And a good surprise it is! Miner’s Lettuce! I have no idea where the seed came from. We do have some planted about 30 feet away and it is up, but very small. This is great! If you have never eaten Miner’s Lettuce, try some. It is sweet and succulent much like regular lettuce. Great in salads. Look at your local Farmers Market – They may have some. I know our does (Purple Sage Farms).

Description
Claytonia perfoliata is a trailing plant, growing to a maximum of 40 cm in length, but mature plants can be as small as 1 cm. The cotyledons are usually bright green (rarely purplish or brownish-green), succulent, long and narrow. The first true leaves form a rosette at the base of the plant, and are 0.5–4 cm long, with an often long petiole (exceptionally up to 20 cm long).
The small pink or white flowers have five petals 2–6 mm long; they appear from February to May or June, and are grouped 5–40 together above a pair of leaves that are united together around the stem to appear as one circular leaf. Mature plants have numerous erect to spreading stems that branch from the base.
It is common in the spring, and it prefers cool, damp conditions. It first appears in sunlit areas after the first heavy rains. Though, the best stands are found in shaded areas, especially in the uplands, into the early summer. As the days get hotter, the leaves turn a deep red color as they dry out.
There are four ill-defined geographical subspecies:
Claytonia perfoliata subsp. perfoliata: Pacific coastal United States and southwest Canada
Claytonia perfoliata subsp. intermontana: interior western United States
Claytonia perfoliata subsp. mexicana: coastal southern California and Arizona south through Mexico to Guatemala
Claytonia perfoliata subsp. utahensis: recognised as local subspecies in Utah.
Uses
The common name miner’s lettuce refers to its use by California Gold Rush miners who ate it to get their vitamin C to prevent scurvy. It can be eaten as a leaf vegetable. Most commonly it is eaten raw in salads, but it is not quite as delicate as other lettuce. Sometimes it is boiled like spinach, which it resembles in taste. [Wikipedia]

Miner’s lettuce
Scientific name: Claytonia perfoliata (Purslane Family: Portulacaceae)
Life stages of Miner’s lettuce
Miner’s lettuce, a native winter annual broadleaf plant, is part of a complex of species and subspecies with slightly varying characteristics. It is found throughout California (except for the lower desert areas) to about 6600 feet (2000 m). Miner’s lettuce inhabits natural plant communities, agricultural land, and urban areas, with a preference for cool, damp conditions. It dries up with the onset of hot spring weather. Although the leaves are sometimes cultivated or collected for salad greens, occasionally it accumulates soluble oxalates, which can be toxic when ingested.
Habitat
Chaparral, oak, woodlands, forests, and coastal sage scrub, agronomic and vegetable crop fields, orchards, vineyards, gardens, yards, and other disturbed sites.
Seedling
Cotyledons (seed leaves) are bright green, slightly succulent, linear and narrow, and broadest at the tip. The first true leaf and later leaves are narrowly to normally lance-shaped with bases that taper to the stalk. These leaves form a basal rosette. Miner’s lettuce seedlings are distinguished from redmaids, which lack definite stalks and have somewhat broader and fleshier leaves.
Young plant
The young plant is found as a basal rosette.
Mature plant
Mature plants have numerous erect to spreading, slender stems that branch from the base and reach up to 8 inches (20 cm) in length. Leaves are mostly basal, slightly succulent, hairless, and bright green. Leaf shape varies from football shaped to triangular-kidney shaped with rounded or pointy tips. The flower stalk appears to “grow through” a circular cuplike structure (bract) that looks like a leaf and surrounds the entire stem. Subspecies perfoliata has football to egg-diamond shaped leaves and subspecies mexicana has egg-diamond shaped to triangular-kidney-shaped leaves.
Flower
Flowers bloom from February through May. Five to forty white to pale pink flowers on slender down-curved stalks cluster above a circular to weakly squared, often cuplike, green structure (bract) that looks like a leaf and completely surrounds the stem.
Fruit
Tiny, egg-shaped, green, open pods, 1/17 to 1/6 of an inch (1.5–4 mm) are enclosed by green petal-like sepals and contain two to six seeds.
Seeds
Glossy, black seeds, about 1/26 to 1/8 of an inch (1 to 3 mm) in diameter, are oval to circular with a white appendage at the point of attachment. [UC Davis]

That is probably way more than you wanted to know. But interesting nonetheless. Try some Miner’s Lettuce. Cheers.