Helianthus paradoxus is found in areas with salinity levels range from 10 to 40 parts per thousand.

Due to its ability to withstand such high levels of salt, H. paradoxus is considered to be a halophyte.

It grows 1–3 meters (3.3–9.8 ft) tall and is branched at the top.

The leaves are opposite on the lower part of the stem but alternate at the top, lance-shaped with three prominent veins, and up to 17.5 centimeters (6.9 in) long by 8.5 cm (3.3 in) wide.

It is found in spring seeps, wet meadows, pond margins, and stream courses.