Heartleaved foamflower (Tiarella cordifolia)

Also known as: Allegheny foamflower, coolwart, false miterwort, false mitrewort, foam flower, foamflower, heartleaf foamflower, heart-leaf foamflower, heart-leaf foam-flower, heart-leaved foamflower, heart-leaved foam-flower
Synonyms: Tiarella wherryi
KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderRosales
FamilySaxifragaceae
GenusTiarella (1)
SizeHeight: 10 - 36 cm (2) (3)

The heartleaved foamflower has yet to be classified by the IUCN.

The heartleaved foamflower (Tiarella cordifolia) is a delicate woodland plant with large, maple-like leaves and erect flower stalks bearing clusters of small, white flowers that give the plant a ‘foamy’ appearance (3) (4) (5). The leaves of this species grow solely at the base of the plant, giving way to a tall flower stalk in the middle (3) (4) (5). This flower stalk is usually leafless, although occasionally it may bear a pair of small leaves (4) (5).

As its common name suggests, the leaves of the heartleaved foamflower are broadly heart-shaped (4) (5) (6), with three to five shallow lobes and unevenly toothed margins (3) (5). Each leaf measures around five to ten centimetres in length and three to eight centimetres in width (5), and grows on a long stalk (4) (5).

The flowering stems of the heartleaved foamflower each bear a narrow, spike-like cluster of flowers, known as a raceme, towards the top (3) (4). Each individual flower measures approximately 0.6 to 0.8 centimetres across (3) and is white to pinkish, with 5 lance-shaped petals (3) (4) (5). The stamens of the flower are slightly longer than the petals, adding to the foamy appearance of the raceme (5), and the anthers are yellow (6).

The fruit of the heartleaved foamflower consists of two capsules of unequal length, and contains many black, shiny seeds (5). The genus name of the heartleaved foamflower, Tiarella, means “little tiara”, referring to the odd form of the fruit, while cordifolia refers to the heart-shaped leaves of this species (3) (5).

Three varieties of the heartleaved foamflower are generally recognised: Tiarella cordifolia var. cordifolia, Tiarella cordifolia var. collina and Tiarella cordifolia var. austrina (1) (5). Many different forms have also been created in cultivation (5).

The heartleaved foamflower can be difficult to distinguish from twoleaf miterwort (Mitella diphylla), but twoleaf miterwort has fringed flower petals and also has a pair of leaves halfway up its flower stalk, which are usually absent in the heartleaved foamflower (5).

The heartleaved foamflower can be found across a large part of the east coast of North America. It ranges as far south as Mississippi and Georgia in the United States, west as far as Wisconsin, and north to Nova Scotia and Quebec in Canada (5) (7).

The heartleaved foamflower is typically found in woods and forests with partial sun and shade. It flourishes in moderately moist environments, and is often found in proximity to streams or in wet ground (3) (5).

This plant is generally found in deciduous, hemlock-hardwood (Tsuga canadensis) or white-cedar (Thuja occidentalis) forests, and is often most common in older second-growth sugar maple (Acer saccharum) forest (5). Trees commonly found around the heartleaved foamflower include the white ash (Fraxinus americana), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), eastern hemlock (Tsuga canadensis) and northern white-cedar (Thuja occidentalis) (5).

The heartleaved foamflower is a perennial species that usually flowers from April through to May (2) (3), although in some areas it may also flower in March, June and July (4) (5). In each raceme, the blooms at the bottom of the cluster flower before the ones at the top (5).

Although no specific pollinator is listed in the scientific literature, it is believed that pollination of the heartleaved foamflower probably occurs by insects (5). The seeds of the heartleaved foamflower start to ripen around five to seven days after the topmost flowers have faded, with the small seed pods splitting to drop their seeds (5).

As well as producing seeds, the heartleaved foamflower also reproduces vegetatively using stolons. These horizontal stems grow from the base of the plant and produce new plants at points along their length, allowing the heartleaved foamflower to create large colonies on the forest floor (4) (5). However, the variety Tiarella cordifolia var. collina differs from the other two varieties of this species in lacking stolons (5).

The leaves of the heartleaved foamflower are semi-evergreen, developing while the leaves of the forest canopy emerge, but not dying back until after the snows melt the following spring (5).

