Some Mites Like It Hot... Ready or Not!

By Krista Harris
ISA Certified Arborist®
July 25, 2024​

As the average temperatures rise, hungry spider mites thrive! These tiny leaf suckers love hot and dry weather and are currently causing many of our beloved foundation shrubs to look sickly and even lose their leaves entirely.

Spider mites on a burning bush

Spider mite damage on burning bush (Euomymus alatus) and on boxwood (Buxus sp.) is common in the summer months. These typically dependably green shrubs will begin to take on a yellow or bronze cast when infested, and, upon closer inspection, a distinct stippling or scratched appearance of the leaves will become apparent. This characteristic pattern is caused by feeding of the mites on the undersides of the plant’s leaves. Many generations of this tiny sucker can occur per summer. A complete generation can take less than a week during 90°F temperatures and without significant rainfall. That’s a lot of babies at 100 eggs per female!

The twospotted spider mite is the species that afflicts the burning bush. These mites will also feed on many other species when available including viburnum, roses, edible plants, perennials and houseplants. In full sun conditions (especially near hardscape like driveways or brick walls) you may see their webbing binding the leaves and even tiny mites moving within the web. This species of mite overwinters as adults in leaf litter and in soil. It's important to clean up and bag any fallen leaves in the fall so that you can reduce the population of these pests before they wake up next spring.

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Burning bush with spider mites

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The boxwood spider mite can only feed on boxwood species. This makes it a “host specific” species of spider mite and will not cause damage to any other plants in your landscape. This mite also differs from the twospotted spider mite in that it creates no webs, it feeds on the upper surface of the leaf as well as the bottom surface and it overwinters as eggs on the boxwood plant.

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Boxwood with spider mites

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If you want to check your plants for these "pepper sized" pests or suspect you may have a growing spider mite issue, the best way is to firmly smack the twig over a white piece of paper. Look closely and you may see tiny mites crawling on the paper.

As a preventative measure, it is a great idea to give both your burning bushes and boxwoods a heavy spray with your hose nozzle. Do this twice a week in hot, dry weather (over 85°F). Concentrate on the undersides of the leaves especially to attempt to dislodge adults and eggs.

Keeping your plants watered during the summer also really helps to curb serious infestations. If plants are stressed for water, they will be much more likely to become overrun with spider mites and also insect pests like scale, aphids and lacebug.

If you would like one of our 20+ ISA Certified Arborists® to scout your landscape for spider mites and give you options to control these proliferous pests, please contact our office at (614) 895-7000 or request a free quote at RussellTreeExperts.com/Quote. We offer many options to get spider mites under control and we will help determine the best course of action for your specific trees and shrubs! Have a great summer and make sure to keep yourself watered as well!

Additional Arbor Ed Articles!

Sincerely,

Krista Harris | Journeyperson, Russell Tree Experts

Krista grew up in the central Ohio area and became an ISA Certified Arborist® in 2017. She graduated from The Ohio State University with a Bachelor of Science in Crop Science and a minor in Plant Pathology in 2000 and has been in the green industry ever since. Her favorite trees are the American sycamore, American beech, and giant sequoia. [BS in Horticulture Crop Science, The Ohio State University / ISA Certified Arborist® OH-6699A / ODA Comm. Pesticide Lic. #148078]

Bagworms: Why they are bad news & How to get rid of them

By Chris Gill
ISA Certified Arborist®
May 23, 2024​

A bagworm on a Colorado blue spruce tree (Picea pungens)

Bagworms are a serious pest to a variety of ornamental plants in our landscapes. Bagworms are the caterpillars of a moth. These caterpillars are called “bagworms” because they wrap themselves in a bag constructed of material from their host plant. The bags camouflage the bagworms from predators as they feed and can also make effective treatments challenging. Understanding their life cycle, preferred host plants, feeding habits, and effective treatment methods are crucial for managing infestations and preserving the health of your plants. 

Life Cycle of Bagworms

Bagworms undergo a fascinating life cycle, transitioning through various stages from egg to adult moth. Let’s start with the hatching of the eggs and the main feeding stage. This is the stage that is the most noticeable and damaging to the host plant. Starting in early June into July, the larvae emerge hungry and begin constructing their protective cases using silk and surrounding plat materials. As they feed on foliage, they expand and reinforce their bags, incorporating leaves, twigs, and other debris to camouflage themselves and deter predators.    

After reaching maturity, which typically takes several weeks, the larvae stop feeding and prepare for pupation. Within the safety of their bags, they undergo metamorphosis, and the males emerge as adult moths and the female bagworm remains in the bag for mating. Once mated the female bagworm lays her eggs and their life cycle is over at this point. There can be as many as 500-1000 eggs. The eggs overwinter inside the dead female's bag and the cycle begins again in the spring.   

