Three Seeded Mercury Weed

Acalypha rhomboidea Common Three-seed Mercury is an annual native wildflower in the spurge family and occurs in all areas of NC. It is native in central and eastern USA and into Canada. This OMAFRA Crops Finally, I know who this fellow is, sort of. Acalypha…somebody, probably rhomboidea, commonly known as three-seeded mercury. He and his brothers are everywhere in my garden. This annual member of the Euphorbiaceae family starts as a thin, erect reddish stem with narrow leaves, about an inch to an inch and a half long, arranged opposite…

Acalypha rhomboidea

Common Three-seed Mercury is an annual native wildflower in the spurge family and occurs in all areas of NC. It is native in central and eastern USA and into Canada. This plant has tiny flowers with large lobed bracts in summer to fall and freely self-seeds. It prefers sun to light shade and will grow in moist to dry clay, loam or rocky soils.

It can be weedy and is not recommended for home gardens. Birds will eat the seeds.

VIDEO Created by Elisabeth Meyer for “Houseplants, Succulents, and Cacti”, a plant identification course offered in partnership with Longwood Gardens.

Form SB_Johnny CC BY-SA 3.0 Leaves Kenraiz CC BY-SA 4.0 Flowers Kenraiz CC BY-SA 4.0 Stem Erin Faulkner CC BY-NC 4.0 Leaves in dappled sunlight Melissa McMasters CC BY 2.0 Leaf close up Melissa McMasters CC BY 2.0

  • Attributes: Genus: Acalypha Species: rhomboidea Family: Euphorbiaceae Life Cycle: Annual Recommended Propagation Strategy: Seed Country Or Region Of Origin: Eastern Canada, central and eastern U.S.A. Distribution: AL , AR , CT , DC , DE , FL , GA , IA , IL , IN , KS , KY , LA , MA , MD , ME , MI , MN , MO , MS , NC , ND , NE , NH , NJ , NY , OH , OK , PA , RI , SC , TN , TX , VA , VT , WI , WV Canada: NB Wildlife Value: Seeds are eaten by birds
  • Whole Plant Traits: Plant Type: Annual Native Plant Weed Habit/Form: Erect Growth Rate: Rapid Maintenance: High
  • Cultural Conditions: Light: Full sun (6 or more hours of direct sunlight a day) Partial Shade (Direct sunlight only part of the day, 2-6 hours) Soil Texture: Clay Loam (Silt) Shallow Rocky Soil Drainage: Good Drainage Moist Occasionally Dry NC Region: Coastal Mountains Piedmont
  • Fruit: Display/Harvest Time: Fall Fruit Type: Capsule Fruit Description: 3 lobes spherical capsule containing three seeds.
  • Flowers: Flower Inflorescence: Insignificant Flower Bloom Time: Fall Summer Flower Size: < 1 inch Flower Description: Mid-summer through fall. A 5-9 lobed bract forms around the inflorecese in the axils of the leaves. There are both male and female flowers within the bract without petals or sepals.
  • Leaves: Leaf Color: Green Deciduous Leaf Fall Color: Brown/Copper Purple/Lavender Leaf Type: Simple Leaf Arrangement: Alternate Leaf Shape: Lanceolate Ovate Leaf Margin: Serrate Hairs Present: Yes Leaf Length: 1-3 inches Leaf Width: < 1 inch Leaf Description: Lanceolate to ovate simple alternate leaves with serrated margins, conspicuous pinnate venation and hairy petioles. 3.5" long and 1" wide. The leaves tend to congregate together near the top of the stems. In the fall leaves can be copper-purple hence the common name.
  • Stem: Stem Color: Green Stem Is Aromatic: No Stem Surface: Hairy (pubescent) Stem Description: The central stem is usually unbranched with lines of fine white hairs or just hairy.
  • Landscape: Landscape Location: Naturalized Area Problems: Weedy
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Acalypha rhomboidea

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Ministry of Agriculture, Food and Rural Affairs

General Description: Annual, reproducing only by seed.

Photos and Pictures


Three-seeded mercury.
A. Plant. B. Portion of fruiting stem showing 1 three-seeded fruit developing from 1 of 4 flowers in a leaf axil.

Stems & Roots: Stems erect, 7.5-100cm (3-40in.) high, simple or branched, slightly hairy; leaves green to bronze-green, 1-9cm (2/5-3½in.) long, lance- to rhombic-ovate on petioles that are 1/3 the length to almost as long as the leaf blade; margins with irregular, rounded teeth.

Habitat: Three-seeded mercury occurs in dry or moist soil in open woods, fields, waste places, ditches and roadsides throughout south-central Ontario.

Similar Species: It resembles young plants of Redroot pigweed but is distinguished by its flowers borne in axillary clusters with bracts having 5-9 lobes and its leaves occasionally a bronze-green colour.

Related Links

. on general Weed topics
. on weed identification, order OMAFRA Publication 505: Ontario Weeds
. on weed control, order OMAFRA Publication 75: Guide To Weed Control

Know thine enemy: Three-seeded mercury

Finally, I know who this fellow is, sort of. Acalypha…somebody, probably rhomboidea, commonly known as three-seeded mercury. He and his brothers are everywhere in my garden.

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This annual member of the Euphorbiaceae family starts as a thin, erect reddish stem with narrow leaves, about an inch to an inch and a half long, arranged opposite along the stem. As it grows, it branches, and leaves are arranged alternately. Here is where my ignorance of botany is exposed:There appear to be small yellow flowers at the leaf axils, but those yellowish bits I see could be bracts, or technically it might be an inflorescence …anyway, if you care to read details about the plant’s structure, you can read the description from the University of Guelph extension, or the Wikipedia site. For me, right now, I know I’m fairly close to identifying the plant.

This summer annual weed is not a nuisance, except that there’s a lot of it in my garden. It doesn’t reseed aggressively like hairy bittercress and it’s not difficult to eradicate. Despite the taproot, the plants are easy to pull. They are also said to be browsed by deer (not if there are phlox and hosta to eat, they’re not).

According to the Southern Living Garden Problem Solver, which may or may not have misclassified this as Acalypha virginica (my plant definitely doesn’t look like the one shown by Illinois Wildflowers.info), many insects love to feed on the leaves. Thus, my sample, with its raggedy, chewn leaves should be pretty typical.

The seeds are supposed to be choice food for mourning doves, whom I would gladly welcome to my garden because I love their call. The buffet is open!