Rubus hispidus – Swamp Dewberry
25 May 2019

After we re-discovered the location of the Liparis liliifolia on the North Tract, Dave and I did a little foraying in the powerline area. We found some patches of Rubus hispidus (Swamp Dewberry) in bloom. It is also sometimes called Bristly Dewberry.

It differs from the other two species of Dewberry (R. flagellaris and R. trvialis) found on the refuge by the lack of prickles or thorns.  R. hispidus usually tends to like wetter areas than the other two species.

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Liparis liliifolia – Purple Twayblade
25 May 2019

This gallery contains 6 photos.

Today, Dave Anderson and I re-discovered the location of a patch of Liparis liliifolia in bloom that Dave initially spotted last year on the North Tract after the blooming season. This is a new record for this species on the … Continue reading

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Which species of Oxalis is this?
18 May 2019

This gallery contains 10 photos.

Which species of Oxalis is this? I suspect it could be Oxalic colorea? Maybe. If not what other species could this be? We have measured the petals to be at least 7 mm, but never more than 10 mm. It … Continue reading

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VIola striata – Striped White Violet

Viola striata is native to Eastern North America and is mostly (not always) found away from the Coastal Plain. On the Refuge, it is found in the floodplain/bottomland woods. It is a caulescent violet meaning that the flowers are found on nodes (or leaf axils) along the above-ground stem and not directly from the crown of the  plant.

The flowers are white with characteristic blue stripes.

This species also has stipules or leaf-like structures on lthe axils of the leaves. It is narrow, about 1 inch long, and and has a teeth-like fringe.

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Viola sororia – Common Blue Violet


Viola sororia also known as Common Blue Violet is an acaulescent violet found in Eastern North America. It is commonly found on the Refuge in hydric habitats like bottomland woods and roadside seepages. It will invade lawns and gardens., and is sometimes considered to be weedy.




There are several different flower color variations of this species. The one pictured here with the alternating blue and white coloration is called the “confederate” form. There are light blue, dark blue, and white forms as well.

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Viola primulifolia – Primrose-leaved Violet


Viola primulifolia or Primrose-leaved Violet.

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Viola pedata

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Viola lanceolata

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Viola eriocarpa

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Viola cucullata – Marsh Violet

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Viola affinis – Sand Violet

This gallery contains 5 photos.

Viola affinis or Sand Violet is an acaulescent violet found in the eastern part of North America from Quebec and Ontario in the south and Florida to Texas in the south. (Acaulescent means the flower rises from a non-leafy stem.) … Continue reading

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Spotlight on Christine McElroy

As the lead of the refuge plant inventory project, I would like to formally acknowledge the important contribution that Christine McElroy has made and is making with restoring voucher specimens in the Patuxent Research Refuge Herbarium. The positive impact of her work cannot be overstated.

Christine has faithfully come to the North Tract Visitors Contact Station almost every Wednesday afternoon since 2017 to repair the specimens and the specimen sheets. Some of the specimens have become loose and detached from their specimen sheets. She has repaired hundreds of these specimens by re-attaching them more firmly to the specimen sheets. This will ensure that the specimens will remain intact for many years to come.

She has also replaced several dozens of older specimen sheet labels which were starting to deteriorate because they are made of acidic non-archival paper. Replacing the labels is done by carefully taking off the old labels from the voucher sheets, photocopying the label’s images to acid-free archival paper, and attaching the new labels to the sheets. Since the new labels are photocopies of the originals, no pertinent collection information is lost. The old labels are filed separately so they are not lost. Replacing the older non-archival paper labels with newer acid-free archival paper labels will increase the durability of the labels. By repairing the specimens and replacing the labels, Christine is increasing the longevity of the specimens and is making the herbarium a more valuable resource for future researchers.

Christine deserves the recognition for her fine work, attention to detail, and devotion to making a good herbarium even better.

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2018 Plant Inventory Progress Report – A Banner Year

Lightbox used for imaging the specimens.

2018 was a banner year for the Patuxent Research Refuge (PRR) Plant Inventory Project (PIP) Team. The biggest event was the digital-imaging of about 4600 Refuge herbarium voucher sheets by the team. The PIP team appreciates Professor Maile Neel, Director of the Norton-Brown Herbarium, University of Maryland for her guidance and assistance in providing the equipment and space to image the voucher sheets and Dr. John Hall of the Mid-Atlantic Megalopolis Project ( for his consultation with this part of the project. The PIP team also recognizes the Herbaria Consortium for providing the Internet portal, technical support, and computer resources to allow the images and accompanying data to be placed on the Internet.

Marnie Whitlock and Elaine Nakash headed up this effort by spending several weekends and countless hours at the University of Maryland in College Park imaging the voucher specimens. They used professional equipment (MK Digital Direct Photo-eBox PLUS) to digitally image the specimens and convert them into a format that made them ingestible to the Consortium database. After each session, Bill Harms uploaded the images to the Consortium database and matched them to the accompanying collection data already on—line in the PRR Herbarium’s portal. The images and the data are accessible online for researchers to view and study.

