Pittosporum crassifolium, karo, stiffleaf cheesewood, kaikaro or kihiki[2] is a relatively fast-growing large shrub or small tree with an erect, fastigiate growth habit.

Juvenile plants often appear different from the adult form as the branchlets are covered with tomentum until they mature and become darker.

[10] Although endemic to the upper North Island of New Zealand, this species has now spread both nationally and internationally and is now considered a weed in areas where it is non-endemic.

The Integrated Taxonomic Information System has compiled a list of these countries which includes South Africa, Portugal, England and America.

[9] Karo can be found in a variety of habitats including forest margins, cliff faces, streamside and rocky areas.

The tomentum on the leaf undersides allow for this species to thrive in coastal conditions because the fine hairs help reduce salt damage and prevent moisture loss.

[9] Towards the end of the flowering period, this species produces green capsules which develop into seedpods with black seeds within.

The ripe seed is on the shrub for approximately six months and ripens in winter which allows plenty of time for dispersal via birds and other animals.

When planted in shade karo will stretch to try and find light; however, in a full sun position it tends to have a compacted habit.

[9] In order for this species to thrive and have optimal plant growth and health, it should be pruned back to the leaf node at least once a year.

The ITIS has found that some of the main predators are; Tui (Prosthemadera novaeseelandiae), silvereye (Zosterops lateralis), western honey bee (Apis mellifera), common bushtail possum (Trichosurus vulpecula), black tailed bumblebee (Bombus melanopygus) and the New Zealand bellbird (Anthornis melanura).