A Taste of Sichuan: Zanthoxylum simulans Jonathan Damery pices have molded the modern world. Several examples of both Zanthoxylum sim- Columbus and his fleet sailed in the name ulans (flatspine prickly ash) and Z. piperitum Sof black pepper. New Amsterdam, the can be found growing in the Arboretum, but the Dutch colonial settlement on Manhattan Island, most notable is a large specimen of the former, became New York in an island trade essentially tucked in just before the smoketree collection pertaining to nutmeg. And the records go on on Meadow Road. This specimen (accession back, to the time when the caravan routes of 1803-77-A) was collected as seed by Arboretum the rising Arab world first introduced exotic taxonomists Stephen Spongberg and Richard Eastern spices to the insipid foods of Europe. Weaver in 1977 from the Forest Research Insti- The worldwide distribution of spice-produc- tute in Seoul, South Korea. ing plant species (and especially the woody The gracefully spreading form of this speci- plants within that group) is limited mostly to men (24.3 feet [7.4 meters] tall, 6.5 inch tropical climates, which excludes the most [16.5cm] diameter main stem) melds easily into common spice plants from the temperate-zone the border of Meadow Road, but even in the tree and shrub collections of the Arnold Arbo- winter it is worth taking a few steps off the retum. Of the few exceptions, the Arboretum is path for a closer view. A spiny plant from twig home to one spice-producing plant of particular to trunk, the spines (or technically prickles in interest—Zanthoxylum simulans, a source of the case of those on the trunk) become enlarged Sichuan pepper. and woody, lending an exotic appearance to the Though not a common spice in American tree. The deep green compound leaves have an kitchens, the signature mouth-numbing fla- attractive glossy sheen, and in midsummer Z. vor of Sichuan pepper is indispensible in the simulans is covered with a greenish white haze regional cuisine of Sichuan, China. It is pro- of small flowers, followed by a prolific display duced from the dried fruit of several differ- of small, round follicles (a type of dehiscent ent species of Zanthoxylum, also known as fruit). At maturity these fruits turn a pinkish- the prickly ashes. The most common sources bronze color and split open, spitting out the are Z. bungeanum and Z. simulans (formerly seeds. The dried follicle is the culinary product, considered varieties of the same species), and Sichuan pepper. Z. piperitum is used for similar culinary pur- On the plains and in upland forests of north- poses in Japan. ern and central China, Arboretum plant explorer E. H. Wilson reported that Zanthoxylum simu- lans grew naturally on cliffs and waysides. In IT is interesting to note that Zanthoxy- cultivation it was grown in dry, hot river val- lum is a member of the citrus family (Ruta- leys. This is a good indication of its adaptability ceae). In the United States, this relationship to a myriad of difficult landscape conditions. has proved to be rather problematic for Sich- uan cooks. Thought to be a potential mode The species is cold hardy in USDA Zones 5 to of introducing citrus canker to American cit- 7 (average annual minimum temperature -20 to rus groves, the United States Food and Drug 10°F [-28.8 to -12.3°C]). Administration forbade its importation for From the bare winter trunks through the nearly forty years, from 1968 to 2005 (though remarkable autumn fruit display, Zanthoxylum serious enforcement only came about in simulans is worth viewing all year long. It is a 2002). The ban was lifted under the stipula- not-so-hidden—but often missed—Arboretum tion that the Sichuan pepper be heated just treasure. enough to kill any infectious bacteria prior to importation. Jonathan Damery is a Curatorial Fellow at the Arnold Arboretum..