trees – Page 9

Time seals all wounds

This is a familiar sight on public-use trails. Something in the human nature cries out to leave a mark, something to indicate that yes, I was here. Perhaps it’s our subconscious recognition that our life is fleeting, ephemeral? Perhaps it’s lovebirds applying superstition to an emblem of their love: as long as this shall remain, so shall we. Or perhaps it’s a declaration of possession, this bit of tree belongs to the carver. Whatever the motivation, the poor trees that find themselves suddenly trail-side usually also find themselves dealing with regular wounds.

Animals, when wounded, regenerate the cells that were killed or destroyed by nearby cells of the same tissue type splitting and multiplying to take their space. If tissue has died but was not removed, the dead tissue is sloughed off or metabolized, then replaced. Trees, on the other hand, simply seal off the wound site and dead or decaying wood, and don’t have the ability to regenerate dead tissue.

Trees wounds can be caused by being scraped, eaten by animals, broken branches, fire or insect attacks. The outer layer of the tree, the bark, is effectively dead and damage to this layer doesn’t result in injury to the tree. For a tree to suffer a wound, the injury must occur to the live wood containing the tree’s food and water transport systems (called the phloem and xylem, respectively). For some species of trees, like beech or maple, the bark is often thin and easy to penetrate (which makes them great for carving your initials into), while for others, such as many pines, the bark can be much thicker.

Trees use two methods to seal a wound. The first is compartmentalization. New wood growing around the edges of the wound creates a sort of “callus”, which effectively walls off the wounded wood from the rest of the plant. This prevents decay and infection from spreading to other parts of the tree. In the above, and below, a branch was broken off at some point in the tree’s life. The large rolls at the sides of the hole is the result of the tree sealing over the wound site with “callus” wood.

In addition to sealing off the wound site, a tree will also try to prevent the spread of infection by using certain chemical and physical responses to pathogens at the wound edge (the way our immune system sends out white blood cells to attack intruders). The exact mechanisms by which a tree does this are not well understood, but often the long-term health and survival of the tree depends on how well it accomplishes this. If pathogens are able to slip past, the whole tree may become sick. As with animals, usually vigorous, healthy trees are able to ward off infection successfully.

It used to be that the use of special tars or paints were recommended to dress tree wounds, such as those from pruning, to protect them from infection and to speed “healing”. In fact, research has suggested that these dressings did little to help, and may actually hinder a tree’s ability to seal a wound, as they may prevent drying and encourage fungal growth, and may interfere with callus growth. Similarly, filling a hollow tree cavity with the intention of increasing the strength of the trunk used to be fairly common practice, but isn’t often done anymore. It’s generally accepted that a tree’s own mechanisms are more successful than ours.

This is the trunk of an arbutus, observed when I was out on Vancouver Island last summer. They’re beautiful trees, with their deep red bark and bright evergreen (but broadleaf, not needle) leaves. Their trunk is cool and silky-smooth to the touch, like a giant piece of hand-worn worrywood, it’s incredibly soothing to run your hand across. I wish we had them here. Just looking at these images and remembering makes me feel calm.

I was so intrigued by this tree, because it seemed to have an unusual method of “healing” wounds. Rather than growing in from the sides to leave a noticeable, sharp scar, like in the first photo, the arbutus almost seems to be lacking bark altogether and just keeps building up layers of wood, filling in wounds, more like how an animal would regenerate cells. Perhaps they fill in their wounds using the same method as the deciduous trees I’m used to seeing, but form smooth, uniform wood where the wound edges meet, due to the lack of rough bark. (Note, Kim, Bert and Ken were here.)

This is the end of a broken branch, after the tree has healed over the wound site. It resembles an amputated limb to me, an even more uncanny resemblance to animal healing. I tried doing a bit of research on how arbutus trees deal with wounds, but I couldn’t find anything very helpful. I will admit that I didn’t spend hours hunting for an answer, so there may be something out there I didn’t get to.

Out in the woods behind my parents’ house there’s an old fence that used to bound part of a field, a long time ago. It predates my parents’ ownership of the place, so it’s several decades old. The tree it was secured to has grown over and around the wires so now it looks like they were drilled straight through the trunk. The scarring created by the wound-sealing process as the tree grew is visible only as a thin line, so the whole thing sort of now resembles a bit in a horse’s mouth.

