Notes on the Salisbury List of Invasive Plants in Sligo Creek

Dorothy Salisbury authored a booklet about Sligo Creek Park and her observations of the plant groups she encountered, reproduced below.

The Plants of Sligo Creek Park by Dorothy Cleaveland Salisbury

1970-1971, First Revision
Published by the Maryland-National Capital Park and Planning Commission

[Officials listed include: ] Mrs. Caroline Freeland, Chairman
W.C. Dutton, Jr., Vice-Chairman
John P. Hewitt, Director of Parks
Stanton G. Ernst, Principal Park Naturalist


Sligo Creek Park is one of the stream-valley parks authorized under the Capper-Cramton Act of Congress of 1930. It includes most of Sligo Creek from the headwaters near Wheaton, Maryland, until it flows into the Northwest Branch of the Anacostia River not far from tidewater. The Park extends for approximately fifteen miles and varies in width from 150 feet to 400 feet, and contains about 500 acres.

The main stream of Sligo Creek rises in a springy area between Arcola Avenue and University Boulevard. Today this area has been filled for residential development and its springs piped into a storm sewer emerging as a flowing stream behind the Arcola Elementary School. At this point, the parkland begins.

A second stream, the West Branch, rises a short distance south of University Boulevard and joins the main stream a quarter of a mile or so above Forest Glen Road.

Below University Boulevard, the stream enters a valley. In places, there is narrow floodplain on one side or the other, and the creek takes practically all the space between the steep slopes in scenic ravines. Much of this area is covered with the natural woods typical of the Piedmont (tulip-poplar, sycamore, oaks, and maple) with some beech, hickory, and pine. The pine is mostly scrub-pine (pinus virginiana) in pockets among the hardwoods. In the understory are dogwood, holly, spicebush, sassafras and viburnums interspersed with saplings of the larger trees. Judas tree or red-bud, witch hazel, ironwood, and red and white mulberry and alders grow along the stream banks. At Parklawn Recreation Center near East-West Highway and Riggs Road, the creek flows out into the open, relatively level land typical of the coastal plain. Because of the steep narrow valley form, much of the native woods were left undisturbed by early settlement. Where the land was comparatively level, it was earlier used for diversified farming.

The underlying rock of the whole area is the Wissahickon Formation of schists and semi-schists, with occasional intrusions of igneous rock. The soil resulting from the disintegration of this rock varies from fine sand to a gravelly loam marked by glistening flakes of mica. This is an acid soil, varying frompH4 to pH6. Hence, the vegetation in the valley includes mostly acid-loving plants. There are almost no marshy spots along the creek, so it lacks such plants as water-willow and pickerelweed which grow luxuriantly along the C&O Canal, and arrowhead and water-purslane are rare here.

Formerly, the stream was fed by small springs from its source to the mouth of Spring Run, the stream from the once-famous Takoma Park Spring which empties into the Sligo at the Parklawn Recreation Center. As building crowded close to the rim of this valley, most of these small streams were cut off and piped into storm sewers. Only the larger streams such as Brashear Run, Longbranch and Spring Run remain, and there are much reduced in flow.

From 1900 to 1920, Sligo Creek was the water supply for Takoma Park, Silver Spring, and Kensington. A dam was built at the end of Geneva Avenue, and a filter-plant and pumping-station erected on the bank. Today, the dam’s pool is silted full and only traces remain of the waterworks buildings.

In its fifteen miles of wandering from the lower edge of the Piedmont to tidewater, the Sligo falls about 400 feet as it flows over low ledges and amongst rocks and stones from one riffle to another with stretches of quiet water between. The stream bed today, floored with sand and gravel, is ten to thirty feed wide and several feet below its banks. In times of drought, the creek may be little more than a series of still pools. When heavy rains fill it to high water or flood stage, it becomes a rushing torrent, overflowing its banks and sweeping all in its path before it, leaving confusion and destruction. Such were the disasterous floods of September 1966, August 1967, and August 1969.

The following lists of plants found in the Sligo Creek Park have been compiled from intimate acquaintance with the park for 25 years. During earlier years, my interest was chiefly in the bird life and I kept notes of only the more striking and unusual plants and on early blooming dates. Since January 1, 1964, I have made an intensive study of the plant life from spring beauties to ponderosa pines. I have visited the park daily or, at least, several times a week with few interruptions. Though most of the time has been spent on the area between Carroll and Wayne Avenues, the remainder of the park between New Hampshire Avenue and University Boulevard has been studied frequently.

