When the General Land Office surveyors were laying their perfectly square sections on the round earth in northeastern Illinois 175 years ago they came across a lot of hazel bushes. American hazel grew in dense thickets scattered across the prairies; it grew in coppices at the edge of woodlands and in the shade of oaks inside the woods. Analyses of survey records suggest that American hazel grew on nearly all our woods and savanna groves and was several times more abundant than any other native shrub.
Hazels are still around, but they are much reduced from their previous abundance. Their thickets are small and widely scattered and many a woodland in our region has none at all.
Most people are familiar with the taste of hazelnuts. Hazels are the small, round filberts in a can of mixed nuts, and the nuts are also popular as a flavoring for coffee. Out in the woods squirrels love 'em, blue jays love 'em, deer love 'em, and if we ever manage to reintroduce wild turkeys into these parts, the turkeys will love 'em too.
The decline of American hazel from the most abundant shrub in the region to relative scarcity follows the same general path that can be traced for hundreds of other native species. And like other besieged natives, hazels are beginning to get some attention from restorationists.
American hazel (Corylus americana) is one of two species of hazel native to the eastern U.S. The other, beaked hazel (Corylus cornuta), has been found in at least one location in the Chicago region, but it is far more common north of here. In the second-growth aspen woods of northern Wisconsin, beaked hazel is all over the place.
Both of these hazels are shrubs. In a relatively shady situation in the woodland they grow only about four feet tall, but in woodland openings where more sun is available they can get up to ten feet tall. Some Eurasian species of hazel are really small trees, and these are the source of the commercial crops.
Hazels spread through their roots, sending out lateral root sprouts that in turn produce vertical stems. The dense thickets created by this growth pattern make hazels excellent sites for the nests of a considerable assortment of woodland and brushland birds.
Hazels belong to the same plant family as birches and alders. One of the family traits of this group is that the male and female flowers are separate, but each plant produces both kinds. The staminate flowers, the ones that produce pollen, hang in long, slender catkins. The pistillate flowers, the ones that will produce the nuts, are at the tips of branches.
The catkins form late in the growing season and stay on the plant through the winter. As early as March they turn a bright yellow as the pollen is released and carried by the wind to the pistils. Bright yellow hazel catkins are a welcome assurance in the dreary late winter that spring is truly coming.
The decline of American hazel is a subject that hasn't drawn much attention until quite recently. Endangered species, plants that are hanging on by their metaphorical fingernails, are the obviously desperate cases. They inspire the creation of habitat-manipulation schemes, captive-breeding programs, and hand-pollination efforts. But the decline of a once-abundant species has to be a matter of major concern. Especially since the decline is obviously not over. Marlin Bowles of the Morton Arboretum has been monitoring tree and shrub densities on plots laid out in oak groves at the Middlefork Savanna in Lake County over the past ten years. In that time the number of living hazel stems has declined by 19 percent. Losing one-fifth of the population in a decade is not good.
Part of the reason for this loss is easy to find. Bowles's counts show during the same ten years an increase in European buckthorn--an imported tall shrub--of 550 percent. Tatarian honeysuckle, another imported pest, increased its stem count by 88 percent. So as a first guess, we can select competition from these exotics as a factor in the losses suffered by American hazel.
The fragmentation of the landscape enters into the mix too. Buckthorn produces small berries that surround hard seeds that can pass undamaged through the digestive system of a robin. So robins and other birds serve as seed scatterers for this species. Because they can fly, they can provide the buckthorn with the means to overcome the problems created by fragmentation.
Hazels have a harder time. You could say that they have adopted a different kind of reproductive strategy. Their heavy nuts are far less likely to be carried any great distance, and if they get eaten the seed is destroyed. The gain from this kind of strategy comes from the large amounts of food stored in the seed. If the nut survives long enough to sprout, the young growing hazel bush has a substantial reservoir of calories available to get it through the difficult early days of life.
In the past hazels probably did most of their reproducing with their root sprouts. Large thickets seem to have been a regular feature of the landscape in savanna groves and open oak woods. A clone of shrubs can move, but it happens very slowly. If you had the temporal perspective of a white oak you could see the root sprouts on the edge of the clone where conditions were getting better begin to survive at a much higher rate than sprouts from elsewhere. And where things got worse, hazels would die out. A green ultra-slow-mo amoeba, the clone would creep toward good times. Excellent in 1800 but hard to apply on I-90.
Grazing hit hazels hard too. Cows eat the plants; pigs eat the nuts. Fire suppression then chipped in by creating lots of dense, very shady woods that are too dim for hazels.
I think hazels fit into the category of creatures that the biologist E.O. Wilson called "obligate fugitives." An obligate fugitive can survive only in the presence of disturbances that do it considerable harm. The classic human counterpart would be the peasant farming the slopes of Mount Vesuvius. Every once in a while a big lava flow is going to come through, but between times, the land is rich.
Hazels are very thin-barked. Their stems are easily killed by fire. And it takes three years for new stems to mature enough to produce nuts. But without fire the woods become too dark for hazels. So "no fire" is catastrophic. As we say in Chicago, "You take the good with the bad."
Marlin Bowles has been planting hazels in places where they used to be but haven't been lately. His sites include Waterfall Glen Forest Preserve in DuPage County, Hickory Creek Barrens in Will County, the Fermi Lab, and Morton Arboretum.
The plantings in these sites were done in a variety of conditions: open ground, woodland edge, grove, shady woods. The plants did well under a variety of light conditions, but competition from other plants had a significant effect on the fortunes of the hazels. Particularly harmful was Hungarian brome, an exotic weed that grows on open ground. Hungarian brome forms a dense sod, and that may be what hurts the hazels.
Marlin Bowles's hazels are still alive and growing, and their relative success in varying circumstances will tell us something more about this plant and about where we might hope for it to live in the future.
Shrubs are becoming a hot topic among people interested in ecological restoration and preservation. Our biggest single problem in protecting natural areas has been coping with European buckthorn. When your biggest problem is too many shrubs, you may not think a lot about how to get more shrubs. However, clearing out the competing buckthorn had to be helpful to our remaining hazel clones. Perhaps with a little push from us, hazels could be available to help feed the wild turkeys that we are certainly going to get--someday.
Hazels were important pieces of our landscape not long ago and they could be--and should be--again.