We all look forward to spring to get back outdoors to our gardens and landscapes. As I watch everything green up, I realize that the seasons of weeds have begun again. Two weeks ago, I cleaned out a flower bed removing the old growth and blown-in leaves as well as digging up grass that had invaded the bed since last fall. Now, just a couple of weeks later I’m seeing that same grass resprouting and it’s time to dig it up again. If only a bed would stay clean until I finished cleaning up the rest of the acre, but no, that’s not how weeds work. Could I apply an herbicide instead? Personally, I prefer not to apply herbicides for environmental reasons. But if I did use them, first, I would have to avoid all broad spectrum non-selective herbicides which kill or damage most plants they come in contact with, whether desirables or weeds. While there are herbicides specific for killing grasses, they also kill other monocots such as irises, daffodils, tulips, crocuses, hyacinths and chives which make up the bed I was weeding. Plants are divided into monocotyledons (monocots) and dicotyledons (dicots) based on having a seed embryo with a single or a double cotyledon, type of venation and arrangement of floral organs. What allows an herbicide to be selective is whether it is meant to control monocots or dicots. Grasses are monocots. Dandelions, for example, are dicots. Spraying without killing my flowers would be challenging. Some broad spectrum, non-selective herbicides are systemic and translocated while others are contact sprays. The active ingredient glyphosate in products such as Roundup, Spectracide Weed and Grass Killer and Ortho GroundClear Super Weed and Grass Killer, among many other products is applied to an actively growing plant where it is absorbed (systemic) through any green tissue such as leaves, stems, or even the green tissue of newly cut stems or suckers. It then moves (translocated) via the plant’s vascular system throughout the plant, which then, in an ideal chemical world, succumbs to the toxic active ingredient. Although in theory, broad spectrum herbicides are non-selective. There are always plants which are resistant and are not affected by the chemical. It is critical to read labels to see if the weeds you are trying to manage are listed as susceptible. Otherwise, you contaminate soil, other plants and possibly waterways and drainages with an ineffective and expensive application of unnecessary chemical. For excellent information on how to manage weeds safely, see University of California Davis’s “Weed Control Using Herbicides” ipm.ucanr.edu/QT/weedcontrolcard.html
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