Feeding Habits

The larval stage of bagworm is the main feeding stage, consuming foliage from their host plants as they construct their protective bags. This feeding stage can last several weeks to a couple of months depending on environmental conditions and the availability of food sources. They use their silk threads to anchor themselves to branches or leaves, where they remain while feeding. As they consume foliage, they gradually defoliate the plant, weakening its overall health and potentially causing significant damage if left untreated. Complete defoliation often leads to plant death. Once the bagworm reaches maturity, they quit feeding and focus on mating.   

Main Host Plants

Bagworms are known to infest a wide range of host plants. Some of the most common host plants for bagworms include:  

• Evergreens: Arborvitae, juniper, cedar, pine, spruce, and cypress are often targeted by bagworms, which can cause severe damage to these trees if left unchecked.  

• Deciduous Trees: Bagworms may also infest deciduous trees such as honey locust, oak, maple, sycamore, willow, and poplar, feeding on their leaves and weakening the overall health of the tree.  

• Ornamental Shrubs: Boxwood, azalea, holly, and other ornamental shrubs are susceptible to bagworm infestations, which can defoliate and disfigure these plants if not addressed promptly.  

While bagworms are adaptable and may infest various plant species, their preference for evergreen trees is most common.  

Colorado blue spruce with bagworms

Twig dieback due to bagworms

Treatment Options 

Managing bagworm infestations can be done in a few ways - culturally, mechanically, or with chemical control methods. The most effective strategy will depend on the severity of the infestation and the size of the plants that are being treated. The following are some effective strategies for treating bagworm infestations:  

• Handpicking: In smaller infestations, manually removing bags from affected plants can be an effective control method. Simply pluck the bags from the branches and dispose of them properly to attempt to prevent future infestations.  You can throw them in the trash or burn them.

• Biological Control: Introducing natural predators of bagworms, such as parasitic wasps, or predatory insects, can help reduce populations naturally without the need for chemical intervention. (Flowers with lots of nectar can attract these predator insects). I like this method but do not recommend relying on it for managing heavily infested plants.

• Insecticides: Applying two well timed insecticide sprays spaced two weeks apart has been the most effective way to control bagworms. Applying the product early while the larva is feeding and in the initial stages of making their bag is essential. Once they have constructed a bag around their bodies, insecticides are far less effective.

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Bagworms may be small but their impact on plants can be quite serious. The damage is not obvious early in the season because the caterpillars and their bags are small, and the bags can be difficult to see until large numbers are present. Bagworms often are not detected by the untrained observer until August after severe defoliation has occurred. Getting to the plants early and detecting a problem can save a lot of headaches. At Russell Tree Experts we are trained to spot bagworms and use the OSU phenology calendar to properly time applications for effective control. 

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Sincerely,

Chris Gill I Regional Manager, Russell Tree Experts

Chris joined Russell Tree Experts in 2015 and has been in the green industry for over 15 years. When not at RTE, he enjoys spending time with wife & son, wakeboarding, and hunting. His favorite trees are the white oak & sugar maple for their beauty and uses beyond the landscape. Chris is an ISA certified arborist, EHAT certified, CPR and first aid certified, holds an ODA commercial pesticide license, and holds a tree risk assessment qualification (TRAQ).

Rhizosphaera Needle Cast: Causes, Symptoms, and Management

By Mike Wilson
ISA Certified Arborist®
May 2, 2024​

Rhizosphaera needle cast is a fungal disease that affects various species of coniferous trees, particularly spruces throughout central Ohio and the midwest, and has become increasingly common. This disease can cause significant damage to tree health and aesthetics if left untreated. Understanding its causes, symptoms, and management strategies is crucial for preventing its spread and minimizing its impact on host trees in your landscape. Rhizosphaera needle cast, or needle cast for short, is primarily caused by the fungus Rhizosphaera kalkhoffii. This fungus thrives in humid and wet conditions, which Ohio is seeing more and more of now. Spores of the fungus are spread through water splash, wind, and contaminated pruning tools, facilitating its transmission from infected to healthy trees. Colorado blue spruce trees (Picea pungens) is especially vulnerable due to the fact that they much prefer dry, arid environments like in Colorado and Utah.

A young Colorado blue spruce tree (Picea pungens) rapidly defoliating

Symptoms

The symptoms of needle cast typically appear on older needles first and progress upwards through the tree. Common symptoms to look out for are:

• Needle Discoloration: Infected needles initially develop yellow or light green spots, which gradually turn brown or purple-ish brown as the disease progresses.

• Needle Dropping: Infected needles may prematurely drop from the tree, leading to sparse foliage and an overall thinning of the canopy.

