The color green is returning to our winter gray-brown ecosystems. The grass in our yards is starting to grow at an interestingly uneven rate. In my own yard places where Izzy has “visited” over the winter seem to be greening up faster and growing more robustly than the place not graced with her “presence (or should I say “presents?”). Lawns are looking shaggy all up and down my street, and they are getting more and more unkempt (or should I say more and more natural?) with each passing day. Some of my neighbors have been out mowing three or four times this season. The sound of their riding mowers roaring past my open windows with their distinctive Doppler whines makes me miss winter and its glorious quiet! Lawn grass that doesn’t look like carpet, for some people, is absolutely intolerable, but the energy and resources that our society pours into lawn care is obscene!
But don’t get me started on lawns!
The woods are greening, too, but much of this is actually not a welcome sign of spring. The first green in the understory of the forests around here is almost all due to the early leafing out of one particularly, noxious, invasive plant: multiflora rose.
Multiflora rose (Rosa multiflora) is an introduced plant species that is native to Japan, Korea, and Eastern China. It was first brought to the United States in the 1860’s for use as root stock for ornamental roses. It was subsequently used as a “living fence” plant, as highway buffer vegetation, and in a variety of disturbed land reclamation programs. Soon, though, the invasive and destructive potential of this plant was recognized. Most states have placed multiflora rose on the “noxious weed” or “banned invasive” lists and are not only preventing its sale and planting and also actively attempting to extirpate it from areas in which has become established.
Multiflora rose can be found throughout the United States except for the Rocky Mountain region, the extreme desert southwest, and most of the state of Florida. It grows rapidly in fields, pastures, roadsides, and sun-lit edges and spaces of a forest. It is especially common in forest sun gaps that are generated by fallen trees. Its rapid growth and tendency to form dense, monocultural thickets allows it to out-compete and over-shade most native plants.
Multiflora rose is a perennial that grows in long (up to 15 feet), arching, thorny stems that are called “canes.” It has compound leaves that usually are divided into 7 to 9 serratedly edged leaflets. The leaves arise alternately on the long canes. Flowers (which form in May or June) are pink or white and very fragrant. They are pollinated by a diverse array of hymenopterans. A pollinated flower will eventually form a small, leathery, red fruit around a single, hard seed. This fruit is called a “hip,” and hips may persist on the
plant through the next winter and, possibly, for several years. Hips are consumed by a wide array of birds (including American robins, cedar waxwings, and northern cardinals). Passage of the seed through the digestive tract of a bird significantly increases the likelihood of the seed’s germination. Birds, then, represent significant ecological symbionts for the multiflora rose by accomplishing both seed dispersal and scarification.
In addition to developing from seed, multiflora rose is also capable of rooting from the tips of its arching canes. New canes grow up and over older canes, then, and form an expanding, dense mass of heavily thorned stems. These thickets allow very little other vegetative growth within them and, thus, represent an ecological disaster for native plant species. These thickets, though, do represent a highly protective microhabitat for many small mammals (like cottontail rabbits and woodchucks) and birds (including bobwhite quail, pheasants, and many small song birds).
Multiflora rose is one of the first plants to leaf out in the early spring. This early start on photosynthesis gives the plant an energetic advantage over its many potential competitors. The shade generated by the its leaves also acts to inhibit the growth and survival of many other spring plants. This is the time of year to look our across our wooded valleys or up and over our forested ridges to get an appreciation of just how much multiflora rose there is in our ecosystems! The early green we see is almost all this invasive plant species (along with some similarly invasive honeysuckles!), and it is shading and crowding out a huge number of our diverse, native plant species!
I have a large multiflora thicket at the bottom of my grassy field. I remember consciously avoiding mowing a spindly little rose cane that was growing out in the field about 25 years ago. I subsequently jogged my mower around the larger and larger and more and more highly branched rose bush, then rose patch, then rose thicket over the coming years. I don’t remember what I was thinking when I let that tiny plant live, but it is now a building sized, dome-shaped mass of heavily thorned, intertwined canes that serves as a roosting habitat for cardinals, a protective cover for a large woodchuck and a couple of rabbits, and black hole that has captured (and kept!) numerous soccer balls, Frisbees, and baseballs. It has also served as a seedling nursery for two mulberry trees that now stretched out over the thicket. These trees are covered with fruit in June and are a favorite feeding and gathering spot for flocks of American robins and cedar waxwings!
No other plants, though, grow under these rose canes. Carefully pushing the thorny canes aside all you see is bare soil without even a hint of the grasses and weeds that were there when the rose cane got started. The rose thicket is making some ecological contributions to my yard and field ecosystem, but it is also taking an awful lot of resources in return!