Native Plant Nurseries Research Articles

Integrating theory and practice: knowledge exchange and engagement of nursery managers in ecological restoration

Ecological restoration requires the social collaboration of all stakeholders. Native plant nursery managers potentially possess substantial knowledge in native plant cultivation derived from their practical experience, and they could also be consumers of information generated by scientists. Furthermore, their active involvement in various stages of restoration projects could enhance efficiency and ensure successful outcomes. In this study, nursery managers from Argentina associated with restoration projects were surveyed to assess their level of knowledge exchange with the scientific community, the degree of participation in restoration projects, and their perceptions regarding this collaboration. The surveys were completed by 39 nursery managers from native plant nurseries in Argentina. Our findings indicated that, although nursery managers often adopted scientific protocols, there remains a significant communication gap between scientists and nursery managers. Nursery managers contributed beyond seedling production, including planning, planting, maintenance, and environmental education. Despite recognizing its importance, few nursery managers participated in project evaluations. Nursery managers could serve as both providers of cultural and practical insights and receivers of novel knowledge from the academic‐scientific realm. Moreover, as the nursery managers are familiar with the local context and can potentially facilitate connections with other local stakeholders, their involvement as additional social actors not only enhances the success but also adds legitimacy to the restoration projects they engage in. Such collaboration is crucial for achieving the goals of both international and national restoration initiatives.

Diversity and risk assessment of Phytophthora spp. found on plant roots in native plant nurseries and interstate shipping nurseries in California

For many nurseries it is difficult to diagnose Phytophthora-infected plants in time to prevent disease incursion and spread, especially if the infection occurs on roots and causes no or limited symptoms on aerial plant parts. Rapid, accurate, and specific diagnostic methods can facilitate the identification and removal of infected plants. This study was conducted to investigate if specific nursery types within California are more likely to have different Phytopthora species and which hosts are more likely to test positive for a Phytophthora species using immunological and molecular diagnostic tools. From Fall 2016 to Spring 2019, we collected 1,180 root samples from 15 nurseries, each in California, that fell into one of three distinct plant-sourcing categories. Plant roots were tested with Phytophthora-specific ImmunoStrips, and positives samples were identified to species-level by qPCR and sequencing. Of the 1,180 samples collected, 262 (22%) were found positive for infection by a Phytophthora sp. and 152 of these samples (58%) could be diagnosed to the species level. Hosts belonging to the genera Ceanothus (Rhamnaceae), Arctostaphylos (Ericaceae), and Salvia (Lamiaceae) tested positive for Phytophthora spp. most often. A total of 18 Phytophthora species were detected from the root samples, most frequently over the course of this study. Despite its high rate of false positives (30%), the ImmunoStrip® Phytophthora assay is useful as a preliminary screening tool for in-field diagnosis of root infection. qPCR testing of positive ImmunoStrip® tests allows for more accurate detection and facilitates species assignment.

Environmental awareness and willingness to pay for biodiversity improvement in Puerto Rico

Biodiversity is vital for sustainable forest ecosystems. However, community values for forest biodiversity depend on environmental engagement, education, and awareness. The objectives of this study are to (1) assess households’ willingness to pay (WTP) for native plant and tree nursery in the Rio Hondo Community Forest (RHCF) of Puerto Rico, with the specific goal of supporting biodiversity and (2) examine the influence of environmental awareness on preferences for biodiversity improvement. Using a contingent valuation method, we find that households are willing to contribute $43/year to support biodiversity in the RHCF by planting native plants and trees, and that environmental awareness increases the support for biodiversity projects. The results suggest that outcomes of economic cost-benefit analyses can depend on environmental awareness. Hence, programs that support environmental awareness can improve economic efficiency of environmental protection projects.

