It has a woody tap root and a woody caudex giving rise to many ascending stems. It has long shoot leaves distinctly petiolate, and slightly winged. The backside of the leaf contains greyish-white hairs that give the underside a lighter appearance.
Salt crystals are often visible and tasteable on the back of the leaves.
Johnston's frankenia's flowers are sessile and solitary. The flowers are white and may nave a pink tinge. There are 6-12 stamens in 2 subequal whorls and the anthers are yellow. Every autumn, from November to February, Johnston's frankenia turns crimson red. This allows for easy detection from the other leafless south Texas shrubs.