of E. jamesii at high salinity treatments regardless of when experiments were conducted. Based on visual quality responses, M. multiflora, L. ×superbum, and L. angustifolia are relatively more salt tolerant, and P. ×mexicali and E. jamesii are relatively more intolerant, than the three other species. Penstemon palmeri, G. viscosissimum, and E. purpurea exhibited intermediate tolerance to salinity with acceptable quality during periods of cool temperatures and lower light intensities.
Low water landscapes are increasing popular and important in the urban areas of the Intermountain West (IMW). Perennial wildflowers are an essential part of low water landscapes, and are a dominant plant type in IMW native habitats. We compared pot-in-pot (PIP) vs. conventional above-ground (CAG) production of six IMW native wildflower species, Mirabilismultiflora, Aquilegia caerulea, Penstemon palmeri, Polemonium foliosissimum, Sphaeralcea grossularifolia, and Penstemonstrictus in #1 (4-L) containers. Media temperature, container-plant water loss, stomatal conductance, and growth were measured during two production cycles per year over 2 years. Growing medium temperatures in the PIP system averaged 10 °C cooler than in the CAG system. Consistent with cooler growing media, overall water loss of PIP-grown plants averaged 10% lower than plants grown in the CAG production system. Lower growing media temperatures apparently affected transpiration, as stomatal conductance was about 60% higher in the PIP system as compared to the CAG-grown plants. The integrated effect of lower growing media temperatures on plant performance resulted in about one-third greater top and root growth for plants growing in the PIP system compared to those in the CAG system. Pot-in-pot production may be an economically suitable nursery system for producing IMW native perennial wildflowers by reducing water loss and enhancing growth.
Although salinity is becoming an increasing concern for landscape plants in many areas of the West, few studies have been carried out to evaluate salinity responses of ornamental plants, especially herbaceous perennials. We investigated salinity tolerance of four traditionally grown and four Intermountain West native ornamental herbaceous perennials. Penstemo×mexicali `Red Rocks', Leucanthemum×uperbum `Alaska', Echinacea purpurea, Lavandula angustifolia, Geranium viscosissimum, Eriogonum jamesii, Penstemon palmeri, and Mirabilismultiflora were irrigated with water containing a mixture of 2 CaCl2: 1 NaCl at salinity levels of 0.33 (tap water control), 2.2, 5.4, and 8.3 dS·m-1 for 8 weeks. Growth, visual quality, and gas exchange were assessed. Mirabilis multiflora and L.×uperbum `Alaska' showed high salt tolerance based on visual quality. No noticeable leaf necrosis was observed for either species at any salinity level. However, over the 8-week period, growth rates for L. superbumwere reduced by 35%, 58%, and 72% compared to the control for the 2.2, 5.4, and 8.3 dS·m-1 salinity levels, respectively. The decrease in growth did not reduce visual quality. Growth rates for M. multiflora were slightly higher than the control for the 2.2 and 5.4 dS·m-1 salinity levels and dropped about 20% at the highest salinity level. Echinaceapurpureashowed the lowest tolerance to salinity, as evidenced by substantial margin burn at all salinity levels as well as high mortality; all plants in the highest salinity treatment died.
We investigated drought responses of Echinacea purpurea, Gaillardia aristata, Lavandula angustifolia, Leucanthemum ×uperbum `Alaska', Penstemonbarbatus`Rondo', and Penstemo×mexicali `Red Rocks' established in a 10-gal pot-in-pot system in northern Utah. Plants were irrigated at frequencies of 1, 2, or 4 weeks between June and Sept. 2004. Osmotic potential, gas exchange, visual quality, leaf area, and dry biomass were assessed. In a confined root zone, P. barbatusshowed the greatest tolerance to drought, avoiding desiccation by increasing root: shoot ratio and decreasing transpiration as water became more limiting. Plants maintained high visual quality throughout the study and experienced little wilt, burn, or dieback. However, P. barbatus above-ground biomass was reduced by 15% for the 2-week treatment and by 40% for the 4-week treatment. Alternatively, G. aristata and L. superbum displayed drought avoidance mechanisms, dying back when water was limiting and resprouting after they were watered. Above-ground biomass declined by 50% and 84% for G. aristata and 47% and 99% for L. superbum, respectively, for the 2- and 4-week treatments. Root mass was affected similarly for both species. However, transpiration remained high for all treatment levels. Leaf burn and reduction in above- and below-ground biomass were also evident for E. purpurea at the 2- and 4-week treatments, but results were not as pronounced as for G. aristata and L. superbum. Overall, P. barbatusexhibited the greatest drought tolerance while maintaining an acceptable appearance. G. aristata, contrary to expectations, did not exhibit drought tolerance with a confined rooting volume, suggesting that it avoids drought in landscapes by means of deep rooting.
A cooperative program to recognize water-wise plants for Utah landscapes was developed by 10 horticulture and water organizations throughout the state. Representatives from each of the organizations met to develop a plant list containing woody and ornamental species that were attractive in the landscape, water conserving, adapted to the climate, and available in the industry. A yellow tag with the words “water-wise plant” outlined by the state of Utah was designed by the committee and used to identify the plants. Tags were provided at no cost to garden centers due to the funding of the organizations. A survey conducted at the end of the first season gave very favorable results. Sixty-seven percent of the participating nurseries indicated they would “definitely” participate in the program again, and 27% indicated they “probably” would participate. The Water-Wise Plant Tagging Program serves as a model of how universities, governmental agencies, and private businesses can work together to accomplish a common goal.