Acalypha Plants - Mercury or Copperleaf - in Eastern North America and Elsewhere

There are a number of reasons that the plants of the Acalypha genus are easily overlooked.  They are small, they look very similar to a variety of other plants (especially those of the nettle family), and most lack showy flowers.

Acalypha are flowering plants, but the flowers are tiny, inconspicuous, and have no floral aroma.  They are thought to be mostly wind-pollinated, contrasting with many flowers that are pollinated by insects or even hummingbirds.  Wind-pollinated plants do not need to attract insect pollinators, so they tend to lack the intense floral scents or colorful blooms.  Think ragweed or oak catkins.

Unlike other wind-pollinated plants, these plants are not a major concern for allergy sufferers--they are tiny plants, growing low to the ground, and producing nowhere near the volume of pollen that large trees or larger plants like ragweed produce.

The seeds of the Acalypha are eaten by birds, including Mourning doves, sparrows, and even some larger game birds.  Mammals, including deer, sometimes eat the leaves as well.  The beetles Hornaltica bicolorata and Margaridisa atriventris feed on these species.

If you learn to identify these plants, and leave them in your garden, you help to provide food for wildlife, supporting biodiversity.  Rather than seeing them as weeds, you can see them as a contributor to natural beauty.

Acalypha are in the spurge family, Euphorbiaceae, which also contains the commercial Rubber tree, and the Castor oil plant.  Most plants in this family have a milky sap which is not only toxic to eat, but toxic to the touch, causing blisters or a rash, and being particularly dangerous if it gets in the eyes.  The plants are not quite as dangerous as poison ivy, but they still warrant caution with handling.

The acalypha plants are different, lacking this sap, which may explain why they are eaten by mammals like deer.  At least two species, Acalypha bipartita and Acalypha indica are used as vegetables in Africa.

Although there are hundreds of Acalypha species worldwide, most of the U.S. only has about 3 species that are common, and perhaps a handful more that are rare.

The three common species in the US are tricky to tell apart, but can be distinguished with a bit of focus, especially if you know what to look for.  The leaf shape, edge of each leaf, and petiole (leaf stem connecting the leaf to the main stem) length are different.  The flower bracts in particular, which are found just where each leaf attaches to the stem, look very different between the three species.

• Acalypha rhomboidea - Also called "Rhomboid mercury", this plant is the most widespread species in the US, stretching from the eastern border of the great plains all the way to the east coast.  Its leaves are more rhombus-shaped, have more pronounced teeth than the other species, and it tends to have glabrous (hairless) stems more than the other species.  It is common and often somewhat weedy.
• Acalypha virginica - Also called "Virginia mercury".  The leaves of this species are a little rounder than rhomboidea, and have only very subtle teeth.
• Acalypha graciliens - Also called "Slender mercury" or "Slender copperleaf".  The leaves of this species are slender, and have the shortest petioles (leaf stems, attaching each leaf to the stem) of the three species.

If you live in other parts of the country, you may not see these species, but there may be other ones native to your region.  Not all of these are annuals.  For example, Acalypha californica is found in the chaparral in San Diego, and grows more like a shrub. Acalypha ostryifolia is found in southern pinelands in the US, and extends into the tropics.  There is even a species, Acalypha portoricensis, endemic to Puerto Rico.

Although the three common Acalypha species in Eastern North America have stable populations, many Acalypha species are rare or even critically endangered, and many have already gone extinct.

In the eastern U.S, there is at least one rare and threatened species in this genus, Acalypha deamii, also called "Deam's mercury".  This plant tends to grow in flooded areas along streambanks, where soil has been deposited by flooding, and where little other vegetation is growing.  This plant is quite rare, and may have been extirpated (made locally extinct) from parts of its range, such as the only county in Pennsylvania where it was known to occur.

The inconspicuous nature of these plants may not help their extinction.  If you live in a region where there are threatened Acalypha species, you can help protect them by supporting the creation and preservation of habitat for them, and also by planting them if you have the right habitat for them in your yard or garden (ideally growing them from seed--never disturb wild populations of an endangered plant).

More people may be familiar with the Chenille plant than with other plants of the Acalypha genus.  This plant is a tropical species from this genus, which has become widely cultivated for its attractive red blooms, which are atypical for this genus.  Take a look at this plant's leaves and growth habit in the pictures below, and you'll see the resemblance to the native species.

Although this plant is not native to the US, it cannot survive in colder parts of the country, so it does not pose a risk of becoming invasive when it is grown as an annual.  I would not recommend planting it in tropical or subtropical regions.

Acalypha are not easily confused with other plants in the spurge family, which is not surprising because they are in many ways atypical examples of their family.  They tend to resemble plants of the nettle family more, however, not stinging nettles themselves, but rather, other small, inconspicuous plants in this family.  In fact, the scientific name for Acalypha is a reference to the greek word akalephes, meaning "nettle", which reflects the similarity. The similarly-looking and similarly-located flower bracts on these plants make them particularly easy to confuse.

The two plants that I find are easily confused with Acalypha are:

• Parietaria pensylvanica - Pennsylvania Pellitory - I find this plant also looks very similar to Acalypha.  It can be distinguished by its narrow leaves that taper off to a narrow but rounded point, and its leaves are completely without teeth.  It also tends to grow in a similar habitat, in disturbed areas, although it seems to have a little more of a preference for shade.  It has a lanky / leggy growth habit, often growing long stems which frequently fall over.  It often tends to prefer slightly drier areas or poorer soils than Acalypha.
• Pilea sp. - Clearweed - Clearweed looks superficially very similar to Acalypha, but it is easily distinguished by its clear stem, and thicker, almost succulent leaves, and its opposite arrangement of leaves on the stem.  Its leaves also have more marked serration, and the overall shape and growth habit are more nettle-like.  I find that it tends to prefer wetter areas more than Acalypha.

If you are creating a native plant garden, engaging in ecological restoration, or just want to encourage more native weedy plants around your garden, both of these species, and all three Acalypha described above, are all native, so if you have trouble distinguishing them, don't sweat--you can leave all of them.

One more genus of plants that can be confused with Acalypha, worth mentioning, are the amaranths, Amaranthus sp, which includes both food species called "amaranth", as well as weedy plants like pigweed.  The leaves and growth habit look the same, but amaranths are easily distinguished by their upright flowers and fruiting bodies, forming in large spikes at the top of the plant.  Once you have observed the plants flower, you can then learn to recognize them earlier in their life-cycles.  There are many different amaranth species, and many look similar to Acalypha, but the leaves often have pronounced visual textures, like more pronounced ridges in the leaves, and can have quite different growth habits, with many species growing much larger, and others growing flatter against the ground.

I consulted these references when learning to ID these plants, and writing this page.  You can find more information here:

• References on Illinois Wildflowers - This excellent website has separate pages on  Virginia Mercury, Acalypha virginica, Rhomboid Mercury, Acalypha rhomboidea, and the rare Deam's Mercury, Acalypha deamii.
• USDA Plants Profiles - Complete with national range maps...separate profiles for each species, all accessible from the master profile for the Acalypha genus.  Hit the "Subordinate Taxa" page to see specific species; 23 species are listed.
• Acalypha - Wikipedia - Wikipedia also has articles on many individual species.