ASHS 2025 Conference

In this study, we evaluated the germination rates of twenty native plant species and their response to cold stratification as well as four chemical solution treatments—water (control), gibberellic acid, smoke water, and gibberellic acid with smoke water. Seeds were evaluated and counted twice a week. Of the twenty evaluated species, sixteen had germination rates over 3%, or 1 seed out of 30. Stratification increased germination by 54% when compared to the control. For chemical treatments, gibberellic acid and gibberellic acid with smoke water were significantly different from the control and increased germination by an average of 47% and 48%, respectively. Six species showed a response to chemical treatment and stratification. Four species showed a response to chemical treatments only, and four species showed a response to stratification only. No growth defects were discovered upon further evaluation after sowing the seed. This study suggested that the combination of stratification with smoke water and/or gibberellic acid has a significant effect on seed germination yield of some native perennials.

Commercial spinach (Spinacia oleracea L.) production is underrepresented in hydroponic production due to inconsistent germination rate, uniformity, and percentage. Seed treatments to enhance germination require tedious decoating of the pericarp or priming with synthetic chemicals. This study was carried out to investigate the effects of plasma activated water (PAW) on spinach seed germination. PAW is generated by applying cold atmospheric plasma to water, resulting in a multitude of direct and indirect chemical reactions at the interface. PAW is rich in reactive nitrogen and oxygen species, and it has been shown to enhance several agricultural processes including seed germination. Seeds of spinach were primed for a set period of time in distilled water (control) or PAW and germinated in petri dishes. After 14 d, seeds that had been primed in PAW for any length of time germinated with greater percentage than control (74.6% and 66.1%, respectively). Optimal priming in PAW was found to be 6 h, yielding a study high germination percentage of 80%. Additionally, seeds primed with PAW improved mean germination time compared to control conditions. This study demonstrates the effectiveness of PAW as a useful tool in seed priming to improve germination.

Kratom (Mitragyna speciosa), a tropical evergreen tree indigenous to Southeast Asia, has gained attention in recent years due to its potential as a natural medicine for pain management and its ability to alleviate symptoms associated with opioid withdrawal. These properties indicate that kratom could be a promising candidate for drug development aimed at addressing the opioid epidemic. Despite growing interest in kratom’s therapeutic applications, its domestic cultivation remains limited, and investigations on vegetative propagation methods are unavailable. The traditional propagation technique, i.e., rooting stem cuttings in greenhouse settings with misting systems, has resulted in inconsistent success and varying quality. To address these challenges and improve propagation efficiency, this study evaluated the use of an aeroponic system to root kratom cuttings in controlled environments under various conditions. Stem cuttings were cultured in aeroponic devices under three photoperiods provided by light-emitting diode (LED) lights in environmentally controlled rooms. Rooting percentages reached 87, 88, and 90% in six weeks under 10-, 14-, and 24-hr photoperiods, respectively. Cuttings rooted three days earlier under 24-hr compared to those rooted at 10- and 14-hr photoperiods. On the other hand, the 14-hr photoperiod led to the highest root dry mass,109% and 14% greater than the 10- and 24-hr treatments, respectively. Furthermore, propagules rooted under 14-hr photoperiod had the highest total root length, 92% and 33% greater than those rooted under 10- and 24-h photoperiods. Additionally, the 14-hr photoperiod significantly enhanced root projected area, surface area, root volume, and number of root forks by 82, 81, 80, and 124%, respectively compared to those rooted under the 10-hr photoperiod, although these enhanced parameters were not statistically different from those rooted under 24-hr photoperiod. Our results showed that photoperiod generally had little effect on rooting percentages, shoot growth (e.g. new leaf number and new leaf area), average root diameter, and number of root tips and crossings; higher rooting quality was produced under 14-hr photoperiod. These findings provide valuable insights for improving rooting of this novel medicinal plant.

