They are annual herbaceous plants that reach heights of 10 to 50 cm. The stem nodes are at most very slightly thickened in this species. In the case of the multicolored hollow tooth, the stem nodes are clearly thickened and hairy with bristles. The leaves of the yellow hollow tooth stand opposite to each other on the hairy and square stem. They are ovate-lanceolate with a roughly serrated leaf margin.
The hermaphrodite flowers are zygomorphic with a double flower envelope. The 2 to 3 centimeters long corollas are pale yellow to whitish, often with a yellow throat and sometimes with small purple throat spots. However, the entire lower lip is never purple, as is sometimes the case with similar brightly colored hollow teeth. Just like the upper leaves, the flowers are downy and hairy with glands. The flowering period in Germany extends from July to August.
This plant is useful.
This plant might be poisonous
How to get rid of: