Dwarf Sumac: North America's Rarest Rhus

James Henderson, Golden Delight Honey, Bugwood.org.

In honor of my conversation with Anacardiaceae specialist, Dr. Susan Pell, I wanted to dedicate some time to looking at a member of this family that is in desperate need of more attention. I would like you to meet the dwarf sumac (Rhus michauxii). Found only in a few scattered locations throughout the Coastal Plain and Piedmont regions of southeastern North America, this small tree is growing increasingly rare.

Dwarf sumac is a small species, with most individuals maxing out around 1 - 3 feet (30.5 – 91 cm) in height. It produces compound fuzzy leaves with wonderfully serrated leaflets. It flowers throughout early and mid-summer, with individuals producing an upright inflorescence that is characteristic of what one might expect from the genus Rhus. Dwarf sumac is dioecious, meaning individual plants produce either male or female flowers. Also, like many of its cousins, dwarf sumac is highly clonal, sending out runners in all directions that grow into clones of the original. The end result of this habit is large populations comprised of a single genetic individual producing only one type of flower.

Current range of dwarf sumac (Rhus michauxii). Green indicates native presence in state, Yellow indicates present in county but rare, and Orange indicates historical occurrence that has since been extirpated. [SOURCE]

Research indicates that the pygmy sumac was likely never wide spread or common throughout its range. Its dependence on specific soil conditions (namely sandy or rocky, basic soils) and just the right amount of disturbance mean it is pretty picky as to where it can thrive. However, humans have pushed this species far beyond natural tolerances. A combination of agriculture, development, and fire sequestration have all but eliminated most of its historical occurrences.

Today, the remaining dwarf sumac populations are few and far between. Its habit of clonal spread complicates matters even more because remaining populations are largely comprised of clonal offshoots of single individuals that are either male or female, making sexual reproduction almost non-existent in most cases. Also, aside from outright destruction, a lack of fire has also been disastrous for the species. Dwarf sumac requires fairly open habitat to thrive and without regular fires, it is readily out-competed by surrounding vegetation.

A female infructescence. Photo by Alan Cressler

Luckily, dwarf sumac has gotten enough attention to earn it protected status as a federally listed endangered species. However, this doesn’t mean all is well in dwarf sumac land. Lack of funding and overall interest in this species means monitoring of existing populations is infrequent and often done on a volunteer basis. At least one study pointed out that some of the few remaining populations have only been monitored once, which means it is anyone’s guess as to their current status or whether they still exist at all. Some studies also indicate that dwarf sumac is capable of hybridizing with related species such as whinged sumac (Rhus copallinum).

Another complicating factor is that some populations occur in some surprisingly rundown places that can make conservation difficult. Because dwarf sumac relies on disturbance to keep competing vegetation at bay, some populations now exist along highway rights-of way, roadsides, and along the edges of artificially maintained clearings. While this is good news for current population numbers, ensuring that these populations are looked after and maintained is a difficult task when interests outside of conservation are involved.

Some of the best work being done to protect this species involves propagation and restoration. Though still limited in its scope and success, out-planting into new location in addition to augmenting existing populations offers hope of at least slowing dwarf sumac decline in the wild. Special attention has been given to planting genetically distinct male and female plants into existing clonal populations in hopes of increasing pollination and seed set. Though it is too early to count these few attempts as true successes, they do offer a glimmer of hope. Other conservation attempts involve protecting what little habitat remains for this species and encouraging better land management via prescribed burns and invasive species removal.

The future for dwarf sumac remains uncertain, but that doesn’t mean all hope is lost. With more attention and research, this species just may be saved from total destruction. The plight of species like the dwarf sumac serve as an important reminder of why both habitat conservation and restoration are so important for slowing biodiversity loss.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]James Henderson, Golden Delight Honey, Bugwood.org.

Standing up for staghorn sumac

I would like you to truly meet staghorn sumac (Rhus typhina). I say "truly meet" because I know many of you probably have some knowledge of this plant already. If your parents were as misinformed as mine growing up, you were probably raised to believe this plant will cause the same kind of contact dermatitis as poison sumac. Not the case! Though they are related, you probably have not come into contact with poison sumac (Toxicodendron vernix) unless you were hiking around in a bog or other high-quality wetland. Even then, poison sumac is not a common species. The point I am trying to make here is that staghorn sumac is not poisonous!