Sligo vegetation is never static. Plants which have been found in past years have in some cases disappeared-from winter-kill, drought, flood, and vandalism. Among the “lost” plants are hepatica or liverwort, trailing arbutus, golden ragwort and Virginia anemone or thimbleweed. Some of these may still be growing in more obscure and less-frequented spots.

There are other plants which maintain a precarious foothold in the park. In some cases, they are represented by only a single stand or even a single plant. Any accident might easily remove any one of them from the list of growing things to be found there. On the other hand, new plants appear, and occasionally, a “lost” plant reappears as did the ivy-leaved morning-glory.

These lists do not claim to be complete, merely extensive. There will always be a chance of discovering something new or something overlooked.

This compilation would not have been possible without the courtesy, interest and cooperation of Mr. Stanton Ernst, formerly Park Naturalist and presently Chief of Interpretation and Conservation of the Maryland-National Capital Park and Planning Commission and his staff at Wheaton Nature Center, to whom I am greatly indebted.

My heartfelt thanks also go to my husband, Elon G. Salisbury,who not only first took me to the Sligo, but who has been my constant companion on my Sligo walks and has encouraged me in all my ecological work, both in the field and at home with my books and typewriter.


The Sligo Creek valley is a relatively poor area for the fern lover. In general, the woods are too open and the soil is too acid and lacks sufficient moisture for many of the ferns. Of the 54 species listed for Maryland and 40 for D.C., I have found only eight species along the Sligo. None of these is more than “occasional.” Several are represented by one or two small stands with very few plants in each.

The Christmas fern, which was present ten years ago (1959)and found frequently all along the park as the most common fern, has suffered from removal by those who fail to realize the damage they are doing to public parkland; and from the natural hazards of drought and winter-kill.

Why horsetail is so rare is a puzzle, since it flourishes in such varied habitats, though it does prefer the sun. The Sligo woods are generally too dry for the clubmosses. Perhaps they too have suffered like the Christmas fern from being gathered for home decoration. Since this is a very slow-growing plant with running rootlets, it is easily destroyed.


(Excluding Trees, Shrubs, and Vines)

This main list of plants contains only those commonly thought of as “Flowering plants” — annuals, biennials, and perennials which, in general, die down each year. For ease of use by the amateur and casual park visitor, separate lists have been made for Trees and Shrubs, and for Vines.

In the Sligo Creek valley, there are fewer of the plants which grow in open sun than might be expected, since only limited areas of such habitat are not mowed. Those which have been listed here are “rare” or “occasional” in appearance.


Most of the trees and shrubs (erect, woody plants) are native to the area and grow in the park naturally, but there are a few which man has planted in the park. Those planted by the park system are mainly to be found along the parkway and as “edge plants” at the parking areas. These include such trees as the white and scotch pines and probably the bald cypress, and include such shrubs as the leatherleaf and double-file viburnums, the weigelias, glossy abelia, and winter jasmine. Japanese barberry, rose of Sharon, panicle hydrangea, wintercreeper, and apple are probably escapees from cultivation.

For convenience, the shrubs are marked with an asterisk.


Except for the morning-glories, these are plants primarily attracting attention because of their creeping, twining, and climbing forms, generally with inconspicuous flowers. Many are natives of Europe, Asia, or South America which have escaped from cultivation or, as the kudzu vine, have been planted on exposed places for ground cover.



Fernald, M.I. Gray’s Manual of Botany, 98th ed. N.Y. American Book, 1950.


Beechcroft, W.I. Who’s Who Among the Ferns. N.Y. Moffatt, 1910.
Cobb, Boughton. A Field Guide to the Ferns. Boston, Houghton, 1963.
Parsons, Frances Theodora. How to Know the Ferns. N.Y. Scribner’s, 1899.


Dana, Mrs. William Starr (Frances T. Parsons). How to Know the Wild Flowers. Rev. ed. N.Y. Dover Pub. Co., 1963, paperback.
House, Homer. Wild Flowers of New York. 2 v. 1918. Albany, N.Y. University of the state of New York.
Peterson, Rogers Tory & McKenney, Margaret. A Field Book of Wildflowers. Boston, Houghton, 1968.
Pohl, Richard W. How to Know the Grasses. Rev. ed. Dubuque, Iowa, Wm. C. Brown, 1968.
Rickett, Harold W. New Field Book of American Wild Flowers. N.Y. Putnam, 1963.


Ibberson, J.E. and others. Common Trees of Pennsylvania. Harrisburg, Pa., Dept. of Forests and Waters, 1963.
Illick, Moseph. Common Trees of Pennsylvania. Altoona, Pa. Times-Tribune, 1925.
Petrides, George A. A Field Guide to Trees and Shrubs. Boston, Houghton, 1958.
Rogers, Julia Ellen. Among Green Trees. Chicago, A.W. Mumford, 1902.
The Tree Book. N.Y. Doubleday, 1913.
Viertell, Arthur T. Trees, Shrubs and Vines. Rev. 1961. Syracuse, N.Y., State Univ. College of Forestry.


