Pittosporum crassifolium aka Karo

Pittosporum crassifolium, or karo, is an evergreen shrub or small tree. It belongs to the Pittosporaceae family. Its native range covers New Zealand’s North Island and the Kermadec Islands. It grows along forest edges and beside streams. Other names include caro, evergreen pittosporum, and parchment bark. Its dense growth makes it useful for screens and hedges.

The plant forms a bushy crown and keeps its leaves year-round. The oblong leaves have dark green upper surfaces. Their undersides have a white-grey, felt-like covering. Small flowers grow in clusters during spring. They have a scent and range from deep red to purple. Garden plants reach about 26–39 feet [8–12 metres] tall. Their spread can exceed 26 feet [8 metres]. They may take 10–20 years to reach full size.

Choose full sun and moist soil that drains well. The RHS also lists partial shade as suitable. Chalk, loam, and sand all suit this plant. It accepts acid, neutral, and alkaline soils. Give it a sheltered site in a mild climate. Its UK hardiness rating is H3, suited to mild coastal areas. PFAF lists USDA zones 8–11. In frost-prone places, the RHS advises growing it under glass. Use a peat-free compost with a loam base for this.

Karo tolerates pruning and exposure to sea winds. It can form a coastal hedge or shelterbelt in mild areas. Its wide root system helps hold sandy ground and dunes. It also suits sunny woodland edges and wall-side borders. The seeds yield a dark blue dye. Its tough wood has a use in inlay work. The plant offers a possible source of saponins for soap. These bitter compounds also have potential as bird deterrents. Rain or washing removes that bitter coating.

Watch for aphids, cushion scale, and pittosporum sucker. Glasshouse red spider mite may also attack it. Powdery mildew and leaf spot are possible disease problems. PFAF reports no known edible or medicinal uses. It also notes that the plant contains saponins. These compounds can harm people, though the body absorbs them poorly. They are much more harmful to some animals, including fish. The lack of known food uses makes this an ornamental plant, not a food crop.