Plus, Finding Success with Mediterranean Ornamental and Semi-Hardy Edible Plants
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From Chasing to Solving Labor Scarcity
Integration of Control Strategies for Management of Phytophthora Root Rot and Ambrosia Beetles in Nursery Trees
Finding Success with Mediterranean Ornamental and Semi-Hardy Edible Plants
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ur industry is booming, and demand has never been higher. As we struggle with the same issues every year, we also face new challenges. The best thing in this industry is that we work together to overcome these challenges. We need to continue to work with our researchers, vendors and other industry leaders to find solutions to the deadlines, shortages, and diseases we’re facing today. Tennessee nurseries and landscapers always have one thing in mind when they go out everyday to serve their customers, and that is quality. With the extremely high demand that we have seen these past few years, it is very difficult to meet the requirements and maintain quality. We as nursery growers, landscapers and horticulturists are always working silently and unseen to take care of the little things that make a huge difference. This is a moment to take a breath and realize that all the hard work is paying off.
I look forward to serving the association as President this year. We are looking forward to working with two new board members this year that are excited to participate in the growth of this association. We are also very excited for the “TNGRO” trade show in Lebanon, TN this fall. It has been three years since we have been able to provide our members with the opportunity to show their products and services. This will be a wonderful chance to meet new customers and catch up with old friends. Spring is around the corner and shipping and planting is about to begin, so don’t forget the small things that continue to bring quality to our customers.
Terri Turner TNLA President 2023
Incoming Turfgrass Extension Specialist
H Meet DR. BECKY BOWLING UT Plant Science’s
ello Tennessee! My name is Becky Bowling, and I have recently been hired as a faculty member in the Plant Sciences Department at The University of Tennessee in the Turfgrass Extension position. I have been an Assistant Professor and Extension Specialist in Texas for the past five years, where I have gained extensive experience working with county agents, sod producers, golf course superintendents, professional lawn care operators, sports field managers, cities, and more. I am looking forward to bringing my experience to Tennessee to build strong relationships with Tennessee’s renowned turfgrass and green industries and their many critical stakeholders across the state. I am looking forward to meeting as many of you as possible during my initial months in this position. My official start date is May 1, 2023.
Until we can meet in person, I would like to share some of my background and experiences. I am originally from Carrollton, Texas (near Dallas). I completed my undergraduate and master’s degrees in Horticulture at Texas Tech University where I primarily focused on sustainable landscape management practices with particular emphasis on native plants. From there, I worked and earned my PhD at the University of Georgia in environmental turfgrass management. For the past several years, my research and extension efforts have focused on evaluating and communicating best management practices for turfgrass to promote environmental stewardship and resource-use efficiency in turfgrass systems and related urban greenspaces. Much of my efforts have centered on water with particular emphasis on water efficiency, water capture, and water quality protection. In my spare time, I hike, practice vinyasa yoga, and spend time with my husband Will and our three pets, Biscuit (dog), Hubert (dog), and Phil (cat).
When I arrive in Knoxville in May, I am looking forward to making purposeful trips across Tennessee to meet with county agents, turfgrass industry leaders, and other critical stakeholders to listen and learn about the Tennessee turfgrass industry and how I can be of the greatest service in my new role. Through these dialogues and coordinated discussions with my new collaborators at UT, I look forward to building a thoughtful and integrated extension and research program that builds on the already incredible UT turfgrass program and supports the Tennessee turfgrass industry across the state.
From my experience in Texas, I have learned the importance of a thoughtful and coordinated approach for building both a successful research and extension program. I thrive in a team environment, and have extensive experience working with scientists, industry leaders, and stakeholders spanning diverse backgrounds, focus areas, and interest groups on collaborative projects. Coming into this new position, I will put the greatest emphasis on listening, learning, and building new relationships as a foundation for my program going forward. I look forward to working along the UT turfgrass team to build a program centered on economic and environmental sustainability leveraging new technologies and outreach tools to have the greatest impact. Please don’t hesitate to reach out to me once I have started. I look forward to getting to know you!
