Nuttallanthus canadensis aka Canada Toadflax

Nuttallanthus canadensis has two common names: blue and Canadian toadflax. Sources also use the name Linaria canadensis. It belongs to Plantaginaceae, the plantain family. This short-lived wildflower is an annual or biennial. It lives for one or two years. Its native range runs from Canada through Mexico. It also takes in parts of the Caribbean and South America. In eastern North America, it grows from Ontario to Florida and Texas.

Plants stand about 0.8–2.7 feet [0.25–0.81 metres] tall. Thin stems grow upright, with flowers above narrow green leaves. Each leaf is simple, with no hairs and smooth edges. The leaves join the stems with no leaf stalks. On taller stems that bear flowers, leaves alternate along the stem. On lower stems without flowers, leaves tend to form pairs. The blades range from linear to narrowly oblong. They are thin strips or narrow shapes longer than wide. They reach about 0.125 feet [0.038 metres] long.

The small flowers range from blue to purple and near-white. They measure about 0.033–0.05 feet [0.010–0.015 metres] long. North Carolina State lists March to July for bloom. Its broader account says bloom lasts into late summer. Seed pods called capsules form after the flowers. They appear from April to September. Each capsule opens and sheds smooth, flat seeds. Wind can then carry the seeds to new sites.

Give this plant full sun and open ground with few competing plants. It grows in grasslands and bare patches. It grows well in dry sand and poor soils with gravel. It also copes with rocky ground and some shade. The soil can hold a fair amount of moisture, too. Once the plant takes root, it copes well with drought. Rich soil with much nitrogen leads to more leaves than flowers. Plants For A Future lists USDA zones 4–8. Sow seeds in spring where the plants will grow. Where winters are mild, fall sowing can yield larger plants.

Use blue toadflax in coastal sites where it can spread, or wildlife gardens. Bees and butterflies come to its flowers for nectar. Common buckeye caterpillars eat its leaves. Its spread can also make it a weed. The supplied accounts name no specific pests or diseases. Plants For A Future lists no known uses as food. It reports no known hazards, but does not confirm safety. It records past use of the leaves for hemorrhoids. It also notes diuretic uses to boost urine flow, and laxative uses to ease bowel movements. These records do not prove that home treatment is safe or works.