Bishop's goutweed (Aegopodium podagraria)

Common Names: goutweed, ground elder, bishop's weed, herb gerard, snow-on-the-mountain, ground ash

Description:

Bishop's goutweed (Aegopodium podagraria) is a fast-spreading perennial ground cover from Europe and western Asia that was brought to North America as a garden plant [1][3]. It escapes yards and gardens and forms dense mats that smother native wildflowers and slow the growth of tree seedlings [1][2]. MISIN tracks it because it is very hard to remove once it takes hold and easily creeps into nearby woods and natural areas [2].

Habit:

Bishop's goutweed is a low, leafy ground cover that grows 1 to 3 feet tall when it flowers [1][3]. Each leaf is divided into three groups of three leaflets; the leaflets are oval to heart-shaped with toothed (saw-edged) margins [1][3]. The most-planted form has green leaves edged in creamy white, while the wild form is solid green ? both spread the same way [1]. In early to mid-summer the plant sends up tall stalks topped with flat, lacy clusters of tiny white flowers, much like other carrot-family plants [1][2]. Crushed leaves give off a faint celery- or fennel-like scent [3].

Look for the low carpet of leaves from spring through fall; it is one of the first plants to green up in shaded gardens and woodland edges [2]. The white flower clusters are easiest to spot in June and July, and the patch visibly widens year after year [1][2].

At-a-glance cues:

1. Leaves divided into three groups of three toothed, oval-to-heart-shaped leaflets [1][3]
2. Common garden form has green leaves edged in creamy white; wild form is solid green [1]
3. Flat, lacy clusters of small white flowers on 2 to 3 foot stalks in June?July [1][2]
4. Long, white, branching underground stems (rhizomes) just below the surface [1][3]

Leaves:

1. Arrangement: mostly from the base on long leaf stalks, plus smaller stalked leaves up the stem [3]
2. Compound: divided into three main parts, each part again split into three leaflets (up to nine leaflets per leaf) [1][3]
3. Leaflet shape: oval with a broad or heart-shaped base, sometimes lobed or mitten-shaped [1][3]
4. Margin: toothed (saw-edged), coarsely to finely [3]
5. Color: solid green in the wild form; green edged with creamy white in the common ornamental form [1]
6. Size: leaflets a few inches long; whole leaves often palm-sized or larger [1]

Stems:

1. Habit: herbaceous perennial ? soft, non-woody stems that die back each winter and regrow from the roots [3]
2. Flowering stems: erect, smooth (hairless), grooved, hollow, and branched near the top [3]
3. Height: up to about 3 feet when in flower; leafy growth often 1 to 2 feet tall [1][3]
4. Scent: faint celery- or fennel-like smell when stems or leaves are crushed [3]
5. Underground: long, white, branching rhizomes (creeping underground stems) that resemble quackgrass roots [1][3]

Flowers:

1. Color: small, white (occasionally greenish-white) flowers, each with five petals [1][3]
2. Arrangement: many flowers packed into flat-topped, lacy compound umbels 2 to 5 inches wide, carried on tall stalks above the leaves [1][2]
3. Bloom time: early to mid-summer, mainly June and July [1][2]
4. Sex: flowers are perfect (each has both male and female parts), typical of the carrot family [3]

Fruit and seeds:

1. Fruit: a small, dry, two-parted "seed" typical of the carrot family, much like a tiny carrot seed [1][2]
2. Shape: small, elongate, slightly flattened and ribbed [1][2]
3. Color and ripening: green at first, turning brown as it ripens in late summer [1]
4. Dispersal: carried short distances by water, moving soil, and contaminated fill [2]
5. Note: plants can set seed, but seedlings are rarely seen ? the plant spreads mostly by its rhizomes [2][3]

Habitat:

Bishop's goutweed is native to Europe and western Asia and was introduced to North America as an ornamental ground cover [1][3]. It is now found across much of the United States and southern Canada [1].

It grows best in moist, well-drained soil in partial to full shade, but it tolerates a wide range of conditions, including sun [1][2]. Typical spots include shaded gardens, old home sites, forest edges, floodplain and disturbed woods, roadsides, and stream banks [1][2]. Its shade tolerance lets it move from yards directly into the forest understory, where it threatens moist woodlands and rare floodplain forests [2].