La Red de Viveros de Plantas Nativas de Argentina (REVINA): Una perspectiva etnobotánica para fortalecer la restauración de ecosistemas en la Argentina

The Argentine Native Plant Nursery Network (REVINA) links different social actors involved in native plant production, their valorization and the restoration of Argentina’s ecosystems. It is essential to strengthen the network in order to meet the country’s restoration goals, considering that the nursery community will generate the plant species that will be the primary inputs for restoration projects. In this paper we study the native plant nursery network, the nursery community and the plants they produce, in order to strengthen restoration projects in Argentina through the survey of the participants of the annual meetings of the REVINA in the period 2016-2020. We observed the network has grown remarkably since its creation, reflecting the increasing interest in native plants in recent years. Most of the plant species grown in the nurseries belonged to the Fabaceae family, are woody, and show a strong bias towards species from the centre-east of the country, in line with the number of nurseries concentrated in that region. A great number of nurseries have a small production, although, over the years, larger nurseries joined the network. The perspective used allowed us to obtain a first list of native plant nurseries and the species they cultivate. Finally, some aspects are proposed in order to strengthen this network of actors and thus be able to fulfill the restoration initiatives of the country.

Caracterización de viveros de plantas nativas y su posible aporte a la restauración de los talares bonaerenses

The talares represent the main native forest of the Buenos Aires province; however, they are in danger. Given their extreme vulnerability, it is not only necessary to promote their conservation, but also their restoration. The native plant nurseries represent a key link in restoration projects. In this work, the first survey of native plant nurseries in the distribution area of talares of Buenos Aires was carried out to characterize and evaluate them as possible restoration nodes. During 2019, surveys to these nurseries were carried out either in person or online. More than 70% of the nurseries were concentrated in the Buenos Aires Metropolitan Area and their objectives comprise commercialization, conservation/restoration or education. More than 60% of the nurseries were less than 5 years old and less than 500 m2 in size, and they do not control humidity, temperature and/or light; however, they have greenhouses. These characteristics seem to reflect an increase in society’s interest on native plants in recent years, which would have led to the development of new nurseries at small scale. The main plant species of the talares were cultivated in these nurseries, so they could be very important actors when planning restoration projects of these forests. We emphasize the importance of consolidating a network of collaboration between nurseries, scientists, protected areas, and government agencies in order to restore this ecosystem. In this way, it is necessary to expand the scope of this study in order to know the native plant nurseries in the rest of the country, associated with other endangered ecosystems, and to be able to evaluate if Argentina is in a position to meet its internal goals and international restoration commitments. We hope that the results of this work will promote joint collaborations to restore the talares of Buenos Aires and other ecosystems in Argentina.

Wild bee functional diversity and plant associations in native and conventional plant nurseries

1. An ongoing challenge in ecology is predicting how characteristics of communities correspond to habitat features. Examining variation in functional traits across species may reveal patterns not discernible from measures of mere abundance or richness. For beneficial insects like wild bees, functional trait‐based approaches are often used to characterise communities in different agricultural habitats.2. However, no such approach has yet been applied in horticultural plant nurseries, which represent intensively managed artificial flowering plant assemblages. Certain nurseries mostly cultivate regionally native flowering plants, allowing one to test how differences between local plant assemblages may correlate with bee functional traits.3. We surveyed bee assemblages at native and conventional plant nurseries in southern California from spring through autumn over 2 years, while also documenting the native status of blooming plants in sampling plots. Bees were classified into different functional categories based on their diet breadth, nesting location, and social organisation.4. At native plant nurseries, we netted proportionally more specialist bee species and fewer generalist species than at conventional nurseries. Nesting location and social organisation of bee samples did not differ between nursery types. Meanwhile, landscape‐level features were not associated with any observed functional trait metrics of bee collections. Furthermore, network‐level specialisation of bee‐plant interactions was higher at conventional nurseries.5. Our results suggest that a horticultural cultivation practice is quantifiably correlated with the functional distribution of resident bee assemblages. These results are important and encouraging to pollinator conservation efforts in nursery systems and other human‐modified landscapes dominated by ornamental plants.

