The seeds remain in the soil during summer and germinate in autumn when the soil becomes moister. Having well-kept, dense summer lawns restricts the ability for seeds to germinate.

Onehunga is often confused for Yarrow because of its finely divided leaves. However, Yarrow is a perennial with a creeping rhizome system under the soil, while Onehunga has shallow fibrous roots. A key characteristic of Onehunga over Yarrow is that it has fewer leaflets per leaf. In late spring and early summer, it produces several clusters of small, spined fruits at ground level. As summer intensifies, the plant dies off and these fruits harden, usually with their spines pointed right into the air, and it is these spined fruits that end up stuck in our unsuspecting feet.