pittosporum

Pittosporum (Cheesewood): Varieties, How To Grow and Care

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Are you looking for a fast-growing, neat, and dense plant for screening or hedging? Pittosporum might just be what you’re looking for, with a variety of sizes and foliage colors available. Read on to learn more about these plants and how to grow and care for them. 

What Is A Pittosporum?

Pittosporums are shrubs or trees of the Pittosporaceae family. There are around 200 species, which are native to Southern Africa, Australia, New Zealand, and Southeast Asia. 

The word Pittosporum basically means sticky seed in Greek. The word is derived from the Greek word for pitch(pitta) which is a substance similar to glue, and seed (spora). These ornamental evergreen shrubs and trees have a neat and tidy growth form and are often called cheesewoods. 

Wild species vary greatly in size and grow anywhere from 6-100ft (2-30m) in height, but fortunately for us, several horticultural varieties have been developed to grow much smaller. 

These plants generally occur in mild climates, where they grow in areas that receive good rainfall and warm conditions without severe frost. Some species are tougher than others and do well in exposed, coastal areas where they may be in contact with salt spray. 

Pittosporums have simple, leathery leaves that are spirally arranged or in whorls. 

Selected Pittosporum Species and Cultivars

Let’s take a look at a few selected species and cultivars of this plant that are best suited to gardening and horticulture.

  • P. tenuifolium – This plant is called kohuhu, tawhiwhi, black matipo, or kohukohu. It is an upright to rounded shrub or small tree with purple to black stems and glossy green leaves with undulating margins. Honey scented maroon-purple flowers are produced towards the end of spring. This New Zealand native reaches 20ft(6m) tall and can be grown in zones 9-11.
  • ‘Tom thumb’ is a dwarf variety of P. tenuifolium that reaches around 5ft (1.5m) in height. This variety produces leaves that start out green but mature into a deep red color, creating an attractive contrasting effect. This shrub can be grown in zones 9-11.
  • ‘Silver sheen’ is another kohuhu variety that is ideal as a screen or hedge. These plants have small, silvery-green leaves and produce maroon to brown fragrant flowers.
  • P. tobira– This popular garden plant is commonly known as the Japanese mock orange. This species makes for a hardy specimen shrub with excellent salt tolerance. The Japanese mock orange grows 8-12 ft(2.4-3.7m) high and 12-18ft(3.7-5.5m) across. This plant produces orange blossom scented flowers in spring. The flowers of this plant occur in clusters and measure 2-3inches (5-7.5cm) across.
  • ‘Wheeler’s Dwarf’ – While most of the available pittosporums take on a tree or large shrub form, this variety reaches just 3-4 feet (0.9-1.2m) in height and 4-5 feet (1.2-1.5m) across. This plant has a rounded mound-shaped growth form, making it ideal as a low foundation plant or container plant. 
  • ‘Mojo’ is another dwarf variety, but this plant has attractive variegated foliage.
  • P. eugenioides– This narrow and upright evergreen tree is commonly known as the lemonwood or tarata.  This tree produces lovely honey-scented, pale yellow flowers in the spring. Lemonwoods have attractive glossy green leaves with white, undulating margins. A large species, this tree reaches over 30ft (9m) and should be grown in zones 9-11 in full sun.
  • ‘Variegatum’ is a popular variety of the tarata that grows as a large, dense shrub. The variegated tarata has beautiful dark green and cream-white variegated foliage. 
  • P. ralphii is another New Zealand native that is tolerant of coastal conditions. This evergreen shrub grows to about 13ft (4.3m) tall and 9ft (3m) across. This species should be grown in a sunny location and can tolerate quite heavy pruning.
  • P. ‘garnettii’ is a hybrid of P. tenuifolium and P. ralphii. This plant reaches 10-15ft (3-4.5m) in height and grows as a dense evergreen shrub with greyish leaves with cream-white to pink edges. Greenish-purple flowers are produced in the late spring. This plant should be grown in full sun in zones 9-11.
  • P. crassifolium– The karo or stiffleaf cheesewood grows to about 16ft (5m) in height and is native to New Zealand. This species has grayish-green foliage and produces deep red to purple flowers. The Karo tree is well adapted to survive strong winds and salt spray but has unfortunately been identified as a possible invader outside of its native range. 
  • P. dallii– grows to around 10ft (3m) as a shrub or small tree with serrated green leaves on purple stems. This species produces fragrant white flowers in summer. This is a relatively slow-growing species that does best when grown in semi-shade.