Blackburnian and I encountered this weird beech tree while out at the Rouge. I have no idea what has happened to its trunk, since it doesn’t seem like the usual pattern of wounding from any sort of animal or insect attack I’m familiar with. It makes me think of parched, cracked soil, but I doubt that dehydration is the cause here. Maybe a beetle or fungus infestation?

This last one is usually referred to as a “burl”, a large growth affixed to the trunk, or sometimes large branches or roots, of a tree. The cause of burls isn’t clearly understood, although it may be due to physical trauma, or insect or fungus infestation. Burls are prized as carving wood, as they have interesting grain patterns that create beautiful finished wood pieces. Check out the size of this one spotted in the Missouri Ozarks!

Hairy berries and velvet twigs

Between all the gray and white and evergreen of the winter landscape, nature provides the occasional little pop of colour. The deep red of sumac berries is one of my favourites. These particular sumac trees were photographed at the Rouge, but really the tree is so common you could find it just about anywhere. It favours scrubby, disturbed and edge habitats, so it’s usually associated with young fields, and woodlot and road edges. The main criteria are lots of sun and well-drained (not swampy or regularly flooded) soil.

There are several species of sumac in North America (and many more through the rest of the world), but the one that grows in abundance here in the northeast is the Staghorn Sumac. It is so named because the velvety texture of the young branches resembles the newly-grown antlers of a male deer (stag). Despite that I associate this feature with sumacs, not all species have hairy twigs.

For most people, probably what comes to mind when they think of sumacs is the brilliant displays they put on in the fall. The leaves change colour most commonly to a brilliant red or red-orange, but can run the gamut from yellow to purple.

Interestingly, individual sumacs are either male or female, but not both on a single tree as is the case with many tree species. Only the female sumacs form berries at the end of the summer, males drop their flowers and then remain bare. While flowering, male plants have greenish-yellow flowers, while those of females are pinkish and much more tightly clustered. This page by Brian Johnston provides an excellent reference to telling the two genders apart.

A grove of sumacs is actually many stems growing from a single root system, and are, as a result, a single plant. Once germinated, a sumac will continue to put out new shoots through “suckers”, long underground roots that pop up a new stem some distance away from the original. Any given stem may last a couple decades, but a root system as a whole can last much longer. New stems can grow up to 15 feet from the mother plant, so sumacs have the ability to spread over a large area of ground, and don’t always respect boundaries like property fences. They spread like crazy, and within ten years can completely take over what used to be an open area (the hill I used to toboggan down as a kid is now completely choked with sumac). A grove forms a nearly continuous canopy that often prevents other plants from growing in the dense shade beneath it.

Sumacs have been used historically in a number of ways. Native Americans would harvest leaves in their fall colours and dry them, then smoke them, often in combination with tobacco. The stems were used to make pipes. The ripe berries, picked at the end of summer, can be soaked in hot or cold water to make a tangy tea-like drink, or as a gargle to soothe a sore throat. The roots can also be made into a tea that was used to stop bleeding. The berries can be used to make dyes. The bark and leaves are full of tannins that have been used in tanning processes.

The berries are rich in fats and vitamins, and are an excellent food source for hungry animals, especially migrating birds. For some reason, however, they’re not a favourite, and berries may remain on trees until spring, when most other food sources have been depleted. Perhaps it’s due to the fuzzy skin? In any case, these spring berry caches can be an important diet item for spring migrants. For this reason sumac would make a great addition to a bird-friendly backyard, but you need to have enough space for them to spread a bit (and for you to have both male and female trees, to get berries), or you’ll be spending a lot of time cutting back saplings! If you have the inclination to try, the trees can be easily propagated from a cutting taken from the root system of a mature tree in late fall, once the tree goes dormant, or by transplanting a young seedling.

Hiking the Rouge

Today was Family Day here in Ontario, a newly-created holiday courtesy of our provincial premiere, who believed that the unbroken stretch between New Year’s Day and Easter was just too long for an employee to reasonably have to suffer through. This was the first year the new holiday has been in effect, and there’s still some kinks to be ironed out. Federal employees such as postal workers and some unionized groups were on the job today because the holiday hasn’t been negotiated into their contracts.

Blackburnian had the day off today, however, and I’m basically self-employed at the moment and take whatever days I want off, so we decided this afternoon to take advantage of the mild temperatures and head out to the Rouge Valley, out in the east near the Toronto Zoo. Back when I was in university I had a job for a couple summers inventorying the birds of the Rouge Park. It was very informal, I basically spent the summer hiking around as I pleased, trying to cover everywhere but not following any sort of rigorous protocol. It was a fabulous job, and I have a very fond spot for the Rouge because of my time spent there getting to know it and its birds. Despite this, I’ve rarely been back since then, and I’d never been there in winter.