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From CHASING to SOLVING Labor Scarcity
Part I: Current Automation Adoption by the US Nursery Industry
By Amy Fulcher 1 , Alicia Rihn 1 , Laura Warner 2 , Anthony LeBude 3 , Margarita Velandia 1 , Natalie Bumgarner 1 & Susan Schexnayder 1
1 University of Tennessee, 2 University of Florida, 3 North Carolina State University
During exit interviews of Tennessee Master Nursery Producer Program, I ask graduates “How is the labor situation at your nursery?” I hear many comments like the following:
“Terrible. We can’t get no help. We’ve got about ½ done what we should have by this time of year. Have 5 guys; I need 10 or 15. It’s been really tough this year. This is the toughest year since I’ve been in business.”
“100% H-2A now, plus one domestic laborer in the winter. Prior to H-2A, one person at work but 8 people on payroll.”
“It is begging. There are no workers. It doesn’t matter what you pay them, no one wants to work. For all nurseries this is our next huge problem. Nursery stock price hasn’t gone up. Same price it was 15 years ago. Liners and baskets went up. Fuel went up. Locked in fertilizer. Prepay or else $800 pallet (if you can get it). Probably will have to do it [H-2A].”
“Not 10 people standing in line to work at our nursery anymore.”
In the U.S., labor costs to produce specialty crops represent nearly 40% of total cash expenses; more even than dairy operations. Across all specialty crops, nursery crops are very manual labor-intensive, which makes the nursery industry particularly vulnerable to labor scarcity. Challenges of hiring sufficient employees are made worse by limited availability of a combined domestic and foreign labor workforce that is increasingly insufficient to meet today’s nursery labor demands. There is no indication that this situation will improve. Across the U.S., nursery producers are exploring automation and other technologies to address labor concerns.
A three-part article series was developed to aid the Tennessee nursery industry as they navigate automation options, automation trends, and the perceived benefits and outcomes of automation, with the goal of helping to prepare nurseries for an increasingly labor-scarce future. In this issue of Tennessee Greentimes, we present Part I, “Current Automation Adoption” that describes growers’ use of a range of container- and field-production automation technologies. In future issues of the magazine, we will share Part II “Advances in Automation within Task,” in which we evaluate the portion of a given task that is automated and compare that to previous automation levels. In Part III “Outcomes from Adopting Automation and Perceived Helpfulness Analysis,” we will present nursery producer perceptions of helpfulness that they associate with specific pieces of automation as well as examine outcomes growers anticipate from using automation.
The information presented in this series is from the Labor, Efficiency, Automation, Production (LEAP) Nursery Labor and Automation Survey that was conducted in 2021 and asked respondents about practices that they used in 2020. The survey was sent to 1,225 employees at a manager or higher position at U.S. nurseries. We compare these national survey results with results from a survey conducted by phone interview in the southeastern U.S. over a period of several years (Posadas, 2018), which for simplicity we refer to here as having been conducted in 2006, and an abbreviated data set from that survey (Coker et al., 2010, 2015). Averages (means) and standard deviations are presented. Mean separation was conducted at a significance level of alpha = 0.05.
3. Conveyers can be used to move plants following potting onto wagons and when orders are pulled to move from wagons to trucks or shipping racks.
Nurseries are adopting automation to help with a range of container and field production tasks (Table 1). Current use of automation technology was highest for use of trucks or tractors with wagons (73.0%) (Fig. 1). Granular fertilizer applicators, potting machines, liquid fertilizer applicators, forklifts, and tree spades were used by roughly 40 – 50% of survey respondents. Mechanical liner setter/planters, tying machines, substrate mixers, conveyer belts, B&B tree handlers, mechanical foliage trimmer/ pruners, and mechanical root pruners are in use at approximately 28 – 35% of responding nurseries. Less than 20% of nurseries responding to the survey are using mechanical bundlers (post-harvest), lifters or shakers, pneumatic c-ring fasteners, horticultural forklifts (Fig. 2), mechanical stake installers, robotic plant spacers, or laserguided spray technology.
The type of production system impacted whether certain automated nursery technologies have been adopted into current use; sometimes as a function of the production method itself (Table 1). Certain technologies were not relevant to respondents, depending upon the type of production system (i.e., container grown, field grown, mixed system container and field) about which they were reporting, and therefore all possible comparisons were not made. For example, “mechanical bundlers” was not a response option for container-only nurseries. More container nurseries (56.7%) and mixed system nurseries (48.1%) adopted liquid fertilizer injectors than field nurseries (23.4%). Survey results suggest that responding field nurseries (10.6%) currently use fewer conveyers than either container (40.0%) or mixed nurseries (42.3%). Field nurseries (25.5%) use lifter/shakers more than mixed operations (1.9%).
