This grower is fairly sure of this plant identification.
Both red and green oak leafed varieties are available as seed. Both are visible on the front rhs of the photo. Two of the best varieties I have come across in terms of sweetness and flavour. Are
quite robust, does fairly well in mild winters.
Lactuca sativa ‘Oak Leaf lettuce’ (Lettuce). This variety has long leaves which are medium green in colour.
They will grow in any moist but well-drained soil with full sun or partial-shade. In a cool climates sow the seeds from early spring to late summer, in a warmer climate sow from autumn to mid-spring. You can propagate from seed. For tender, succulent leaves it is important that there is no check in growth, so ensure the soil remains moist. Shade the young plants in hot weather and feed at intervals with weak liquid manure. Harvesting may start in Early summer. Harvesting may end in Mid autumn.
Italics = data drawn from parent genus or speciesView Full Plant Finder Record