Whether it’s a simple poly house or a more complex greenhouse structure, annual inspections and year-end maintenance tasks are critical. Chris Kirschner, regional sales manager at Atlas Manufacturing, describes what to look for and what to consider before the next growing season.

What are some important steps to take before buttoning up an overwintering structure?

Boots on the ground, eyes on the greenhouse! Look at your buildings with a walk around looking at the outside of the building but also inside looking out. Are there gaps around shutters or vents, doors or openings? Are there holes in your covering? Now is the time to order your poly patch tape to make any repairs. Check to make sure your poly inflation fan is working properly and order a spare. Are there places that need caulked to stop heat from leaking out or cold air from coming in? Check thermostats and heater and/or fan settings and make any necessary adjustments. This is also a great time to winterize or blow out water lines outside of the house.

What signs of wear on film determine that it’s time for a replacement?

No one really likes to fix something that’s not broke, but going into winter with covering that is marginal is not ideal. Inspect your covering closely. Overall, it may look fine, but look closely at the poly all the way around the perimeter. Everywhere the poly is held down by a fastener is a likely wear spot and could show some sings of tearing. Look closely at the poly where it crosses the structure’s framing, such as bows or purlins. Has it rubbed and turned gray? That “graying” could also be hiding small cracks or tears. Check the age of the covering. Keep updated records and consider using a Sharpie to write the install date somewhere on all your coverings. Try to use the same spot on every house if possible. A piece of poly film that looks fine but has been on for eight years needs to be replaced regardless of how it looks.

How significant is light transmission when it comes to film? How severely can the lack of light affect crops?

Light transmission is key. When trying to equate light transmission, on average, a rough idea of growth to light is equal. Therefore, just increasing your light transmission by 1-2% will give you an increase in plant growth of 1-2%. When you think of a double poly film covering having a light transmission range of 75-85% on average, discoloration or yellowing can greatly reduce this, which reduces plant growth. If you can increase plant growth by 5%, you might just pay for that new covering one year earlier.

When it comes to structures, in what instance(s) should growers not skimp on budget?

Do not skimp on loading and engineering. Never try to build a structure that doesn’t meet the snow and wind loads required for your area. You may have every intention of taking the covering off in the winter before storms, but in two or three years when the market has changed, you might need that space. If you’re going to take up precious land and put up a greenhouse, do it right and make sure that it’s versatile and will be able to react with changing markets and customer’s needs.

What are some structure upgrades that typical nursery growers should

consider? Just a few years ago, technology to remotely access and control your greenhouse was expensive and, in most cases, cost more than the average hoop house. Today that’s not the case. While you’re attending to other chores, crops, travelling, managing people or whatever your daily schedule demands, physically checking the temperature or manually turning equipment on or off just doesn’t add up. Technology now allows you to receive alerts when temps fall out of the parameters. You can adjust temperatures from your phone. You can regulate the watering or light cycle with the push of a button. Don’t get stuck in the dark ages. With automation, you’re not just saving time, you’re saving money and energy. By reading graphs and looking at your temps and energy use, you can make changes to optimize your efficiency. You’d be surprised at what little investment this can take.

For more: https://atlasgreenhouse.com

Age affects us all. Some may think younger is better while others think age holds the key to wisdom and security. The same arguments could be made for pine bark substrate age and its effect on crop production management strategies. Over the decades, a lot has been speculated but very little has been proven regarding the physical, chemical, hydrological and biological effect that aging has on pine bark substrate materials. There are so many variables that factor into the investigation of age on organic materials and how other inputs, additives and biological entities interact and respond to these changing properties. As seen in the cover photo, age certainly has a visual influence on pine bark, but what changes are present that we cannot see? This article will highlight some of what has been studied in the past and present regarding changes in pine bark substrates.

