When Caring Becomes Meddling- Part 1

Well hello there! It’s been awhile. I’ve been hibernating from the internet- it tends to be my habit during the cold winter months. For me, if the activity doesn’t involve bundling up and moving around in a snowy landscape, then it falls by the wayside until the world begins spinning towards spring again.

I love the winter landscape. It is during these (sometimes) snowy months that the world is stripped down to it’s bare bones and a raw beauty emerges- one that can’t be seen when the distractions of foliage and flowers fight for our attention. In the winter, form and structure prevail (accentuated by a blanket of freshly-fallen snow)… and it is glorious!

Winter is also an interesting time of year because landscape issues tend to really stand-out in the barren world: poor branching structure that arises from incorrect pruning is no longer masked by foliage, evidence of disease in landscape plants can often be revealed as sight-lines into tree and shrub canopies open up, and finally, questionable horticultural practices can stare us in the face.

On one wintry run I stumbled upon this…

Now orange emerging from a trunk is not exactly a normal thing to see, especially during the winter, so this definitely stood out like a sore thumb. Sure, some fungal diseases produce bright orange fruiting bodies during the growing season (i.e. various rust diseases or Chicken of the Woods/Sulphur fungus) but this was something different. This was an intentional placement of spray foam into a cavity within the tree… and it wasn’t just this one little spot, the tree was full of these patch jobs!

Let’s backtrack for a minute and take a look at wounds and cavities…

Cavities of various sizes and locations on the tree can be found everywhere!

Cavities are the result of decay (which in turn is caused predominantly by fungi and also bacteria). Improper pruning techniques as well as storm or construction damage are just a few examples of injury that can result in decay within a tree. In general, trees are able to ‘compartmentalize’ decay- separating diseased wood from healthy wood with a type of barrier within the tree. While the process of decay is one that a tree cannot halt, it is one that the tree can effectively slow through compartmentalization (with some tree species better at it than others). Trees will also react to decay by trying to outgrow it- adding more wood to the area near the problem (a way of reinforcing the weakened area).

Cavities in the making: the removal of large branches coupled with poor pruning cut locations means that the tree’s ability to heal itself has been compromised. Without being able to heal, the wound site/excess material begins to decay and this eventually leads to cavity formation (The photo on the right illustrates more advanced decay giving way to a cavity).

Gardeners, homeowners, and tree lovers tend to be meddlers. We look at cavities and decay and instantly feel the need to do something to help the tree. The thing is, the tree doesn’t necessarily need our help and it is quite possible that we can make things worse. If we do anything that compromises the barrier between diseased and healthy wood, we can speed the progression of decay within the tree (this is obviously bad!).

So what’s up with the expanding foam?

The rationale behind the use of expandable foam is that it can keep animals and moisture-holding debris out of the cavity. It also fills the space where water could otherwise collect. Moisture is necessary for the proliferation of decay organisms so the idea behind the expandable foam is to eliminate this scenario.

Being a flexible and non-abrasive material, it is also thought that expandable foam is kind to the interior of the cavity as the tree sways and grows around it- it will not rub and break through the ‘barrier’ between healthy and compromised wood- a concern with concrete or bricks- fillers that have been historically implemented to fill cavities. (Concrete, brick, mortar and stones have NO place inside the cavity of a tree! Incidentally, our case study tree had also been filled with concrete in some places. Poor thing.)

With all that said- if the expandable foam is not applied correctly, it can trap moisture within the cavity and hold it there. It can also prevent a tree from properly healing over. The type of foam used, how the foam is pared down to the cavity, as well as the coating used over the foam are all considerations for proper application of this technique. For these reasons, I would argue that the use of expandable foam in cavities is an arboricultural practice that should only be prescribed and implemented by a professional (ISA certified arborist) in very select cases. Even with that, I can not find any recent scientific research that suggests expandable foam is a valuable cavity repair technique. Finally, it is also important to keep in mind that when “decay is at play, get the professional’s say” (yes, I made that up just now)- decay can affect the structural integrity of the tree, so it is important that an arborist is brought-in to examine the extent of the decay and determine if any actions are required to mitigate the problem.

