About Linaria tristis (L.) Mill.
Linaria tristis (L.) Mill. is an annual herb that ranges from hairless to sparsely covered in short soft hairs, and grows 10 to 40 centimeters tall, occasionally reaching up to 50 centimeters. Its stems grow erect or ascending, are slender, and usually branch out from the base. Leaves are arranged alternately, shaped linear to narrowly linear-lanceolate, between 15 and 35 millimeters long (sometimes as short as 10 millimeters) and 0.5 to 2 millimeters wide. They have smooth entire margins, are stalkless, and feature a single prominent midrib. The inflorescence is a loose raceme, and is sometimes reduced to just one solitary flower growing from a leaf axil. Pedicels are slender and held erect to spreading. The calyx is deeply divided into five segments; the lobes are linear to narrowly lanceolate, nearly equal in size, and measure 3 to 6 millimeters long. The corolla is zygomorphic and bilabiate, colored pale yellow to yellowish-white, and sometimes marked with faint violet or brownish veins on the flower palate. The upper lip has two lobes, and the lower lip has three lobes. The floral spur is slender, straight to slightly curved, and is as long as or longer than the rest of the corolla tube. There are four stamens, arranged in two pairs of unequal length; the style is slender, and the stigma is capitate. The fruit is a globose to subglobose capsule that dehisces through pores at its apex. It produces numerous seeds that are discoid, broadly winged, and brown to dark brown, and are adapted for wind dispersal. Flowering occurs mainly from March to June, with timing varying based on latitude and seasonal rainfall. In the Iberian region, Linaria tristis is distributed across central and southern Spain, and parts of Portugal. Peripheral records of the species from northwestern Africa have been published, but these are often considered marginal or uncertain in regional floras. This species grows in open, dry habitats including sandy fields, fallow land, rocky slopes, road verges, and other disturbed sites. It occurs from sea level up to approximately 1,200 meters, or 3,900 feet, in elevation. It prefers well-drained, often nutrient-poor soils, and full sun. Linaria tristis is primarily pollinated by bees that are able to reach nectar inside the floral spur, a pollination pattern that is typical for the genus Linaria. As a winter or early-spring annual, it completes its full life cycle rapidly before summer drought begins, and persists between growing seasons as a soil seed bank.