Pine bark may be used as a fresh, aged, or composted product. As my colleague Dr. James Altland (USDA scientist) has stated in some of his works, “there is no general agreement as to what constitutes fresh, aged, or composted when it comes to bark.” I agree with his assessment. What most believe to be acceptable (or at least workable) definitions would be that fresh bark has only been removed from freshly harvest logs for a short amount of time (days to few weeks) and has been processed to reduce its particle size suitable to be used in/as a substrate. Aged bark is bark that has been processed and often screened before being stacked/piled in windrows in open spaces and allowed to sit for a period of weeks to many months (Fig. 1). Aging bark does not include the addition of a nitrogen source to accelerate or enhance the degradation process. Aging piles may or may not be frequently turned (aerated) or managed in other ways. Composting bark includes the addition of a nitrogen source and the controlled turning and management of piles/windrows to speed the degradation process as much as possible in efforts to stabilize the bark material. The majority of pine bark supplies in the Southeastern U.S. are aged and not composted, but some proper composting operations do exist. For the purpose of this article, as well as most published works on the topic, bark will be referred to as fresh and aged (not composted).

Fresh and aged bark materials that can be found at numerous bark suppliers and can range in color, particle size and shape, as well as smell and chemical composition as seen in Figure 2. While both aged and fresh pine bark can be used successfully, little research has been done to investigate the differences between fresh and aged materials, as well as pine bark of specific ages. Additionally, the actual age of pine bark used for research in the literature is usually not reported, making it hard to extrapolate anything more than general trends for bark that is considered “aged.” To gain a greater understanding of the effects of aging and pile management on pine bark substrates, a 12-month study was conducted at a pine bark supplier in Eagle Springs, North Carolina, which included replicated windrows of specifically processed, screened, and monitored bark inventories (Fig. 3). This long-term project was initiated with the objectives of tracking and quantifying the chemical, physical, hydrological and biological changes that occur over time in bark materials. At each month, these bark piles were methodically sampled and analyzed. Some of the monthly tests included sand content (contamination from the wind and from the act of turning the bark piles every month; Fig. 4A), pH (Fig. 4B), and seedling germination trials as a method to detect bark phytotoxicity (Fig. 4C-D). In this article we will highlight only some findings from the pH and PGR trials conducted on some of the bark ages.

Nitrogen

A thorough search through the published scientific literature only provides a few papers that summarize experiments investigating nitrogen use/tie-up of fresh or aged pine bark during crop production. Studies dating back to 1979 through 2008 that evaluated numerous woody plant species under various growing conditions reported that nitrogen was not the limiting factor in any plant growth differences that were observed when plants were grown in fresh or aged pine bark. These reports, a total of seven, associate the growth differences found in their studies to irrigation management, bark particle size, plant available water, or some degree of early onset phytotoxic effect from fresh bark on young plant growth. The nitrogen fertilization trials conducted were not very through in covering a wide range of bark ages but instead most only compared fresh bark to barks aged for many months or even years. However, when no convincing scientific evidence can be found in the literature to suggest a significant immobilization of nitrogen by fresh bark to the extent of it negatively affecting plant growth, it is worth noting. Until some definitive evidence is provided, there seems to be little concern of nutrient management issues for growers who may choose (or have to) use fresh bark.

pH

Pine bark is highly acidic, with a pH range generally between 3.8 to 4.5. Several sources disagree whether the pH goes up or down with aging and/or decomposition, which may be due to the fact that pH may decrease if bark piles are improperly managed and have gone under anaerobic conditions during the aging process. Other researchers have found no changes in pine bark pH based on age, while some have indicated that there may be an increase in pH when the bark has a higher percentage of fine particles. To better understand the effect that age has on pH and pH response in pine bark a study was conducted where samples of pine bark aged for 0, 3, 6, 9, or 12 months were amended with various lime rates to investigate effects of pine bark age on lime efficacy. Pulverized 100 mesh dolomitic limestone was incorporated at rates of 0, 4 and 8 lbs/yd3. On 1, 3, 5, 7, 14 and 21 days after limestone amendment pH was measured using the 1:1 extraction method. We found that pH increased rapidly one day after lime addition, with slight increases during days 3 through 5, and a general stabilization for the remainder of the sample days (Fig. 5). Lime had the greatest pH response in fresh bark (0 month) at both the 4- and 8-pound rates compared to older barks. As bark age increased there tended to be a lower pH response to lime additions, possibly due to chemical changes in the bark over time that increased its ability to buffer pH change. If growers choose to grow in fresher bark, management of pH should be monitored closely both in pre-plant lime additions and during crop production.

