Pyracantha koidzumii aka Formosa Firethorn

Pyracantha koidzumii, or Formosan firethorn, belongs to the rose family. This shrub comes from Taiwan, once known as Formosa. It grows in rocky valleys, coastal sites, and thickets. It keeps all or much of its foliage through winter. Its dense growth has several stems and stiff, upright branches. Sharp thorns end some side branches. Garden plants reach 6–12 feet (1.8–3.7 metres), with a similar spread. NC State gives a taller limit of 18 feet (5.5 metres).

The glossy, dark green leaves grow in an alternate pattern. Each leaf is simple and broadest above its middle. The tip looks blunt and often has a shallow notch. Leaf edges are smooth or have small teeth near the tip. Leaves measure about 0.08–0.25 feet (0.025–0.076 metres) long. Young stems start red, then take on purple tones. These leaf shapes help distinguish it from scarlet firethorn.

Small white flowers form clusters in late spring to early summer. Each flower has five petals, and the blooms smell unpleasant. Bees and other pollinators visit them. Round fruits turn orange-red or red as fall begins. They measure about 0.02 feet (0.006–0.007 metres) across. Dense fruit clusters can remain through winter. Birds eat the fruit, adding wildlife value to the planting. Flowers and fruit develop on older growth.

Grow this firethorn in full sun or partial shade. Shade reduces its fruit crop. It prefers soil that drains well yet holds some moisture. Loam suits it, though reports differ on heavy clay. It tolerates dry soil and suits hot, dry sites. Growth is fast when conditions suit it. NC State lists USDA zones 8–10; Oregon State suggests some zone 7 tolerance. Protect it from cold winds. Plants For A Future reports scab and fireblight risks. These may increase in acid, sandy soil.

The thorny growth suits barriers, espaliers, and single specimen plants. It resists deer damage, but needs pruning for a neat outline. Pruning must account for flowers forming on older wood. Plants For A Future lists the fruit as edible, with little detail. Its safety warning draws on the genus, not confirmed species-specific findings. It raises possible cyanide risks in leaves and seeds. It warns against eating bitter fruit or seeds. The source lists no known medicinal uses.