Slender Toothwort

Several notorious weeds reside in the mustard family (Brassicaceae), including the annual pest bittercress (Cardamine pensylvanica). I haul away buckets of it early in the spring from my bulb beds and dig it under in my vegetable garden. Yet in this group of troublesome characters there is a marvelous beauty, our native slender toothwort, also known as beautiful bittercress (C. nuttallii, or C. pulcherrima if you go by the old name).

Slender toothwort grows as a low-spreading perennial, above which stand loose clusters of showy flowers. Cord-like, slightly fleshy rhizomes explore the soil just beneath the surface, rooting at the nodes. From these arise leaves on modest stalks generally reaching 5 cm (2 in.) or so high in colonies growing in the open. Somewhat shiny leaves vary from being entire and orb- to heart-shaped to slightly lobed and, less often, deeply lobed, even to the point of being compound. Rather than being bitter, as might be inferred from the common name, the leaves have an almost pleasant horseradish taste.

Stems arise from the rather attractive carpet of basal leaves to a height of 10 to 30 cm (4 to 12 in.). Prominent, narrow leaves decorate the stem just above the halfway point. A handful of flowers loosely crowns the slender flower stalk, often mixed with slender greenish seed pods. The flowers are widely described as being pink to purplish, but most populations I have seen on Vancouver Island are white to pale pink. Each bloom consists of four small green to purplish sepals cupping four showy petals, each about 1 cm (1⁄2 in.) long. There is a single, pin-like pistil surrounded by six stamens. The flowers have a delicate, almost sweet scent. Flowers bloom in early spring, late March to early April in downtown Victoria. Interestingly, the large flowers of this species of bittercresses are pollinated by insects. The small-flowered weedy ones mostly pollinate themselves - no wonder they reproduce so prolifically!

The natural habitat of slender toothwort includes dry to moist woodlands to open woods, often under deciduous trees. In British Columbia the species occurs widely on south and east Vancouver Island and the adjacent mainland, with an odd isolated population well north along the coast. Southward, slender toothwort ranges to California, mostly west of the Cascade Mountains.

This plant merits much more experimentation in the garden than has taken place so far. In the Royal BC Museum Native Plant Garden it grows in spring sun and under deciduous trees in moderate summer shade. The basal leaves form an attractive low ground-cover that seems to keep other plants at bay. The richer the soil the taller and more robust the flower stalks. Potential interesting combinations include planting a large patch with widely scattered camas bulbs (Camassia species) or with native shooting stars (Dodecatheon). This toothwort readily trans-plants in the moist winter and early spring months. It grows well from seed too, as its weedy annual relatives suggest. There always seem to be lots of rooted rhizomes without flower stalks to provide a supply of propagation material. Slender toothwort is notably well mannered in the garden and mostly stays where it is put, a real plus for small woodland corners.

Despite the spicy taste of the leaves there is no record of the species being used by First Nations people. The leaves have potential as a native green to add a pleasant zing to salads. A similar plant, known in Europe as Lady's smock (Cardamine pratensis), has rhizomes that somewhat resemble teeth. For this reason the belief was widely held that it was useful for toothaches.

Whether good for teeth or good for salads, this native woodlander deserves much more attention as an attractive garden plant. Search out a source and try a small patch.

The following plants are hardy to the zone number indicated:
• Cardamine nuttallii (slender toothwort, beautiful bittercrest) - zone 7
• Cardamine pratensis (Lady's smock) - zone 5

An expert on native plants, Richard Hebda is curator of Botany and Earth History at the Royal British Columbia Museum in Victoria.

• pest management,
• slender toothwort,
• perennials,
• native plants,
• gardens,
• groundcover,
• Plants,