Staghorn sumac should be celebrated. Few trees can grow in such degraded soil like this tree can. In fact, it is most often encountered in roadside ditches and at the edges of farm fields. In the fall their canopy turns a brilliant shade of red. Seeing a large patch of sumac in full fall color rivals even maples for intensity. Because of this, staghorn sumac can make a beautiful landscape tree. It forms numerous clones from underground roots so that it is rare to see just one tree. Take a step back and look at a staghorn sumac population. They seem to always take on a dome-like shape. Their cloning habit is what gives sumac stand their dome-like appearance. Once a single individual becomes established, it sends out suckers in all directions. The farther out you go from the center of the dome, the younger the clones get.

Since all individuals that sprout from the original tree are clones, entire patches are usually either male or female. Female trees are those that produce the characteristic red, fuzzy seed spikes. The seeds are acrid, oily drupes that are low in fat. Because of this they do not readily spoil and thus stay on the tree in perfect condition all through winter and even into the next season. All of this adds up to sumac seeds being some of the most highly sought after late winter survival foods for birds and mammals. When everything else has been consumed or has spoiled, sumac drupes become very important meals. It is estimated that over 100 bird species will consume sumac fruits. Insects also relish this tree. Countless numbers of them feed on the leaves, flowers, and seeds.

Most importantly in this day and age, the dead stems and branches of this plant make perfect nesting sites for our native solitary bees. They have a soft pith that is easily hollowed out to make egg laying chambers. From carpenter bees to mud wasps, you can find dozens of species nesting in a sumac patch.

Finally, a delicious but tart tea can be made from steeping the seeds in cool water. The longer they steep the stronger the tea. In the heat of summer it is quite refreshing. However, you may want to filter it through a coffee filter before drinking to avoid ingesting the multitudes of larvae that feed in and among them.

Listen to Episode 297 about sumacs and sumac relatives!

Further Reading: [1]

A Closer Look at Poison Sumac

Photo by JH Miller and KV Miller licensed by CC BY-NC-SA 3.0

Poison sumac (Toxicodendron vernix). The very name is enough to send chills down the spine. At least where I live, this small tree is a bit of a unicorn, often heard of but never seen. That is, unless you know where to look.

A denizen of high quality wetlands, this species is not often encountered by your average hiker. It has a rather spotty distribution in eastern North America as well. I have heard it been said that the best way to find a poison sumac tree is to trip and fall in a bog. The first branch you grab onto will be that of a poison sumac.

Photo by Freekee licensed by CC0 1.0

All jokes aside, coming across one in the wild can be fun. They are a beautiful tree. A member of the family Anacardiaceae, it resembles North America's other sumacs (Rhus sp.), which often gives those innocuous trees a bad reputation. Like its other cousin, poison ivy (Toxicodendron radicans), poison sumac does produce urushiol. Interestingly enough, humans are said to be one of only a small handful of mammals that are susceptible to this compound. The reaction we have to it is not an inherent property of urushiol. Its effects on humans are the result of an allergic reaction. It is said that poison sumac can produce a much harsher reaction than poison ivy. I am one of the lucky ones who does not seem to be allergic to it, which is good news for me as my first encounter with this plant involved most of my face.

Poison sumac fruits are an easy way to tell this tree apart from other sumacs because they produce white-ish fruits, rather than red. Photo by Brett Whaley licensed by CC BY-NC 2.0

Also like poison ivy, poison sumac produces nutritious fruits that birds are particularly fond of. Migratory song birds, especially those that live and breed in wetlands, are the main seed dispersal agents for this species. All in all, the ecological value of species like poison sumac far outweigh the anxieties we feel about them. It is important not to live in fear of species like this. With a little attention to detail, contact can be avoided. Moreover, because it lives in high quality wetlands, the odds of the average person coming into contact with this tree are relatively small compared to other plants. I can only speak highly of a species like this. I just wish we had more high quality wetlands around where they could grow.

Photo Credits: [1] [2] [3]

Further Reading: [1]