In the case of the ‘foam tree’ above, many of the cavities (and resultant patches) are small- there really was no need to meddle. There are also very large cavities and areas of significant decay on both the trunk and primary branches of this tree- these issues would certainly not be solved by expandable foam and require the attention of an ISA certified arborist. So in the end the liberal placement of foam patches has accomplished nothing for this tree except the creation of a blight on the winter landscape… and the inspiration for a blog post ;)

Stay tuned… while we are talking about meddling, no discussion would be complete without addressing wound dressings… coming up in a future post!

The sun is setting on winter… thoughts now turn to spring!

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References:

American National Standard for Tree Care Operations- Tree, Shrub and Other Woody Plant Management- Standard Practices (Pruning). ANSI A300 (Part 1)-2008.

Gilman, Edward F. 2002. An Illustrated Guide to Pruning, 2nd Edition. Delmar, Cengage Learning.

Lilly, Sharon J. 2010. Arborists’ Certification Study Guide. International Society of Arboriculture.

Smiley, E. Thomas. Bartlett Tree Experts. (n.d.) Research Laboratory Technical Report: Cavity Filling. https://www.bartlett.com/resources/cavity-filling.pdf

University of Florida. (2020, January 21) Landscape Plants. Hollows and Cavities. https://hort.ifas.ufl.edu/woody/cavity.shtml

All Wrapped up

Well the gardening season is essentially complete but there has been one final task that I recently ‘wrapped up’ (pun intended) ahead of winter; that task would be, you guessed it…. wrapping some evergreens with burlap screens.

When the world around is brown- it is time for other plants to shine… why would you want to cover them up? Photo credit: Annie Spratt on Unsplash

Now, it should be known that I am of the opinion that any plant that needs to be ‘under cover’ during it’s moment to shine is not worth growing. After all, why do we plant evergreens? For the fact that they are ever GREEN! They provide a dash of that glorious colour when the rest of the world is brown… or white if you are lucky enough to have snow.

A good example of ‘stealing a plant’s thunder’ is evident when you look at evergreen holly (Ilex ). Not only does this plant have stunning green leaves, but it also has absolutely gorgeous red berries that almost sparkle in the otherwise sleeping late fall and winter landscape. How terribly unfair does it seem to screen-out this kind of beauty?

There are, however, some evergreens that have other moments of glory- such as Rhododendrons with their spectacular floral displays in the spring. In the case of these plants, a burlap screen is an acceptable practice in my mind if it means keeping these specimens happy and flowering properly.

The Burlap Screen- How it Works

As human beings, we are used to bundling in warm clothing during the cold winter days or curling up in a warm blanket to get cozy. In the case of plants, it is important to note that the intention of a burlap screen or wrap is not to keep a plant ‘warm‘ rather it is to prevent water loss from the plant and the associated damage that it causes.

The Threat of Desiccation (this should bring back memories of science class…)

Water moves through a plant from it’s roots (taken in from the soil) to it’s leaves, where any unused water then exits the plant via pores in a process known as transpiration. Transpiration occurs at much higher rates in warm weather when plants are actively growing and it significantly drops (or becomes virtually non-existent) when plants are dormant (i.e winter). During the growing season, water is replaced within the plant by uptake from the soil. In the winter, however, water in the soil is frozen and it becomes inaccessible to plant roots. Therefore if water is lost, it cannot be replenished. The result? The plant begins to dry out or desiccate with the damage beginning at the tips/margins of the leaves and working backwards. This type of damage is also called winter burn. Leaves damaged by winter burn not only look unsightly, but if desiccation is severe, the leaves are also no longer able to properly function as ‘light-harvesting/ food-making’ sites for the plant come spring. If damage is extensive enough, the overall health of the plant can suffer.

So what are the factors that draw water out of a plant?

1. Warm sunny weather can stimulate photosynthesis (and, by association, transpiration)

2. Wind promotes the evaporation of water from the leaf; this speeds up water loss as water is constantly drawn away from the plant in windy weather.