• Black Fruiting Bodies: Under close inspection, black fruiting bodies (spores) of the fungus may be visible on the surface of infected needles, particularly during humid conditions. This shows up as very fine black peppering found on the underside of the needles.

Black fruiting bodies (spores) of the fungus fungus Rhizosphaera kalkhoffii on the surface of infected needles

Effective management strategies of Rhizosphaera needle cast involves a combination of cultural practices, chemical control, and preventive measures.  

Cultural Practices

• Proper Tree Spacing: Ensuring adequate spacing between trees promotes good air circulation, reducing humidity levels and minimizing fungal growth.

• Pruning: Prune infected branches to improve air circulation within the canopy and remove sources of fungal spores. Also, lightly elevating the canopy of a tree above the ground can help increase airflow.

• Mulching: Apply a layer of organic mulch around the base of trees to retain soil moisture and reduce stress, which can help trees resist fungal infections. 
  

Chemical Control

Apply fungicidal sprays containing active ingredients such as chlorothalonil or copper hydroxide during the spring months as new growth is emerging. Multiple applications in 10 to 14-day intervals applied annually are most effective, however, there is no end-all cure for this fungal disease.

Preventive Measures

• Monitoring: Regularly inspect trees for early signs of infection, especially during periods of high humidity.

• Water Management: Avoid overhead watering and excessive irrigation, as these practices can create ideal conditions for fungal growth. Water trees in the morning to avoid foliage staying wet overnight.

• Plant Selection: Some other options that may be suitable for your landscape include, but are not limited to: Concolor fir (if you desire the silvery blue color), Norway spruce, green giant arborvitae, and Canadian hemlock.  

Purple-ish brown needles

Rhizosphaera needle cast poses a significant threat to the health and vitality of coniferous trees, particularly Colorado blue spruce. By understanding the causes, symptoms, and management strategies associated with this fungal disease I hope that you will, as a Colorado blue spruce owner, help keep these beautiful trees healthy. Through a combination of cultural practices, chemical controls, and preventive measures, it is possible to mitigate the impact of Rhizosphaera needle cast and preserve the beauty and ecological value of our coniferous forests and landscapes. Please reach out to Russell Tree Experts if you suspect your trees are infected or need advice on proper maintenance as our ISA Certified Arborists® (myself included) are happy to take a look! Have a happy summer and we look forward to helping you with your trees!

Sincerely,

Mike Wilson I Regional Manager, Russell Tree Experts
Mike joined RTE in 2013 and has been in the green industry for over 14 years! He is an ISA Certified Arborist® and a graduate of Oregon State University. Mike is an outdoor enthusiast and a US Army Medic Veteran!

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Right Tree, Right Place!

By Mitch Lippencott
ISA Certified Arborist
April 11, 2024

Much of the tree work our arboriculture division at Russell Trees Experts performs is a direct result of trees and shrubs being planted in inappropriate locations.

When we prune trees to clear a house, roof, or utilities, it's often because a large tree was planted too close, or a smaller tree should have been used. When we shear shrubs to stay below windows or to not encroach on walkways, a smaller, narrower shrub would not have needed maintenance. When we repeat micronutrient fertilizations or fungicides, it's usually to support a tree that doesn't belong in its environment. In short, we make wrong trees fit in wrong spaces.

The unfortunate fact is most trees and shrubs need a specific set of conditions to thrive - they can't just go anywhere. While figuratively forcing square trees in round holes is good for our business, the savvy gardener will not pick out a tree they 'like' and plant it in a spot where they think it 'will look nice'. Instead, they will study the conditions of their site, then choose the tree that best fits those conditions.

So how can you, the savvy gardener, 'study' your planting site? It's more than looking out the window once. Measuring is a good idea, but still not enough. Instead, examine your area from multiple vantage points, during multiple weather conditions, and multiple times of day.

Does rainwater pool anywhere? Where does the sun hit, and for how long?  Which direction does the wind come from? Where would privacy be preferred? These, and many more questions should be incorporated into the plan.

While this seems cumbersome, the process can be broken down into five important factors: size, water, soil, exposure, and goals.

1) Size

Yes, plants can be pruned to keep them smaller, but most don't want to be! Severe pruning and shearing can cause stress, which in turn, makes plants less capable of defending themselves against diseases and insects; especially near a house or patio. Research plant sizes and don't get greedy - if a plant gets too big for your space, it's out of contention.

2) Water

As the global climate continues to change, Ohio is experiencing warmer, wetter winters and springs. Few plants can tolerate both wet and dry conditions. So if your area is wet most of the year, only water-loving plants should remain in the candidate-pool. Forcing dry-footed plants to wet soils will likely leach away vital nutrients and cause fungal infections. Conversely, heavy drinkers in dry soils will likely need continuous watering, which is time-consuming, expensive, and environmentally careless.

