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.

I just read an article by Alan Armitage where he states that America has been “Hydrangized.” As usual, Alan is spot on. Hydrangea sales continue to grow, year after year. As a category, it is the top-selling genus for Spring Meadow, and as a liner grower, we are in a position to see and evaluate trends. Not that this is a new trend: it dates back to the zenith of Martha Stewart and her beautiful multi-page spreads featuring blue and pink blooms, obviously photographed in hydrangea-friendly, maritime climates such as Vancouver or Cape Cod. At the same time, Gen-Xers (and more recently, millennials) began buying starter homes and pulling out the old junipers and yews once favored by their elders. These new generations were looking to add more color to their yards, and few shrubs offer up as much color as a hydrangea. At that time, our nursery offered 53 varieties of hydrangea, 30 of which were Hydrangea macrophylla. Today, we offer roughly that same number of varieties, but only 14 are macs. This is telling, and we will speak more about this market shift later in the article.

Since Y2K, hydrangea sales numbers have grown exponentially. And to give you an idea how the market has changed, we currently offer only four of the same hydrangea cultivars listed in our 1999-2000 catalog. The species have changed, the cultivars have changed, but hydrangeas are more popular than ever. Clearly, the steady stream of new varieties has grown and sustained the hydrangea market.

Mike Dirr and Bailey Nursery’s introduction of Endless Summer Hydrangea macrophylla ‘Bailmer’ pp#15,298 in 2001, with its blue pot and massive marketing campaign, played a huge role in the shift. With the added benefit of remontancy (blooming on new wood without vernalization), who in their right mind, living in Middle America, would want to buy ‘Glowing Embers’, ‘Merritt Supreme’, ‘Nikko Blue’ or another old-fashioned cultivar that might not bloom? The hope and dream of every gardener in Middle America has been to have a hydrangea with big blue flowers, from June until October, regardless of cold winter or spring frost. Everyone was elated with the development, until they found out the dream was, in fact, just a dream. It turned out that remontant hydrangeas did best in milder climates where the older varieties already did well: without a killing frost, you got the spring and summer blooms, as well as the autumn blooms. The problem, particularly with some of the earlier introductions, is that if the plant dies back from winter damage or is cut back in fall or spring, it takes time to grow new stems and flower buds, leaving cold-climate gardeners disappointed, if not downright pissed off. The dream was too good to be true.

The good news is that plant breeders, including Bailey, Spring Meadow, and others kept at it, crossing remontant hydrangeas with hardier species such as Hydrangea serrata, the mountain hydrangea native to colder continental regions of South Korea, China and Japan. This next generation of hydrangeas had better stem and bud hardiness, which resulted in more reliable plants. Endless Summer Bloomstruck (‘PIIHM-II’) and Tuff Stuff Ah-Ha (‘SMNHSDD’) have proven to be reliable bloomers in our trials here in Michigan. However, the more I looked at, trialed, and examined Hydrangea macrophylla, how it grows, and how, when, and where the flowers emerge, the more questions I had about creating a better hydrangea.

While remontancy is a nice benefit, it provides mostly late-season blooms. Improvements in stem and bud hardiness have helped give us more early-season blooms, but the species has its limits. So what else could be done to improve it? I finally found my answer in a research paper by Dr. Timothy Rinehart, a USDA scientist, who noted that a number of hydrangeas on the market appeared to rebloom but were not actually remontant. He speculated these plants were capable of producing vernalized buds at nodes well-below the normal blooming terminal flower bud, which reduced the chance of winter kill, frost damage and even well-intentioned pruning. I began examining the plants in our breeding program for this ability to make vernalized flower buds on the stem within inches of — and even below — the soil line. Combining this trait with remontancy and improved bud hardiness results in a much more reliable hydrangea that can bloom in the spring, summer, and fall, as exemplified in the Let’s Dance series, particularly Let’s Dance Cancan (‘SMNHSI’). With every passing year, Hydrangea macrophylla is getting better. The truth is, however, we are still a long way off from one with the reliability and flower power of Hydrangea paniculata, or our well-adapted, native Hydrangea arborescens and Hydrangea quercifolia. With more breeding and a bit of luck, our dreams may yet come true. Until then, other Hydrangea species will lead the way.

The average homeowner or landscaper wants real-world performance and reliability, both of which Hydrangea paniculata and Hydrangea arborescens deliver in spades. These species flower on new wood, and are much better able to cope with spring temperature swings. Both species are hardy, heat tolerant, adaptable to a range of soils and grow in sun or modest shade. Here, too, breeders have made incredible advances, which you can read about in my May 2019 column on Hydrangea paniculata breeding, “Standing on the shoulders of giants” (bit.ly/tim-wood-giants). With regards to Hydrangea arborescens, the game-changer came in 2009 when Dr. Tom Ranney and his team at North Carolina State University released Invincibelle Spirit H. a. ‘NCHA1’, the first pink flowered Annabelle-type hydrangea. While not a perfect plant (it has since been replaced with Invincibelle Spirit II H. a. ‘NCHA2’), it opened the door to the creation of a series of seven new, sterile, reblooming cultivars offering pink, red, mauve, white and green flowered forms, many of which are dwarf or compact and all with sturdier stems than ‘Annabelle’ and the original Invincibelle. It is garden performance and flowering reliability combined with these breeding advances that have grown the hydrangea market to record levels and shifted our product mix in favor of H. paniculata and H. arborescens. Add all of that to a new generation of homeowners that wanted to come home to a more colorful, low-maintenance yard and you get a rapidly growing hydrangea market that appears to have no end.

Opinions expressed are those of the author and do not necessarily represent the views of GIE Media, Inc.