Stratified substrates may offer some advantages in containerized plant production, but their function in the propagation environment has not been extensively studied. We tested unrooted cutting root develop and plug stability with four herbaceous species [Agastache × ‘Sunrise Red Improved’, Cuphea hyssopifolia 'Maria' (Floriglory®), Gaillardia ×grandiflora 'Eclipse' (Lunar®), and Salvia ×jamensis 'Ignition Purple' (VIBE®)] in stratified propagation substrates. We used small, round pots to mimic a liner cell (top diameter 63.2 mm, depth 61.2 mm, volume 140 cm3 ). The control was a commercial propagation mix. We created top and middle-stratified treatments, using amendments of coarse perlite, fine coconut shell biochar, and parboiled rice hulls. The top-stratified treatments had 3 cm of an amendment material on top, with the control substrate underneath. The middle-stratified treatment contained the control on the top and bottom, with a 2-cm layer of amendment in the middle. We tested the species in separate experiments, with 7 replications each, in an approximately 30 day experiment. We repeated the experiments in a second cycle. At harvest, we assigned each cutting a plug integrity rating on a 0 to 5 scale: 0 = no visible roots, unstable, 1 = minimal roots, one or two roots visible, unstable, 2 = moderate roots, more than two roots but large spaces with no roots, partially unstable, 3 = acceptable roots, many roots with only small gaps, stable, 4 = optimum roots, many roots with full coverage, stable. Most of the stratified substrates had lower ratings than the control (P < 0.05). The top stratified rice hull treatment had a lower mean rating than the control for every plant in every cycle. Cuphea and Gaillardia with middle perlite stratification were not significantly different than the control in both cycles, while all top stratified mixes had significantly lower ratings than the control for Cuphea. Root growth in stratified substrates was similar to the control in the majority of cases. Cuphea cuttings had lower total root length (mm) than the control in all top stratification treatments and the middle perlite treatments in both cycles (P < 0.05). Some non-significant trends in the data repeated in both cycles, showing repeating patterns between the stratification treatments. Stratified substrates generally had lower plug integrity than the control, with few significant root growth effects.

Achimenes are rhizomatous gesneriads that can be used as flowering houseplants or grown in hanging baskets and mixed containers. Achimenes are typically asexually propagated from scaly rhizomes. The potential exists to propagate from leaf cuttings, however, there is limited published information on this propagation method. Thus, a leaf cutting study was initiated to further investigate the effects of indole-3-butyric acid (IBA) and propagation time on root development, plantlet, and rhizome production. We tested three Achimenes cultivars, ‘Charm’, ‘Apricot Glow’, and ‘Pink Cloud’. A total of 96 leaf-cuttings per cultivar were obtained from pre-flowering plants. Leaves were treated with one of four treatments; control (water), 1,000, 3,000, and 8,000 ppm of powder rooting hormone and were propagated under mist for a period of 3, 6, or 9 weeks. Data collection included root fresh and dry weights, plantlet number (stolons that emerged above the media surface), and rhizome development. In addition, root development was qualitatively evaluated on a scale from 1 = no rooting to 5 = prolific rooting. Propagation time significantly impacted each variable for all cultivars (p < 0.0001). Root ratings showed that all cultivars had ratings of 5 at 6 and 9 weeks, significantly higher than at 3 weeks. Generally, root dry weights significantly increased with increased propagation times. The interaction between rooting hormone and propagation time was significant for ‘Charm’ and ‘Apricot Glow’ for plantlet production. Increased plantlets were observed as both hormone concentration and propagation time increased, although not always significantly. ‘Apricot Glow’ leaf cuttings treated with 1,000 ppm and propagated for 9 weeks produced the most plantlets (1.6), however, plantlet number was not significantly different between hormone concentrations. Rhizome development significantly increased as propagation time increased for all cultivars (p < 0.0001). Rhizome number of all three cultivars significantly increased by double or triple for cuttings grown for 9 weeks compared to the 3 weeks. Our findings suggest that rooting hormones are negligible in enhancing propagation of Achimenes leaf cuttings for the cultivars evaluated. Propagation duration has a greater impact on growth and development than treatment concentrations. In this study, minimal differences in growth and development were observed after 6 weeks. This suggests that the ideal propagation period is within 3 and 6 weeks. Additional leaf cutting research is warranted to evaluate subsequent growth and development of Achimenes plants.

