View from the Plum Canyon area toward San Felipe Wash and High­way 78.

Driv­ing east along High­way 78 through wind­ing Sen­tenac Canyon, the view into Yaqui Flat sig­nals the last bend. A slow approach through these final turns is a good idea, as the heavy guard rail on the north edge of the nar­row high­way warns. Old road cuts can be seen slic­ing abrupt­ly across the right and left slopes of the mod­ern high­way, and just into the first straight­away is the wide Plum Canyon turnout with the road entrance to Plum Canyon at its east end.

Plum Canyon is usu­al­ly best between April and May of any year, as it’s low­est ele­va­tion at the high­way, around 1,700 feet, brings the wild­flow­ers and best hiking/camping tem­per­a­tures after March. Some of the cold­est tem­per­a­tures to be found in San Diego can be found here in mid­win­ter. Its high­er ele­va­tions (2,200′) can still mean cool­er tem­per­a­tures for fall vis­its by ten degrees, when it’s still in the 90’s in Bor­rego Valley.

The access to the canyon is imme­di­ate to the inter­pre­tive sta­tion at the far east end of the turnout which, inci­den­tal­ly, is part­ly carved from the old align­ment of the ear­li­er road used from Julian to Kane Springs, just west of the Salton Sea.  Peter and Paul Sen­tenac were area cat­tle­men who, once upon a time, used a nat­ur­al access up the west fork of the canyon for an eas­i­er pull of wag­ons and live­stock to get to the ver­dant grass­es at Scis­sors Cross­ing, eas­i­er at the time than the now High­way 78 which cuts through nar­row and boul­der-strewn Sen­tenac Canyon. Still, Sen­tenac Canyon was no pic­nic for high­way builders when its time came around 1915, as evi­denced by the derelict bridge that once spanned the nar­rows at about mid-canyon.  The canyon is the main trib­u­tary of waters shed­ding off the east slopes of Julian and Vol­can moun­tains; but far­ther east, as it becomes San Felipe Creek, this large vol­ume of water runs large­ly under­ground.  It can be a tor­rent in sum­mer thun­der­storms and in some win­ter storms, but is meek by the time it reach­es the flat desert. One of its wells, in the area of Bor­rego Moun­tain, was a life-saver for the Anza Expe­di­tion in 1775, about 20 miles down­stream from Plum Canyon.

Below: Cac­tus blooms seem quite com­pet­i­tive once the deci­sion is made by their inner clocks to pro­duce their col­or. And col­or is the name of the game. At near­ly the edge of the vis­i­ble spec­trum (and pos­si­bly leav­ing it) the plant can be seen sev­er­al hun­dred feet away. To an insect, pos­si­bly far­ther. After all, the bees and bee­tles must be able to find these “bea­cons of the desert” in the lim­it­ed time they have avail­able to gath­er food energy.