Põõsas on tihe, 50–60 cm kõrgune. Õied kollased või valged, asetsevad maapinna lähedal. Pärast õie tolmlemist hakkab kasvama tugev õieraag günofoor, mis 5.–6. päeval pöördub alla, kuni surub rao otsas asuva teravatipulise kaunaalgme mulda.
legume of the pea family (Fabaceae), grown for its edible seeds
Hariliku maapähkli viljad arenevad ja valmivad maa all. Kuivas õhus valguse käes kaunad ei arene. Sellist kohastumust nimetatakse geokarpiaks. Sellele viitab ka taime liigiepiteet hypogaea, mis tõlkes tähendab maa-alune või salajane.
The peanut is an annual and can either be an erect shrubby plant, 45–60 cm (18–24 inches) high with short branches, or have a spreading form, 30–45 cm (12–18 inches) high with long branches that lie close to the soil. The stems are sturdy and hairy and bear pinnately compound leaves with two pairs of leaflets. The flowers are borne in the axils of the leaves and feature golden-yellow petals about 10 mm (0.4 inch) across. The oblong pods have rounded ends and are most commonly 25–50 mm (1–2 inches) long with two or three seeds; the pods are contracted between the seeds and have a thin, netted, spongy shell.
