By Mike Donahue

Moapa Valley Progress

We Southern Nevada gardeners are often overwhelmed with all the nitpicking details to which we’re required to pay attention in order to successfully produce healthy plants whether for eating, smelling, sitting under or what have you. (Most often it’s a combination, but who’s counting?)

All gardeners have a check list of important considerations that include, briefly, soil, water, amendments, fertilizers, insects, plant variety and species, mulch, compost, and on and on. The list is really endless and it seems there’s always something else cropping up to which we have to pay particular attention in order to keep our plants growing, thriving and producing.

Climate is probably one of the top two or three concerns for gardeners. Like the weather, according to Mark Twain, it’s something everyone talks about but no one does much about it.

While there’s little we can do to significantly alter our climate, the U.S Department of Agriculture (USDA) has made it extremely easy for us to determine, first, just exactly what our climate is and, second, what plants will do best where we live.

For the first time in decades, the USDA has issued a new plant hardiness zone map that provides gardeners with a standard by which they can determine precisely which crops are most likely to do well at a given location – like Moapa Valley.

The new map, which can be found on the USDA website, uses 30 years of weather data to describe and identify individual climate zones in the U.S. It lists average minimum temperatures for each of the different latitudinal zones with each zone based on 10 degrees Fahrenheit.

Although it’s no real surprise to us gardeners, the new hardiness zone map has revealed there has been a gradual northward warming trend in general across the country, although the USDA refuses to label that trend “global warming or climate change.”

“Climate changes are usually based on trends in overall average temperatures recorded over 50-100 years,” according to the USDA website. “Because the (new map) represents 30-year averages of what are essentially extreme weather events (the coldest temperature of the year), changes in zones are not reliable evidence of whether there has been global warming.”

Essentially, the warming trend means some areas are able to sustain plants that would have struggled before because of a cooler climate. And yes, a couple of degrees can make a huge difference to some plants.

Additionally, the USDA has added two new zones to the map in hotter climates this year. There are now a total of 13 zones with zone 1 being the coldest (-60 to -50) and zone 13 being warmest (60 to70) and is found only on Hawaii and Puerto Rico.

Nevada’s zones range from 4 in the north (-30 to -25) to zone 10 in the extreme south and near the entrance to Death Valley (30 to 35). Moapa Valley, which did not change, is in zone 9 (20 to 30). Our area is further broken down into two subzones including 9a in the upper valley (20 to 25) and 9b in the lower valley (25 to 30).

“Across the country, people will be seeing where there are some changes,” according to undersecretary of Agriculture Catherine Woteki. “There is some shifting in zones, but this we attribute to using new average minimum temperatures.”

For the first time, the USDA information is available as an interactive GIS-based map, for which a broadband Internet connection is recommended, and as static images for those with slower Internet access. Users may also simply type in a ZIP Code and find the hardiness zone for their area.

No posters of the USDA Plant Hardiness Zone Map have been printed. But state, regional, and national images of the map can be downloaded and printed in a variety of sizes and resolutions. The map can be accessed at http://planthardiness.ars.usda.gov/PHZMWeb/# where you enter the zip code of the area to see.

Comments and suggestions for the Garden Spot are always welcome. It appears the first and third Wednesday’s of the month. Email ideas, observations or questions to mouse@mvdsl.com.