The top photo is an image of the valley, taken from the top of a high bluff overlooking the Rouge River. Blackburnian’s standing at the top of the cliff, to give you a sense of scale. This isn’t a little bluff that you’re going to shimmy down to the water. The Rouge Valley contains two primary rivers, the Rouge and the Little Rouge, which joins it. This is the Little Rouge. Doesn’t look so little here, but the Rouge is a bit wider and deeper. Most of the river is upland forest, but there’s the odd patch of wetland here and there.

The Rouge is a gorgeous, mature woodland through most of the Park’s valleys, and it can be easy to lose yourself among the extensive habitat. However, reminders of the city next door are hard to ignore. On the horizon are apartment buildings and rooftops. The trails run 1.6 km along either side of the river, between two roads. Road noise from the city carries the short distance into the park. People come out here to walk their dogs, and many of the dog owners don’t pick up after their pets.

Or themselves.

But the scenery is beautiful. The trails cover a number of different habitats, starting in scrubby meadow at the edge of the woods, passing through a powerline corridor, and then entering into mature upland forest. It’s a mixed deciduous-coniferous forest, with the evergreen component mostly hemlock. The trees here are no western Red Cedars, but put in perspective are pretty impressive themselves.

We didn’t see many birds. Of course, winter birding is like that, very hit-or-miss and sparse even when there’s hits. This guy was the indisputable highlight of the outing. A Hermit Thrush, very out of place in the Toronto snow. Seeing a Hermit in the Toronto area isn’t unusual, per se, but it’s certainly very uncommon. This is the first one I’ve seen around here in the winter. Virtually all Hermits leave the province for the winter, though they don’t go far and may winter in the northeastern states.

This guy had found himself a stash of Black Cherry berries. I didn’t even notice the cherries until I saw him pop one. I watched him eat three or four before a movement I made, possibly shifting my weight or adjusting the camera, startled him and he flew off to a nearby hemlock.

Frozen berries such as these are a large component in many overwintering birds’ diets. Two species of northern birds (Pine Grosbeak and Bohemian Waxwing) will feed pretty much exclusively on frozen berries such as crabapple, chokecherry, buckthorn, hawthorn, etc. There seemed to be a fair bit of Black Cherry in the forest, which should give the Hermit Thrush lots to eat.

The first group of birds we came across were these robins, perhaps 20 of them. Nearly all robins leave the Toronto area in the winter, too, although in recent years increasingly more will stick around through the winter and feed on frozen berries in the woods as well as urban gardens. Another great reason to plant berry-bearing bushes!

We found a few groups of chickadees foraging in cedar stands along the floodplain of the river. Blackburnian pished at all of them, but these were the only group to respond strongly. They were seriously pished off! You can even see the right one yelling, “dee-dee-dee-dee-dee!” Chickadees drop the “chick-a” from their call when they’re responding to perceived threats or dangers. Some research has suggested the number of “dee”s is correlated with the seriousness of the threat, with more meaning a greater danger.

This Red-breasted Nuthatch pished in with one of the flocks of chickadees. It was the fourth and final species of the outing. I was thinking as we were leaving that it wasn’t a great diversity or abundance of birds, and would’ve made for a very lacklustre Christmas Bird Count. I loved the haziness of the periphery of this image created by peeking through a gap in the foliage.

We walked nearly 4 km on very uneven, slippery trails (not groomed trails, so they were simply packed down by many feet, and every step you were trying not to slide). It’s the furthest I’ve walked since the fall, I’m pretty sure, and the addition of the trail condition means we’ll probably be feeling achey legs tomorrow! Ah, but it was good to get out.

The Black Knot

Edit: This post was recently included in the March edition of the Festival of Trees, a blog carnival focusing on, you guessed it, trees. You can check out the full edition at Orchards Forever.

There is a bush in the backyard, behind the house, growing beside a large stump. The stump is what remains of a mature pine that came down before I was around, struck by lightning. The shrub and stump were a play-spot for my sisters and I when we were young, and I remember picking blackcaps from the canes that grew under its branches.