3) Soil

Soils vary greatly by location, but in general, central Ohio soils have a heavy clay texture with poor drainage, and a neutral pH (neither acidic, nor alkaline). Undisturbed soils tend be more loamy and acidic. New builds and urban areas tend to be more compacted and alkaline. Plants in soils not matching their needs can suffer from fungal infections, nutrient deficiencies, and instability due to poor root growth.

4) Exposure

While sun and wind are obvious factors, deer-resistance, salt tolerance, limited root space, planned or recent construction, and known insect pests or pathogens are other common exposures in our region.      

5) Goals

I will discuss this more thoroughly in a future article because this is the most fun part - this is where all of your research and observation pay off and your plant starts to work for you! Privacy, traffic noise reduction, food production, bird watching, and a created, desired aesthetic are all examples of good planting goals. Luckily, there is a plant for every size and for every site, so be diligent and find exactly what you need. Scott Zanon's excellent guide Landscaping With Trees in the Midwest lists trees for a variety of situations, including photos, plant sizes, and recommended cultivars.

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Pairing the correct plant to the correct location may take time and research, but it is the best path to a long-lasting, low-maintenance garden. When planting your next tree, thoroughly observe your site before heading to the nursery, then limit your search to the trees that match those conditions. Just don't get too carried away - we still have a business to run over here! ;-)

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Sincerely,

Mitch Lippencott I Regional Manager, Russell Tree Experts

Mitchell Lippencott joined Russell Tree Experts in 2020 and has been in the green industry for over 20+ years with a diverse background ranging from working for a landscape design company, a retail garden center, and two municipalities! Mitch is an alum from The Ohio State University, a licensed pesticide applicator, a qualified tree risk assessor, and an ISA certified arborist. Outside of work, he enjoys traveling, cooking, and gardening.

10 Boxwood Alternatives

Dear Reader,

My introduction into the horticultural world was working at a small retail nursery in the early 2000s. Back then, when a customer would ask for an easy to grow, low maintenance, no brainer plant, boxwood is what we would often recommend. Fast forward twenty years and today boxwood have to contend with boxwood leaf miner, boxwood psyllid, spider mites, volutella stem canker, winterburn, boxwood blight and most recently, a new disease known as boxwood dieback. Historically, Boxwood have been appreciated in the landscape because they are evergreen, deer proof, compact, easy to manipulate and respond well to pruning/shearing. But they are no longer the maintenance free, easy to grow plants they once were. 2023 was a particularly bad year for boxwood in central Ohio and every arborist, landscaper and plant person I know was overwhelmed with calls from desperate clients willing to try anything to restore their boxwood to how they once looked. Many of the boxwood installations I observed this year are beyond preservation. Others will likely recover over the next two to three growing seasons but may look a little rough along the way. Much of the damage that occurred to boxwood this year is a result of the cold weather event we had just before the holiday season of 2022, where temperatures changed from 40 degrees Fahrenheit into the negatives in less than 12 hours. There is no topical spray or any professional service that can be offered to combat this sort of environmental event. And many of the boxwood that were able to survive the initial cold temperatures succumbed later to disease spreading pathogens seeking a stressed and vulnerable host. Even under normal weather conditions, most boxwood require regular applications of insecticides and dormant oils to protect them from insect pests that have taken advantage of their abundance. The best management strategy for the prevention of disease and insect pests on our plants is to use plants that do not get those diseases and insect pests. So as you are wrapping up your Fall landscape plantings or making plans for next Spring, consider something new for your hedges, accent plants and foundation plantings. Here are 10 suggestions for plants to consider with similar characteristics to boxwood.

1. Blue Holly

Blue holly (Ilex x meserveae) is a hybrid between the cold hardy Asian prostrate holly (Ilex rugosa) and English holly (Ilex aquifolium). It is one of my personal favorite evergreen shrubs and has lustrous dark green/blue leaves and dark red berries on female plants that ultimately feed the robins and mockingbirds around late winter to early spring. Individual plants form a shrubby upright to pyramidal habit and can grow 8 to 12 feet in height by 6 to 8 feet in width. Blue holly (Ilex x meserveae) can easily be pruned into hedges and can be kept at any height or width with minimal, annual pruning. They are cold hardy to -20 degrees Fahrenheit and adaptable to both full sun or partial shade. Several cultivated varieties of this hybrid exist with my personal favorites being Blue Princess and Blue Prince.

NOTE:  Holly plants require a male pollinator to achieve fruit. Make sure to include at least one male plant (like Blue Prince), and possibly more depending on the size of your Holly plantings to improve fruiting.

Negatives: Blue holly (Ilex x meserveae) can have significant leaf burn when temperatures drop below -10 degrees Fahrenheit (although established plants recover quickly in the Spring). They are susceptible to phytophthora (root rot) in poorly drained sites and deer browsing during the winter when snow persists for days at a time.