PGRs

The application of plant growth regulators (PGRs) to control excessive growth, and increase marketability, of containerized crops is common practice in the horticulture industry. The primary benefit of PGRs is to allow the production of compact, uniform crops, that can be more tightly spaced in the growing area. One of the most common application methods of PGRs are substrate drenches. One of the concerns with drench applications is adsorption of active ingredient by organic substrate components. Previous works over the decades have shown that pine bark in substrates can reduce the efficacy (growth control) of PGRs. With pine bark being a common substrate component and age of pine bark possibly differing among suppliers, more scientific data was needed to describe differences between ages and management practices that can maximize effectiveness of the substrate at these different ages. Although studies have investigated different variables that may influence PGR efficacy in pine bark substrates including percent incorporation, bark particle size, and fresh versus composted pine bark, no information was available on the effects of pine bark age on PGR efficacy.

A project in 2017 amended pine bark aged for varying lengths of time with Canadian sphagnum peat at ratios of 60:20 and 40:40% (v:v) peat: pine bark, with the remaining 20% being perlite. Substrate blends were fluffed and wetted by hand to a moisture content of 60% prior to pH adjustment and potting. A control substrate blend of 80:20 (v:v) peat: perlite was also included. Marigold and sunflower plugs were transplanted into 12.7cm azalea containers and plants were fertilized twice a day at each watering with 150 ppm nitrogen from a water-soluble fertilizer. Twenty days after planting, 3 fl oz of solution containing either 0, 1, 2, or 4 mg of active ingredient (a.i.) per container paclobutrazol (Piccolo 10XC; Fine Americas Inc., Walnut Creek, California) was applied to each container as a substrate drench. The experiment was a completely randomized design with six replications of six substrates x four PGR concentration combinations. Although not always significant across all PGR rates, there was a general trend of reduced growth control with increasing age of pine bark as seen in the 40% bark inclusion rate at the highest rate of PGR application (Fig. 6). Not shown are the plants grown with 0 PGR application which showed minimal growth differences which supports what we see in Figure 6 to be a result of the PGR and not a major growth retarding influence of fresh bark on the growth of these two species. This data indicate aged bark may cause a greater reduction in drench applied PGR efficacy (reduced growth control) compared to fresh bark but it is unclear if it is the bark chemistry, particle size, or other variable affecting the PGR growth control response.

Bark age does seem to have some effect on various plant growth parameters and cultural management strategies, but the effects do not appear to be greatly inhibiting or difficult to address. Based on the literature over the past four decades, pine bark age does not greatly influence nitrogen or other nutrient regimes but it may offer challenges to irrigation (plant available water) or other chemical applications like pH or PGRs in certain crop production systems. Bottom line, as long as pine bark is not toxic, which most all accounts show that it is not unless growing seedlings or herbaceous plants in very fresh bark with small particle sizes, crops can be grown in any age of pine bark with no serious detriment as long as adjustments are made where needed. When growers factor in the cost differences of fresh versus aged bark (including volume delivered per truck and overall transportation costs) compared to the costs associated with managing crops in fresh pine bark there may be some changes that make sense/cents. As always, it is suggested to have conversations with bark suppliers or other knowledgeable substrate experts to explore options before deciding to convert entire operations to bark you are not used to.