Pittosporum Flowers

Size and flower color vary across the species but flowers all have 5 petals and become woody fruits that split open. The seeds are contained in a sticky substance, explaining the origin of the plant’s name. 

Pittosporum flowers vary in color by species and can be anything from greenish, maroon, purple, or white. 

Cheesewoods generally flower in the spring and summer months, depending on the species, and many have beautifully fragrant blossoms reminiscent of honey or citrus flowers that are particularly lovely in the evenings.


pittosporum hedge

How To Grow a Pittosporum

No special preparations are needed to grow these plants from seed except perhaps to give the seeds a wash with soapy water after harvesting as they are sticky when collected from the ripe, splitting capsules. Plant these seeds in late winter.

Pittosporums can be grown from semi-ripe cuttings taken in the fall. 2.5-3 inch (6.3-7.5cm) long cuttings inserted in a free draining medium that is capped with sand, is the best technique. The larger green-leaved species tend to root best. (1)

Cheesewood plants can be grown in a variety of well-drained soils. Water these plants weekly until established and they’ll be quite drought resistant when mature, just be careful not to overwater or grow in poorly drained substrates as they are quite susceptible to root rot. 

Most pittosporums should be grown in full sun locations, although some species such as P. dallii will do better in partial shade. Smaller varieties such as ‘Wheeler’s Dwarf’ and ‘Mojo’ make great container plants.  

Pittosporums do best when grown in USDA zones 9 through 11, although some species do fine in zone 8. In colder areas, these plants will need to be grown in containers and overwintered indoors.

Care and Maintenance

P. tenuifolium can be lightly pruned in late spring just to keep it neat and symmetrical (2).  Generally, however, these plants need little pruning. 

P. ralphii may need more frequent trimming to keep its growth form bushy and compact. P. tobira tends to rejuvenate more slowly than the other species after pruning. (3) 

Most pittosporums will grow naturally with a single stem or leader. Prune these plants just after flowering to avoid affecting the next year’s flowering. 

These are pretty fast-growing plants, quite capable of growing 2ft (0.6m) a year, although their growth rate will slow as they mature.

Generally, pittosporums have good resistance to pests and diseases but may be affected by mealybugs, aphids, cottony cushion scale, and sooty mold.

Cottony cushion scale is a pest that particularly affects the pittosporums and citrus plants. These sapsuckers can cause leaf drop and even mortality in plants, especially in stressful times like drought and cold. Products for scale such as Safari can be used to successfully control this pest on pittosporums. 

Another unfortunate side effect of cottony cushion scale on your pittosporums is the likelihood of developing sooty mold as a result of the honeydew produced by the scale (4). Sooty mold in itself is not a serious condition but may be unsightly.

You can control sooty mold by washing it off with a strong flow of water or a mild solution of soapy water. Remember though, as long as you have scale on your pittosporums, sooty mold is probably going to be present. 

Uses

Horticultural Uses

These plants have many uses. P. tenuifolium can be used as a focal plant but also works great as a screen, hedge, or windbreak because of its rapid growth rate. Dwarf forms like ‘Tom Thumb’ do great as container plants, foundation plantings, and as a taller ground cover.  

P. tobira, ralphii, and crassifolium are especially well suited for use in coastal areas because of their high tolerance for salt spray. Pittosporum plants can also be grown as bonsais. 

Pittosporum hedge has good sound deadening properties and specimen plants can even be pruned into basic topiary shapes.

Human Uses

There are records of some pittosporum species being used medicinally in both Southern Africa and New Zealand. Traditional uses of these plants include the treatment of mouth, chest, and skin ailments, as well as stomach pains and fever. 

Wildlife Uses

Pittosporums are not particularly attractive to wildlife. These plants do attract bees and other insect pollinators but are not eaten by deer, which is a bonus if these animals have access to your yard. 

FAQs

Conclusion

Pittosporums are a great evergreen option for a variety of uses in the garden. While these plants aren’t as showy as other options, they look great anyway and stay neat without needing too much maintenance.

References

Reference list

(1) Toogood, A. Plant Propagation: The Fully Illustrated Plant-By-Plant Manual Of Practical  Techniques. 

(2) Brickell, C. Encyclopedia Of Plants And Flowers. American Horticultural Society. 

(3) Brickell, C. & Joyce, D. Pruning & Training: What, When And How To Prune. 

(4) Frank, S. & Baker, J. Cottony Cushion Scale: Entomology Insect Notes

https://content.ces.ncsu.edu/cottony-cushion-scale

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*image by Marinodenisenko/depositphotos

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