Marnie holding a specimen for imaging.

We used a barcode on each voucher sheet that corresponds with the specimens’ accession numbers to keep track of the sheets when we transported the between the Refuge and the University of Maryland.

Professor Maile Neel and Marnie Whitlock

Dr. John Hall, Marnie Whitlock, Bill Harms, Elaine Nakash

The project to image voucher specimens and make them available to the public on the internet is a joint effort of many educational institutions and governmental organizations throughout the USA and the world, and is funded in large part by the National Science Foundation. The Refuge Herbarium participates in this effort as a member of the North American Network of Small Herbaria (NANSH). The Refuge should be proud to be associated with this project.

Since 2017, PIP team member Christine McElroy, has devoted her Wednesday afternoons to mounting specimens and restoring  a countless number of voucher sheets that needed repair. Through her efforts, the longevity of the specimens will be extended and the herbarium will be an even more valuable resource.

PIP team members collected an additional 200-plus specimens for the herbarium and added about 10 new species to the refuge list. Thank you to Dave Anderson and Matt Beziat for their assistance in this portion of the project.

We are also excited to welcome a Lichen Survey Project led by Helga Matausch.

The PIP Team participated in Refuge events at the Wildlife National Wildlife Center.

Boxes of voucher sheets ready for imaging.

Elaine and Marnie busy at work.

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17 February 2019 – Palmettos in Myrtle Beach

This gallery contains 3 photos.

Today, my wife Becky and I paid a short visit to Myrtle Beach, South Carolina. Visitors to Myrtle Beach can’t help but notice the Palmettos planted around the city and other cities in the area. Here are some photos of … Continue reading

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16 February 2019 – My first encounter with Spanish Moss (Tillandsia usneoides)

Today I had my first encounter with Spanish Moss (Tillandsia usneoides). We saw it growing on trees throughout Florence, South Carolina. Spanish moss frequently grows on trees in tropical and subtropical regions. Around Florence at least, they seem to be partial to the Southern Live Oak (Quercus virginiana). It is native to much of the Southern United States from Southeastern Virginia south to Florida and west to Arkansas and Texas. It also is native to Bermuda, Mexico, the Bahamas, South America, Central America, and the West Indies. It has reportedly become naturalized to Queensland, Australia and French Polynesia. It is not a true moss but rather it is an epiphytic flowering plant. Here are a few pictures we took of it. Some trees were almost completely covered with it.

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8 October 2018 – Washington County Cactus Foray

Today, Joe Metzger and I went on a foray to locate two populations of cactus in Washington County, Maryland.

Voucher specimen of Opuntia cespitosa collected by Clyde Reed at Kemps Mill in June 1952



The first one was a reported population of Opuntia cespitosa in Kemps Mills where Clyde Reed collected a voucher specimen in June 1952. We drove the entire length of Kemps Mill Road and did not see any cactus. We also located Kemp Mill’s itself, but did not see a suitable habitat in the vicinity. Unfortunately, Reed’s voucher label does not reveal an exact location.  The only real clue was a reference to “limestone ledges.”




Snug Harbor Lane. Cliff is on the right

Along Kemps Mill Road, we spotted a limestone cliff face which could have been the “limestone ledges” referred to by Reed on the voucher label. We make a cursory look at the cliff face and did not notice any spot that might have supported cactus. We could not see the upper parts of the cliff from the road. These areas are more sunny and might be a good place to look another time. The cliff face however sported a lot of interesting flora.  It was located near a KOA campground and faced mostly to the west. We will attempt to locate the population again another time. Hopefully, we just missed finding it and the population is still around. If you have a good idea where it is located let us know.

Juvenile Cliff Brake Fern plants with some small Ebony Spleenwort.


On the cliff face, we spotted some presumed fern gametophytes and several fall blooming species in the family. It looks like an interesting site to return to in other seasons.


Lock house at Dam 5 with retaining wall at base.



We continued our foray to the Dam 5 area of the C & O Canal where there was a reported population of Opuntia humifusa s.s.This time we were successful. The cactus was located at the base of a retaining wall below a lock house. Based on the small size and location of the cactus population, we concluded that it was probably planted and not naturally occurring.

Opuntia humifusa below retaining wall at Dam 5






If you know of any other cactus populations in Washington County we would be interested in learning about them. There are some cactus populations in Allegany County which we will be trying to re-locate, probably next spring. If you think you might like to participate, there is plenty of time to plan a foray.



Here are some photos of other plants we saw while looking for the cactus.

