Tree of the Week: Arrowwood Viburnum (Viburnum dentatum)

The arrowwood viburnums (Viburnum dentatum) are currently flowering in the arboretum. As shown in the photo above, this species produces large clusters of tiny white flowers. The individual pictured above is our tree of the week—one of seven arrowwood volunteers.

Our tree of the week grows on the west side of Mickle Hall, at the top of a slope in a mostly sunny location. This specimen is at least 14 years old. Over the years it has been trimmed to resemble a multi-stemmed small tree, but it would have preferred to grow as a large, spreading shrub.

Not all of the arrowwood viburnums are flowering as marvelously as this one. The other six volunteers, for the most part, are sparsely decorated, perhaps because of their low-light growing conditions.

A frantic pollinator was also examining this particular arrowwood. These beautiful flowers have a definite fragrance, but not a pleasant one.

A few twigs were snipped for closer inspection. An individual leaf is about the same size as a flower cluster.

Arrowwood viburnum twig

This flower cluster measures more than 3½ inches wide.

The fresh, velvety leaves appear opposite from one another along the twig.

Opposite leaf arrangement of arrowwood viburnum

Twigs and leafstalks are textured, not smooth. Leaves are noticeably soft and fuzzy.

Leaf shape varies. On the left, we have an orbicular shape with an obtuse tip. The center leaf has a more characteristic deltoid shape. On the right, a cordate shape is apparent. But for each leaf, the margins are toothed (dentate).

The upper surface is green while underneath, leaves are light green, almost white.

These new leaves vary in size, ranging from 3 to 3½ inches wide.

Our center leaf is 3¼ inches wide.

Leafstalk measures ½ inch long, and the leaf measures 3⅜ inches long.

The slender trunks have dark grey bark.

One year ago today this same little tree was flowering. You can see proof here.

You can find additional photos of the arboretum's arrow wood viburnums here. 

For more information about this species consult the following:
United States Department of Agriculture
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
University of Arkansas

Tree of the Week: Rusty Blackhaw (Viburnum rufidulum)

Our tree of the week is a rusty blackhaw (Viburnum rufidulum). Its clusters of fragrant, white flowers have drawn our attention. You can find this specimen in bloom in the arboretum, and this species is also readily found in the many wild places of northwest Louisiana.

In 1996, Jack Price donated a large rusty blackhaw to the arboretum collection. Professor Ed Leuck planted it soon thereafter. Today we are looking at a plant that is nearly a quarter of a century old.

For most of its tenure in the arboretum, this rusty blackhaw has been considered a large shrub. However, its sprawling growth over the past several years necessitated regular pruning to allow passage along the sidewalk. As a result, our once large shrub has taken on the appearance of a multi-stemmed small tree.

The large flower clusters make the rusty blackhaw a standout specimen this week. From a distance you can appreciate the white pompoms covering the tree, and then up close you can delight in the pleasant fragrance.

This flower cluster measures approximately 4 inches in diameter.

The fresh new leaves are shiny and green above. The maroon leafstalk is 3/4 of an inch, and the leaf itself is nearly 4 inches. Leaf shape varies on the rusty blackhaw. This particular leaf has an elliptic shape; the leaf tip comes to a point.

Underneath, leaves are pale green. On some leaves you might find tiny rust-colored specks.

There is a fine serration on the wavy edges.

Here we have an example of leaf-shape variation. This leaf is 3 inches in length and has a rounded tip.

Rusty blackhaw twig with characteristic maroon leafstalks.

The maroon color isn't as noticeable from below.

But zooming in on the leafstalk, we see the characteristic rust-colored particles.

Detail of rust-colored hairs on leafstalk

Not all rusty blackhaws are multi-stemmed, but our tree of the week certainly is!

New shoots (suckers) can be found around the base of the blackhaw. The mower does most of the work clearing the suckers.

The asymmetrical growth of the multiple stems produces interesting outcomes.

Rusty blackhaw bark is rough and gray with an orange hue.

Other portions of the trunk have a clear block pattern.

Younger, smaller portions of the trunk have smooth, gray bark.

You can see older images of this specimen here.


For more information about this species consult the following:
United States Department of Agriculture (zoom-in on distribution map)
Texas A&M University (Aggie Horticulture)
University of Florida (IFAS Extension)

Viburnum dentatum

The deltoid-shaped leaves of Viburnum dentatum are oppositely arranged.

Terminal clusters of Viburnum dentatum berries turn bluish-black upon ripening.

Viburnum rufidulum

 

 

 

 

Viburnum ashei