Flower:

Loosely branched racemes at the top of the plant. Flowers are about 1/6 inch across with 4 yellow petals. In the center are 6 yellow stamens and a stout style. Flowers may close up on warm sunny days.

The 4 sepals surrounding the base of the flower are oblong-elliptic, hairless, green with whitish edging. The clusters elongate as the plant matures, with flowers open at the top and fruit forming below. 

Leaves and stems:

Basal leaves wither away by flowering time. Stem leaves are alternate, lance-linear to lance-elliptic, the lowest leaves up to 3 inches long and less than ½ inch wide, becoming smaller as they ascend the stem. Edges are toothless or with minute sharp teeth. Surfaces are hairless to sparsely hairy with mostly star-shaped trichomes (hairs).

Leaves are stalkless but with a pair of lobes at the base that may be clasping. Stems are mostly erect, unbranched or loosely branched, hairless in the flower clusters and hairless to sparsely hairy near the base, with star-shaped trichomes mixed with a few, shorter, unbranched trichomes.

Fruit:

Fruit is a capsule up to about 1/3 inch long, oval but tapering at the base somewhat like an inverted pear, with a distinct rib around the edge, an obscure midvein, and the remains of the persistent style at the tip. The fruit stalks are ascending to spreading and up to ¾ inch long.

Inside the capsule are about 10 reddish to yellowish brown seeds 1 to 2 mm long.

Notes:

Large-seeded False Flax was an occasional weed found on roadsides and agricultural fields, but hasn't been recorded in Minnesota since 1927. It may have been introduced as a contaminant in flax seeds in the 1800s, but was intentionally planted on a small scale in the early 1900s as a food crop and fuel oil for lamps. More recently it has gained some popularity for industrial uses including biofuels, chemicals and animal feed as well as cooking oils, becoming more attractive as a crop due to its tolerance for marginal lands and drought and pest resistance. Even though it may become more common in agriculture, it has a low risk of becoming much of a pest plant beyond its plantings. It's been grown for centuries in Europe and Asia and selective cultivation has had its toll. Wild forms are now rather rare, and studies in Canada found seeds from cultivated populations did not remain viable for much more than 2 years.

Large-seeded False Flax is very similar to the related Small-seeded False Flax (Camelina microcarpa), which has paler yellow flowers, fruits about half the size, and is hairier, with the unbranched trichomes more numerous and longer than the star-shaped trichomes. Of note is we grew this plant in the garden just to get some images. Checking on it repeatedly throughout the day across its flowering period, we never once saw the flower petals spread out; they were always closed up on both sunny and cloudy days.