Tag Archives: Insolation

Latitude and Energy: A Beginning Point

45º!  In my previous post I suggest, for reasons of solar gain and intensity, that we gardeners might have better luck choosing plants for our gardens if we chose them from our own latitude, north and south.  The intensity of the sun’s radiation varies with latitude, decreasing as we move away from the equator toward the poles.  Like all horticultural suggestions you should take this with a grain of salt…er, soil.  Follow that line around the Earth from Portland and you can run into a lot of difficulty.  Spin a globe and take a look.  Following the 45 parallel east takes us along the Columbia Gorge, across the Blue Mountains, Hell’s Canyon, the resort town of McCall, Idaho, elevation one mile, the Frank Church River of No Return Wilderness and more of the Rockies, on across the northern Plains, through South Dakota, Minnesota, Michigan, our ‘frozen heartland’ and east through New York and just outside Portland, Maine.  These are highly varied landscapes with conditions almost always colder, different rain patterns, more extreme weather conditions than ours with corresponding plant communities.  In Europe 45º passes through northern Provence, with weather strongly influenced by the adjacent Mediterranean Sea and the massive Sahara Desert that lies beyond, the Piedmont region of Italy, Croatia, the Black Sea, the Steppe country including Uzbekistan, into northern mountainous China and southern Mongolia and finally, the Japanese island of Hokkaido, its capital, Sapporo, a couple degrees south, with its remarkable annual ice festival. 

The list of landmarks found along the southern 45th is very short, as the vast majority of its length is defined by open ocean.  Still it crosses New Zealand’s South Island, only again making landfall in the south of Argentina where it narrows down toward the continent’s southern tip and the Chonos Archipelago of small Chilean islands comprised of submerged mountain tops.  On the later the landscape is dominated by compact cushion plants.  These few places have strong maritime influences and are much effected by the unimpeded weather sweeping off of Antarctica.  Much of this sounds limited and extreme when I think of plants adapted for our region. Continue reading