Reproduction:

Bishop's goutweed most often arrives as a garden plant and then refuses to stay put. It creeps outward on branching underground stems, so it can spread under a fence from a neighbor's yard or escape a flower bed into the lawn and nearby woods [1][2]. People also move it by accident ? in dumped yard waste and in fill soil that contains rhizome pieces [2]. Even a small fragment of rhizome can grow into a new plant, which is why digging and disposal must be thorough [1][2].

The plant spreads mostly by these creeping rhizomes rather than by seed; its efficient underground growth lets a patch expand into a dense, connected colony [4]. Flowers can produce seed in summer, but seedlings are rarely found in the wild [2][3]. For control, this means timing matters less for seed and more for the roots: dig when the soil is moist and remove every rhizome fragment before the patch widens further [1][2].

Impact and Damage:

For homeowners, the main problem is in the garden. Bishop's goutweed forms a thick mat that smothers flower beds, crowds out ornamental plants, and creeps into lawns, and it is very hard to get rid of once established [1][2]. It is not known to harm people or pets.

In natural areas, it forms dense, connected colonies that out-compete native wildflowers and other ground-layer plants, lowering plant diversity [1][4]. By shading the forest floor, thick goutweed cover reduces the number of tree and shrub seedlings that can take hold, which over time can change how a woodland renews itself [1][2]. Researchers note that the plant's efficient rhizome growth and ability to share resources across a colony help it dominate the ground layer [4]. Dense patches may also alter how leaf litter breaks down and how nutrients cycle in the soil [2]. It is a particular concern in moist and floodplain forests [2].

Similar species:

The white-edged garden form of bishop's goutweed is hard to mistake, but the solid-green form can be confused with other carrot-family plants and a few common species.

Wild chervil (Anthriscus sylvestris) is another spreading invasive with flat white flower clusters, but its leaves are fern-like and finely divided into many small segments, unlike goutweed's broader, three-by-three toothed leaflets [1].

Poison hemlock (Conium maculatum) also has white umbrella-shaped flower clusters, but it grows much taller, has purple-blotched stems and lacy, finely cut leaves, and is highly poisonous ? worth learning to tell apart for safety [1].

Elderberry (Sambucus species) shares a similar toothed-leaflet look ? the name "ground elder" comes from it ? but elderberry is a woody shrub, not a low ground cover [1].

Queen Anne's lace (Daucus carota) has the same lacy white flower clusters, but its leaves are ferny and finely divided and its stems are hairy, while goutweed's stems are smooth [1].

Monitoring and rapid response:

Signs to watch for:

1. A spreading low carpet of leaves ? green, or green edged in creamy white ? in shaded beds, lawn edges, and woodland borders, greening up early in spring [1][2]
2. Flat, lacy white flower clusters on 2 to 3 foot stalks in June and July [1][2]
3. A patch that visibly widens year after year and resists hand-pulling [1]

What you can do:

1. Dig out small patches rather than pulling ? the rhizomes snap, so use a spade or fork to lift the entire white root network, removing every fragment; this works best in spring when the soil is moist [1][2]
2. Cut or mow the flower stalks before they set seed to slow the spread, though this alone will not kill an established patch [1][2]
3. Smother small patches with thick cardboard or black landscape fabric for at least one full growing season; results vary, so check the edges for escapees [1]
4. Bag and trash every rhizome fragment ? never compost it or dump yard waste in the woods, since fragments easily resprout [1][2]
5. For natural area crews: map patches, tackle small outlying patches and floodplain-forest occurrences first, repeat digging or smothering over several years, and stop dumping of fill and yard waste that carries rhizome pieces [2]

When to call a professional:

1. Large, established patches that keep resprouting from the roots despite repeated digging [1][2]
2. Infestations in floodplain forests, stream banks, or other sensitive natural areas [2]
3. Any large-scale or right-of-way situation beyond what hand tools can manage
4. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Wisconsin Department of Natural Resources. Bishop's Goutweed (Aegopodium podagraria), Invasive Species Fact Sheet. dnr.wisconsin.gov
2. Maine Department of Agriculture, Conservation and Forestry, Natural Areas Program. Goutweed (Bishop's Weed) ? Aegopodium podagraria. maine.gov
3. University of Massachusetts Amherst Extension, Weed Herbarium. Aegopodium podagraria L. extension.umass.edu
4. D'hertefeldt T, Enestrom JM, Pettersson LB (2014). "Geographic and habitat origin influence biomass production and storage translocation in the clonal plant Aegopodium podagraria." PLOS ONE 9(1):e85407. doi.org/10.1371/journal.pone.0085407

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