Friday, January 11, 2013

Roundup—plant killer and soil feeder

Some might wonder why a Natural Gardener would use glyphosate salts, originally sold under the brand name Roundup and now available in a host of cheaper generic forms. 
“Natural” gardening is not “organic” gardening.  We aren’t concerned with not using artificial chemicals as much as we are with not interfering with natural processes that maintain ecosystem health.  An organic gardener may till the soil and leave it naked; the natural gardener avoids tilling and keeps soil covered with mulch.  An organic gardener may use “natural” plant-based pesticides like pyrethrins or nicotine that kill indiscriminately; a natural gardener will use only pesticides that target a single type of pest, preserving predators and keeping in mind the danger of building resistance in the target.
Gardening is mostly killing plants.  Glyphosate is a plant killer that is safe for people and most animal life; insects are in far greater danger from the surfactant added to help it stick than from the active ingredient.  It is also less of a danger to nearby plants than other herbicides, as it must be sprayed on a green surface of a growing plant to have any effect on it.  It does not penetrate brown bark.  It does not travel through soil or persist for long; it sticks to soil particles and is eaten by microbes in three days to a week or so, depending on temperature.
If a plant has a lot of food stored in its roots, glyphosate will not kill it with a single spray; it takes two sprays in a growing season to kill blackberries and dandelions.  If a large bush or tree catches a little spray on a branch, the branch may be affected but the rest may not show any damage.  Glyphosate damage shows up in yellow new growth that is often dwarfed; it also cause “witch’s broom” growth of twigs.
The downside of glyphosate is that it is also a powerful fertilizer, being an amino acid, glycene, with a phosphate group attached.  Animals kick that weird amino acid out of their bodies; plants try to fit it into their proteins as they grow, and the proteins don’t work.  Amino acids are full of nitrogen, so it becomes high nitrogen and phosphate fertilizer as it breaks down.  It should be used sparingly, but frequently enough to prevent flowering and seeding.  If sprayed in flower, many weeds can ripen seeds before they die.
Unlike chemical fertilizers and like organic fertilizers, it feeds soil microbes first.  Worms and pill bugs consume the soil and dead plants to which the microbes are attached.  Moles follow, eating the worms.  Spraying a large area is like a dinner bell to moles.
             Pill bugs eat dead leaves and seedlings.  When they are done eating and multiplying on dead, enriched vegetation, they proceed to the only food available; your seedlings.  Until their population crashes, it can be impossible to grow much of anything from seed in an area treated with glyphosate and then mulched with compost, wood, and bark, which pill bugs don’t eat.  But they love carrot seedlings; planting a lot of carrot seed can distract them from other seedlings long enough for your preferred plants to grow out of danger.

Published at under The Natural Gardener #9.

1 comment:

  1. I use very little glyphosate these days; the fertilizing effect is too powerful. But when a place is completely out of control, it can be used to gain the upper hand.

    Also, it is useless try to kill annuals in cool weather, as they immediately go to seed, no matter how young. One ends up with much the same seed load from a lot of little plants rather than fewer big ones that are far easier to pull. Plus, you've fertilized the next crop of weeds.