Hobblebush

The other day, I was walking to a job site in Lichfield, CT when I came across a tall shrub with some lovely white flowers. The first time I passed by, I was focused on what I had to be doing for work and assumed that the shrub was a flowering dogwood (Cornus florida), a species known for its large white flowers. When I passed by again later that week, however, I took a closer look and was excited to find that it was actually something a bit more interesting (at least in my opinion) - a hobblebush! 

A hobblebush (Viburnum lantanoides) in Lichfield, CT

The hobblebush (Viburnum lantanoides) is a kind of viburnum, a diverse, cosmopolitan genus of shrubs and small trees found throughout the temperate regions of the northern hemisphere, as well as in mountainous parts of the tropics. Like many North American viburnums, the hobblebush is an understory shrub that only grows to up to about 10 or 12 feet at maturity. The species gets it common name from its branches' ability to take root when they touch the ground, creating a maze of branches and stalks that "hobble" anybody trying to pass through even a thicket of relatively short individuals. Hobblebush prefer cooler weather and can be found throughout northern New England and Atlantic Canada, as well as down the spine of the Appalachian Mountains as far south as Georgia. In Connecticut, they are mostly found in the mountainous western portions of the state, where I haven't spent as much time - hence my excitement and my initial assumption that it was a more common dogwood.

My first encounter with a hobblebush came while I was working in New Hampshire on a general ecology project that included regular observations of plant phenology. The term phenology refers to the timing of an organism's life history events, such as flowering or leaf color change in plants. Our project involved collecting standardized data on a number of different local species to see how their phenology was changing in response to climate change and other factors over the course of the study. Collecting the phenology data was one of my favorite parts of the project, not only because it helped me to learn how to identify a lot of native plants, but because it made me much more aware of the seasonal changes that plants go through. In the case of the hobblebush, it also helped me to realize that this species is one of the coolest plants in New England. 

A young hobblebush celebrating spring.

Literally every stage of hobblebush's yearly growth cycle has something physiologically or aesthetically interesting about it, starting in the winter before leaf-out. As you can see in the picture above, the hobblebush has a unique growth form that kind of makes it look like candelabra or, in this case, a little person throwing his hands up in celebration. The buds at the end of each branch consist of two, interlocking parts that field guides often compare to hands clasped in prayer. When spring arrives, the two halves of the bud break apart and each one unfurls into a wrinkled, young leaf, as shown below (this is my favorite part of hobblebush phenology - I think it looks really cool). Over the next few days, the leaves continue to grow and unfurl until they reach full size at about 4 to 7 inches in length. Mature leaves are green and heart shaped with serrated edges. 

Hobblebush bud (top) and young leaves (bottom). The bud splits down the middle and each half unfurls into a young leaf (1).

The hobblebush develops two kinds of flowers during May and June. In the center of the cluster are tiny, paler flowers which contain the plant's actual reproductive organs - the stamen, which produces pollen (sperm cells), and the pistil, which produces the ovule (egg cells). The larger, white flowers around the outside of the cluster are sterile and appear to function only to attract pollinators such as the spring azure butterfly (Celastrina ladon), which uses the hobblebush as one of its primary host plants. This is, of course, different from many other plants, which have both the pollinator attracting petals and reproductive parts of the flower all in the same structure. Once the flowers have been fertilized, they develop into clusters of small, red berries that turn dark blue as they ripen in the fall, providing an important, late season food source for many birds and mammals. The berries are also edible for humans when ripe, though I've never tried them - reportedly, they are very seedy and taste a bit like dates or raisins.

The unique, two-part flowers of a hobblebush; note the showy, sterile flowers around the outside of the cluster.

Like most temperate viburnums, the hobblebush is deciduous. Thus, as the growing season comes to an end in the fall, their leaves begin to change color and fall off. This process is called senescence. The leaves of a hobblebush turn a dark red or purple, and they tend to do so gradually, meaning that before they have fully changed, many individuals have green leaves beautifully striped or splotched with color. As in every other stage of their life cycle, the hobblebush enters winters dormancy with style. 

Hobblebush leaves beginning to change color.

So yeah, if you have a local hobblebush, make a point of visiting as often as you can throughout the year to see all these interesting life stages for yourself! And if you can't find one - well, we can't all be as cool and graceful as the hobblebush (I'm certainly not anyways), but there are still plenty of other plants out there with interesting life cycles that are worth learning about. You can even help ecologists to learn more about phenological changes by participating in citizen science projects such as Nature's Notebook. The data collected for these kinds of projects are very important for determining how the phenologies of plants and other organisms in their environment will change as temperatures warm due to climate change. Depending on the exact mechanism by which an organism times its life cycle - if it is temperature based or sunlight based or based on something else - and how other organisms that it competes with or depends upon time their life cycles, important ecological relationships can be disrupted by changes to one or more these factors. For example, if a plant flowers in response to a particular day length and its pollinator emerges in response to a particular temperature cue, warming temperatures can result in a disconnect between the pollinator and the flowers, preventing the plant from reproducing and the pollinator from feeding. 

These are complicated problems, and it may be hard to solve them in any other way besides limiting warming as much as possible (a novel idea, I know), but if there are other, adaptive solutions, such as human-assisted migration, understanding exactly how different species are affected is the first step to identifying them. 

Sources:

GoBotany (2023). Viburnum lantanoides - hobblebush. Native Plant Trust. https://gobotany.nativeplanttrust.org/species/viburnum/lantanoides/ 

Kricher, J. and Morrison, G. (1988). Eastern Forests: A Field Guide to Birds, Mammals, Trees, Flowers and More. Houghton Mifflin Company. 

TWC Staff (2022, October 21). Viburnum lantanoides. Lady Bird Johnson Wildflower Center Plant Database. https://www.wildflower.org/plants/result.php?id_plant=vila11

USDA NRCS National Plant Data Team (N.A.) Viburnum lantanoides. USDA Plants Database. https://plants.usda.gov/home/plantProfile?symbol=vila11  

Photo Credits:

(1) "Hobble-Bush" by Picture This CC BY 4.0