2. Privet

Privet (Ligustrum spp.) is a densely branched shrub with dark green to yellowish green leaves that can easily be manipulated into rounded plants and hedges. Privet (Ligustrum spp.) is fast growing and adaptable to a wide range of soils and growing conditions; I’ve observed many well kept privet hedges that would give boxwood a run for its money during the spring or summer. The foliage persists late into the fall often turning purple but is not evergreen. There are no serious disease or insect problems and oftentimes plants seem to thrive with neglect. Several different species and many different cultivars exist for a range of size, texture and leaf color.

Negatives: Privet (Ligustrum spp.) is not native to central Ohio and can easily spread by seed into native areas and out compete native species. They are also not evergreen.

3. Wintercreeper euonymus

Until recently I have always considered this species of euonymus to be best used as a ground cover or climber on a tree or trellis. More and more though, I’m seeing it in the landscape pruned into a very small and cute hedge or sculpted into 1 to 2 feet tall and wide mounds looking very similar to boxwood. Euonymus in general is fast growing and adaptable from full sun, to full shade, and to just about any landscape situation that isn’t a swamp. Leaves are evergreen most winters (leaf drop can occur when temps drop below -20 F) and there are dozens of cultivated varieties for leaf size and color. I’m partial to the green and white variegated cultivar ‘Emerald Gaiety.’

Negatives: Wintercreeper euonymus (Euonymus fortunei) is not native and can easily naturalize and take over unmanaged native areas. They can be susceptible to euonymus scale and difficult to treat successfully once a population is established.

4. Spirea

There are several species and dozens of different cultivars of spirea that mimic the compact and rounded habit of boxwood. They can be grown as separate plants, planted in masses or managed as a hedge. Spirea can grow in most landscape situations and will perform well in any soil that is not excessively wet. Spirea are easy to grow, have little insect or disease problems, respond well to pruning and shearing, and are cold hardy and adaptable to full sun and partial shade. Spirea are deciduous but even without leaves, the stems and twigs are so dense that the structure of the plant still provides texture and interest in the winter landscape.

Negatives: Spirea are not evergreen. They can get powdery mildew but it has little impact on the overall health of the plant. Spirea may also be somewhat overused in the landscape but for good reason - it is almost impossible to kill.

5. Japanese HollY

Japanese holly (Ilex crenata) is another compact evergreen shrub with a rounded habit and dark green foliage through the growing season and through the winter. They can grow 3 to 5 feet in height and width, although I have observed larger plants in arboreta. Japanese holly (Ilex crenata) is cold hardy to - 20 degrees Fahrenheit and adaptable to both full sun or partial shade. They respond well to pruning/shearing and can be used in hedges, foundation plantings, or in masses. Several different cultivars are available for different sizes, colors, and superior cold hardiness.

Negatives: Japanese holly (Ilex crenata) is slow growing and not tolerant of high pH soils. They are a preferred host to spider mites during extended periods of drought. Japanese holly (Ilex crenata) is not well known in Ohio and could be difficult to source. I would avoid using the upright cultivar ‘Sky pencil’ unless in a warmer protected spot with exceptionally well drained soil.

6. Globe arborvitae

Globe arborvitae (Thuja occidentalis ‘Globosa’ or ‘Little Gem’) is a compact and rounded form of our native eastern arborvitae. Its leaves are bright green in the spring and summer but turn more bronze or yellowish green during the winter months. Globosa arborvitae is a dwarf form and matures to only 5 to 6 feet tall and wide. They are very adaptable to different soil types and respond well to pruning and shearing. Globosa arborvitae can be used as a specimen plant or accent plant as well as in hedges or foundation plantings. Little gem arborvitae has essentially the same habit as globosa arborvitae but are smaller, maturing to a height of about only 3 feet tall. Either cultivar will perform well from full sun to partial shade (but they should have at least a half day of sunlight).

Negatives: Deer will eat arborvitae to bare wood when hungry. They are also a preferred host to bagworm and spider mites.

7. Yew

Yew (Taxus spp.) is a hardy and easy to grow evergreen shrub. I use them primarily for screening in the parts of my garden that receive less sun, but they can be easily manipulated and sculpted into tight hedges, mazes, and formal shapes in the same fashion that we often treat boxwood. Yew are very adaptable and urban tolerant and can withstand almost any amount of pruning. They will grow well in sun and shade and have few disease or pest problems. If they are used as an alternative to boxwood, I recommend the cultivars ‘Runyan’ or ‘Densiformis’.

