Common Dittany


aka American dittany, Maryland dittany,
frost mint, stone mint, sweet horsemint,
fairy skirts
Cunila origanoides

Like the blue curls in my last post, common dittany is in the mint family. It has the characteristic square stems and paired leaves, not to mention a marked fragrance like oregano or thyme, but the flowers are a little atypical. They lack “lips”, and have two stamens rather than four. The flowers are found in terminal clusters and in axillary clusters on the upper portions of the stems.

This species is a perennial subshrub that grows to about one foot tall, with branches often sprawling or flopped over. I came across a single specimen in the Serpentine Barrens Conservation Park, growing in textbook common dittany habitat: dry soil, shade from trees overhead, and little to no competition from other plants on the forest floor.


There are about a dozen species of Cunila. All except this one are native to South America and southern North America (as far north as Mexico). C. origanoides‘ range includes an area somewhat to the east and west of the Appalachians, from southern New York through South Carolina, and the Ozarks, with a few scattered occurrences elsewhere.

The plant probably got its common moniker “dittany” from a similar looking old-world herb, dittany of Crete (Origanum dictamnus). The specific epithet origanoides means “like oregano”. Native Americans made a tea of common dittany for a variety of medicinal purposes, but please note that it does not have FDA “generally recognized as safe” status (according to The Herb Society of America).


Blue Curls


aka forked bluecurls,
bastard pennyroyal
Trichostema dichotomum

This mint family member will get your attention. The flower has five petals, two up and three down. But the speckled middle lower petal extends far out from the others, and the four stamens protrude and curl dramatically. The plant itself shows the usual mint family characteristics of paired leaves on a square stem.

Trichostema is from the Greek and means “hair-like stamens”, while dichotomum refers to the way the plant grows (forking in pairs, typical of the Lamiaceae).

Blue curls is a short (to 18 inches) annual plant of dry, sunny places, such as the power line clear-cut in Serpentine Barrens Conservation Park where I found dozens of specimens. They were growing in a swath of orangegrass plants, another species I only just learned about.


According to various sources, blue curls blooms from August through October. I don’t know if that’s the case in the Maryland Piedmont, but I’ll keep an eye open for them when I go back to that area.

This is one of twelve species of Trichostema native to North America; only two others can be found in this area, and both are on the Maryland DNR’s RTE (rare/threatened/endangered) list. T. dichotomum ranges from Quebec and Ontario south to Florida, Texas to the southwest, and Iowa to the northwest. It’s rare in Indiana and threatened in Michigan. In Maryland look for it in the Piedmont as well as parts of the coastal plain, the Blue Ridge, and the ridge and valley provinces.


Serpentine Barrens Conservation Park


common buckeye (Junonia coenia), common in open areas throughout Maryland

Serpentine barrens are geological areas containing soils derived from serpentinite rock. These soils are characterized by high concentrations of certain elements (such as chromium, cobalt, and nickel), low concentrations of others (such as nitrogen and phosphorus), and an imbalance of calcium (low concentration) to magnesium (high concentration). The chemical makeup of the soils usually results in low water availability. Altogether, the conditions limit which species of plants can grow there.

Serpentine soils can be found worldwide, but serpentine barrens are found only in certain parts of the Appalachian Mountains and the Pacific Coast Ranges. In the east, the largest of these ecosystems are found in Pennsylvania, and in Maryland, at Soldier’s Delight Natural Environment Area (1,900 acres in Baltimore County) and the Serpentine Barrens Conservation Park (256 acres in Montgomery County).

The latter is the place mentioned in my last post. I can’t even find a formal map of the area, but it’s apparently divided into three units. The larger serpentine barrens area seems to occur north and south of Travilah Road, from about Piney Meetinghouse Road in the east to about Sandy Branch in the west. The two North Units are on either side of the Pepco right-of-way that extends west from Piney Meetinghouse Road, south of the stone quarry.

I couldn’t find an exact count of RTE (rare, threatened, endangered) plant species in this park, nor could I find a list, but it’s well known as an RTE hot spot. I didn’t find any RTEs last week, but I did find five species that I haven’t seen elsewhere in the Piedmont.

One of the neat things about this particular serpentine barrens is that despite what you’d expect from the name, most of it is forested. Years ago when I lived in the area I would drive by and wonder why all the trees seemed so stunted. They’re short enough that you might think the area an early-stage successional woodland, but actually it’s climax-stage. On careful observation you can see that the trees are mostly much stouter than trees of the same height in neighboring areas.

More on the “new to me” species in coming days.

Further Reading (in addition to the links above):
Serpentine Barrens (DC Great Outdoors)
North America Serpentine Flora (Smithsonian Institution National Museum of Natural History)
Serpentine Soil (Wikipedia)
Natural Communities – Serpentine Grasslands (Maryland DNR)
a detailed geological map (note: this map can be fussy and not load properly, but if it does load will show the extent of the ultramafic rock formation underlying the Serpentine Barrens Conservation Park, the major rock being serpentinite)