These are included in books listed under Flowers and in Petrides and Viertel listed under Trees and Shrubs.


Prior to January 1970, the Sligo Creek Valley between Maple and Carroll Avenues supported a fascinating and diverse variety of plant and bird life. It was a unique area for plants requiring open sun. Since it is now largely altered in the names of “progress” and artificial “beautification,” the area as it was should be described for the records.

The few feet near the top of the creek bank between the Maple Avenue bridge and the entrance to the path was crowned by a hedge of buffaloweed and with silvervine fleeceflower and cleavers clambering over it. In late summer, the buffaloweed held aloft its tall candles and the vines were filled with their inconspicuous flowers.

The entrance to the path was marked on the right by a large, symmetrical clump of speckled alder. Its greening and lengthening catkins were one of the first signs of the coming Spring in the park. When they were at full growth, the whole shrub was a parasol dripping with catkin fringe. Much of the alder has been cut away, leaving only a haggled remnant of its former symmetry. Two large red oaks stand across the path from the alder. At their base grew two or three plants of broad dock, one of the few stations of this plant in the park.

For the first fifty yards or so, there was a fairly wide strip of bottomland before the slope to high ground began. The slope on the Washington Sanitarium side was covered with an open woods of beech, tulip, oak and sycamore, with an occasional hickory. On the creek side there was also water birch. Below the forest trees was an understory of spicebush, dogwood, arrowwood, and along the creek bank, witchhazel and redbud. Underneath was a groundcover of many plants. On the right side of the path grew an early magnolia, a small volunteer appletree, a rose of Sharon shrub, two or three small arbor vita or white cedars, and a white mulberry and two small hemlocks. Today only the mulberry and hemlocks remain. For this distance the path was an obscure double track, as an occasional truck had been in this far to service gas, water and electric lines.

On the bank of the creek just beyond the alder, grew two jacks-in-the-pulpit. Farther along, taller and larger plants filled the bottomland. Here in April, a fine plant of golden groundsel stood out amidst the green. This was the only one in the park. Across the path from it was a plant of spreading dogbane. In late Spring, it was covered with tiny white and pink bells and later with long, slim green seedpods. Behind the dogbane grew a cutleaf coneflower with its golden blossoms, the original wild plant from which the goldenglow of the gardens was developed.

The bottomland section on the right of the path I called “the weedpatch.” In the Spring, before the taller plants had developed, the low, moist section was filled with Spring beauties, mayapples, and a patch of the dainty yellow coradylis (coradylis flavula) two feet or so in diameter, with more plants scattered among the other flowers. This too was the only station of this plant, since a small clump of it at the edge of the playground was destroyed by the mowers. As Summer came, this section was filled with ragweed, field garlic, false nettle, garlic mustard, galinsoga or quickweed, and honewort among others.

On the edge of the path, in front of the false nettles and others were a very few plants of clearweed (pilea pumila), germander and perilla with its scalloped and ruffled leaves tinted with reddish bronze. Beyond these, a single plant of clotbur (Xanthium chinense) crouched close to the ground. Under a tulip tree, the ground was blanketed with pachysandra and at the bend, under the rose of Sharon, grew a sturdy stool of common wintercreeper, both spots of springlike green even in the midst of the snow.

The bottomland space on the left of the path, beyond the dogbane and cutleaf coneflower, was filled with asters-white wood aster, calice, heath and small white aster-daisy fleabane and several goldenrods. In the damp spot where underground water from a broken pipe or underground spring keeps a small puddle most of the time, lady’s earrings and lady’s tearthumb or red-leg, the smartweed with the dark triangle on its leaves, grew luxuriantly.

In the median strip between the two paths, a few stalks of meadow or spiked lobelia and Venus’s-looking-glass grew among the self-heal and grasses.

Beyond the fleabane and asters, several stalks of the blue lettuce (lactuca floridana) towered above wine raspberry canes and hoary tick-trefoils. At a bend in the path, a small stream flowered from an old pipe sunk in the ground (either from a leak or an underground spring). About this stream-head was a small chokecherry with other shrubs. The birds delighted in this shallow, running water for bathing and drinking; and in the chokecherry with its long white fingers of bloom in May and dark berries in the fall.

Beyond the “water-hole,” the path turned as the steep slope came close to the creek, giving scant room even for the path itself. At its foot, dogwood saplings, low-bush blueberry and a plant of American poison hemlock crowded for a foothold. The creek side was lined with ironwood, redbud and witch hazel.

