Warm-Summer Humid Continental
The native range of garden orach, or mountain spinach (Atriplex hortensis), can be broadly described as Eurasian. It includes the Mediterranean hills, the Alps, and parts of Western Asia into Siberia. The warm-summer humid continental climate (Dfb) is a prevalent climate in all of these regions.
For comparison, some places near Las Vegas with warm-summer humid continental climates are Ely, Eureka, and Wells, Nevada.
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 garden orach
Italics = Las Vegas climate info
In the native range of Atriplex hortensis, the coldest month averages below 32 F. All months average below 71.6 F. (1)
Las Vegas is much warmer than this. The coldest month in the Las Vegas area (December) averages around 48 F. Five months average above 71.6 F. (15)
At least four months average above 50 F. (1) Summers are fairly warm.
In the Las Vegas area, summers are very hot. All but the two coldest months (December and January) average above 50 F. (15)
“The Alps are a classic example of what happens when a temperate area at lower altitude gives way to higher-elevation terrain. Elevations around the world that have cold climates similar to those of the polar regions have been called Alpine. A rise from sea level into the upper regions of the atmosphere causes the temperature to decrease.” (2)
This progression through climate zones corresponding to rising altitude can be compared to the climate zones found on Mount Charleston near Las Vegas. The Mount Charleston climate ranges from hot desert conditions at the base to arctic conditions at the top. The upper-middle altitudes of Mount Charleston in some ways resemble the native habitat of orach.
The humid continental (Dfb) areas in Atriplex hortensis’s range receive significant precipitation in the form of rain and snow, especially compared to desert regions. Precipitation amount varies. Mean precipitation in the Alpine areas may be around 100 inches per year. (2)
The Las Vegas area is much drier than this, with average annual precipitation around 4 inches! Orach growing in the Las Vegas area will benefit from regular watering.
“No significant precipitation difference between seasons.”
Precipitation levels vary considerably between seasons in the Las Vegas area. There is more than twice as much precipitation in winter as in spring. (16) Late winter rains can be taken advantage of for planting orach.
Some areas in the Alps “experience periodic flooding from rapid snowmelt and runoff.” (2) Snowmelt starts in mid-late spring, after 6-7 months of accumulating snow. “High-water levels in streams and rivers peak in June and July when the snow is still melting at the higher altitudes.” (2)
This is an interesting pattern to keep in mind when planning how and when to water garden orach. The flash floods that occur periodically in the Las Vegas area may in some ways resemble Alpine floods. Snowmelt patterns in the Alps can be compared and contrasted with snowmelt patterns in our local Spring Mountains.
The Foehn wind is a weather pattern strongly associated with the Alps. It is a warm, dry, downslope wind. (18) A Foehn wind occurs when an airflow from the Mediterranean reaches the south side of the Alps and rises up the slopes. The air expands and cools as moisture carried in the air condenses into precipitation and falls on the south side of the mountains. The dried-out air then passes over the mountains and descends on the north side. “As the air descends the leeward (northern) side it is compressed resulting in a dry, warm turbulent Foehn that can melt snow at a ferocious rate.” (17, 18)
The Foehn wind can be compared to the similar Santa Ana winds originating in the Great Basin Desert and affecting Southern California. (17,18,19) Orach’s heat tolerance and wind-adaptedness may or may not be related to the Foehn wind or winds like it, but this weather pattern does figure into orach’s native climate.
Southernmost Siberia (Dfb climate) has “ exceedingly fertile chernozem soils” (14), or black soils high in humus (organic matter.) (20,21)
Las Vegas area soils are not at all like this. The rich constitution of South Siberian soils may be something to keep in mind when preparing and maintaining soil for garden orach.
1 “Köppen climate classification” article, Wikipedia. https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification
2 “Alps” article, Wikipedia.
3 “Atriplex hortensis” article, Wikipedia.
4 “Atriplex hortensis.” Flora of China website.
5 “Atriplex hortensis.” Missouri Botanical Garden website.
6 “Atriplex hortensis.” Floridata website.
7 “Orach–Atriplex hortensis.” Electronic Data Information Source (EDIS,) The University of Florida’s Institute of Food and Agricultural Sciences website. edis.ifas.ufl.edu/mv103
8 “Orach Growing Guide,” Cornell University website.
9 “Orach.” Wild Garden Seed website.
10 “Orach.” Mountain Valley Seed Co. website.
11 Moore, Thomas. Epitome of Gardening. Adam and Charles Black, 1881.
12 “Tartary” article, Wikipedia.
13 “Tartary.” Encyclopædia Britannica: A Dictionary of Arts, Sciences, and General Literature. Day Otis Kellogg, 1881. https://books.google.com/books?id=22QukXXxjcwC
14 “Siberia” article, Wikipedia.
15 “Climate Las Vegas– Nevada.” U.S. Climate Data website.
16 “Monthly Temperature and Precipitation Normals for Las Vegas, NV. Las Vegas Online Entertainment Guide. http://www.lvol.com/lvoleg/hist/weather.html
17 “What is the Foehn? And how does it affect weather in the Alps?” weathertoski website.
18 “Föhn (foehn) wind.” Weather Online website. http://www.weatheronline.co.uk/reports/wxfacts/The-Foehn-foehn-wind.htm
19 “Santa Ana winds” article, Wikipedia.
20 “Chernozem” article, Wikipedia.
21 “Chernozem” definition, Google Dictionary.