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posted: 9/15/2013 7:56 AM

Red oaks: Where and how they grow

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  • Pin oak leaves are highlighted by the sun at Dick Young Forest Preserve in Batavia.

       Pin oak leaves are highlighted by the sun at Dick Young Forest Preserve in Batavia.
    Laura Stoecker | Staff Photographer

  • The distinctive designs of the bark of the northern red oak tree.

       The distinctive designs of the bark of the northern red oak tree.
    Laura Stoecker | Staff Photographer

  • A side-by-side comparison of oaks in the red oak family. From left: shingle, hills, black, northern red and pin oak leaves and their respective acorns. Red oak members take two years for their acorns to develop and drop, unlike members of the white oak family.

       A side-by-side comparison of oaks in the red oak family. From left: shingle, hills, black, northern red and pin oak leaves and their respective acorns. Red oak members take two years for their acorns to develop and drop, unlike members of the white oak family.
    Laura Stoecker | Staff Photographer

  • Northern Red Oak acorns are large in comparison to other oaks in the red oak family.

       Northern Red Oak acorns are large in comparison to other oaks in the red oak family.
    Laura Stoecker | Staff Photographer

  • Laura Stoecker/lstoecker@dailyherald.comPin oaks are in the red oak family, and have small acorns. Red oak members take two years for their acorns to develop and drop, unlike members of the white oak family.

      Laura Stoecker/lstoecker@dailyherald.comPin oaks are in the red oak family, and have small acorns. Red oak members take two years for their acorns to develop and drop, unlike members of the white oak family.

  • Shingle oaks have a totally different leaf type than other members of the red oak family. However, they are indeed native to Illinois, just not to Kane County.

       Shingle oaks have a totally different leaf type than other members of the red oak family. However, they are indeed native to Illinois, just not to Kane County.
    Laura Stoecker | Staff Photographer

  • Another member of the red oak family is the Hill's oak. Red oak members take two years for their acorns to develop and drop, unlike member of the white oak family.

       Another member of the red oak family is the Hill's oak. Red oak members take two years for their acorns to develop and drop, unlike member of the white oak family.
    Laura Stoecker | Staff Photographer

  • A red oak seedling not generating well at Tekakwitha Woods in St. Charles. Red oaks need lots of sunlight and are often shaded out by invasive buckthorn and honey suckle, or are chewed on by deer.

       A red oak seedling not generating well at Tekakwitha Woods in St. Charles. Red oaks need lots of sunlight and are often shaded out by invasive buckthorn and honey suckle, or are chewed on by deer.
    Laura Stoecker | Staff Photographer

 

The searing heat of the summer day seemed inescapable. I tramped through the tall grass and headed for shade. A grove of oak trees looked promising.

Reaching the hillside grove, I leaned against one of the massive trunks and wiped my brow. A heaven-sent breeze rustled the leaves above, and the sanctuary of the oak grove was, for the moment, the most beautiful spot on earth.

The oaks that created this oasis on the prairie were black oaks. Black oak trees belong to the red oak group. In this column we'll take a look at the red oak group -- who they are, where they grow, and what the future holds for islands of oak groves in a sea of suburbia.

The red oak group as a whole has two main characteristics: pointed leaves ending with small bristle tips, and acorns that take two years to develop. Each species within this general group shares these two traits; each has additional, unique characteristics that separate it from the others. Fortunately for us, it's easy to learn the distinguishing characteristics.

The group's namesake, northern red oak, is a tall forest tree that favors deep, moist soils on upland sites. Northern red oaks can reach more than 100 feet tall in good conditions, with trunks three or more feet in diameter. These stately trees stand out in the forest by their beautiful bark. It's dark at maturity, with silvery flat stripes running up and down the tree. These were described to me years ago as "ski tracks" and that image has stuck in my mind ever since. Look way up the trunk of a tall red oak tree, and you'll see the tracks.

The leaves of northern red oak have between seven and 11 bristle-tipped lobes. These can be tricky to distinguish from some of the other red oaks. The acorns, though, are a dead giveaway. They're large -- about 1 inch long, and they seem to bulge out of the acorn cap. This cap looks like a beret atop a person's head.

You may see "mini" red oak acorns fastened tight to the tree. These are next year's fruit. As with all members of its group, the northern red oak acorns remain on the tree and take their time maturing. They will ripen and fall the second year.

