BSk, Dfa, Dfb
Cold Steppe, Hot- and Warm-Summer Humid Continental
The origin of the cultivated green bunching onion is somewhat obscure, but a possible wild ancestor is Allium altaicum, which occurs in a climate band stretching across northern China (Heilongjiang, Inner Mongolia, Xinjiang) and into neighboring Kazakhstan to the west. (1,4) We can take the climates of these regions as jumping off points for exploring the climate conditions associated with bunching onions.
Here are some regional climate factors to bear in mind, and how they compare to our local climate:
*Please note –
Bold = Regional climate info associated with possible bunching onion ancestor Allium altaicum
Italics = Las Vegas climate info
The cold steppe climate (Bsk) areas of this region are semi-arid grasslands that receive about 10-20 inches of rain per year. (9)
The semi-arid steppe climate is significantly wetter than the Las Vegas arid desert climate; roughly 2.5 to 5 times wetter. Cold steppe regions can be found to our north and east. Elko, Reno, Sparks, and Winnemucca are some places in Nevada with similar climates. Beyond Nevada, we can look to places like Denver, Colorado and parts of the U.S. Great Plains for other examples of this climate. (9, 10, 11)
If you carefully observe your growing space and find a spot that is relatively Reno-like (wetter and cooler than most of your space,) then this might be a good microclimate for growing green onions!
“Mean yearly temperatures are less than 64 degrees, and decrease in higher elevations.” (9) Summer days can be warm or hot in some parts of the region. Temperatures fluctuate between extremes during the year in the landlocked interior Asian areas, due in part to the absence of any nearby ocean with its moderating maritime influence; and also due to the presence of mountains blocking the moisture that does travel this way by air. (9) Winters can be extremely cold.
The cold steppe climate is significantly cooler overall than the Las Vegas climate. In the Las Vegas area, the mean yearly temperature is around 69 degrees. (12)
While summer temperatures in Las Vegas are generally warmer than those in the steppe and continental climates being discussed, it would seem that A. altaicum is adapted to a variety of summer temperatures, including warm and hot temperatures. (7,9)
We experience wild temperature fluctuations here in the landlocked and mountain-adjacent eastern Mojave Desert, too. Our winters are less harsh than those in the region being discussed. If the extreme temperature fluctuations in the regions associated with these wild onions is any indication, then bunching onions should have little trouble adapting to our climate in this respect.
Moving on now from the Bsk to Df regions…
The humid continental climate (Df) regions in A. altaicum‘s range receive at least 20 inches of rain per year. In Central Asian Df areas, summers may be cool and generally drier than winters. Winters are “quite harsh, with bitter winds and abundant snowfall.” (9)
A. altaicum grows in these moist conditions, as well as in the semi-arid conditions described above. This indicates their adaptability.
Las Vegas winters are mild by comparison to winters in these areas. If the wild onion A. altaicum’s growing patterns are an indication, then bunching onions should have no trouble surviving Southern Nevada winters once established.
These wild onions are also adapted to windy areas. Wind tolerance is an important factor to keep in mind when designing a Las Vegas area garden.
Eastern Chinese Df areas are influenced by the summer monsoon, with wetter summers.
The wet summer monsoon has a definitive influence on weather patterns in much of China. Monsoon season is likewise a major climate factor in Southwestern U.S. desert regions. Monsoon moisture is extremely slight in the Las Vegas area when compared to the rainfall that monsoon-influenced humid continental areas receive.
A. altaicum must be hardy in many ways to flourish among the fluctuations and extremes described here. While all of the indicators above point toward the likelihood that bunching onions would prefer a wetter climate than ours, the bunching onion plant’s compactness and apparent adaptability is a saving grace here. You can grow a good amount of green onions in a small space by taking advantage of a microclimate niche in your growing area that is relatively moist.
1 “Scallions: Allium fistulosum” page, Growing Taste: A Home Food-Gardening Resource website.
2 “Allium fistulosum” article, Wikipedia. https://en.wikipedia.org/wiki/Allium_fistulosum
3 “Kazakhstan” article, Wikipedia.
4 “Allium altaicum” article, Wikipedia.
5 Peel, M. C., Finlayson, B.L., and McMahon, T.A. (University of Melbourne.) “Updated world map of the Köppen-Geiger climate classification.” Hydrology and Earth System Sciences. October 11, 2007.
Map enhanced, modified, and vectorized by Ali Zifan. “Kazakhstan map of Köppen climate classification.” Wikimedia.org.
6 “Climate: Inner Mongolia.” Climate-data.org. https://en.climate-data.org/region/796/
7 “Xinjiang” article, Wikipedia.
8 Lucky Dragon Hotel and Casino website
9 “The Climate of Central Asia.” USA Today website.
10 “Köppen climate classification” article, Wikipedia.
11 “Nevada” article, Wikipedia.
12 “Climate Las Vegas – Nevada.” U.S. Climate Data website. http://www.usclimatedata.com/climate/las-vegas/nevada/united-states/usnv0049
13 “China” article, Wikipedia. https://en.wikipedia.org/wiki/China#Landscape_and_climate
14 “Climate: Heilongjiang.” Climate-Data.org.
15 “East Asian Monsoon,” article, Wikipedia.
16 “Allium altaicum.” Plants for a Future website.