In recent winters I’ve noticed a few black, crusty growths forming on some of the small branches. It’s a familiar phenomenon, but one I hadn’t investigated before. When I was much younger we had a plum and a cherry tree on the property, and I recall plucking ripe plums from the branches of the one, and my parents complaining (good-naturedly) about the birds eating the fruit from the other. Both gradually succumbed to a crusty black fungus, and while the cherry struggles on, the plum long ago died and came down (although I did notice a hopeful new sapling right beside where it used to be).

So to see these growths forming on another tree I knew as a kid, I thought I’d investigate. Turns out, it’s fairly common. It’s a fungus, Apiosporina morbosum, known by the common name “the Black Knot” (which sounds rather dramatic). It almost exclusively infects trees of the genus Prunus, which includes cultivated species such as plum or cherry, or wild native species such as chokecherry or black cherry. The little shrub in the backyard is a chokecherry.

This little tree, although I didn’t try to identify it, is probably a black cherry, the most common Prunus species in these woods. It has a substantially more progressed infection. The fungal spores infect the young buds of the tree when it’s just leafing out in the spring, and it takes a few months for the infection to appear. Initially just look like thick brown galls. Eventually, the following spring or summer, the bark splits and the gall turns into these charcoal-black, crusty growths.

The fungal growths are most often seen on smaller branches, but like in the above photo, can sometimes spread to the trunk of the tree. Although an infection on a branch can compromise the branch’s growth and create disfiguring contortions (such as the first photo), it only kills the branch if the growth completely encircles it (called “girdling”). Any portion of the branch above the fungus will die. If the fungus girdles the trunk of the tree, the whole tree will die. The fungus will continue to spread over many years, and eventually will either compromise the tree so severely it will die, or girdles the trunk causing death.

The fungal spores are released by splashing rain and carried by the wind, and mild spells during the spring rains trigger their production and release. Once a tree’s infected, an individual growth will only live a couple years (after which it dies and turns whiteish-pink, colonized by another species of fungus), but during that time it has the ability to spread to other areas of the tree.

The good news is, you can do something about it if one of the trees in your yard becomes infected. It’s simply a matter of removing the infected bit, cutting back to 10 or 20 cm below the infected bit (since the fungus travels under the bark and may be present outside of the growth). This is best done in the winter while the tree and fungus are both dormant, and the fungus should be burned or otherwise disposed of so it doesn’t infect other trees.

So there’s some hope for the little shrub, and perhaps if I prune it this winter I can keep it from spreading to the mature chokecherry that shades the kitchen window. Now just to dig the gardening shears out from where they’ve been packed away for the winter…

Snowstorm, the day after

I took a break this afternoon to wander outside and enjoy the snow of yesterday. It had stopped snowing last night, and the day dawned clear, with a gorgeous blue sky and brilliant sunshine. These are the sorts of days that I love about winter. That, sitting by the fire, and fat softly-falling snowflakes. I could do without the slushy, slippery roads, the freezing rain, the bitterly cold winds (although these are all easier to take while sitting by the fire). The bright white snow and blue sky wonderfully set off the green conifers and red dogwood.

The snow in the front yard was clean and pristine, stretching out beneath the big trees. I can’t bring myself to walk through it, it doesn’t seem right to spoil something so clean and fresh and full of promise. I’ll leave that to the squirrels and rabbits, and I skirt around.

The smooth white of the unbroken snow makes a great canvas, catching the shadows of the big maple above. It seems somewhat abstract, like something that should be hanging in a museum somewhere. Nature is a great artist.

One downside to all this snow is the necessity of clearing it from the driveway so people can come and go. Here a snowball has rolled down off the giant snowbanks created by the plow (they were at least up to my waist in front of the house, and can be larger along the drive). My parents have an old 1945 Ford tractor that my dad has managed to keep running all these years and has hooked a plow to, used primarily in the winter for clearing snow. It’s been a faithful machine, and, given the length of the driveway (see the second photo), let’s hope it continues to be!

All this deep snow can be a challenge to ground-foragers such as the juncos and tree sparrows. At these times feeders become an invaluable resource that allows more birds to survive the harsh weather than might be able to without a supplemental food source. My mom tries her best to keep the feeders stocked through the winter, though wading through knee-deep snow can be a challenge. Certainly appreciated by the birds!

I wasn’t the only one out enjoying the fresh snow. The two younger horses were having a grand old time frolicking in the white stuff, throwing up plumes of it as they raced through. After a few laps around the field they pulled up near the gate where I stood, their bellies caked with snow, their nostrils wide as they panted deeply. But their eyes sparkled with energy and enjoyment.

Mine too.