Dirca palustris L.

Nomenclature and growth form

Dirca palustris L., commonly called leatherwood, is a widely branching, usually multi-stemmed woody shrub that reaches a maximum vertical height of 3 meters. Leatherwood is monoecious, and produces bisexual flowers.

Flower shape and perianth

The pale yellow, bell-shaped flowers are made up of joined sepals with no petals. They are borne in axillary clusters of 2 to 7 flowers.

Flower stamen count

Each flower has 8 long stamens.

Inflorescence stalk dimensions

The stalks of the flower clusters measure 1⁄8–3⁄8 inch (3–10 mm) long when the plant is flowering, and elongate to about 1⁄4–1⁄2 inch (6–13 mm) by fruiting time.

Individual flower stalk characteristics

The stalks of individual flowers are smooth and grow up to about 3⁄8 inch (10 mm) long; sometimes 2 or more of these stalks are fused nearly all the way to their tips.

Flower bud morphology

The flower buds are small and conical, with 4 distinct dark, silky bracts that remain on the plant after flowering.

Flowering period

It blooms from late March to April, and flowers before new leaves emerge. The flowers fall off as the new leaves expand.

Fruiting period

Leatherwood produces fruit from May to June.

Fruit characteristics

The fruit is an oval to egg-shaped drupe, usually pale green or yellowish, and sometimes strongly tinged with red or purple; it often turns darker and redder as it ages. Each fruit contains a single, dark brown seed.

Leaf arrangement and size

The leaves are simple, alternately arranged, and 3.5–7 cm (1.4–2.8 in) long.

Leaf surface development

Immature leaves have a hairy surface, are light green in color, and become smooth as the leaf matures.

Leaf stalk characteristics

The leaf stalks are short, hairy, and hollow. The next year's leaf buds are hidden and covered by the base of the leaf stalk.

Bark characteristics

The bark is mostly smooth and gray on old stems, roughened at the base of old trunks, and becomes very tough.

Wood characteristics

The wood is soft, white, and brittle when dried.

Twig color and texture

The twigs are yellowish brown or reddish brown and smooth. Stems have circular scars marking the start of each new growth cycle.

Twig flexibility

Twigs are very flexible, and can be bent or even tied into knots without breaking. They are enlarged at the joints.

Host plant association

D. palustris is a host plant for the leaf-mining larvae of the moth species Leucanthiza dircella.

Broad distribution range

Its natural distribution extends from New Brunswick to Ontario in the north, and from northern Florida to Louisiana in the south. Within this range, its distribution is restricted to very specific site conditions, so the species occurs sporadically.

Forest habitat types

It is found almost exclusively in mesic, relatively rich hardwood forests or mixed conifer-hardwood forests.

Regional abundance

It is most commonly encountered in the northern part of its range, and is a dominant shrub in some hardwood forests of the upper Great Lakes Region.

Specific habitat and cultivation

Rich woods, sometimes swampy, are its main habitat, and it is occasionally cultivated.

Identification challenges

It is often hard to recognize, because its flowers emerge just before leafing, last a very short time, and D. palustris often grows mixed with the much more common spicebush, which also produces small yellow flowers before leaves that emerge at roughly the same time in early spring.

Closest relative

Its closest relative, western leatherwood, grows across the continent in the San Francisco Bay Area.

Pharmacological and dermal effects

This plant is known to act as an emetic, laxative, and vesicant; some people develop severe skin irritation after contact with its bark.

Fruit toxicity

The fruits are mildly poisonous to mammals.

Isolated chemical compounds

Eight novel organic sulfur compounds, called dirchromones, have been isolated from dichloromethane extracts of the roots, bark, and wood. These compounds, the first sulfur-containing compounds identified in the family Thymelaceae, were found to have cytotoxic and mild antibacterial effects.