It’s always nice to see the sun in the winter… but it can cause problems for some of our garden plants.

To protect or to not protect? That is the question.

In general, plants that I typically protect for the winter months include:

If a burlap screen can keep this beauty flowering properly, then bring on the screen! (Photo credit: Yoksel Zok on Unsplash)

• Broadleaf evergreens which have the potential to lose a great deal of water to the air due to the large surface area of their leaves (as opposed to the needles or scales that adorn other evergreens). Broadleaf evergreens are the main type of plant that I will protect with a burlap screen if they are situated in a sunny and/or exposed location. Examples of broadleaf evergreens that may need some protection include:

  • Rhododendron

  • Pieris

  • Boxwood (Buxus spp.)

  • Evergreen holly (Ilex)

• Recently planted evergreens or tender trees/shrubs (those planted during the latter half of the growing season) have under-developed root systems, which means their ability to take up and supply the plant with moisture from the soil is not yet optimized. These plants are therefore more prone to becoming drought-stressed (and in turn they are more likely to suffer winter burn/desiccation). A screen to minimize unnecessary water loss can be the difference between the plant surviving it’s first winter in the garden, and shopping for a replacement come spring. Some of the most commonly planted trees and shrubs in this category include:

  • Cedars (Thuja)

  • Falsecypress (Chamaecyparis)

  • Yew (Taxus)

  • Boxwood (Buxus)

  • Japanese maple (Acer palmatum)

• Plants with tender buds can gain some protection from a burlap screen. While it won’t protect buds against cold temperatures or even damaging temperature fluctuations, a burlap screen can prevent desiccation of the buds from drying winds. This is especially valid for plants that flower on old wood (trees and shrubs that are going into winter with their flower buds ‘locked and loaded’, ready to burst forth in the spring). For these plants, if the buds do not survive the winter, the flower show in the spring is reduced or eliminated. If spring-flowering trees and shrubs are located in exposed, windy areas a screen can certainly provide some protection. A couple examples of plants with buds to protect include:

  • Redbud (Cercis)

  • Mophead hydrangea (Hydrangea macrophylla)

• Plants exposed to salt spray from roads generally appreciate having a screen erected to prevent the spray from landing on the foliage or branches (this spray can contribute to the burning of leaves, needles and buds). Some plants are more salt tolerant than others, so before planting by a roadside, it is important to consider a plant’s salt tolerance.

A picture-perfect burlap screen protecting a line of Hydrangea paniculata from sidewalk and road salt, snow piles from sidewalk plowing, and the exposure that comes with an open corner lot. I marvel at the meticulous work of this homeowner’s work every year!

Tips for Screening and Wrapping (and I am not talking Christmas presents!)

• Where possible, burlap should be stapled or zip-tied to stakes or other supports to create a screen/wrap for the plant (see photo below). This is much more desirable than putting burlap directly onto the plant for a couple reasons. First of all, wet burlap that freezes onto foliage can cause damage to the foliage. Secondly, the lack of airflow within a completely bundled-up plant can promote disease problems.

• If a plant must be wrapped, don’t pull in the foliage tightly; wrap the burlap only tight enough that it stays in place and secure it by spiraling twine down and back up the plant.

• Wait until the weather is consistently cold to erect burlap screens. This allows the plants to ‘shut down for winter’ without any external influences; protection is then erected as a final ‘security blanket’. Stakes can always be installed during the warmer fall months and the burlap attached to them once the weather turns consistently chilly.

• Remove burlap when a plant can once again access water from the soil (when the soil thaws).

• Over the course of the winter, check on the burlap to make sure it has not collapsed onto the plant that you are trying to protect! Make adjustments when necessary.

A plant wrapped with burlap. Note the metal frame that is being used to keep the burlap from making direct contact with the plant beneath.

Now it’s time to bundle up… to bundle up your plants. Just remember to do so sparingly… a garden full of burlap screens is certainly not necessary from a horticultural standpoint, or desirable from an aesthetic standpoint; after all, a winter garden can be a thing of beauty too!

Always a cheery winter sight! Photo by Peter Lewis on Unsplash