Miner’s Lettuce

Spring is known for brightly colored flowers, but but it also brings many less obvious but equally charming little plants such as Miner’s Lettuce (Claytonia perfoliata). This small, bright green plant is best known from shady, often moist areas in a large variety of vegetation types. The plant is easily recognized by the leaves that are fused into a circle, completely surrounding the stem. The delicate white flowers are born at the top of the stem, in the center of the leafy collar.

As the name implies, the leaves are edible, often used either raw in salads or boiled like spinach. Because the plants are high in vitamin C, gold rush miners ate them to prevent scurvy, giving the species its common name.

Description ^{2,4,26,34,59,145}

Miner’s lettuce is a small, herbaceous, slightly succulent annual plant of early spring; it grows to 12 inches (30 cm) tall but is usually much smaller. Leaves are of three types. The earliest leaves are basal and are narrowly oblanceolate, narrowing to a short petiole. Later basal leaves are oval to triangular, held aloft on long petioles. The two cauline leaves lack petioles and are opposite on the stem, fusing at their bases to form a collar around the stem. The collar is rounded usually with two oblique angles which may be tipped with a minute point. Leaves are usually bright green, sometimes streaked with white and occasionally reddish. Leaves are variable in size; with little time spent, we located fused cauline leaves as small as 3/8 inch (0.9 cm) and as large as 3 1/2 (9.2 cm) in diameter. Leaf size and shape form the basis for division into subspecies.

Flowers occur in one or more clusters rising from the center of the fused leaves; the lowest cluster lacks a stem. Tiny flowers are bisexual, radially symmetrical, less than 3/16 inch (5 mm) across. The five white petals are usually rounded, but may occasionally be notched at the tip. There are two sepals, five stamens and one pistil with three elongate stigmas ascending to spreading. Bloom time is March to May in coastal Southern California¹ but much later in more northern areas or at higher elevations.⁸⁹

The fruit is a green egg-shaped capsule enclosed by the two sepals. There are usually three glossy black seeds, less than 1/8 inch (3 mm), each with a white spot at the point of attachment. When ripe, seeds are forcibly expelled from the capsule.

Classification ¹⁴⁵

Miner’s lettuce is a dicot angiosperm recently moved into the new family Montiaceae from the purslane family (Portulacaeae) on the basis of molecular evidence.⁷ This is a small family. One other genus, Calandrinia (red maids) is found in the Reserve.⁴⁸

A variable number of subspecies of miner’s lettuce are recognized,³⁴ although some botanists^26,59 express doubt over their validity and even the Jepson eFlora² seems apologetic: “subspecies difficult because of environmental modification of character states, genetic mixing among polyploids, and geographic overlap of distinct, self-pollinated forms.” Only one subspecies has been described from the Reserve, ssp. perfoliata.⁴⁸ This subspecies and ssp. mexicana are described from nearby Torrey Pines State Park.¹ The differences between these two are small differences in the shapes of their older basal leaves and the existence or not of small points on two angles of the fused cauline leaves.^2,26 Using these characteristics, we have found both subspecies in the Reserve, with ssp. mexicana being the more common. We have also found plants that seemed to be intermediate.

Ecology  

Many flowering plants have adaptations, sometimes elaborate ones, to minimize self-pollination. In contrast, miner’s lettuce is usually self-pollinated, although insect pollination is known.^59,145 This strategy allows the population to increase rapidly from a few individuals; it may be an adaptation for reproduction in a place or time when the presence of insects is unpredictable.

Miner’s lettuce is a prolific seeder with long-lived seeds that may build up a large seed bank in the soil, and under some circumstances, post-fire sprouting followed by abundant seed production can provide rapid cover even in full sun.⁵ Self-pollination may aid in this rapid growth. Newly produced seeds provide important food for birds such as Mourning Doves and Meadowlarks.¹⁴⁷

Human Uses  

Miner’s lettuce is high in vitamin C, and there is a long history of culinary use,¹⁴⁶ although a few sources warn that plants may accumulate oxalates, which are toxic when eaten in high amounts or by sensitive individuals.¹⁴⁴ Note that many familiar foods contain oxalates, including rhubarb, spinach, nuts and chocolate.⁴¹

Native Americans harvested the stems, leaves, and blossoms and ate them fresh or boiled.⁷⁵ Indians from Placer County are said to have placed the leaves of miner’s lettuce near the nests of red ants where they picked up formic acid from the traversing ants. This gave the leaves a vinegary taste – a home made salad dressing³⁴.

The common name, miner’s lettuce, comes from the days of the gold rush when leaves were eaten to ward off scurvy.

Interesting Facts ¹⁴⁶

Miner’s lettuce is widely naturalized in Europe. It is thought to have been introduced to Kew Gardens in England in the 18th century  by the Scottish naturalist Archibald Menzies, who collected seeds from Washington state. Appreciating it as a source of vitamin C, the British introduced miner’s lettuce to Cuba and then to Australia. By the mid-19th century, seeds were being sold widely for salad greens and the plant was becoming a weed.

This may be one of the few instances in which an edible native plant from North America has become established as a weed in Europe. In exchange we have received such tasty but difficult-to-control plants as radish, fennel, mustard, dandelion and purslane.