An Accreditation Program to Produce Native Plant Nursery Stock Free of Phytophthora for Use in Habitat Restoration

Widespread Phytophthora infections have been discovered in nursery stock used in California restoration plantings. In response, Nursery Phytophthora Best Management Practices (NPBMPs) designed to exclude Phytophthora from nursery plants were developed to address the need for clean planting stock in restoration projects. A pilot program to implement the systematic use of the NPBMPs, Accreditation to Improve Restoration (AIR), was developed and started in 2018. As of 2020, 13 northern California restoration nurseries have been evaluated, and five have met all the program requirements. In 564 tests conducted over 4 years with a sensitive leachate baiting protocol, no Phytophthora was detected from over 20,000 nursery plants produced in compliance with the NPBMPs. In comparison, Phytophthora was detected in 25% of tests conducted on partially compliant stock and in 71% of tests from nurseries following few or no NPBMPs. The AIR pilot program has demonstrated that container stock free of detectable Phytophthora can be reliably produced by adhering to an integrated program of clean nursery production practices. To obtain Phytophthora-free plants for habitat restoration, informed clients were willing to pay increased costs required to produce NPBMP-compliant nursery stock.

Phytophthora Introductions in Restoration Areas: Responding to Protect California Native Flora from Human-Assisted Pathogen Spread

Over the past several years, plantings of California native plant nursery stock in restoration areas have become recognized as a pathway for invasive species introductions, in particular Phytophthora pathogens, including first in the U.S. detections (Phytophthora tentaculata, Phytophthora quercina), new taxa, new hybrid species, and dozens of other soilborne species. Restoration plantings may be conducted in high-value and limited habitats to sustain or re-establish rare plant populations. Once established, Phytophthora pathogens infest the site and are very difficult to eradicate or manage—they degrade the natural resources the plantings were intended to enhance. To respond to unintended Phytophthora introductions, vegetation ecologists took a variety of measures to prevent pathogen introduction and spread, including treating infested areas by solarization, suspending plantings, switching to direct seeding, applying stringent phytosanitation requirements on contracted nursery stock, and building their own nursery for clean plant production. These individual or collective actions, loosely coordinated by the Phytophthoras in Native Habitats Work Group ensued as demands intensified for protection from the inadvertent purchase of infected plants from commercial native plant nurseries. Regulation and management of the dozens of Phytophthora species and scores of plant hosts present a challenge to the state, county, and federal agriculture officials and to the ornamental and restoration nursery industries. To rebuild confidence in the health of restoration nursery stock and prevent further Phytophthora introductions, a voluntary, statewide accreditation pilot project is underway which, upon completion of validation, is planned for statewide implementation.

General attributes and practice of ecological restoration in Arizona and California, U.S.A., revealed by restoration stakeholder surveys

Ecological restoration has become increasingly important in conservation. Yet, synthesized statistics are scarce with respect to essential characteristics of restoration activities. We surveyed restoration stakeholders in the U.S. states of Arizona and California to evaluate key attributes in restoration activities including ecosystems of focus, goals, size, cost, duration, and the prevalence of recommended restoration practices. We also examined how some of the attributes varied with size of restoration, ecosystem type, and state identity. While enhancing biodiversity and increasing plant cover were common goals in the two states, restoration in California also focused more on wildlife habitat re‐establishment and weed control. Restoration in Arizona was implemented more in arid/semiarid systems, larger in size, shorter in duration, used more passive restoration, spent more on equipment, and was less likely to source plants from native plant nurseries. Labor was the most expensive restoration component regardless of state identity and ecosystem type. Per unit area cost of restoration decreased with increasing size of restoration. Yet, the decline in this cost was more strongly explained by moving from mesic to arid/semiarid ecosystems. Duration of restoration projects increased with size of restoration and in more mesic ecosystems. Overall, restoration in mesic ecosystems, compared to arid/semiarid systems, was smaller in size, higher in cost, and longer in duration. These results confirmed that ecological and socio‐political conditions impact restoration goals and practice, with implications of how research can further support practitioners to achieve restoration success under practical constraints revealed by these results.