Negatives: Yew are susceptible to deer browsing

8. Japanese Plum Yew 

Japanese plum yew (Cephalotaxus harringtonia) is similar to yew, but with longer and glossier needles. I have planted this in more than one rural location and my experience so far is that deer will not touch them. Japanese plum yew (Cephalotaxus harringtonia) should be considered by anyone that likes yew but has given up because of continual deer damage. There are several different cultivars selected for a range of different sizes and habits but ‘Duke Gardens’ is the cultivar I recommend for central Ohio gardens and for anyone wishing to experiment with using Japanese plum yew (Cephalotaxus harringtonia) to replace boxwood. This cultivar matures to approximately 2 to 3 feet in height, approximately 3 to 4 feet in width and is cold hardy to - 20 degree fahrenheit.  There are no serious pest or disease problems.

Negatives: Straight species is not cold hardy in true zone 5 winters (winters that reach -20 F). I observed significant winterburn in the plants in my garden from the cold snap we had just before the holiday season of 2022.

9. Inkberry 

This is one of the boxwood alternatives that I think has the most potential. Inkberry (Ilex glabra) is native to the east coastal plains of the US and is a compact evergreen shrub with lustrous, dark green leaves during the growing season. Foliage can bronze somewhat during the winter months. Without pruning, inkberry (Ilex glabra) can reach heights of 6 to 8 feet tall with a width of 8 to 10 feet wide. Female plants can produce a small, pea-sized black berry (hence the name inkberry) that is edible to birds. Inkberry (Ilex glabra) performs well from full sun to full shade (foliage density is better with at least 5 to 6 hours of sunlight) and is cold hardy to - 20 degrees fahrenheit; although I have observed winterburn in exposed plants during winters with temperatures that have dropped below zero for extended periods of time. Inkberry (Ilex glabra) responds quite well to heavy pruning or shearing and has strong regenerative growth in established plants. They can easily be used as individual specimen plants or in hedges. I recommend using the cultivars ‘Cape Cod’ or ‘Compacta’ if available. These selections maintain a more rounded and compact habit with less pruning.

Negatives: Inkberry (Ilex glabra) is not tolerant of excessively high pH soils and plants can lose lower leaves and become quite leggy if not well managed. I have observed significant deer browsing during periods of extended snow cover in landscapes with a high deer population.

10. Canadian Hemlock

Canadian hemlock (Tsuga canadensis) is one of my favorite evergreen trees. It is a native and graceful evergreen tree with glossy dark green needles that also responds well to aggressive pruning. When my wife and I moved into our current home in 2008, we planted 36 Canadian hemlock (Tsuga canadensis) on 5 foot centers around the perimeter of our front and side yards. We keep these plants sculpted into a tight 6 feet tall by 3 feet wide pyramidal shaped hedge which we prune once a year in the late spring, approximately a month after new growth has pushed out. This could make an excellent replacement for a tall boxwood hedge.

Negatives: Canadian hemlock (Tsuga canadensis) is susceptible to deer browsing during the winter months with extended periods of snow. They are a preferred host to spruce spider mites when under stress. Canadian hemlock (Tsuga canadensis) also have poor tolerance to drought.

These 10 plants are just the beginning of the conversation regarding boxwood alternatives. There are dozens of other cultivated varieties of chamaecyparis, juniper, spruce, pine, fir, leucothoe, etc that could fulfill the same niche in many of our gardens. I believe there is a perfect substitute out there for every plant. The perfect substitute for your needs will depend on your individual situation and landscape.

Sincerely,

TJ Nagel I Scheduling Production Manager, Russell Tree Experts

TJ loves trees. He is an avid gardener and plant collector. TJ graduated from The Ohio State University with a B.S. in Agriculture with a major in Landscape Horticulture and minor in Entomology. TJ is an ISA Board Certified Master Arborist and well versed in Plant Pathology. TJ joined Russell Tree Experts in 2012.

Illustrations by Kenny Greer, Russell Tree Experts

The Year of the Ugly Boxwood

Dear Reader, 

My good friend and arborist colleague Cat Baumgartner wrote the below article for the Inniswood Garden Society’s quarterly member newsletter (known as The Image). As soon as I read it, I knew that I wanted to share it with all our readers. Cat does a thorough job of describing the most serious problems we have had with boxwood this year and she explains them well and in simple terms. She has generously agreed to let us republish it. Photos within the body of Cat’s article are courtesy of Joe Boggs, OSU extension educator for Hamilton County.

- TJ Nagel, Russell Tree Experts

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The Year of The
Ugly Boxwood

by cat Baumgartner, Oakland Nursery

I don’t have a simple answer. Or there are multiple answers, and your boxwood might have one, or several of the problems at once.

I’ll go over the likely suspects for this year- including winter damage, or ‘winter burn’, Boxwood Leafminer, Volutella Blight, and THE Boxwood Blight.