Since the 2006 nursery survey, automation of nursery tasks has roughly doubled, yet automation of tasks remains below 35% when averaged across all types of tasks. Some types of automation have been adopted more quickly than others. The current survey found that conveyers ( Fig. 3 ), although a technology newly available for the green industry, were as widely adopted (33.3%) as other pieces of automation that have been available for field and container production for a long time, such as B&B tree handlers (33.3%) and substrate mixers (35.2%). In the 2006 nursery survey, just 2% to 9% of nurseries used conveyers for moving plants, with the exact percentage varying by the specific plant handling task (Coker et al., 2010, 2015). 1 2 3
Figure 1. Wagons are widely used to transport plants within nurseries.
Figure 2. A horticultural forklift can be used to move plants and impose the desired spacing when they are placed in the production block.
Figure
Table 1. Nursery use of automation and mechanization technologies as determined in a survey of decision-makers representing the U.S. nursery industry. The survey was conducted in 2021 and asked about practices that respondents used in 2020.
Total Number of Observations
z Significance was tested using ANOVA and Tukey’s honestly significant difference test at a significance level of 0.05. Within comparisons between production methods, presence of an * in the corresponding cell indicates that the automation technology used was different between the two production types being compared; an NS in the corresponding cell indicates that there was not a significant difference between the two production methods; – in the corresponding cell indicates the comparison was not made because the automation technology was not applicable either to one or both production methods.
Several factors can influence which automation is readily adopted. Some forms of automation, such as tractors, trucks, and wagons, have multiple uses within nurseries, whereas some of the lesser-adopted automation technologies have very specialized applications. For example, robotic plant spacers, mechanical stake drivers, and pneumatic C-ring fasteners are all helpful in reducing manual labor, yet each accomplishes only one specific nursery task. Other types of automation require a large capital expense that may be cost prohibitive for smaller nurseries and other nurseries that operate with smaller profit margins. In the 2020 survey, nursery producers responded that purchase and installation and related costs associated with automation technology were the highest-ranked barriers to automation (Rihn et al., 2022). In addition, some automation is not stand alone but rather necessitates more involved planning, additional space allocation, and other changes that can increase the overall complexity and costs of adopting the technology. As an example, investing in a potting machine includes a capital expense of at least $50,000, as well as a protected structure such as a building, plus access to 3-phase electricity and/or a generator (Fig. 4 and Fig. 5). Adoption of a potting machine may also require additional hoppers, a dedicated front-end loader, more tractors and tracking trailers, and drivers to achieve maximum efficiency. Ironically, a potting machine may require a significant amount of task-dedicated labor at fixed time periods to maximize its production capacity. One Tennessee nursery recently adopted a potting machine that requires approximately 15 workers to maximize its pots-per-minute output capacity.
While cost is a known barrier to adopting some automation technologies, there are programs that can make automation and other capital improvements more affordable. Tennessee nursery producers have a unique opportunity to invest in automation through a partnership between the Tennessee Department of Agriculture’s (TDA) Tennessee Agriculture Enhancement Program https://www.tn.gov/agriculture/farms/taep. html and the University of Tennessee’s Tennessee Master Nursery Producer (TMNP) Program www.tnmasternursery.com. Following TDA acceptance of their application, growers can fulfill their eligibility for enhanced levels of cost share, currently at 50%, with a current TMNP certification, versus just 35% cost share without the TMNP certification. Some of the technology that growers can apply for include automated irrigation controllers, sprayers, and potting line equipment.
AUTOMATION Side Benefits
In 2020, the LEAP Team held national listening sessions and talked with nursery leaders from across the U.S. Many growers on the call had already taken the plunge and invested in automation. Other than labor savings, what were some of the most common benefits that they listed? Product consistency, predictability of task completion, and timeliness of tasks leading to more uniform products. By better controlling when crops are pruned, the production manager can better control when they will be in flower or achieve market size. By investing in potting technology, large volumes of a crop type, such as crops grown on contract that need to be ready for sale at the same time, will be potted within a smaller time window and reach their “finished” size together. For example, one nursery was able to accept an order that was due in eight weeks because the nursery was able to pot 19,000 plants in three days. If done by hand, the potting step alone would have taken the nursery three weeks to complete. One of the take-home messages from the listening sessions was that nursery producers who invested in automation did not just achieve labor savings, they gained better control of their production schedules and gained new sales opportunities.