The stream and path bends again opposite the mouth of Brashear Run. From here to Carroll Avenue bridge, both stream and path take a steeper pitch. Before the installation of the new sewer pipe (1963) in the streambed, the creek had been a series of cascades over rocks and ledges. The path beside it still descends in three or four steps over rock ledges with comparatively level stretches between. At the bend, starry campion was among the first midsummer flowers to bloom, the only stand along the Sligo. Fortunately, it has spread back up the slope; so it is presently secure. Opposite the path was a patch of agrimony. The upper rock step was matted with partridgeberry vine. At the base, by the first tall tree, grew a few stalks of broom rape, a ghostly plant which has no chlorophyll. Near it a few plants of thimbleweed and alumroot with bronze-green blooms held sway.

Below the ledge, a narrow strip of level ground was covered with hog-peanut vines, and over them, two or three tick-trefoils, mainly naked-stem and whorled. Hidden below was a single plant of butterfly pea, its orchid-like flowers sheltered from all but the most prying eyes. On the right, between the path and the creek, there is a triangle of ground. This spaces was filled with plants of arrowwood, deutsia, smooth hydrangea, maple-leaved viburnum and other shrubs.

Near the end of the level stretch, witch-hazel bushes draped with grapevine (almost meeting over the path) made a cave of greenery where catbirds and cardinals nested and horsebalm flourished. Out from the cave, white avens, white vervain, elephant’s foot, wild strawberry and Indian strawberry crowded the path’s edges. Here is a section of the slope near the Washington Sanitarium with no tall trees, but covered with brush and blackberry canes with a single dwarf blackberry vine at the edge. The canes remain, at least some of them, but the dwarf blackberry vine is gone as is the single tall swamp sunflower that marked the lower edge of this narrowest spot in the path. Here the path was barely “footprint wide” for several steps. On the very rim was a row of pale St. Johnswort.

Just beyond was a double rock step by a sewer manhole. Here was another, smaller bed of lady’s earrings and Spanish needles with their lacy fern-like leaves and tiny gold stars, and later with their barbed needles. From here to the bridge the path was lined with goldenrods (early and the elm-leaved), wavy -leaved and heart-leaved asters, and pokeweed with dark red berries, a chosen food for many birds. Among these, a few stalks of ironweed and Joe-Pye weed towered. Here too was another less desirable plant growing in profusion -the poison ivy-some of which is left. A strikingly beautiful double-file viburnum which grew on a widened spot between path and creek was dug out.

Many of these plants mentioned here have not been found anywhere else on the Sligo. Most of the others are rare plants in the park. This is an example of the uncertainty of supposed wildlife and wildflower sanctuaries.

Information about Dorothy Salisbury

From page 34 of A History of Sligo Park Hills by Clarke Stout, 1974.

Dorothy Cleaveland Salisbury has been an amateur botanist and ornithologist since childhood. For six years she has served as Chairman on Conservation of the Maryland State Society, Daughters of the American Revolution, and for two years Senior National Chairman on Conservation for the Children of the American Revolution. She is a graduate of St. Lawrence University (A.B.), Cornell University (M.A.), and the University of Illinois Library School (B.L.S.), and worked as a college librarian for over twenty years.

During the past 25 years, Mrs. Salisbury has carefully documented the plant life of the Sligo Creek Park area to compile this botanical listing. In publishing the results of her study, The Maryland-National Capital Park and Planning Commission wishes to express its sincere appreciation to Mrs. Salisbury.

FOSC member Joe Howard was one of a group who encouraged Dorothy Salisbury to print her plant list. He attended a celebration dinner in her honor when the list came out.

Salisbury lived in Sligo Park Hills, off Piney Branch Road. Friends of Sligo Creek member George Neighbors made a community history available which contains a paragraph describing a planting Salisbury directed in the park, apparently in 1974. Whatever unusual plants we find in the Park now could be the result of her replanting effort. It reads:

In October the MNCP&PC[sic], under the supervision of Dorothy Salisbury, set out about two hundred wild flower plants in Sligo Creek Park to replace those previously washed out by floods. A wide variety of plants included Canada violets, cardinal flowers, columbines, Dutchman’s breeches, wild geraniums, hepaticas (liverwort), joe-pye weeds, nodding trilliums, showy orchids, Oswego teas and Virginia anemones. Most of the plants were set out between Piney Branch Road and Carroll Avenue. Mrs. Salisbury plans to sow black-eyed Susan seeds in the early spring of 1975, re-establishing this Maryland State Flower in the park. Members of the Garden Club contributed $25 toward this project of beautification.