I’ll start with winter burn. Boxwood store a lot of their energy in their leaves through the winter. When we get extreme cold and wind in the winter, the leaves will lose more moisture. If the ground is frozen or dry (or worse, both), the leaves lose moisture faster than the roots can replace it, and we get the ‘burn’, where they turn a straw color and die, staying attached to the stem. It wasn’t noticeable until early spring, because evergreens have a delayed reaction to stress. It’s why we can cut down trees for Christmas and they don’t immediately turn brown, often lasting months. We did have greater than normal rainfall last year, but the three months leading up to late December were on the dry side. So, the ground was dry leading up to the extreme cold event that hit in late December creating a Double Whammy. There was a lot more winter burn this spring than I’ve seen in decades. It looks like straw-colored sections in the shrubs, often in a random pattern.

Photo courtesy of Joe Boggs, OSU extension educator for Hamilton County. 

Next, there are different blights out there that can affect boxwood. ‘Blight’ is a general term for a plant disease, typically caused by a type of fungus. Most of them are less common and less damaging than the blight striking fear in the hearts of gardeners that is Calonectria pseudonaviculata, called simply “Boxwood Blight”. There have been some isolated cases in the Greater Columbus area. The main symptom though is defoliation. You’ll have green leaves, then they’ll start looking funny, and rapidly progress and fall off the stem. In a matter of weeks, you can go from a healthy-looking plant to one with sections with completely naked stems. Definitive identification requires lab testing. Other blights can show similar symptoms, but since some are more treatable, confirming which type of blight your boxwood might have is recommended before removing plants. If you do have “Boxwood Blight,” replanting with more boxwood is not recommended, so confirmation of what kind of blight you have will also tell you what you can plant in that spot. Most of the damage we’ve been seeing is NOT “Boxwood Blight.”

Photo courtesy of Joe Boggs, OSU extension educator for Hamilton County. 

Volutella Blight or Pseudonectria Canker (Pseudonectria buxi) can be damaging but is not necessarily a death sentence often just affecting individual stems and not whole portions of the plant. Symptoms can be seen if the stem is sliced into, showing dark brown streaking just under the bark. Most twigs infected with Volutella blight will turn straw colored and die. In most cases dead stems from Volutella canker can be easily pruned out and the remaining portions of the boxwood will fill in slowly over time. 

This year we also had frost damage in May. If leaf buds are still tight, frost is not a problem. If the new leaves have emerged, but have ‘hardened off’, it is also not a problem. But if the new growth is timed so that it is new, fresh and tender, and then we have a late freeze, the new growth is damaged, turns that sad straw color, and is aesthetically at least, a problem. A healthy shrub can put out another round of growth, and it is not a long-term problem. Trimming off the burnt new growth is all that needs doing.

Photo courtesy of Joe Boggs, OSU extension educator for Hamilton County. 

Boxwood Leafminer, an insect pest, is an ongoing problem. The damage from leaf miner is more generalized, an ‘all-over’ bad look rather than the chunky sections dying back. The adults lay eggs in the new growth in mid-spring, and as the larval stage hatches and begins to feed on the interior tissues, the leaves start looking bad, often having a blistered or bubbled effect, usually easier to see from the bottom of the leaf.   

Preventative sprays can thwart adult leafminers from laying eggs in the new growth, but need to be applied as you see the new growth. Systemics applied in the Fall or Spring can also provide control but know that boxwoods are insect pollinated. 

If you don’t have Boxwood blight, you have two options. Cut out the dead branches and let the plants regrow which may take three years or more to totally restore, in good condition, or replace the plants.

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A Final Note…

Since Cat wrote her article, we have had several boxwood shrubs test positive for yet another disease, Colletotrichum theobromicola (also referred to as boxwood dieback). This is a new disease for central Ohio and symptoms look similar to other blight diseases with the random dieback of twigs and straw-colored foliage. However, in addition to twig dieback, the pathogen also causes leaf spots that appear white in the center surrounded by dark brown margins as well as a bright black discoloration just beneath the bark along the twigs. The jury is still out on the best way to attempt to manage this disease but for now, good cultural practices such as removing symptomatic plants and sterilizing pruning tools between pruning different plants are the best-known strategies. Fungicides might also be helpful, but efficacy has not been determined. Laboratory testing should be used to confirm boxwood dieback because it can easily be misdiagnosed as other blight diseases. 

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Twig Dieback (Colletotrichum theobromicola)

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Leaf Spotting (Colletotrichum theobromicola)

As we continue to have more problems in the landscape with boxwood, it may be time to consider alternative plants that can achieve a similar function. Stay tuned for my boxwood replacement article later this Fall.