Brian Jackson is an associate professor and director of the Horticultural Substrates Laboratory at North Carolina State University (Brian_Jackson@ncsu.edu). Laura Barth is a former graduate student.

All it took to hook Alexander Martin was a STIHL MS271 chainsaw. From there, he has taken his interest in tree care all over the place, including a stint abroad in Germany.

Martin still remembers the exact make and model of the chainsaw his neighbor showed him at age 13. Martin and his father had been cutting firewood, but his neighbor — an arborist — implored Martin’s dad to buy a better chainsaw. The neighbor promised that if Martin would take the lessons seriously, he’d teach Martin the basics of arboriculture.

Martin was young, but once he learned he could climb trees for a living, he fell in love with the idea. It didn’t hurt that using the equipment looked like a lot of fun.

“At 13 years old, I thought, ‘Well, that’s the coolest thing I’ve ever heard,” he says. “I still think chippers and trucks are the coolest things you get to use.”

At 16, Martin started working part-time as a contracted arborist. The gig worked out well because, as he puts it, he weighed just 110 pounds and climbing came easy.

But Martin’s biggest move had yet to come. Prompted by curiosity in his family’s heritage and in learning a new language, Martin left his home in Manitoba, Canada, to spend six months in Germany. Though he wasn’t necessarily there strictly for arboriculture, he was immersed in the differences between their practices and those in Canada.

For example, Martin learned that arboriculture is a much more social experience with clients in Europe. When they’d do tree removals, there would be people with natural discontent with having trees removed. They would come out and ask questions about what was happening, why a tree needed to come down and what they hoped to see there in the future.

Martin says that understanding the sentimental, emotional value behind these trees has led him to approach removals with compassion. Sometimes, trees have been up in a client’s yard for decades. Seeing it go can be difficult, and because of his experience in Germany, Martin has gained an understanding of these complex emotions from clients and brings more compassion to jobsites.

“Germany’s outlook on urban forestry is a lot different,” he says. “I don’t think I was ever disadvantaged by moving around so much, but I do think that it was overly beneficial because I experienced stuff in Germany… that can be slightly mimicked here.”

In 2017, Martin landed a job at Timberland Tree Service, and in 2019, he enrolled in the urban forestry program at the University of British Columbia. He intends to earn both a master’s degree and a doctorate, but for now, he’s enjoying his time at the UBC program. It only started a few years ago, but Martin says they’ve enlisted the help from some of the industry’s best to serve as professors.

“Now that I’m at UBC, it’s one of the best decisions I’ve ever made,” he says. “There are professors who are just outstanding in their field. There were people that I heard of through my professional career and now I get to learn from them and study from them.”

Martin is interested in one day running a consulting-type company. While he’ll always be the 13-year-old kid who fell in love with the cool chainsaws, chippers and trucks, he’s finding a new calling in teaching others about trees. Just recently, he was looking at a client’s tree that had mites in it, but if they had simply Googled what the issue with their tree was, they’d have never successfully identified the problem.

“I really like consulting because it’s one thing to talk to other professionals, but there’s something really nice about talking with folks and educating them about trees,” Martin says. “The whole industry’s exciting to me. It’s hugely dynamic, and it keeps changing. Learning with those changes to the industry is the most unique part of it. There’s constantly new information coming out. Staying on top of it… is a critical, important role for horticulturists.”

Author’s note: Student Spotlight brings you the perspectives of horticulture students and insights into the future of the industry.

Japanese painted ferns play an important and significant role in our shaded and partly-shaded gardens. By offering the combination of substantial texture along with the eye-catching and variable colors of silver and burgundy, these ferns should be on the radar for any gardener that can grow them successfully. The popularity of these painted ferns has helped mobilize not only more gardeners seeking them out at local nurseries and garden centers but breeding and selection work, which continues in earnest to develop and offer selections with differences both subtle and more pronounced. The intent of this article is to not only extol the merits of these ferns but to examine some of the best selections on the market today based on personal experience, both formal and informal trialing and observations over many years.

