Trees in bloom

Crabapple blossoms

The trees were all in flower when I was at my parents’ last week. Some trees have already flowered and finished, such as the cherry, but most of the trees were just at their peak, or on the downside of flowering but with plenty of blossoms left. I enjoy the flowering trees, and it’s a shame that their blooming period can’t last longer. However, I suppose it makes it that much more enjoyable while they do.

One of my favourites for its gaudiness is the crabapple. The tree in my parents’ backyard must be getting on in years as I can always remember it being there. Yet it continues to put on a good show in the spring. The tree’s proximity to the birdfeeders means it’s usually full of birds of different sorts, and in the spring the contrast of an Indigo Bunting or Blue Jay among the fuchsia flowers is particularly eyecatching.

The flowering trees that we typically think of are all fruit trees of one variety or another. Although many trees “flower”, the ones that produce these large, colourful flowers do so in order to attract polinators. Once the flowers are pollinated they set seed and develop fleshy fruits to attract animals, their primary seed-dispersal method. Other trees with less showy flowers usually develop seed pods or cases. This isn’t an exclusive relationship, however, as there are trees with large flowers that produce seed pods, and fruit-bearing trees that don’t put on gaudy shows like this.

Apple blossoms

The flowering tree that most people probably think of in the spring is the apple. There are several apple trees on my parents’ property, and all of them are also quite old, by fruit tree standards. Having never been pruned, they’re large, magnificent trees, which flower beautifully in the spring but don’t produce a lot of fruit. The apples they do grow tend to be small and usually slightly bitter; not so appealing to people, but the horses still love them.

The apple blossoms have a single style, the female reproductive organ, in the centre of the flower, surrounded by many anthers. Each flower blossom produces a single fruit once pollinated.

Hawthorn blossoms

Although superficially similar in appearance, the hawthorn’s white flowers can fairly easily be told from those of the apple tree. They have many styles in the centre of each flower, each of which, when pollinated, produces a seed. The flowers also grow in “corymbs”, or groups, and the hawthorn fruits (called, appropriately, “haws”) form in clusters as a result.

Hawthorns are generally known for the long, sharp thorns they produce, but their flowers can be just as memorable. The hawthorn trees my parents have are also very large, having grown in the open, unobstructed by other foliage.

Chokecherry blossoms

In the winter I clipped the infected branches from the chokecherry bearing Black Knot, and this spring it’s been blooming prolifically. Unlike the domesticated cherry, both chokecherry and black cherry produce flowers (and subsequently fruit) in long racemes. As a kid I liked to pick the stems of ripe fruit and slide my finger down it to collect a handful of berries; what happened to the berries after was less important, it was the satisfying way they popped off the stem that appealed to me.

Lilac blossoms

This last one isn’t really a tree but a very large shrub, lacking a clear main trunk. The lilac is one of those that doesn’t produce fruit, but instead develops clusters of small seed pods. Like the others, the lilacs near my parents’ house have grown quite large, and over the years have produced fewer blossoms. They remain my favourites, though. I absolutely love the intoxicating smell of the clusters of flowers, and am sad when they finish blooming each spring. Someday, when I own my own house, there will be a large lilac bush planted at the corner.

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.

Black Knot

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.

Black Knot

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…