Phytophthora pathogens threaten rare habitats and conservation plantings

Phytophthora pathogens are damaging native wildland vegetation including plants in restoration areas and botanic gardens. The infestations threaten some plants already designated as endangered and degrade high-value habitats. Pathogens are being introduced primarily via container plant nursery stock and, once established, they can spread to adjacent areas where plant species not previously exposed to pathogens may become infected. We review epidemics in California – caused by the sudden oak death pathogen Phytophthoraramorum Werres, De Cock & Man in ‘t Veld and the first USA detections of P. tentaculata Kröber & Marwitz, which occurred in native plant nurseries and restoration areas – as examples to illustrate these threats to conservation plantings.

Development of an Embryo Rescue Protocol for Butterfly Weed

We documented a successful embryo rescue (ER) protocol for butterfly weed (Asclepias tuberosa), a member of the milkweed family (Asclepiadaceae). Milkweed (Asclepias sp.) includes more than 100 species native to the United States, is an important pollinator plant, and has many commercially desirable traits. However, there is little commercial production outside of native plant nurseries because milkweed species are typically seed-grown and suffer from low seed set during pollination, late-term abortion of seed pods, and nonuniform germination. This project determined the optimal growing media (study one) and embryo maturity (study two) to recover mature seedlings from excised embryos and compared the results to those of traditional methods of seed germination (in soilless substrate). Study one investigated three different media: Murashige and Skoog (MS) medium at full strength and half strength and woody plant medium. MS medium at half strength was optimal for butterfly weed germination and maturation, with greater root and shoot lengths at the time of harvest. In study two, the effects of MS medium at half strength on embryo maturation 90, 60, and 30 days after pollination (DAP) were investigated. The optimal time to harvest embryos was 60 DAP; embryos at 30 DAP were capable of germination but not maturation. A mean germination rate of 97.4% was observed when using embryo rescue, but it was 72.3% with mature seed germinated in soilless substrate typical of commercial production. A similar increase in germination rates was observed for all embryo maturities when compared with seed germinated using soilless substrate. The protocol developed for this study should help to standardize production, reduce propagation time, and improve the commercial acceptance and profitability of milkweed.

Assessment of the nursery species pool for restoring landscapes in southeastern Brazil

Brazil has committed to fulfilling international restoration goals and to enforcing environmental legislation that will require private landowners to undertake ecological restoration of 21 million hectares of degraded and deforested landscapes. To support a broad range of restoration practices, a well‐established supply chain capable of representing regional plant diversity is essential. This study investigated the restoration species pool in native plant nurseries in São Paulo state, located in southeastern Brazil, and evaluated their geographic distribution, similarity of their plant stocks, and the proportion of species represented from regional floras. Despite a lack of technical assistance and a significant presence of nonnative species (126 species, average 7.5 species/nursery), we found an impressive native species richness in plant nurseries (561 species, average 86.4 species/nursery) from both the Atlantic Forest and Cerrado domains, representing 38–44% of regional floras. There was a huge bias toward tree and shrub species (96.6%) and an absence or underrepresentation of other growth forms, as well as of savanna specialists, animal‐dispersed, and threatened species. The dissimilarity of species observed among the different nurseries surveyed highlights their role in representing regional diversity, which reflects their regional seed collection practices. Effective assistance and training are essential to address issues related to misidentification of species, underrepresentation of most functional plant groups, and the presence of nonnative species, as well as to support the supply chain, which is currently undergoing a market downturn.

Phytophthora Species Are Common on Nursery Stock Grown for Restoration and Revegetation Purposes in California.

