Karo

Sun

Full sun or partial shade; growth is densest in good light.

Water

Water regularly while establishing. Once rooted, it tolerates dry spells, though prolonged drought can thin the foliage.

Soil

Well-drained sandy, loamy or stony soil, including coastal soils; avoid ground that stays waterlogged.

Height

15-25 ft (4.5-7.5 m)

Spread

10-15 ft (3-4.5 m)

Flowers

Spring to early summer; small clusters of dark red to purple flowers, with a sweet scent most noticeable in the evening.

Foliage

Evergreen. Thick, rounded to oval grey-green leaves with rolled edges and pale, felted undersides; young shoots are also softly hairy.

Growth

Moderate to fast in mild conditions.

Care needed

Low

• Pollinators
• Drought tolerant
• Heat tolerant
• Wildlife
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   2.4 ft (0.72 m)

2. After 1 year

   7 ft (2 m)

3. After 2 years

   11 ft (3.4 m)

4. After 3 years

   15 ft (4.7 m)

5. After 5 years

   20 ft (6 m)

   full size

About 4 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Invasive in

the US and Australia

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Water deeply during dry weather for the first two growing seasons.
• Apply a 2-3 in (5-8 cm) mulch over the root area, keeping it clear of the trunk.
• Plant in freely draining ground; use a raised position where winter drainage is poor.
• Feed lightly in spring only if growth is weak or the soil is very poor.
• In colder districts, choose a sheltered position away from frost pockets.
• Remove seedlings and, where practical, seed capsules where escape into nearby vegetation is a concern.

Pruning. Trim hedges after flowering, avoiding cuts during frost or extreme heat. For a specimen shrub or small tree, remove dead, damaged and crossing branches in late spring and shorten wayward shoots selectively.

Spring

Plant in colder districts once the risk of hard frost has passed; water thoroughly.

Late spring

Check for winter damage and prune back dead shoots once new growth shows.

Early summer

Trim hedges after flowering and check stems and leaf undersides for scale insects.

Summer

Water young plants deeply during dry spells and take semi-ripe cuttings.

Autumn

Plant in mild coastal climates while soil is warm, and remove unwanted seedlings.

Winter

Check drainage and protect young plants with horticultural fleece during unusually severe frost.

• Use as an informal coastal hedge to filter wind and salt spray.
• Place behind flowering shrubs and perennials as a dense grey-green backdrop.
• Train as a small, multi-stemmed tree beside a sunny terrace where space allows.
• Combine with grasses, rosemary and lavender in a well-drained coastal or gravel garden.

Garden styles it suits: Coastal, Mediterranean, Dry gravel garden, Low-maintenance, Green on green and Native hedgerow.

Plant it with: New Zealand flax, Rosemary, Lavender, Rock rose, Lomandra and Coastal rosemary.

Wildlife: The scented flowers attract insects, including evening visitors. Birds eat or carry the sticky seeds and can spread the plant into nearby habitats; dense foliage also provides shelter.

• Scale insects can weaken shoots and cause sticky honeydew; prune heavily infested growth and treat remaining insects with a suitable horticultural oil according to its label.
• Sooty mould grows on honeydew from sap-feeding insects; control the insects, then wash affected foliage where practical.
• Waterlogged soil can cause root rot and dieback; improve drainage and avoid frequent watering of established plants.
• Hard frost can scorch foliage or kill young shoots; use a sheltered site and wait until late spring before removing damaged growth.

Not generally regarded as toxic to people, cats, dogs or horses, but species-specific safety information is limited. The capsules and sticky seeds are not food; discourage chewing or eating them and seek medical or veterinary advice if ingestion causes symptoms.

Where it spreads. Spreads by bird-carried seed and is invasive in coastal California and parts of south-eastern Australia, including Victoria and Tasmania. It also naturalises beyond its native northern range in New Zealand. Check local weed guidance before planting near coastal scrub or other natural vegetation.

• Kohuhu (Pittosporum tenuifolium)

  Usually has smaller, thinner, often wavy-edged leaves and dark stems; its leaves lack karo's conspicuous pale felt underneath.

• Japanese pittosporum (Pittosporum tobira)

  Has glossy green leaves without felted undersides and cream-white flowers that age yellow, rather than dark red flowers.

• Pohutukawa (Metrosideros excelsa)

  Also has leathery leaves with pale felt beneath, but its leaves occur in opposite pairs and its flowers form conspicuous red brush-like clusters.

Karo is the Māori name; Pittosporum refers to the resinous coating on the seeds, and crassifolium means thick-leaved.

Propagation. Sow cleaned, ripe seed in a free-draining seed mix; germination can be slow and uneven. Take semi-ripe cuttings in summer, keeping them humid but not waterlogged.

Accepted botanical name

Pittosporum crassifolium

Native range

Kermadec Is. and New Zealand North.

Measured

Average height 1000 cm.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.