Diseases caused by soilborne pathogens are a major limitation to field grown nursery production. The application of cover crops for soilborne disease management has not been widely investigated in a woody ornamental nursery production system. The objective of this study was to explore the impact of winter cover crops usage on soilborne disease management in that system. Soils from established field plots of red maple (Acer rubrum L.) with and without winter cover crops (crimson clover (Trifolium incarnatum L.) or triticale (× Triticosecale W.)) were sampled following the senescence of the cover crops. Separate bioassays were performed using red maple cuttings on inoculated (with Phytopythium vexans, Phytophthora nicotianae or Rhizoctonia solani) and non-inoculated field soils. The results indicated that winter cover crop usage was helpful for inducing soil disease suppressiveness. There was lower disease severity and pathogen recovery when the cover crops were used compare to the non-cover cropped soil. However, there were no differences in maple plant fresh weight and root weight between the treatments. The rhizosphere pseudomonad microbial population was also greater when the cover crops were used. Similarly, the C:N ratio of the soil was improved with the cover crop usage. Thus, in addition to improving soil structure and reducing erosion, cover crops can provide improved management of soilborne diseases. Therefore, stakeholders can consider cover crop usage as an alternative sustainable management tool against soilborne diseases in field nursery production system.

Root zone temperature (RZT) in nursery containers commonly exceeds ambient temperature during the growing season, negatively impacting crop growth and quality. Black nursery containers absorb radiant heat resulting in excessive RZT, yet other types of containers and different substrates can moderate RZT. We conducted studies in Tennessee and Alabama to evaluate the effects of container type and substrate on RZT and growth of ‘Green Giant’ arborvitae (Thuja standishii × plicata ‘Green Giant’). Trade gallon arborvitae were transplanted into black, white, or air pruning containers filled with pine bark (PB) or 4 PB: 1 peatmoss (v:v) (PB:PM). Plants grown in PB:PM were larger and had greater shoot and root biomass than plants grown in PB, likely due to increased volumetric water content. Plant growth response to container type varied by location, but white containers with PB:PM produced larger plants and greater biomass compared with the other container types. Root zone temperature was greatest in black containers and remained above 38 °C and 46 °C for 15% and 17% longer than white and air pruning containers, respectively. Utilizing light color containers in combination with substrates containing peatmoss can reduce RZT and increase substrate moisture content thus improving crop growth and quality.

Container-grown nursery crops are commonly exposed to root zone stress due to inadequate moisture and supraoptimal root zone temperature (RZT). Compost substrates can improve water and nutrient retention but plant responses can vary due to physical and chemical properties. Dark color containers absorb solar radiation through the container side wall leading to excessive heat buildup in the substrate, yet white containers can reduce RZT. Compost substrates and container color were examined for effects on RZT and growth of “Green Giant” arborvitae (Thuja standishii × plicata “Green Giant”). “Green Giant” arborvitae were transplanted into white or black containers (11.3 L) filled with a pine bark substrate (PB) or PB mixed with compost (C) at two different proportions [PB:C (9:1) and PB:C (7:3)]. White containers reduced maximum RZT by up to 7 °C and RZT remained above 38 °C for only 3% of the time compared to 21% of the time in black containers. Shoot growth increased over 50% in white containers compared to black containers. Compost increased substrate volumetric water content (VWC), increased shoot growth by up to 24%, and reduced total irrigation volume by up to 40%. Utilizing white containers for minimizing RZT and compost-amended substrates to maintain adequate VWC can improve root and shoot growth and overall crop quality while reducing nursery production inputs.

Early season monitoring of nutrient stress is important in red maple (Acer rubrum L.) and flowering dogwood (Cornus florida L.) to optimize management practices and ensure healthy crop production in containers. Two different irrigation systems (drip and overhead irrigation) were used in this study. Two rates (low and high) of controlled-release fertilizer were used with no fertilizer as a control treatment. Data were recorded for plant height, stem diameter, substrate pH and electrical conductivity (EC), chlorophyll content, normalized difference vegetation index (NDVI), visual observation of plant quality, and leaf nutrient content. The results of this study showed that the increase in plant height and stem diameter was greater among the fertilized maple tree, whereas no differences were observed in the flowering dogwoods for an increase in plant height. NDVI was greater for drip irrigation for both fertilizer rates in both red maples and flowering dogwoods. A positive correlation of 73% to 83% was observed for red maples and 79% to 83% was observed for flowering dogwoods between handheld NDVI and unmanned aerial vehicle-mounted NDVI sensors. In red maple, a high fertilizer rate resulted in greater substrate pH, whereas in flowering dogwood, no differences were observed. Varied responses were observed among the treatments for nutrient content; however, both rates of fertilizer application were sufficient for both tree species. Drip-irrigated red maples had higher nitrogen and phosphorous content, whereas nitrogen content was higher in both irrigation systems in flowering dogwoods. This study provides useful insights into understanding the effect of nutrient stress on tree growth and the application of sensing technology for the monitoring and early detection of nutrient stress in container-grown nursery crops.

Weed control is critical in cutting propagation to maximize root growth and liner quality, but hand weeding is time consuming and not cost efficient. Pre-emergence herbicides are widely used in container-grown nursery crop production, but concerns of potential phytotoxicity have limited widespread use in propagation. Mulches are a viable alternative for weed control but few products have been evaluated in propagation. Five pre-emergence herbicides and five mulches were evaluated for rooting stem cuttings of three nursery crop species and for control of four weed species. Mulches were applied (0.8 cm depth) prior to sticking cuttings while pre-emergence herbicides were applied (low labeled rate) two weeks after sticking cuttings. Rooting percentage, root dry weight, and shoot dry weight were not affected by pre-emergence herbicide or mulch, except for butterfly bush (Buddleja davidii ‘Nanho Blue’) which was severely injured when treated with the pre-emergence herbicide isoxaben. Oxyfluorfen + oxadiazon provided excellent control of all tested weed species and has potential to be used in propagation of a number of crops. Mulches did not provide adequate weed control, but increased application depth may enhance efficacy and should be further evaluated.

Newly up-potted ‘Soft Touch’ Japanese hollies (Ilex crenata ‘Soft Touch’) were grown in Mobile, AL in 1.5 L containers to evaluate the effects of growth from black or white container colors and container spacing (jammed or spaced) in relation to root zone temperature. Two treatments, container color and container spacing, were evaluated and root ratings were reported. At termination, an interaction was observed in growth from 43 to 141 days after potting between container color and spacing. Both white container treatments and the black-jammed treatment experienced 36% and 21% more growth than black-spaced plants. Root ratings for white containers (jammed and spaced) were 42% greater than for black-spaced. Black-jammed root ratings were 25% greater than black-spaced. Black-spaced containers experienced the greatest number of time intervals over the critical temperature of 39 °C when compared to other treatments. Results suggest that ‘Soft Touch’ holly may be grown at final spacing when using white containers and have little impact from elevated root zone temperatures.