Prickly spider-flower

Appearance

''Grevillea juniperina'' has a spreading or erect habit and it grows to between 0.2 and 3 m in height. The branchlets are thick and sturdy. The prickly leaves are generally stiff, and are 0.5–3.5 cm long and 0.5–6 mm wide. They are crowded along the stems. Flowering occurs throughout the year, peaking between mid winter and early summer, though varies between the different subspecies. Subspecies ''allojohnsonii'' flowers from September to February, subspecies ''trinervis'' flowers from August to December, and subspecies ''juniperina'', ''amphitricha'', ''sulphurea'', ''villosa'' and ''fortis'' flower in August and September. The spider-flower arrangement of the inflorescence has several individual flowers emerging from a central rounded flower head—reminiscent of the legs of a spider. The flowers are red, pink, orange, yellow or greenish, and are mostly terminal—arising on the ends of stems—though they occasionally arise from axillary buds. They are 2.5–3.5 cm long. The perianth is finely furred on the outside, while the pistil is smooth; it is 1.5–2.7 cm long. Flowering is followed by the development of seed pods, each capsule is 10–18 mm long, and releases one or two seeds when ripe. The narrow oval seed is 7.5–12 mm and 2.2–3.3 mm wide, with a swelling at the apex and a short wing. Both surfaces are covered with tiny hairs.

Similar species include the Wingello grevillea , which can be distinguished by its prominent midvein on the leaf undersurface, and the red spider-flower , which has wider leaves with lateral veins and longer pistil.

Distribution

Unlike other Proteaceae generally not found on clay soils, ''Grevillea juniperina'' subsp. ''juniperina'' is found in Cumberland Plain and Castlereagh Woodland communities on clay-loam soils, growing alongside such species as forest redgum , mugga ironbark , thin-leaved stringybark , broad-leaved red ironbark , grey box , white feather honeymyrtle , boxthorn , sickle wattle and ''Dillwynia tenuifolia''. ''Grevillea juniperina'' subsp. ''sulphurea'' is found on gravelly alluvial soil alongside ''Leptospermum'' species, and ''G. juniperina'' subsp. ''trinervis'' is found on alluvial soil with poor drainage in woodland or along riverbanks in association with snow gum , mountain gum , ''Dillwynia retorta'' and river lomatia . The annual rainfall in regions where ''G. juniperina'' grows is 600 to 800 mm .

Habitat

Unlike other Proteaceae generally not found on clay soils, ''Grevillea juniperina'' subsp. ''juniperina'' is found in Cumberland Plain and Castlereagh Woodland communities on clay-loam soils, growing alongside such species as forest redgum , mugga ironbark , thin-leaved stringybark , broad-leaved red ironbark , grey box , white feather honeymyrtle , boxthorn , sickle wattle and ''Dillwynia tenuifolia''. ''Grevillea juniperina'' subsp. ''sulphurea'' is found on gravelly alluvial soil alongside ''Leptospermum'' species, and ''G. juniperina'' subsp. ''trinervis'' is found on alluvial soil with poor drainage in woodland or along riverbanks in association with snow gum , mountain gum , ''Dillwynia retorta'' and river lomatia . The annual rainfall in regions where ''G. juniperina'' grows is 600 to 800 mm .Killed by bushfire, ''Grevillea juniperina'' regenerates afterwards by seeds that germinate after lying dormant in the soil, stimulated by exposure to heat and smoke. Plants over 1 m high produce more seed. Intervals of 10 to 15 years between fires are thought to be most beneficial for the species' survival, as this allows seed numbers to build up in the soil over time. ''Grevillea juniperina'' can also colonise disturbed areas, though overgrowth of ''Bursaria spinosa'' can negatively impact its spread.

''Grevillea juniperina'' is pollinated by birds, with bees also recorded visiting flowers. The leaves are food for caterpillars of the cyprotus blue . A springtail species of Australian origin—''Calvatomina superba''—was found on ''Grevillea juniperina'' cultivated at the Lost Gardens of Heligan in Cornwall.