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Common Name Gray Dogwood
Latin Name: Cornus racemosa
[Pronounced: "CORN-us race-uh-MOH-sah"]
Type of Plant: Woody Shrub
Identification Helps: A non-descript woody shrub, up to 2 meters (6 ft) or taller, with white flowers and berries as shown in the photo.
Similar Species: There are two or three similar Cornus dogwood shrubs on Ohio prairies, but gray dogwood is by far the most common. Consult a technical manual to identify the others.
Preferred Growing Conditions in the Wild: This plant grows in all but the driest or soggiest prairie soils.
Seasons of Growth and Bloom: This common native shrub blooms in late spring and early summer.
Natural Distribution in Ohio: Gray dogwood is found profusely throughout Ohio and is by no means restricted to prairie sites.
Description and General Information: Cornus racemosa is one of the most common woody shrubs on neglected prairies and is found in untended hedgerows, fencelines, and abandoned fields. The species invades and overtakes open areas left un-mowed or unburned. It is a pioneer woody plant that tips a prairie toward forest in the absence of periodic fire.
A prairie left unburned for several years will universally be invaded by seedling gray dogwoods, from seeds dropped by birds. Shrub stands of thick dogwoods are ideal habitats for a large number of birds. Larger landscapes would do well to provide such habitats, so long as the dogwoods are not allowed to eventually overtake local prairies.
Prairie managers should be aware of the pluses and minuses of this plant, a species that many would not regard as a real prairie plant since it grows so commonly on non-prairie sites and so quickly overtakes and destroys untended prairies.
But in presettlement Ohio prairies (all of which were frequently burned by Native Americans), there were scattered dogwood shrub patches. Prairie chickens are thought to require accessible shrub patches as thick protective cover from various predators. The inclusion of shrub patches as a minor fragment of large prairie landscapes is natural and appropriate, providing habitat for various shrubland birds and insects.
Unfortunately, however, the appearance of gray dogwoods in prairies must be closely monitored and diligently controlled. Untended prairies are overtaken and shaded out by dogwoods in the following (often insidious) sequence.
At first, for a year or two, only a few scattered, small (2 ft or less) dogwood stems are noted among the prairie grasses and forbs. These small plants fail to flower or set seed. They appear altogether innocuous, if even noticed at all.
But in a few years, gray dogwood shrubs appear all over the prairie. They begin to flower and set seed, and grow to four or five feet. After a season or two of this, the shrubs appear to be encroaching upon the prairie grasses and forbs. Suddenly, the prairie manager perceives a problem. The prairie is being overtaken by woody dogwood shrubs. If nothing is done, the prairie will soon be shaded out and will disappear.
Consequently, the prairie is often burned, to suppress the dogwoods. In almost all cases, when burned before the shrubs have completely overtaken the prairie, the burning seems to completely wipe out the dogwoods. In the summer after a good spring burn, the dogwoods will seem to have been completely eliminated.
But in fact, only the above-ground stems will have been killed by the spring fire. The sturdy roots will have been untouched and will re-sprout a host of new, albeit small, stems. Where the original shrub had three or four stems, the new replacement stems will have doubled. For the first year, they will be small, usually less than a meter (3 ft) tall. Unless specifically searched for, the multiple-stem re-growth will go unnoticed.
But in the second growing season, the shrub-infested prairie once again will appear to be in the process of being overtaken by now taller gray dogwood. The prairie manager will prescribe another spring burn, which like the first one, will burn off the above-ground stems and appear to clean things up once again.
Unfortunately, this sequence of biennial or triennial prairie burns is often continued, with apparent successful dogwood suppression resulting from each one. But after two or three rounds of this, after six to eight years, the dogwoods win the battle. When the dogwoods finally shoot up 10 or 20 new post-burn stems, the resulting dense shrub begins to cast so much shade on adjacent prairie plants that they can’t grow well. When the prairie manager sets another fire to control the proliferating dogwoods, there isn’t enough fuel to kill the woody stems. A crucial tipping point has been reached, where fire no longer controls the dense and shading dogwoods. Unless physically removed by hand or the most powerful brush-cutting mowers, the prairie will be lost to the shading dogwoods.
To keep this scenario from happening, prairie managers must, as the Native American did for centuries in Ohio, burn shrub-invaded prairies annually and sequentially. After three or four consecutive spring burns, the dogwoods die out. They can’t withstand multiple consecutive annual burns. They easily survive, even thrive, on consecutive biennial or triennial burns.
Therefore, intelligent prairie management will divide prairie landscapes into a number of large prairie islands, some of which are being burned annually, with a few being burned less often. A good prairie landscape has patches or islands in all stages of vegetational succession, with the majority of the area with no dogwoods, and some smaller, peripheral areas with a scattering of native shrubs.
In short, biennial or longer sequence prairie burning always eventually results in the loss of an Ohio prairie to dogwood invasion. Annual burning, at least for a sequence of several years, always retards or suppresses the loss of the prairie to dogwood shading.
Except on the steepest, isolated slopes (very rare), Ohio prairies were all the result of frequent annual fires set by Native Americans. Any prairie left unburned will soon succeed to dogwood brush.
A note on mowing. Mowing can have the same shrub-suppressing effects as burning. But mowings must be performed at the proper times. Too often, prairie managers confronted with a dogwood brush problem choose to mow off the brush in the dormant seasons, usually in late fall or early winter. Such mowings, however, are even less effective in controlling the dogwoods than a burn. The mowing merely lops off the above-ground stems when the plant has most of its energy stored in the roots. When the shrub re-sprouts the following growing season, it will shoot up a host of new and stronger stems. After two or three rounds of this, the shrubs will have overtaken the entire site.
The only way mowing can suppress dogwoods is to conduct a second sprout-loping mowing in June, after the new sprouts have used a great deal of root-stored energy to re-grow. But this right at the start of the prairie flowering season, and many prairie managers would prefer not to mow then, when birds are on nests in the prairie.