One of the major threats to the heartleaved foamflower is removal of the forest canopy, due for example to clearcutting and forest thinning. The removal of the canopy exposes the ground-dwelling heartleaved foamflower to excessive amounts of light, which can dry up the soil and prevent the plant’s shallow roots from getting enough water (5). Forestry activities can also disturb the soil and cause mechanical damage to heartleaved foamflower colonies, and this species may be particularly sensitive to the fragmentation of its habitat. It is also poor at re-colonising isolated forest patches after disturbance (5).

Another threat to the heartleaved foamflower is the non-native earthworms that have been introduced to the Great Lakes region, which previously lacked native earthworm species. These worms, which have been both accidentally and deliberately introduced, have since spread rapidly. They pose a significant threat to the heartleaved foamflower, along with many other North American hardwood forest understorey species, due to their ability to consume the leaf litter layer much faster than the fungi which normally dominate these forests. This creates ideal conditions for bacteria which convert ammonium to nitrates, and these nitrates are easily leached out of the soil. This in turn starves native plants of nutrients and allows the rapid spread of exotic species (5).

The heartleaved foamflower may potentially be affected by the spread of non-native plants such as buckthorn (Rhamnus spp.), Asian honeysuckle (Lonicera morrowii) and garlic mustard (Alliaria petiolata), which can shade out native plants. Global warming may also pose a threat to this species, for example through increased drought. Habitat fragmentation and man-made barriers to plant dispersal could prevent the heartleaved foamflower from shifting its range in response to changing climatic conditions (5).

The leaves and roots of the heartleaved foamflower have been used by Native Americans for a range of medical purposes, including as a mouthwash for mouth sores, as an antacid, and as a treatment for diarrhoea (4) (5) (6). This plant is now popular in cultivation, and both legal and illegal collection may pose a potential threat to wild populations (5).

Some of the most threatened populations of the heartleaved foamflower occur in Wisconsin and the Upper Peninsula of Michigan (2) (3) (5). One possible reason for its scarcity in these areas is that they are on the edges of the species’ range and therefore its growth is limited by the climate and by the marginal habitat. Another reason may be that these regions lack sufficient pollinators of the heartleaved foamflower (5).

Currently, extensive conservation efforts are being made in the Wisconsin Chequamegon-Nicolet National Forest and the Ottawa National Forest to preserve their single occurrences of the heartleaved foamflower. Public education and outreach will also be important in the protection of this species, particularly for areas where it occurs on private land (5).

Outside of these marginal areas, the heartleaved foamflower is reported to be widespread and relatively common. However, very little is currently known about its life history and ecology, so further research and monitoring are needed to help develop viable conservation plans for this attractive woodland plant (5).

Find out more about the heartleaved foamflower and its conservation:

More information on the issues surrounding non-native earthworms in the Great Lakes region:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

  1. Integrated Taxonomic Information System (ITIS) (February, 2012)
    http://www.itis.gov/
  2. Wisconsin Botanical Information System: Wisconsin State Herbarium - Tiarella cordifolia (July, 2011)
    http://www.botany.wisc.edu/herbarium/
  3. Robert W. Freckmann Herbarium, University of Wisconsin-Stevens Point - Tiarella cordifolia (July, 2011)
    http://wisplants.uwsp.edu/scripts/detail.asp?SpCode=TIACOR
  4. Church, B. (2006) Medicinal Plants, Trees, & Shrubs of Appalachia: A Field Guide. Lulu.com, Raleigh, North Carolina.
  5. Fields, D. and Brzeskiewicz, M. (2002) Conservation Assessment for Heart-leaved Foam-flower (Tiarella cordifolia). USDA Forest Service, Eastern Region, Parks Falls, Wisconsin. Available at:
    http://www.fs.fed.us/r9/wildlife/tes/ca-overview/docs/plant_Tiarella_cordifolia-Heart_Leaved_Foam_Flower.pdf
  6. Samuels, T.M. (2005) A Georgia Native Plant Guide. Mercer University Press, Macon, Georgia.
  7. USDA, ARS, National Genetic Resources Program: Germplasm Resources Information Network (GRIN) (July, 2011)
    http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?431961