Carolina Buckthorn Recovery

The Carolina Buckthorn seems to be recovering from its earlier infestation of Asian Soybean Aphids.  Those plants that hosted just a few aphids appear almost normal.

Plants that were hardest hit still show the curled leaves that afforded shelter to the aphid colonies. 

Despite their odd appearance, the damaged leaves remain alive and green.  I assume they are still performing their photosynthetic duties, but at a much less efficient level.

New leaves are developing in a normal manner.  It’s encouraging to see that they aren’t yet showing any signs of drought stress.  These plants are growing on an extremely dry site and most of the other plant species in the area are looking distinctly wilted.

Presence of the Asian Soybean Aphids on the Carolina Buckthorns is a fairly recent phenomenon.  I imagine now that they are here, the aphids will continue to be an annual event.  Being at the extreme northern edge of their range already puts the buckthorns under a certain amount of stress.  Dealing with annual aphid damage will certainly add to that stress.  I’m wondering how long it will be before I begin seeing a dieoff of Carolina Buckthorn.

I took this as a bit of positive news.  A few of the plants are producing a bit of fruit.  Of course I’m also aware of the fact that stress can act as a stimulus to produce more fruit before death occurs.  I guess I’ll just have to wait a few years to see how things are trending.

Dead Carolina Buckthorn

It’s sad to witness the death of a tree that you’ve come to know and enjoy. I’ve been watching this Carolina Buckthorn for the last 15 years. I’ve seen it fully loaded with leaves and admired its production of bright fruit. It’s had its setbacks over the years, but it has always managed to pull through.

It stands on the lower portion of a north facing slope at the edge of a mixed stand of cedars and oaks. Carolina Buckthorn is an understory tree and does best when lightly shaded by its neighbors. This location sheltered the tree from drying winter winds and seemed the ideal place for this type of buckthorn to grow.

The first signs of trouble were early loss of leaves and poor fruit production. The next season began with several dead branches and undersized leaves. Leaves again dropped early and no fruit was produced. It was obvious that the tree was on its way out. Growth during the last year was in the form of spindly shoots coming up from near the base. These died before the summer was over and that was the end of the tree.

The trunk and larger branches are still strong and are being colonized by lichens. Carolina Buckthorns are uncommon in Ohio and it’s that fact that initially caused me to be interested in this tree. I soon learned that Carolina Buckthorn was quite an interesting species in itself. It would have been worth studying this tree even if it were the most common plant around. There are still plenty of Carolina Buckthorns growing at Blue Jay Barrens, but none that I know as well as I knew this guy.

I noticed swellings and long fissures at the upper end of the three year old branches. I wonder if these had anything to do with the death of the tree. I said that I knew this tree well, but I don’t remember seeing this condition when the tree was still alive.

Whittling away some of the bark didn’t shed much light on the cause of the deformity. The wood was swollen and the bark was thickened. It looks as though this might have been a point of branching that died back. It seems that something else also had to happen for this growth to be formed. I guess I’ll have to check some other Carolina Buckthorns to see if they show any signs of the same affliction.

Carolina Buckthorn

Carolina Buckthorn, Rhamnus caroliniana, is one of my favorite shrubs. Part of the attraction is the sheer beauty of the plant itself, with its large glossy leaves. The second reason has to be the fact that the plant is a rarity in Ohio.

I normally find this shrub growing on the edges of the prairie openings or as an understory plant in the cedar thickets. In one area it grows on an open ridge top. There’s evidence that the ridge top was much more closed in the past. There are old tops from large cedars that were probably cut for logs about 30 years ago and several skeletons of Redbuds that must have lived along with the cedars. Small Carolina Buckthorn now grow along with the tall grasses.

There were a couple of large Carolina Buckthorns that lived on this ridge, but they were killed by extremely cold temperatures about 20 years ago. This shrub is a southern species and the populations here are at the extreme northern limit of their range. This ten foot specimen represents a large size for this area. I would try a couple of these as landscape shrubs around the house, but I know they will suffer the loss of their top growth every few years.

Where once there was one large shrub, there are now dozens of smaller plants. The short plants are usually protected by a covering of snow during the coldest part of the winter. Once they reach a height that exceeds the typical snow levels, the top growth suffers frequent die backs. Only a few of the hardier plants seem to survive to get any real height.

The dry, rocky conditions in which the Carolina Buckthorns grow doesn’t seem to have any adverse impacts on the plant. Even during the hottest and driest of summers, the shrubs present a perfectly healthy appearance.

Even though the population itself seems healthy, there are always some individuals that show signs of disease. Several of the little plants on this ridge top show signs of canker growth that is probably the result of some fungus infection. It makes for some odd shaped plants when you add disease damage to that already inflicted by the weather. Even under ideal conditions, these diseased individuals would probably never grow large enough to produce fruit.

Carolina Buckthorn

Autumn is an ideal time to locate and monitor certain trees and shrubs. Each species tends to make the transition from summer to winter in a unique fashion that makes them easily identifiable at a certain point. The leaves of the Carolina Buckthorn, Rhamnus caroliniana, maintain their waxy shine and begin to yellow late in the season. This is a southern shrub that has its northern limit in extreme southern Ohio.

A deer trail runs just to the left of this medium sized Buckthorn and a buck deer has found the trunk to be a nice place to rub. Carolina Buckthorns suffer a lot of hardships in this area. Extreme cold temperatures during the winter can kill the top growth on these shrubs. This little clump contains some big specimens compared to the others found at Blue Jay Barrens.

This group is growing beneath a couple of fairly large Black Walnut trees. Many shrubs would not be able to grow in this location because of the juglones produced by the walnut. Maybe the Carolina Buckthorn is a suitable companion plant to the walnut and enjoys less competition from other shrubs in this location.

Carolina Buckthorn leaves always look as though they’ve been waxed and polished. It would make a wonderful landscape plant if it weren’t so susceptible to winter-kill.

One of the key characteristics of this shrub is the naked bud. The tiny beginnings of next year’s leaves are exposed for all to see, instead of being covered by bud scales. The buds are a great help to identifying Carolina Buckthorn in the winter. Years ago I was walking near the creek when I came across a huge patch of buckthorn. I was getting ready to record this exciting find on my map, when I took a closer look at a twig and discovered I was looking at a cluster of little Pawpaws. About that time a Blue Jay started chattering in the tree above me and I’m sure it was laughing at my blunder. Pawpaws have terminal buds very similar to those of Carolina Buckthorn and I had made the classic mistake of making a rapid identification based on one quickly glimpsed character.