Northern berry crops including blueberry (Vaccinium spp.), lingonberry (V. vitis-idaea L.), cranberry (V. macrocarpon Ait.), cloudberry (Rubus chamaemorus L.) and huckleberry (V. membranaceum Douglas ex Torr.) are native to the North. Their health promoting role in anti-oxidant, anti-inflammatory, anti-ulcer and anti-tumor activities is due to their high contents of bioactive components. Although conventional methods of berry crop propagation are successful, for producing a large number of disease-free high quality plants, in vitro propagation (micropropagation) is more desirable. With the introduction of in vitro culture techniques, it is widely used to produce the true-to-type plants for year around multiplication. Propagation in vitro, using semi-solid and liquid media in different bioreactor systems, has advanced a multi-billion dollar industry in various crop plants globally. However, stresses during in vitro culture can provoke a range of genetic and epigenetic variabilities in the genome of the micropropagules leading to somaclonal variation. These variations (genetic or epigenetic) in micropropagated berry crops that include increased shoot and rhizome growth, berry production and/or antioxidant properties, might be useful for early establishment and berry production to the northern growers. This review updates the propagation technologies used in northern berry crops along with the evaluation of clonal fidelity and somaclonal variation in micropropagated plants. The existing gap in literature will be covered.

Prairie willow (Salix humilis) is a compact shrub willow native throughout the eastern United States. Aside from its desirable habit, attractive flowers and foliage, and pervasive ecological associations, prairie willow demonstrates profound adaptability in its native range, offering potential for urban green infrastructure applications. The dwarf variety (S. humilis var. tristis) is particularly favorable for horticultural applications due to its pronounced short stature. However, prairie willow exhibits a unique recalcitrance to traditional asexual propagation techniques commonly employed with willows. Tissue culture, a highly effective means for propagating recalcitrant woody plants, has not been explored for prairie willow. Given its potential horticultural value, tissue culture serves as a promising alternative for commercializing this taxon. This study explored the impact of four concentrations (0mg/L, 0.1mg/L, 1mg/L, and 10mg/L) of the common shoot-inducing hormone BAP (6-benzylaminopurine, a cytokinin) on initial growth in culture. Plant material was harvested from actively growing softwood tissue on a greenhouse-grown stock plant of the dwarf variety (USDA-GRIN accession AMES35806) and was trimmed to 1-2cm single-node explants (N=80, n=20). Sterilization involved an initial rinse in tap water with Tween-20, followed by a 30-second soak in 70% ethanol, a 5-minute soak in 0.9% sodium hypochlorite, and intermittent 5-minute rinses in sterile distilled water. Explants were stuck in 15mL falcon tubes with 4mL of media (2.41g/L woody plant media 30g/L sucrose 7g/L agar BAP). Culture tubes were placed on a light rack (18.3°C) with continuous light (40 watt fluorescent) and monitored weekly. The number of expanded buds and contamination rates were recorded. Contamination rates were low (12.5%), indicating successful sterilization. Development was slow across all treatment groups, suggesting the need for stock plant rejuvenation before propagule harvest. However, days to bud break indicated that 0.1mg/L BAP may result in the quickest shoot proliferation. Percentages of explants with expanded buds by week 5 were 13% (0mg/L), 68% (0.1mg/L), 41% (1mg/L) and 6% (10mg/L). All explants in 10mg/L exhibited browning and necrosis by week 5, while all but 5% of explants in 0mg/L remained green despite limited bud expansion. Future trials will investigate rejuvenation and alternative cytokinins to generate a complete protocol for introducing prairie willow into tissue culture. This research supports the integration of this versatile plant into commercial production, enhancing the ornamental plant palette for challenging urban landscapes.