Working as the director of horticulture for 21 years at Rotary Botanical Gardens (Janesville, Wisconsin), I was directly involved in the design and construction of a fern and moss garden in 2005 that was intended to grow and display as many ferns as we could possibly accumulate in this Midwest climate. At its peak, this garden (affiliate garden for the Hardy Fern Foundation) contained over 250 different types of ferns that were being trialed for hardiness and adaptability in our climate.

One of our focus collections were Japanese painted ferns. We started with the popular Athyrium niponicum var. pictum (USDA Hardiness Zone 4-8) which wasn’t new for us and already had some notoriety, particularly after receiving the Perennial Plant of the Year award in 2004 from the Perennial Plant Association. At the time, there were a couple of other varieties and we were seeing some of the earliest of the painted fern crosses with lady fern (Athyrium filix-femina). These hybrids tended to combine the best traits of both parents and new hybrid selections continue to appear. At one point, we amassed over 30 varieties of Japanese painted ferns and hybrids for side-by-side comparisons in a partly-shaded garden with good soils, excellent drainage and a supplemental irrigation system (when needed). Having multiple specimens of all of these painted fern selections, we were able to do our own, “side-by-side” observations for the past 15 years. New selections on the market were aggressively sourced and became part of these ongoing trials as well.

It is important to mention that Richard Hawke, plant evaluation manager and associate scientist at the Chicago Botanic Garden (Glencoe, Illinois), did a trial of painted ferns and lady ferns from 2002-2014. This study included the evaluation of 11 selections of painted fern (Athyrium niponicum) as well as four of the painted fern hybrids. This study is certainly worthy of review at chicago botanic.org/downloads/planteval_notes/no39_ferns.pdf. Hawke’s observations are fairly consistent with ours although our trial did go on to broaden the scope of the collection to absorb new acquisitions. Our pH was a neutral 7.0 as compared to the higher pH of 7.5 in the Chicago Botanic Garden trial and it’s likely we applied more irrigation on a regular basis.

Painted fern coloration

The foliar merits of these ferns are quite apparent and amazing in the garden. The frosty white to “steely-grey” fronds may have hints of maroon depending on the season and the variety. The coloration on painted ferns has not only variability between selections (very subtle at times) but there is transition of the coloring depending on the season. Japanese painted ferns upon emergence tend to have more burgundy and muted tones of silver and depending on the variety, certain colors become more prevalent as spring progresses in to summer. In our trials, we even noted that the best foliage coloration for most varieties typically became more pronounced and established after multiple years in the garden. The burgundy tinting can be quite variable but is more intense for certain varieties like ‘Burgundy Lace’, ‘Pewter Lace’ and ‘Regal Red’. Additionally, the degree of “silvering” is also variable with some varieties like ‘Silver Falls’ being promoted specifically for a more intense silver. The feature of “cresting”, meaning fanned ends to the fern foliage (pinna), has appeared in at least three selections to date and while not unusual in some other species, does add an extra dimension of interest. ‘Applecourt’ was the first Athyrium niponicum to offer this feature and continues to be popular. ‘Crested Surf’ is an exciting new, crested selection and the hybrid painted fern, ‘Ocean’s Fury’ (hybrid) offers a taller form with plenty of cresting and a moderate amount of “silvering” on the foliage. An interesting novelty, the variegated selection, ‘Lemon Cream’ features creamy yellow variegation but very little observable silver or burgundy.

