Water Willow

There’s something refreshing about seeing all these green, grassy-looking plants growing right in the Potomac River every summer. They aren’t grasses, though; they’re water willow (Justicia americana; Acanthaceae), an emergent aquatic whose rhizomes form vast stands of plants in the shallow waters of ponds and streams.

The plants will grow to as much as three feet tall, sending up long stems with tight clusters of flowers on the ends. Only a few stems at a time will bear flowers, but the blooming period of a colony can last two months or more.


Water willow is native to eastern North America, ranging from Texas and the eastern Great Plains northeastward to New York, Ontario, and Quebec. It’s endangered in Iowa and threatened in Michigan.



Of the roughly dozen and a half species of Justicia found in North America, this one is by far the most northern species. One other occurs in the southern part of the Mid-Atlantic, and one in the Mid-West; the rest seem to be found only in Florida, Texas, or the Southwest.

Last spring I found the closely related Justicia californica in Anza-Borrego Desert State Park; it grows as a shrub or tree in the Sonoran and Mojave Deserts.

Hard to believe they’re in the same genus.


It tickles me that a bedrock terrace can maintain a pond, providing habitat for so many wetland plants. Only a few dozen feet away from that pond grow plants like big bluestem grass, that prefer much drier habitats.

And in between, there are low-growing swaths of fogfruit.

I’m not sure if technically fogfruit is a mudflat ephemeral, but the plants don’t seem to appear until river level drops, and then they pop up from the muddy shores, the rhizomes forming large mats of vegetation that stand about 12 to 18 inches tall.

Phyla lanceolata (formerly Lippia lanceolata) is in the Verbenaceae, a family of about 1,000 species in about 30 genera. Plants in this family can be found worldwide, but most of the species are tropical; P. lanceolata is one of the more northerly occurring ones. There are about a dozen species of Phyla, maybe half of which are native to North America. This one is found in much of the US, excepting New England, the northern Great Plains, and the Pacific Northwest. Populations seem to be concentrated in the Mid-West and along the Mississippi River corridor. It’s endangered in New Jersey and rare in Pennsylvania, and the only species of Phyla found in Maryland.

The inflorescence of fogfruit is fairly typical of plants in the Verbenaceae, the individual flowers clustered together in a tight spike. (It looks to me a lot like lantana, a common garden plant.) The individual flowers have five petals, fused together into a tube with irregularly spreading lobes. Many but not all of the flower clusters I’ve seen have this wonderful arrangement: yellow-throated flowers alternating with mauve-throated flowers.

About that common name… to some it’s “fogfruit”, to others it’s “frogfruit”. Wondering if the latter was a mispronunciation of the former, I was all set to do some real book research, but looked first on the internet, where I found, unsurprisingly, that it’s already been done:

In the end though, frogfruit with its alliterative cadence may simply be easier to say than fogfruit…

Either way, it’s a charming little thing.

Common Arrowhead

The bedrock terrace I’ve been writing about supports a surprising number of wetland plants. This one, Sagittaria latifolia, is not only a wetland obligate, it’s an emergent: an aquatic plant that roots in shallow water and produces stems, leaves, and flowers above water level.

Typical of monocots, S. latifolia has floral parts in multiples of three, with three sepals and three petals. The flowers are typically unisexual, the male flowers having numerous yellow-anthered stamens, the females having numerous green pistils. In bisexual flowers, the stamens ring the pistils, as shown here. The flowers are usually borne on racemes, sometimes on panicles, with flowers in whorls.

Although S. latifolia is found in every state in the union except Nevada and Alaska, and in much of southern Canada, it’s most common in New England, the Mid-Atlantic, and the Upper Midwest. (It’s also in Hawaii, but considered alien there.) It’s endangered in Illinois, but considered weedy by the Southern Weed Science Society.

S. latifolia is in the Alismataceae, or water plantain family, which comprises anywhere from 80 to 120 species in about 15 genera, depending on which authority you consult. The Alismataceae is cosmopolitan, but most species are native to North America.

Common names include common arrowhead, wapato, wappata, and katniss. Some names refer to the plant’s appearance or habit: arrowleaf, bull-tongue, water-archer, water-lily, waxflower. Other names refer to edibility: Chinese-onion, duck-potato, muskrat-potato, swan-potato, swanroot, and tule potato.

Bewitched by Buttonbush

As soon as I finished shooting swamp candles Tuesday morning, I turned my attention to a nearby buttonbush. The sunlight was no longer quite so golden, but it was still making great shadow play among the plants.

Cephalanthus occidentalis (Rubiaceae), also called buttonwillow, honeyball, and pond dogwood, ranges from Nova Scotia and Ontario south to Florida and Texas, and is also found in parts of Arizona and California. There are records of it in every Maryland county except Washington.

The multiple stems of this shrub can grow to about twelve feet tall, and the plant can be 6 feet across or more. Foliage is dense and a pleasing shade of green, and how can you not love that inflorescence?

The flower heads measure about one inch across and bear dozens (hundreds?) of flowers, each of which consists of four fused petals, four stamens, and one very long style.

The flowers attract butterflies and bees, and later in the season the seeds attract birds.

Buttonbush is a wetland obligate, meaning that in natural conditions it will be found in wetlands. But there are quite a few of them on the bedrock terrace, which is a dry place except for seasonal flooding and rains. There isn’t much soil there, and no groundwater.


Knowing this, I had assumed it wouldn’t make a good garden plant, but I asked the question on a native plant discussion site and got a lot of encouraging replies. It seems that once established, buttonbush does quite well in drier soils. Hooray! Now I just have to find a place for one in my garden.

Golden Glow

this little pond is about 20 feet above the river; currently at least six species of plants are blooming around (and in) it.


Feeling down after a not-too successful photo shoot, Tuesday morning I headed back to one of my favorite spots, a bedrock terrace that has a wide array of summer-flowering plant species.


It was early enough that the rocks were casting deep shadows, and as I scrambled up and over them, the rising sun spilled gold onto this small stand of flowers. I visit that terrace often in the summer, but had no idea swamp candles were there!

There’s just no substitute for good light.


Lysimachia terrestris (Primulaceae) is one of about 15 species of Lysimachia in Maryland. Maybe half of those can be found in the Piedmont, and four of those are alien.

Lysimachia ciliata; shockingly I don’t have a newer (better) picture than this


More often I see fringed loosestrife (L. ciliata), a dainty thing often overlooked, since the flowers are nodding. It likes drier soils and maybe more shade than swamp candles.

Lysimachia quadrifolia




Another common one is whorled yellow loosestrife (L. quadrifolia). I saw lots these in June on Sideling Hill (the Ridge and Valley physiographic province), but there are records for it almost everywhere in the state. All of them were growing in deep shade.



For a native loosestrife, though, this species is exceptionally showy.

Swamp candles can be found primarily in New England, the mid-Atlantic, and the upper Midwest; they can also be found in scattered populations in parts of the South. They’re endangered in Kentucky and Tennessee.


As the common name suggests, they like having their feet wet. It’s a little unusual to find them in a place like this bedrock terrace; generally they’re along the banks of the Potomac, not as in-the-water as water willow, but close by, in areas that are probably under water early in the season, before river level drops. Nearby you might see monkeyflower, American germander, and halberd-leaved rosemallow; the first two are blooming now; the latter is just about to.