REFERENCES and ADDITIONAL RESOURCES
Coker, R.Y., B.C. Posadas, S.A. Langlois, P.R. Knight, and C.H. Coker. 2015. Current mechanization systems among greenhouses and mixed operations. Bulletin 1208. Mississippi Agriculture and Forestry Experiment Station. http://www.mafes. msstate.edu/publications/bulletins/b1208.pdf
Coker, R.Y., B.C. Posadas, S.A. Langlois, P.R. Knight, and C.H. Coker. 2010. Current mechanization systems among nurseries and mixed operations. Bulletin 1189. Mississippi Agriculture and Forestry Experiment Station. http://www.mafes. msstate.edu/publications/bulletins/b1189.pdf
Posadas, B.C. 2018. Socioeconomic determinants of the level of mechanization of nurseries and greenhouses in the southern United States. AIMS Agriculture and Food 3(3):229-245.
Rihn, A., M. Velandia, L.A. Warner, A. Fulcher, S. Schexnayder, and A. LeBude. 2022. Factors correlated with the propensity to use automation and mechanization by the U.S. nursery industry. Agribusiness. 2022:1-21. https://doi.org/10.1002/agr.21763
Figure 4. Building, conveyers, hoppers and other costly infrastructure may be needed when investing in a potting machine.
Figure 5. A generator necessary to operate a portable potting machine.
Integration of Control Strategies for Management of Phytophthora Root Rot and Ambrosia Beetles in Nursery Trees
By Madhav Parajuli* and Dr. Cansu Oksel**, Dr. Jason B. Oliver, Dr. Karla M. Addesso, and Dr. Fulya Baysal-Gurel
Tennessee State University, Otis L. Floyd Nursery Research Center
*PhD student & **Postdoctoral Researcher
How do Phytophthora root rot and ambrosia beetles interact to make nursery problems worse (and which host plants are most likely to be affected)?
Ambrosia beetles (Xylosandrus spp.), woodboring insects, and Phytophthora spp., soilborne pathogens, are economically important and destructive challenges to both susceptible trees during nursery production and trees being established in landscapes. Root and crown injury caused by Phytophthora may block the intake and movement of nutrients and water, leading to root mortality and plant death. Infection with Phytophthora is more prevalent and made worse when environmental conditions adversely impact the plant like high temperature, excessive moisture, oxygen deficiency, ethylene, and carbon dioxide production in the root zone. Ambrosia beetles use host plant cues to locate and then colonize the main trunk and branches of highly stressed or recently killed trees, primarily by seeking airborne plant stress-related volatile compounds like ethanol. Phytophthora may increase the production of stress-related ethanol from infected host plants; and thus, increase the attraction of ambrosia beetles. Some of the ornamental trees affected by Phytophthora include cherry (Prunus spp.), dogwood (Cornus spp.), maple (Acer spp.), oak (Quercus spp.), and rhododendron (Rhododendron spp.). Common host plant species attacked by ambrosia beetles include cherry ( Prunus spp.), crapemyrtle ( Lagerstroemia spp.), dogwood (Cornus spp.), golden rain tree (Koelreuteria spp.), magnolia (Magnolia spp.), maple (Acer spp.), oak (Quercus spp.), redbud (Cercis spp.), and styrax (Styrax spp.). Many tree species that are susceptible to ambrosia beetles and Phytophthora are also flood intolerant. Working to address all of the pest and environmental challenges simultaneously will provide more effective control than dealing them individually.
How do we monitor symptoms of Phytophthora root rot infection and ambrosia beetle attacks?
Phytophthora infection may result in dark brown to black discoloration in infected host plant roots and the crown region that can lead to complete root decay ( Fig. 1 ).
Figure 1. Dark brown to black discoloration can be seen on roots and the crown of a tree infected by Phytophthora.
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Pests ( and Plant Disease ) in the Spotlight continued
Leaves lose their luster and may show signs of premature leaf aging, changing color from green to light green and then pale yellow or purplish brown. As the infection progresses, yellowing and wilting symptoms can be visible in foliage and stems, which may be followed by stunted growth and tree mortality. Ambrosia beetles excavate tunnels into the wood (i.e., xylem) forming ‘toothpick’-like extrusions of excavated wood, sawdust and frass (debris or excrement produced by insects). These toothpicks are often the very first indication of beetle attacks (Fig. 2).
