Leonurus cardiaca

Motherwort

Lamiaceae (Mint Family)

Leonurus cardiaca is a odd, but orderly-looking, exotic plant that thrives on roadsides, in abandoned fields and, like the one at right, along irrigation ditches.

It's probably native to Asia, but people started growing it in Europe centuries ago, mostly for medicinal use. Europeans brought it to North America to help bees make honey.

The Bee-keeper's Guide: Or Manual of the Apiary of 1882 calls L. cardiaca the best of all honey plants: "It is long in bloom, the flowers afford fine honey at all times, and it is a favorite with the bees," adding, "once introduced in waste places, it is sure to hold its own until it becomes desirable to extirpate it, when, at man's bidding, it quickly lets go its hold so that it is not a dangerous plant to introduce."

That last part's a bit sketchy. Today it grows all over North America and , in some areas, it's considered a noxious weed.

The flowers bloom on the top half of the plant. They're tucked into the leaf axils and wohrl around the stem.

The arrangement is more obvious when the flowers are gone.

The calyx under the flower is green and bell-shaped. Each calyx has 5 long, narrow lobes that taper to a sharp point.

The lobes are irregular. It's easier to see on a dried calyx after the flower is gone.

The bracts are opposite and look like 3-lobed leaves on long stalks.

The flowers are pink, white, purple and hairy. They look a bit like little space aliens.

At the base, they're long tubes, as you can see to the right. Then the tube divides into two lips, an upper (on the right below) and a lower.

The upper lip is pink and white, convex and has long, white hairs. The lower is white with purple splotches and splits into 3 lobes: two small lobes on the sides and a long, narrow one at the bottom.

The flowers bloom in July and August. During those 2 months, each flower blooms for about 2 weeks. The blooming periods of flowers overlap -- on the same plant and on other plants.

Each flower has 4 stamens. They develop first, then spread out: 2 upper and 2 lower.

A few days later, the pistil grows out between the upper 2 stamens. It has a split style that becomes receptive to pollen.

The pollen can come from pistils on the same flower, other flowers on the same plant or flowers on different plants.

All those options keep the likelihood of pollenation high.

Each flower produces a schizocarp that has 4 chambers with a single nutlet in each chamber. The seeds are sharply angled and the color varies from brown to reddish-brown.

The leaves on L. cardiaca vary a lot, even on the same plant. In general they grow opposite along the stem on fairly long stalks. They're bigger at the bottom of the plant. Each leaf is palmately-lobed, meaning the lobes look vaguely like fingers sticking out from the palm of your hand.

The number of lobes ranges from 3 to 5 and they usually narrow to a point.

The edges of the leaves are serrated.

The blades are dull to dark green, can have some small hairs, and the veins are prominent.

The stems start out erect, but tend to sprawl as the plant matures.

They can grow from 0.5 m - 1.5 m (2' - 5') and they sometimes branch.

The stems are square in cross-section, they have ridges and short hairs. They vary a bit in color and can be purplish at the nodes.

Common Names: