Considered by some to belong to the Citrus genus, while genetically different enough to grant it its own, Poncirus, by others, the bitter orange is a uniquely interesting large shrub I was ecstatic to find loaded with fruits when wondering through the gorgeous Giardini Pubblici Indro Montanelli in Milan back in October. I still have to write about it in detail on this blog, but I have a passion for raising citrus plants indoor from seed, and with five species (seven plants in total) currently growing in my living room, it’s quickly getting out of control.
This species has some peculiarities which set it well apart from your common citruses though, the most relevant being its hardiness. Native to Northern China and Korea, it is hardy to -15
°C if placed in a sunny, sheltered position on well-draining soil. Being deciduous and performing a great deal of photosynthesis in its young branches are adaptations that help make this feat possible. Interestingly, it is genetically close enough to other citruses to hybridise with them and, more commonly, to be used as a rootstock in grafting to improve cold resistance in more tender species.
The small, yellow fruit is downy like a peach and very fragrant, with a sweet floral scent similar to that of the blossom, but it’s actually extremely bitter and mostly filled with seeds. It can be used to make a marmalade and a dry seasoning powder, but is also an ingredient of Chinese medicine.
The seeds require cold stratification to germinate, so after washing them well I placed them over a layer of moist sand in a sealed container at the bottom of my fridge. I’m curious to see if I will be able to raise this species successfully in my allotment here in Scotland, and it might give me the opportunity to experiment with grafting my other citruses and test their ability to survive a Scottish winter outdoors, obviously with plenty of protection still provided.
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