Other visible symptom of ambrosia beetle attack includes small, round exit holes that may exude sap (Fig. 3). Severe ambrosia beetle infestations interrupt movement of nutrients and water in attacked host plants, causing branch dieback and wilting, and eventually tree mortality. Overwintering female ambrosia beetles exit galleries as early as March in Tennessee, generally following several consecutive days in which temperatures reach about 70ºF. Phytophthora is also severe during the summer when warm temperatures are favorable for infection.
Figure 2. Adult ambrosia beetles are attracted to the trunk of a flooded and infected tree. Toothpick-like frass and sawdust structures emerge from the tree following beetle attack.
Figure 3. An ambrosia beetle exit hole and sap drainage are visible on the smooth bark of flowering dogwood.
How can we reduce severity and limit damage caused by Phytophthora root rot and ambrosia beetles?
Because root rot disease caused by Phytophthora appears to increase host plant attractiveness to ambrosia beetles, perhaps through release of ethanol, several management actions can help protect crop plants from ambrosia beetle attacks.
I. Use good sanitary measures
Growing healthy trees, thereby reducing stress-related ethanol production, is a best management strategy for ambrosia beetles. A first step is to make sure only disease-free trees are being planted. After planting disease-free trees, root rot diseases caused by Phytophthora can be managed by implementing good sanitary measures. It is important to prevent introducing pathogens into a nursery by monitoring newly received plants, including their root systems. Ideally, new plants are held in an area quarantined from main production blocks while being screened and observed. If diseased trees are observed in the field, limit spread by immediately removing infected plants, plant debris, and fallen leaves from the growing area. Sterilize pruners and use proper pruning practices when removing plant tissue that are exhibiting initial signs of ambrosia beetle attack or plant pathogen infection. It is essential to sanitize any equipment before moving from one nursery plot to another.
II. Consider cover cropping for field production systems
Mixed cropping, intercropping, and crop rotation are important practices that can reduce the inoculum buildup of Phytophthora. Cover crops that belong to the Brassicaceae family such as mustard, turnip, arugula can be incorporated into the soil to control Phytophthora root rot and this process is widely known as biofumigation. Winter cover crop usage (crimson clover or triticale or mixed crimson clover and triticale) can provide improved management of Phytophthora root rot.
III. Practice good water management through proper irrigation and enhanced drainage
Flooding of nursery plant root zones is the main factor contributing to both ambrosia beetle attacks and Phytophthora infection in susceptible host plants. Soil flooding causes direct stress to the plant by depriving oxygen to the roots, and it provides a mechanism for spread of soil- and water-borne oomycete pathogens, including Phytophthora, from host to host. Flooded trees (especially flood intolerant species like dogwood) produce greater amounts of ethanol, a volatile cue used by ambrosia beetles to locate susceptible hosts. Moreover, environmental stress factors predispose trees to pathogen infection by reducing host plant defenses. Monitoring soil moisture levels in locations of fields where potential host plants are planted could allow risk forecasting for ambrosia beetle and pathogen infestations and provide a possible preventative tool.
IV. Select effective chemical management options
The best control strategy against ambrosia beetles and Phytophthora is to avoid plant stress factors that enhance these destructive issues. Use good sanitation practices and avoid planting disease-infected plants. When infestations are likely or actively occurring, however, several classes of fungicides and insecticides will provide preventative and curative effectiveness against ambrosia beetle and Phytophthora. In a recent field study in McMinnville, TN, dogwood trees exposed to Phytophthora cinnamomi and flooding had a large number of ambrosia beetle attacks. The combination of fungicide mefenoxam + insecticide permethrin was the most effective treatment in reducing Phytophthora root rot severity and ambrosia beetle attacks in dogwood trees that were exposed to the pathogen and flooding stress. Mefenoxam was drenchapplied 18 days before Phytophthora inoculation and 21 days before intentional flooding. The same trees also were sprayed with permethrin two days before flood initiation. The combination of mefenoxam + activated charcoal + kaolin also significantly reduced the number of ambrosia beetle attacks. Charcoal + kaolin was sprayed two days after flooding. The application of activated charcoal and kaolin may block or absorb ethanol emissions from stressed trees. In another study, fungicide active ingredients applied preventively or curatively (i.e., fluxapyroxad + pyraclostrobin), and preventatively (i.e. mefenoxam) reduced ambrosia beetle attacks and Phytophthora in flooded dogwoods. The preventative application was performed seven days before flooding and the curative application was performed 24 hours after flooding using a spray-to-drench (sprench) application to the lower trunk and potting substrate surrounding the base of the plant. Because ambrosia beetles feed on symbiont ambrosia fungi, the application of systemic fungicides like fluxapyroxad, pyraclostrobin, and mefenoxam also may provide protection against symbiont fungi. When the ambrosia beetles are not able to farm fungi in the tree, the adult beetles will not make galleries. Other treatment options showing promise for repelling ambrosia beetles include methyl salicylate (MeSA), a host defense and signaling compound, combined with verbenone (a bark beetle anti-aggregation pheromone). Research is on-going with regard to the best formulation, rate, and application methods for MeSA and verbenone.