Phytophthora tentaculata was detected for the first time in North America in 2012 in a nursery on sticky monkeyflower plant (Diplacus aurantiacus) and again in 2014 on outplanted native plants. At that time, this species was listed as a federally actionable and reportable pathogen by the USDA. As a result of these detections, California native plant nurseries were surveyed to determine the prevalence of Phytophthora species on native plant nursery stock. A total of 402 samples were collected from 26 different native plant nurseries in California between 2014 and 2016. Sampling focused on plants with symptoms of root and crown rot. Symptomatic tissue was collected and tested by immunoassay, culture, and molecular techniques (PCR). Identifications were made using sequences from the internal transcribed spacer (ITS) rDNA region, a portion of the trnM-trnP-trnM, or the atp9-nad9 mitochondrial regions. Phytophthora was confirmed from 149 of the 402 samples (37%), and from plants in 22 different host families. P. tentaculata was the most frequently detected species in our survey, followed by P. cactorum and members of the P. cryptogea complex. Other species include P. cambivora, P. cinnamomi, P. citricola, P. hedraiandra, P. megasperma, P. multivora, P. nicotianae, P. niederhauserii, P. parvispora, P. pini, P. plurivora, and P. riparia. A few Phytophthora sequences generated from mitochondrial regions could not be assigned to a species. Although this survey was limited to a relatively small number of California native plant nurseries, Phytophthora species were detected from three quarters of them (77%). In addition to sticky monkeyflower, P. tentaculata was detected from seven other hosts, expanding the number of associated hosts. During this survey, P. parvispora was detected for the first time in North America from symptomatic crowns and roots of the nonnative Mexican orange blossom (Choisya ternata). Pathogenicity of P. parvispora and P. nicotianae was confirmed on this host. These findings document the widespread occurrence of Phytophthora spp. in native plant nurseries and highlight the potential risks associated with outplanting infested nursery-grown stock into residential gardens and wildlands.

Growing Pains: Hopes and Heartaches at Native Plant Nurseries

Growing Pains: Hopes and Heartaches at Native Plant Nurseries

Forest recovery in an Australian amenity landscape: implications for biodiversity conservation on small-acreage properties

Some urbanising rural (i.e. ‘amenity’) landscapes have seen an increase in forest cover over recent decades. Small-acreage landowners are key stakeholders in this forest recovery and its future ecological trajectory. Using 17 qualitative case-studies of small-acreage properties located in the Noosa hinterland in south-east Queensland, this study explores the types and condition of forests on these properties, the landholder’s differing forest management perspectives, practices and outcomes, and the implications for local biodiversity conservation. The properties contained a diverse mix of managed and un-managed natural and planted forests. Invasive weed species were a common component. Protecting and enhancing the ecological values of amenity landscapes will require an increase in active, best-practice forest management on small-acreage properties. Small-acreage landowners will require greater access to labour support and other subsidised resources to implement recommended practices. Such practices include controlling and reducing the spread of invasive weeds and soil erosion, reducing fire hazards, and positively influencing the rate and pathway of succession in regrowth forests. Peer-mentoring programs incorporating guided tours of ‘model’ small-acreage forests, and supporting landowners to establish their own small native plant nurseries and engage with local community nurseries (i.e. supplying seeds, volunteering labour), could help to increase small-acreage landowners’ forest management interests, knowledge, skills and activity. Long-term cooperative, cross-boundary forest management projects with on-going monitoring and adaptive management guided or implemented by skilled professionals are needed in amenity landscapes, particularly to increase the success of restoration interventions in weed-dominated regrowth forests. There is also a need for long-term socio-ecological analyses of amenity landscapes’ diverse and evolving small-acreage forests to better inform their future management.

