On Gardening: Lightning

By Shirley Barker
Thursday January 28, 2010 - 08:35:00 AM

By Shirley Barker 


Seldom do we in Berkeley wake to the flash and rumble of lightning followed shortly after by a cloudburst. This year we seem to have received more lightning strikes than usual, and rainfall by the end of January exceeded average amounts, with two potentially wetter months ahead. 

In other words, we are right on track for our two-season climate of summer dry, winter wet. 

Gardeners who grow vegetables know that rain leaches nitrogen from the soil and take care to replace this necessary nutrient with compost and manure. There is little we can do toward replenishing nitrogen in this way when paths are too soggy to be trodden. Instead, now is the time, between breaks in the weather, to cover planting areas lightly with a porous mulch such as hay, which will protect the soil and, as it breaks down, nourish it with nitrogen as well as improve its texture—its tilth. 

If the area selected for planting (which means sunny, for vegetables) is choked with crabgrass or oxalis, it can be so thickly mulched that by April, such pesky intruders will have disappeared, and the ground will be in just the right condition to receive plants of choice. The same is true for heavy clay soils. The rain will work layers of mulch into it, slowly transforming the clay particles into a plantable tilth. 

Other sources of nitrogen are green cover crops sown in fall and dug under in spring, a sensible idea if one had thought of it at the time, and the growing of legumes, which capture nitrogen from the air by means of pearly nodules on their roots, visible on sturdy kinds such as fava beans. 

All these strategies are well known to the most novice gardener. Less well known is the role that lightning plays in adding nitrogen to the ground. Combined with rain, it is a good example of how nature thinks of everything. Indeed, it is lightning’s ability to engender usable nitrogen that captures the imagination. It is disappointing to find in Rodale’s Encyclopedia of Organic Gardening no mention of lightning’s contribution to plant nutrition. Their term “nature’s bad actor” may carry weight in view of lightning’s capacity to destroy buildings. All catastrophes, as we can so painfully see in Haiti and Pacifica, are largely based on our inability to build our shelters with such materials as to minimize body damage caused by extreme natural forces that at the same time give protection on a daily basis. 

In contrast, the nitrogen cycle is well illustrated in Robert Christopherson’s Elemental Geosystems. Here, lightning is depicted not just as an actor in this cycle, it is the star performer. Our planet’s atmosphere, composed largely of the “essential reservoir” of nitrogen, enjoys 8 million lightning displays a day. The bacteria in those fava bean nodules are hard at work grasping this nitrogen from the air. How lightning is formed is not yet fully understood; this for me adds to its awesome power. An entry in Wikipedia describes our awe, our fear, as “irrational” and gives this fear a name, astraphobia. Naming this fear does nothing to lessen it, for it is in fact entirely rational. Lightning strikes without discrimination, and if we get in its way we will be killed. 

Thunder, describes Christopherson, is simply the consequence of abruptly heated air, caused by electrical discharges, displaying the flashes that we call lightning, in temperatures ranging from 27,000 to 54.000 degrees Fahrenheit. The violent expansion of this superheated air creates the sonic bangs of thunder. The energy from such high temperatures is more than enough to form ozone from oxygen which immediately reacts with atmospheric nitrogen. After other chemical processes, ultimately and in the presence of rain this leads to forms of nitrogen in the soil that most plants can use. 

If we continue to dismiss such powerful displays of force by nature, we can expect more human catastrophes. Perhaps our forebears had a keener recognition of our vulnerability. The thunderbolt was and is used as an appropriate symbol of power over life and death. Zeus was fond of throwing his thunderbolt at people (or fellow gods) who irritated him. Thor was known as the Thunderer. Today, the beautiful cast-bronze vajra is an important and significant feature in Tibetan Buddhism. Echoes of this thunderbolt can be seen in royal scepters. 

Although it would be more accurate to call these lightning bolts, it is enough to know in this miserable weather that, thanks to our climate pattern, it will not last, that our precious reservoirs are filling, and that our fields and gardens will be naturally fertilized.