Fern breeding

I’m quite excited about the future of the hybrid painted ferns with both lady fern (Athyrium filix-femina) and Japanese painted fern bloodlines. These crosses have resulted in taller ferns that offer their colorful contributions at the 24- to 36-inch range whereas the majority of Athyrium niponicum selections hover at the 15- to 18-inch height. Both ‘Branford Beauty’ and ‘Branford Rambler’ are early results of these crosses and are still sought out for their vigor and proven performance. The ‘Ghost’ fern, in my opinion, set the standard for the hybrids by offering a very silver fern that could reach 30 inches in height. The foliage upon emergence is a silvery green but with enough sunlight, a true silver materializes in summer. The crested form ‘Ocean’s Fury’ is a nice selection (mentioned above) but I’m very excited about the relatively new ‘Godzilla’ hybrid which truly looks like a Japanese painted fern but twice the size. There is a lot more burgundy in ‘Godzilla’ than ‘Ghost’, but both have limitless applications out in the partly shaded garden.

Attributes

Painted ferns and their hybrids tend to have an arching habit, and all exhibit some degree of the silvering mentioned previously. Colors may be more muted in deeper shade, so some degree of sunlight helps with more intense coloration. Morning sun or dappled afternoon light seems to be sufficient for maximizing painted fern coloration. While I’ve seen painted ferns alive in the deepest of shade, they were not robust specimens and didn’t exhibit significant coloration. Keep in mind that these plants prefer consistent moisture and do prefer soils rich in organic matter. I don’t view these as drought tolerant ferns for any great length of time during the heat of summer. While durable once established, drought conditions will adversely affect these painted ferns in a dramatic and quick fashion. Further south in their growing range, they should be provided more shading to maintain the integrity of the foliage and help conserve surrounding moisture and plant health. Providing supplemental moisture as needed is ideal as is having decent soils at the time of installation. As mentioned, soils rich in organic matter that are consistently moist but well-drained seem ideal for these selections.

The growth rate of painted ferns is fairly moderate by roots as they will slowly colonize an area. ‘Branford Rambler’ seems to spread quicker than others which is a feature that is touted. They are easy to divide and move as you like although this process is ideal at the beginning or end of the growing season. With very few insect or disease issues, the ferns should look great throughout the season if given ample moisture. While deer resistant, rabbits have been known to take a nibble, particularly on the tender new growth in spring. Any fronds that turn brown during the season can simply be cut out.

Used as specimens, Japanese painted ferns offer that pop of foliage color with silver highlights not only offering “brightness” in our shadier gardens but at dusk, that coloration really shines. I’ve seen masses of painted ferns used along streams and ponds that really offer wonderful interest. Hawke describes painted ferns as both elegant and utilitarian and further describes their value as accents or in massed plantings. Using many specimens together creates a “collective groundcover” that is clearly defined and can be under-planted with the earliest of spring blooming bulbs or other companion plants. Sloped areas in shade can utilize masses of painted ferns to help serve as erosion control.

Neighbors for your painted ferns will be dictated by the conditions but if you have good soil and adequate moisture, consider companion plants such as false forget-me-nots (Brunnera), Ligularia, Hosta (particularly blue), Helleborus, toadlilies (Tricyrtis), and coral bells (Heuchera) with maroon foliage. Painted ferns also look great combined with bleeding hearts like ‘Gold Heart’ (Lamprocapnos spectabilis), lungworts (Pulmonaria) and variegated Jacob’s ladder (Polemonium reptans ‘Stairway to Heaven’). Take advantage of the silver and burgundy highlights of the ferns and combine accordingly making sure all participants are happy in their combined setting. I’ve seen painted ferns and their hybrids also used successfully in containers for the season then planted out to permanent spots in fall. The silver fronds also have value in fresh flower arrangements.

Those that garden in any degree of shade do quickly appreciate the value of continued and substantial foliage interest from their plantings. While flowers are still part of the equation for many perennials in shade, the tapestry and combination of textural and colorful foliage is what truly completes the scene. The contribution of immediate fine texture and hints of silver and burgundy from the gamut of painted fern selections offers extended illumination in our shadier respites. These plants will continue to be in high demand and new selections and hybrids will undoubtedly make future appearances.