LIGHT-EMITTING DIODE LIGHTING FOR FOREST NURSERY SEEDLING PRODUCTION©

Crop lighting is an energy-intensive necessity for nursery production of high-quality native plants and forest tree seedlings. During the winter months (especially in northern USA latitudes) or overcast or cloudy days, the amount of solar radiation reaching greenhouse crops is insufficient resulting in growth cessation, early terminal bud formation, and failure of seedlings to reach target height for outplanting (Tinus, 1995; Lopez and Runkle, 2008). In light of this, nursery growers have added supplemental lighting to increase the daily light integral (DLI), defined as the photosynthetic light received over the course of the day for seedling production (Torres and Lopez, 2010). A wide range of supplemental light sources are used in nurseries to control plant development and manipulate plant quality (Tinus, 1995; Bourget, 2008). However, the problem with most lighting systems, such as high-pressure sodium (HPS) lamps, is that they do not provide the light spectrum that is most efficient for photosynthesis in plants. In addition, because of the huge amount of electrical energy required, using HPS as supplemental lighting, for most reforestation and native plant nurseries, is economically impractical.

First detection in the US: new plant pathogen, Phytophthora tentaculata, in native plant nurseries and restoration sites in California

Phytophthora tentaculata Krober & Marwitz, has been detected in several native plant nurseries in 4 California counties and in restoration sites on orange sticky monkey flower (Diplacus aurantiacus subsp. aurantiacus (W. Curtis) Jeps. [Scrophulariaceae]), toyon (Heteromeles arbutifolia (Lindl.) M. Roem) [Rosaceae]), coffeeberry (Frangula californica (Eschsch.) A. Gray [Rhamnaceae]), and sage (Salvia spp. L. [Lamiaceae]). These findings are the first detections of P. tentaculata in the US and the first ever on these host plants. Phytophthora species are a known problem in horticultural nurseries, but little attention has been placed on native plant or restoration nurseries. The potential for plant pathogens to be outplanted along with native plant nursery stock is very high, posing a threat to neighboring forests.

Monarch waystations: Propagating Native Plants to Create Travel Corridors for Migrating Monarch Butterflies

Monarch waystations have tremendous potential for native plant nurseries, agencies managing public lands, and even the general public. Popularized by Monarch Watch, these specialized pollinator gardens provide habitat (food, shelter, and water) for monarch butterflies (<i>Danaus plexippus</i> L. [Lepidoptera: Nymphalidae]) on their long migrations. Using source-identified and locally adapted seeds and nursery stock of milkweed (<i>Asclepias</i> L. spp. [Asclepiadaceae]) and flowering nectar plants, conservation groups and backyard gardeners can create critical habitat for this beleaguered butterfly. The unprecedented popular support for the plight of the monarch has made it a charismatic microfauna and has focused much-needed attention on the proven success of using native plants for restoration purposes. TD Landis 2014. Monarch waystations: propagating native plants to create travel corridors for migrating monarch butterflies. Native Plants Journal15( 1): 5- 16.

A modified sickle bar mower increased flexibility for harvesting native plant seeds

For native plant producers, many challenges of seed collection stem from differences in plant form and physiology, diverse equipment needs, multiple harvest requirements, and hand-collection constraints. One of the major problems facing native seed producers is the inability to effectively manage the range of heights of various crops with standard mechanical equipment. To solve this problem, the Cardno JFNew Native Plant Nursery has developed an adjustable height harvester using a modified skid steer sickle bar mower and an industrial-size leaf vacuum. This machine, operated by a single person, can then be used to rapidly harvest seeds from a variety of plant types.

Monarchs (Danaus plexippus) and milkweeds (Asclepias species): The Current Situation and Methods for Propagating Milkweeds

An international effort is under way to conserve populations of the monarch butterfly ( Danaus plexippus L. [Lepidoptera: Nymphalidae]). Monarchs complete an impressive migration each year, flying from winter roosts on the California coast and the central mountains of Mexico to breeding areas throughout North America. Monarchs depend on habitats along their migratory paths that contain milkweed species ( Asclepias L. [Apocynaceae])—larvae are obligate feeders on leaves, and adults visit flowers for nectar. More than 130 species of milk-weeds grow in North America and are readily propagated using seeds, or in some cases, cuttings. To assist monarchs and other native pollinators, native plant nurseries and their clients can incorporate milkweed species into restoration plantings in suitable habitats within the native range of individual species.