Sincerely,

TJ Nagel I Scheduling Production Manager, Russell Tree Experts

TJ loves trees. He is an avid gardener and plant collector. TJ graduated from The Ohio State University with a B.S. in Agriculture with a major in Landscape Horticulture and minor in Entomology. TJ is an ISA Board Certified Master Arborist and well versed in Plant Pathology. TJ joined Russell Tree Experts in 2012.

English Ivy: the Silent, Selfish Assassin

English ivy climbing the trunks of your trees can look so natural and attractive in the landscape.  It is a lovely and effortless groundcover with glossy, emerald, evergreen foliage.  However, English ivy is also a non-native species in the US and will clamber defiantly into your tree’s canopy, threatening the tree’s ultimate survival.  You may be tempted, as I have been, to allow this beautiful European invader to engulf the scaffold limbs of your defenseless trees, but please do not be misled by this aggressive charmer.  English Ivy seeks to deprive your trees of water and nutrients at first, and over time, envelop the tree’s crown and hinder its ability to create food for itself through photosynthesis.  The tree is ultimately outcompeted by the vine and slowly declines, while the ivy thrives on its new framework, acquiring all the water, soil nutrients and sunlight for itself.

English ivy can be a very heavy burden for your tree to bear.  It can ascend 100’ and achieve 12” diameter stems.  The sheer weight can weaken limb attachments, causing failure of limbs or entire trees, especially in wind or snow events.  Vigorous vines can block natural air and sun penetration to the bark and encourage pest and disease development.  When bark is thickly concealed by vines, tree decay and diseases are also very difficult to observe and can go unnoticed. 

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If you have unwittingly endangered your trees by allowing English ivy to establish itself on their bark, take action now to exterminate this clingy aggressor.  The vines should be cut at the base of the tree, removing a 2-3” section from each stem.  Repeat this process at 4-5’ up the trunk.  Carefully spraying or painting the section still attached to the roots with herbicide will help ensure the ivy does not regrow.  Maintaining all English ivy 3-4’ away from the trunk is also a great habit.  Do not attempt to remove the severed vines from the tree’s bark.  This very grippy greenery is firmly attached using modified stem roots called “hold fasts” and removing the vine will remove the tree bark as well.  The remaining, now dead, vines can be safely removed without causing damage to the bark in 2-3 years, if you find them unsightly.

Process to abate English Ivy from a tree

4 weeks after Russell Tree Experts abated the English ivy on a large American sycamore specimen

Please call our office at 614-895-7000 or fill out the quote request form on our website if you would rather trust our skilled arborists to tackle this important, life-saving task for you.  Your trees will express their gratitude with many more years of healthy, unrestricted growth!

Have a great spring everyone!

Krista Harris | Regional Manager, Russell Tree Experts

Krista grew up in the central Ohio area and became an ISA certified arborist in 2017. She graduated from The Ohio State University with a Bachelor of Science in Crop Science and a minor in Plant Pathology in 2000 and has been in the green industry ever since. Her favorite trees are the American sycamore, American beech, and giant sequoia. [BS in Horticulture Crop Science, The Ohio State University / ISA Certified Arborist® OH-6699A / ODA Comm. Pesticide Lic. #148078]

🚫Tree of Heaven

>>>DO NOT PLANT OR ALLOW TO GROW ON YOUR PROPERTY<<<

General Info

• Latin Name: Ailanthus altissima

• Native Range: China

• Growth Rate: Fast

• Mature Height: 40 – 60’

• Mature Spread: 25 – 40’

Arborist Thoughts

• Introduced from China in the late 1700s as a shade tree and horticultural specimen, this tree now threatens to overwhelm our native areas and landscapes.

• Its ease of establishment, prolific seed production, rapid growth, absence of significant disease/pests and ability to out compete other plants with allelopathy (producing toxic compounds to poison its competition) has made it possible for Tree-of-Heaven to invade natural areas and suppress the growth of native trees.

• Tree of Heaven is considered an invasive species and should be ruthlessly eliminated.

• DO NOT PLANT OR ALLOW TO GROW ON YOUR PROPERTY

🚫Callery Pear

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>>DO NOT PLANT<<

General Info

• Latin Name - Pyrus calleryana
• Native Range - China and Korea
• Growth Rate - Fast
• Mature Height - 40–60’
• Mature Spread - 25–40’ 

Arborist Thoughts

• Cherished for its white flowering show in the Spring but dreaded for its poor structure, weak stem attachment and susceptibility to fireblight (a lethal bacterial disease) and lecanium scale (a challenging insect pest to manage).

• This tree has reached epidemic proportions through over planting and by the high volume of escaped seedlings along highways, abandoned fields and unmanaged areas. 

• Ohio added Callery pear to the Invasive species list in 2016.

• One of the most likely tree species to fail under wind or ice load.

• DO NOT PLANT