Our neighbor’s Japanese cheesewood (Pittosporum tobira) is blooming, and it smells great, like sweet citrus. I’ve been wanting to learn a little more about the plants around me so I think I’ll start with this one.
Some photos:
According to Kew’s Plants of the World Online, it’s native to Japan, Korea, Nansei-shoto, Taiwan, and Vietnam. (“Nansei-shoto” is the official Japanese name for the Ryukyu Islands.)
Wikipedia says, ‘The binomial qualifier tobira derives from the Japanese name for the plant. The genus name Pittosporum derives from the Greek substantives pitta (meaning “pitch”) and sporos (meaning “seed”) in reference to the resinous substance that surrounds the seed.’ And also: ‘Its Japanese name, tobera, comes from “tobira no ki” which roughly translates to “door tree”. This is because the plant emits a foul odour when leaves or branches are cut and so it was hung up in doorways during Setsubun along with the heads of sardines.’
So, its scientific name means “pitch seed door tree”.
iNaturalist currently has 6,390 observations for Pittosporum tobira. 164 of those are in South Korea out of 511,576 observations total in South Korea. 140 of those observations are in California out of 18,173,092 observations in California. So, in South Korea, where it’s native, it makes up around 0.032% of observations and in California, where it’s not, it makes up around 0.0008% of observations. Could we use comparison of ratios like these to identify native ranges?
A 2017 handout from the California Invasive Plants Council [PDF] recommends Pittosporum tobira as a shrub to consider as an alternative for some more invasive species. So, seems like it’s not that invasive?
There’s an illustration of it on page 153 of Volume 3 of “The illustrated dictionary of gardening” from 1889 (well out of copyright):
San Marcos Growers (Archive) says, “Pittosporum tobira has been in cultivation in California since first being introduced in 1858 by Colonel J.L.L. Warren.” And also: “A dense, mounding evergreen shrub that grows to 15 feet tall and 12 feet wide. The spring-blooming creamy-white flowers have a similar fragrance as orange blossoms and green berries that mature to brown with orange seeds follow the bloom… Plant in full sun to shade and irrigate occasionally to regularly – as with most Pittosporum this plant is relatively drought tolerant in coastal California gardens once established but looks best with an occasional deep watering. Hardy to at least 15 F. A very adaptable shrub that will tolerate seaside conditions, inland heat and alkaline soils.”
Sounds like it’s also useful for protecting rat brain cells: “We observed that an aqueous extract of this medicinal plant exhibited significant neuroprotection against glutamate-induced toxicity in primary cultured rat cortical cells from methanol extracts of the seeds of P. tobira.” Moon HI, Park WH. Four carotenoids from Pittosporum tobira protect primary cultured rat cortical cells from glutamate-induced toxicity. Phytother Res. 2010 Apr;24(4):625-8. doi: 10.1002/ptr.3019. PMID: 20041415. (Archive)
According to the ASPCA: “Non-Toxic to Dogs, Non-Toxic to Cats, Non-Toxic to Horses”.
So, maybe good for rat brain cells, not deadly to cats and dogs.
(I release theses photos into the public domain. These works are marked with CC0 1.0, https://creativecommons.org/publicdomain/zero/1.0/.)
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