To improve application timing of chemical-based ambrosia beetle treatments, ethanol-baited traps can be used to monitor seasonal beetle flight activity near ornamental nurseries. Several companies sell slowrelease ethanol lures, which can be placed in various commercial traps or homemade soda bottle traps. Generally, a beetle-killing agent like soapy water or low toxicity antifreeze (propylene glycol) is placed in the bottom of the trap. Be aware that large numbers of non-pest ambrosia beetles also may respond to ethanol-baited traps, so a good approach is to monitor traps for large numbers of beetles when temperatures are near 68ºF and to take captured specimens to local Extension offices for assistance with beetle identifications.
For more information about ambrosia beetle and Phytophthora, please visit our recent publication at: https://academic.oup.com/jee/article-abstract/115/4/1213/6619515 and https://www.sciencedirect.com/science/article/abs/pii/S0261219419301747
For soda bottle traps, visit: https://stopab.org/wp-content/uploads/2022/08/JC-Clemson-Ambrosia-beetle-brochure.pdf
Finding Success with Mediterranean Ornamental and Semi-Hardy Edible Plants
Semi-Arid Loving, Half Hardy(?), and Perfect Plants for Your Garden
Dr. Andy Pulte, Distinguished Lecturer (UT Plant Sciences) and Director of UT GATOP Arboretum and Education Center (Knoxville)
Commonly referred to as Mediterranean in origin, there is a somewhat confusing (and decidedly oversimplified) group of plants that come from a similar region of the world. What gardeners and the public may infer from the word “Mediterranean” is somewhat ambiguous, and in practical terms may be most associated with a climactic region that is most often associated with dry summers, mild winters, and lean soils. Parts of California certainly supply the conditions that are described as a “Mediterranean climate.” I often hear people suggest certain plants prefer “Mediterranean” type conditions. And in fact, it is true many of the plant species that we say prefer “Mediterranean” type conditions have originated from the Mediterranean basin, which covers portions of three continents (Europe, Asia, and Africa). For those of us who garden or sell plants in the Southeastern U.S., we know without a shadow of a doubt that we do not live in a Mediterranean climate. We commonly experience hot, humid summers and cool, wet winters. However, some edible, ornamental, and medicinal plants from the Mediterranean basin continue to be tried, and occasionally will thrive, and so are increasing in popularity in regional gardens. I have grown and enjoyed all of the plants that I will describe below. One plant not mentioned, Olive (Olea europaea) (Photo 1), which is the quintessential botanical indicator of a true Mediterranean climate, is not known to be reliably hardy in the southeastern U.S. However, I do keep an olive tree in a container as an example for students and drag it into our greenhouses at UT’s campus every winter.
If you choose to add any of the following plants to your garden, or if you want to suggest them for customers, I have some basic recommendations. First, realize that most of these plants can be marginally hardy across the state. All species are worth growing, but these plants are also susceptible to the impacts of our regional climate. Second, all of the following plants perform best when planted in spring and placed in full sun after the soil has warmed and the fear of frost has passed. This timing will give the plants an entire growing season to establish before experiencing what winter may have to offer. Also, do not prune any of these plants as fall approaches or during the winter. If pruning is desirable, do so only after your frost-free date is well behind you (in Knoxville’s USDA Plant Hardiness Zone 7, May 1st is a safe bet). Lastly, when establishing new plants, I suggest planting slightly above grade and mounding soil up to their roots to reduce the chances of waterlogging the root zone. Or even better, try growing these plants in containers with increased drainage (note: plants in containers may have greater need of winter protection). All the following plants may not be “forever plants” in your garden or the gardens of your customers. However, you may get several years of enjoyment out of them before plants succumb to winter injury or our region’s high humidity.