Symphyotrichum lanceolatum (Willd.) G.L. Nesom –
Panicled Aster

Symphyotrichum lateriflorum (L.) Á. Löve & D. Löve. –
Calico Aster

Solidago flexicaulis L. –
Zigzag Goldenrod

Solidago caesia L. –
Blue Stemmed Goldenrod

Symphyotrichum shortii (Lindl.) G.L. Nesom –
Short’s Aster

Ageratina cf altissima (L.) R.M. King & H. Rob. –
White Snakeroot

Symphyotrichum sp. –
Unknown Aster

Laportea canadensis (L.) Weddell –
Canadian Wood Nettle

Ipomoea lacunosa L. –

Sicyos angulatus L. –
One-seeded Bur Cucumber or Star-Cucumber

Woodsia obtusa (Spreng.) Torr. –
Bluntlobe Cliff Fern

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25 August 2018 – Finding Cactus at Weinberg Park

Rangers Matt Grey and Chris Winton

Had an awesome time with Rangers Matt Grey and Chris Winton of Anne Arundel County Park and Recreation this afternoon scouting out the cactus at Weinberg Park in Pasadena. The site was near an old homestead. We could see two stone columns which could have come from a gate entrance. I understand that there is other evidence of a homestead at the site.

The site showed definite signs of anthropogenic disturbance likely from the folks who previously lived here. The soil was well-drained sand on a bluff above the bay. There is a high probability the cactus was planted and they were growing in an area about 15 feet by 15 feet. There were outlying scattered plants in the area as well.

Yucca flaccida growing nearbby

We also spotted some Yucca flaccida (weak-leaf yucca) which was planted nearby.  This, when combined with the planting of cactus, suggests that someone wanted to create a desert-like appearance at this site.

The morphology of the plants conform with a determination of Opuntia humifusa s.s. We did not find spines on any of the plants and there were mostly 4 to 5 (6) areoles per diagonal row on the cladodes. The seeds were 4.0 to 4.8 mm long.

We plan to re-visit the site in the spring to note the flower coloration.

Click here for collection data details.

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22 August 2018 – Maryland Cactus Sites

This is a working draft list of locations where cactus has been found in Maryland, excluding the Eastern Shore. (Eastern Shore sites may be added later.) If you know of a location not listed here, let me know at botanybill (at) and I will put it on the list. Also if you would like to claim a site to watch, let me know.


Alleghany County

  • Flintstone – (at least three stations) – Opuntia humifusa s.s.

Anne Arundel County

  • Global Command Antenna Field, Davidsonville
  • Hancock’s Resolution – Field north of house
  • Hancock’s Resolution – Planted in garden – Opuntia cespitosa
  • Jug Bay, Parking Lot Meadow
  • Jug Bay, Sand Barrens, Parris Glendenning Area (Wayson’s Corner?) (More info)
  • Jug Bay, South Farm
  • Milt’s Sand Pit, Sands Road –  large population – old field (More info)
  • Patuxent Research Refuge, Lake Allen – large population – Opuntia cespitosa – Bill Harms (More info)
  • Patuxent Research Refuge, East of Tipton Field – likely planted many years ago – Opuntia cespitosa – Bill Harms
  • Sandy Point State Park – Extirpated?
  • Weinberg Park – Opuntia humifusa – probably planted.
  • Wooton’s Landing – assumed to be planted in two stations.

Baltimore County

  • Factory Road – planted possibly from nearby wild stock – Opuntia cespitosa. (More info)

Calvert County

  • Broome Island
  • Flag Ponds

Carroll County

Charles County

  • Chapman State Park

Frederick County

  • East of Emmitsburg

Howard County

  • Main Street, Elkridge – Planted next to a parking lot – Opuntia humifusa s.s. (more info)

Montgomery County

  • Bear Island
  • southern end of the Billy Goat A Trail in C&O Canal NHP
  • Plummer’s Island – Extirpated
  • River Road, SSW of Poolesville

Prince George’s County

  • Billingsley House
  • MacGruder’s Landing
  • Nottingham Road – apparently planted – tentatively Opuntia mesacantha ssp. mesacantha
  • Priest Bridge
  • Queen Anne Canoe Launch – open meadow – apparently Opuntia humifusa s.s.
  • Rte 301 – small number of plants – planted

St. Marys

  • Commander’s residence USN Solomon’s Recreation Area in Lawn
  • Patuxent Naval Air Station, East side of Security Road at NE corner air station.
  • Piney Point

Washington County

  • Kemps Mill
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13 August 2018 – Queen Anne Canoe Launch

Had an awesome time today with Michael Ellis, park ranger and invasive plant specialist for the Maryland-National Capital Park and Planning Commission, Parks and Recreation. We visited two sites where prickly pear was growing.


FIRST SITE – The first site was an open meadow near the Queen Anne Canoe Launch Patuxent River Park. The meadow was a restoration project and had an old field look about it.  Based on the fact that the cladodes had no spines and mostly four or five areoles per diagonal row, these plants appear to be Opuntia humifusa s.s. We will be returning in the spring to look for flowers in bloom.

Cactus pad next to driveway.SECOND SITE – The second site was an old driveway off of US Route 301 in Bowie. The woods were overgrowing the driveway which was apparently no longer in use. We saw a few plants on the left side of the driveway, which we assumed to be planted by past owners.


Many thanks to Michael for taking time out of his job to show me around.

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11 August 2018 – Cactus in Elkridge

On the way home from Glen Arm, Maryland this morning, I stopped off at a location here in Elkridge where someone planted some prickly pear cactus evidently many years ago next to a parking lot.  The plants key out to Opuntia humifusa sensu stricto.

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