Gas plant and Herbaceous plant

Gas plant noun - Eurasian perennial herb with white flowers that emit flammable vapor in hot weather.

Herbaceous plant and gas plant are semantically related. In some cases you can use "Herbaceous plant" instead a noun phrase "Gas plant".

Herbaceous plant noun - A plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests.

Gas plant and herbaceous plant are semantically related. Sometimes you can replace phrase "Gas plant" with "Herbaceous plant", this phrases are similar.