Photo 1: Olive europaea
As an example, right before Christmas 2022, an unprecedented cold snap killed or severely damaged many of the plants listed below. There is no reason to stop growing these plants altogether or stop promoting their use. In fact, past experience and all indications suggest that retail consumers and residential will want to replace these plants during spring 2023. So this cold snap provides a great opportunity to introduce consumers to species and cultivars that are known to thrive in our region.
Rosemary
(Salvia rosmarinus)
Native Range: Africa, Europe (Portugal and N.W. Spain), western Asia
Rosemary becomes a woody shrub across time and can grow to 2 – 4' tall. Plant near sidewalks and walkways for passersby to brush as they move past. Many cultivars are being tested for cold hardiness, but ‘Arp’ is still the standard. ‘Madalene Hill’ which is also known as ‘Hill Hardy’ may be the second cold-hardiest rosemary we can grow. Flowers can be pink or white but are most often blueish purple. Flowering time is also cultivar dependent, with some blooming in spring and summer while others bloom in the fall or early winter. [Note: This plant species was formerly Rosmarinus officinalis.]
Bay
(Laurus nobilis)
Native Range: Northern Africa, western Asia, southern Europe
Bay is most commonly known as the leaf you pick out of your soup, or crab boil, before you dig in to eat – bay leaf comes from an evergreen tree or large shrub known for its aromatic foliage. Bay is beautiful in a container that can be moved indoors for winter protection or can be planted in a highly sheltered spot. Laurus nobilis is truly a Zone 8 plant. I have seen specimens survive for several years when planted in just the right spot with good drainage where they may then grow to several feet in height.
Pomegranate
(Punica granatum)
Native Range: Middle and western Asia
Possibly hardier than its typical Zone 8 listing, some Tennessee gardeners have started growing pomegranate not for its fruit, but its flowers. Plants grow as a multistemmed shrub with flowers that range between red, bright orange, and salmon-colored and can look like a small carnation on many ornamental cultivars. If temperatures go below 10ºF, plants are often killed back to the ground but will often persist and rebound from their existing root system.
Photo 2:
‘Hill Hardy’ Rosemary
Photo by Andy Pulte
Photo 4a: Ornamental Pomegranate
Photo by Bill Klingeman
Photo 3: Bay
Photo by Andy Pulte
Photo 4b: Dwarf Pomegranate
Photo by Bill Klingeman
Fig (Ficus carica)
Native Range: Western Asia, southeastern Europe
Fresh figs from your garden are a true delicacy, which makes fig a musthave plant for many Tennessee gardeners. Figs are large shrubs that sometimes reach over 15' high and wide. After mild winters when stems persist, gardeners are often treated to both a late spring and a fall crop of figs. There are many cultivars to choose from, but the best advice is to get several so you can expand your harvest window. Different cultivars will produce their fruits at slightly different times and also can provide a diversity of tastes to explore.
Common sage (Salvia officinalis)
Native Range: Spain, western Balkan Peninsula, Asia Minor, and northern Africa
Very commonly grown in Tennessee gardens, common sage is by far the hardiest of the plants listed, provided they are given good drainage. Common sage grows as a small, woody, sub-shrub that has more or less glaucous, wooly, resinous leaves. Many cultivars are grown as potherbs or spices, with others used strictly as ornamental plants. These are valuable garden additions when planted on the edge of a sunny border with good drainage.
CONCLUDED ON PAGE 28
Photo 5: Fig
Photo by Andy Pulte
Photo 6a: Sage
Photo by Andy Pulte
Photo 6b: Sage
Photo by Andy Pulte
Feature continued
English
Lavender (Lavandula angustifolia) Native Range: Primarily Mediterranean climactic regions of Europe, Spain eastward to Italy
Not really originating in England at all, but English lavender was given that moniker by English gardeners. Many cultivars are sold, yet few persist well into the dogdays of summer. All selections require excellent drainage and good air circulation for success. We have all been impressed with the cultivar ‘Phenomenal’ which is actually a Lavandula x intermedia hybrid cross between English Lavender and Lavandula latifolia (Portuguese Lavender). To keep plants from becoming leggy, prune flowers off as they start to fade.
Photo 7: English Lavender
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