f 
I 
looking along the tracks to where they 
curve out of sight gives me a powerful 
urge to find out what lies beyond the 
bend. While walking in pursuit of this 
ever receding goal, 1 find the opportu- 
nity to observe plants and animals and 
to enjoy the surrounding landscape, 
whether rural or industrial. Seldom- 
used rural lines are ideal for a study of 
plants because the relative infrequency 
of maintenance insures a large weed 
population. Urban settings, however, 
can be just as interesting, for even a 
well-maintained, plant-free main line in 
the middle of a large city usually has in- 
frequently used loops or sidings on 
which plants can grow in astonishing 
numbers and variety. 
The railroad line where I carry out 
most of my fieldwork crosses a swamp 
on a raised embankment, intersects sev- 
eral roads and farm tracks, branches to 
form a siding for a farm-supplies depot, 
goes through a cut in a hill topped by 
cornfields and pastureland, parallels a 
creek, and passes through stretches of 
both deciduous and coniferous wood- 
land, all in the space of a few miles. 
Built on a bed of imported cinders or 
stones, homogeneous from one end of 
the line to the other, a railroad would 
be monotonously uniform without such 
variety in its surroundings. As the envi- 
ronment of a railroad changes, so does 
the vegetation adjacent to, and en- 
croaching on, the tracks. 
The number and diversity of plants 
along a railroad are generally greatest 
near an intersection with a road. Com- 
mon roadside weeds, such as Queen 
Anne’s lace ( Daucus carota ), ragweed 
(Ambrosia artemisiifolia), and wild 
parsnip ( Pastinaca sativa), are well rep- 
resented at these locations. The seeds of 
many of these plants can be found in 
dried soil material scraped from the un- 
derside of motor vehicles. Picked up 
from plants growing along roadsides, 
these seeds may shake loose as the vehi- 
cles bounce over the uneven road sur- 
face at a railroad crossing. Roadside 
plants that become established at cross- 
ings may then spread along the tracks 
in both directions as their seeds are dis- 
persed by the wind or by passing trains. 
Weeds of dry fields and meadows are 
also abundant along railroad tracks 
close to crossings. At railroad crossings 
that transect farm fields, pastureland 
weeds, such as clovers ( Trifolium spp.), 
horseweed ( Conyza canadensis), and 
wood sorrels (Oxalis spp.), are found 
growing in larger proportion than road- 
side species. These species are undoubt- 
edly spread to railroads by farm 
vehicles as they cross the tracks in tran- 
sit from one field to another. 
The best way to gain an appreciation 
of the changes in plant distribution 
along a railroad is to walk alongside the 
tracks from one road crossing to the 
next, especially if the distance between 
the two is at least a mile. Most of the 
plants are clustered within a few yards 
of the road edge at each crossing, with a 
long stretch of almost bare cinders be- 
tween crossings. The few scattered 
plants that do grow along the tracks in 
these otherwise bare stretches usually 
belong to species different from those 
found near the road. Representative of 
the vegetation immediately surround- 
ing the tracks, the plants that grow on 
the railbed may be grasses where the 
line is in a cut, horsetails near a marsh 
or swamp, or small tree seedlings, 
doomed to a brief life, where the line 
passes through a patch of woodland. 
Plants that grow along railroads are 
subject to both stress and disturbance. 
Stress includes all conditions that act to 
restrict the growth of a plant. A short- 
age of water is probably the major 
stress factor for railroad plants because 
water drains quickly through the po- 
rous cinders or gravel, particularly if 
the railroad is built on a raised embank- 
ment. In addition, railroads are gener- 
ally open, exposed places where the hot 
summer sun and the wind quickly dry 
the cinders, even after the heaviest of 
showers. After spending many July and 
August days bent over the burning hot 
rails collecting data, I have come to ap- 
preciate the baking heat that railroad 
plants must endure. Some essential 
minerals may also be in short supply be- 
cause of rapid leaching. Shortages of 
Robert M Arnold 
60 