What's red about the northern red oak? You have to cut into the bark to see. The inner bark is pinkish more than red, but quite distinctive in freshly cut wood. Otherwise, the only red thing about the red oak is the autumn foliage. A beautiful red it can be, too.

Black oak is another member of the red oak group. Although similar in many respects to northern red oak, it possesses, as Donald Culross Peattie wrote in "The Natural History of Trees," "a rough, unbending grandeur of its own."

Black oak can grow tall and straight like northern red oak, but it can tolerate sandier, drier and coarser soils than red. It can grow in open, dry savannas and hills made of porous glacial till. In these conditions, black oak is often a gnarled-looking but picturesque tree.

At first glance, the black oak leaves are quite similar to northern red oak's. Each leaf has seven to nine bristle-tipped lobes. Black oak leaves, however, have deeper sinuses, or indentations, between the lobes. Turn over a black oak leaf and look closely -- there's a layer of fine, rust-colored "fuzz" underneath. You might need a hand lens to see this.

And while you've got that hand lens out, look at the acorns. They, too, are fuzzy, particularly inside the acorn cap. The scientific name Quercus velutina refers to this velvety characteristic. Black oak acorn caps, unlike the tight berets of red, are shaggy and bowllike, covering up to one-third of the nut. The caps also have small, overlapping scales that look like shingles on a roof. Further, if you cut open the nut with a pocket knife, you'll see that it's a distinctive yellowish color.

Black oak bark is similar to that of northern red oak, ski tracks and all. The inner bark, like the acorn meat, is yellow to orange -- not at all like the pink-tinged inner bark of red.

Pin oak is another type of red oak that grows in our area. It's not native to Kane County, but it's common in landscape plantings. Pin oak leaves are similar to the previous two species, but the sinuses are very rounded and very deep, reaching almost to the middle vein of the leaf.

The main trunk grows straight. For this reason, people like to plant it as a street tree. The lower branches droop, but overall the tree has a pyramidal shape. Numerous short spurs grow from the branches; these are the "pins" of pin oak. The bark is light and thin -- quite unlike the dark, tough bark of northern red or black oak.

Pin oak's scientific name Quercus palustris means "oak of the swamp." This species can tolerate wet clay flats, often referred to as flatwoods. It's a tree well suited for bottomlands, whereas the other red oaks in our area are upland dwellers.

Often, pin oak leaves are light green and kind of sickly-looking, indicating the tree is suffering from an iron deficiency. This problem led the late Dick Young, author of "Kane County Wild Plants and Natural Areas," to look askance at the use of pin oaks in landscaping.

"(They are) widely planted for ornamental purposes that often backfire," Young wrote. "We commonly see this yellowing, skeletonized, nursery-recommended oak as a bleak front yard emblem of wasted money and hope."

Best to let pin oak grow in clay-lined flatwoods where it does best.

Close kin to the previous oaks is Hill's oak. It shares leaf characteristics of both black and pin oaks, and the bark is similar to that of pin oak. Hill's oak differs mainly in its fruit. The acorn is uniquely elongated with a pointed base. There's considerable hybridizing between these species, and you may find individuals with a mixture of features.

The future of oaks

Red oaks were once numerous in Kane County. But just as with white oaks, the red oaks are in serious decline. Only ten percent of the county's original oaks remain, and there are scant few seedlings to build new generations of these great trees.

The challenges to oak regeneration are formidable: loss of habitat, competition with invasive species, and an increase in herbivores. When the tall, stately oaks fall, there are few progeny to replace them. Turf grass and asphalt are not inviting to sprouting acorns. Invasive species that shade out seedlings. Saplings are browsed by deer. The shifting climate and change in soil conditions contribute to the stress on oak trees. All these factors have taken a tremendous toll on our native oaks.

In my mind's eye I return to the oak grove on the prairie where I sought refuge from the heat. I remember the venerable, old trees and the comfort they gave on that hot summer day. I listen in my memory for the sough of their summer leaves. Our long-ago ancestors called these sacred groves, and I understand why. These are special places, and priceless trees.

Valerie Blaine is an inveterate oak nut, and a naturalist with the Forest Preserve District of Kane County. Email her at blainevalerie@kaneforest.com.

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