I'm fascinated by the Victorian era (1837-1901), as it represented the Golden Age of Science. Back then, scientific inquiry was practiced by innately curious individuals who didn't consider it a profession. Humans began to become curious about new places, animals and peoples simply to gain knowledge wealth, rather than material wealth. Great organizations of explorers began during this time, including the Royal Geographic Society (1830) and the National Geographic Society (1888). At their annual meetings, explorers gathered to present their latest findings and discoveries about the natural world. These legendary explorers included Sir Richard Burton, David Livingston and Henry Morton Stanley.
This also was a time of escalating popularity for great zoological and botanical gardens, in which specimens of strange plants and animals were maintained. The interest quickly spread to wealthy individuals anxious to possess their own collections of exotic life.
By the turn of the 20th century, China had opened to exploration. Word quickly spread about the fantastic plants existing in one of the most ecologically diverse areas of the world, extending from the Siberian Peninsula to the tropical forests of South China-Vietnam. Plant explorer E. H. Wilson described China as "The Mother of all Gardens," and it became the primary source of plant materials for the formal gardens of Europe and America. If a plant were from China, it earned a premium price in the nursery and landscaping industry. During the post-World War II American economic boom, even average American homeowners could get plants of Chinese origin.
This era of unregulated importation of foreign plants into the U.S. has had significant impacts on the quality of whitetail habitat. That's because many of the beautiful plants finding their way into the yards and landscapes of the Baby Boomer generation didn't want to stay put. Many produced seeds, fruits and nuts highly attractive to wildlife, especially birds. Urban centers thus became sources for pioneer plants invading the suburbs, and then surrounding farms and woods.
And it didn't stop there. Scientific agriculture demanded new, more productive plants and animals. Government agencies such as the Soil Conservation Service, The U.S. Department of Agriculture, state extension services and even wildlife agencies eagerly promoted exotic plantings to improve forage production and/or wildlife cover. Agencies often cost-shared the planting of exotics to enhance wildlife habitats lost to more efficient agriculture. (Ironically, some of the same agencies now cost-share eradication of the same plants they once promoted.)
Although there are perhaps hundreds of such exotic pests, let's focus on the major culprits. Many came from China and the Far East, but a handful aren't even foreign in origin. They've proved to be invasive because of changes in the way land here in North America is managed.
Japanese honeysuckle (Lonicera japonica) originated in Asia and came to North America in the 1800s. It was first planted in 1806 on Long Island, New York, as a landscape plant and for erosion control. Today, it's found in all but seven of the continental states and has been around so long it's considered "native" by many landowners.
Since becoming naturalized in North America, Japanese honeysuckle has also been planted for wildlife, primarily as forage. Frankly, it's the only invasive plant I consider useful for whitetail forage, because it's one of the few they relish. The negative is that it can crowd out native forage species, creating huge monocultures of thick vines.
Bush honeysuckles (Lonicera sp.) aren't to be confused with Japanese honeysuckle in any way. I've never found them useful as deer forage. They represent a group (Amur, Morrow's, Tartarian and Belle honeysuckles) imported from Eurasia in the 1800s for erosion control and wildlife cover.
There also are native bush honeysuckles that have lost ground to the exotic varieties, which grow into dense stands that crowd out quality whitetail and bird plants. Seeds are dispersed by birds feeding on them to acquire energy for migration.
Barberry (Berberis thunbergii) is a plant I first encountered while working with New York landowners to improve habitat. The plant forms understory thickets of thorny shrubs deer evidently don't like to eat. The dense stands prevent tree regeneration and growth of desirable herbaceous plants. Unfortunately, some states make chemical control of such species difficult, due to environmental concerns.
Macartney rose (Rosa bracteata) and multiflora rose (Rosa multiflora) Asian invasives once promoted by government agencies as wildlife habitat. During the conversion from sharecropping to more efficient agricultural systems, dense fencerows occupied by native shrubs used as cover by quail and other game birds were eliminated. To offset this, thousands of acres of roses were planted in the eastern U.S.
The shift of small family operations to larger corporate farms, cattle operations and timberland led to a proliferation of dense rose thickets. Deer will browse these thorny plants, but the thickets prevent movement of many animals. Diversity of wildlife foods also is significantly diminished.
Autumn olive (Elaeagnus umbellata) and Russian olive (Elaeagnus angustifolia) were introduced in the 1830s from Asia for wildlife cover and food. As late as the 1970s, these species were heavily promoted for developing game bird cover and songbird food (berries). As with many other invasives, they quickly spread and formed impenetrable thickets armed with thorns. I've never seen deer eat the berries or browse the plants in any quantity. Both species are well adapted to a variety of soil types and temperature extremes.
Chinese privet (Ligustrum sinense), imported in 1852, is an ornamental landscape plant that's become naturalized. Its fragrant, showy flowers are relished by homeowners until they discover how quickly the plants spread. In much of the South, privet has become a dominant understory plant, crowding out key deer forages. It's difficult to eradicate once established, as its prolific berries are spread by songbirds.
Privet now occurs in over 450 U.S. counties. It's proven to have caused the extinction of some native plants preferred by deer.
Chinese tallow tree (Triadica sebifera) is one of the most difficult invaders to control. It can convert diverse woodlands into monocultures of these short trees. It's primarily a Southern problem, having been introduced in South Carolina in the 1700s. This tree is virtually impossible to eliminate once established. The milky sap is reportedly toxic to animals and other plants.
Kudzu (Pueraria montana var. lobate) was imported for erosion control and forage. It was brought to the U.S. in 1876 for the Philadelphia Centennial Exposition. Over 1 million acres were planted by the Soil Conservation Service in the 1930s and '40s. In the '50s it was recognized as a serious invasive, but by then it was too late to stop the spread. Much of the South now has it.
Although this Asian perennial can be used as forage, there aren't enough deer to keep up with its growth. The vines quickly grow into the forest canopy and engulf large areas in what appear as surreal forests of soft green "posts," represented by trees that have succumbed to the vines. Kudzu has been reported to grow over a foot a day and 60 feet annually.
King Ranch bluestem (Bothriochloa ischaemum var. songarica) is an Old World grass that grows in dense bunches, with spreading culms that quickly choke out the diversity of prairie plants needed by wildlife. I've never seen deer eat this grass; even cattle dislike it. For years, some resource professionals encouraged introducing such Old World bluestems because of their rapid growth and resistance to grazing. However, "KR" now has spread over much of Texas, choking out desirable wildlife plants in the process.
A native plant can become "invasive" when changing land use gives a distinct advantage to a plant normally occupying only marginal habitats. Good examples include yaupon holly (Ilex vomitoria) across the South, various cedars and junipers ((Juniperus sp.) in the Midwest and Southwest, prickly pear cactus (Opuntia sp.) in Texas and southern wiregrass (Aristida beyrichiana) in the Deep South. I've had to deal with all these plants, and others, on private lands managed for deer.