Thursday, February 18, 2010

When Chemical Herbicides are Justified

The ideal hard and fast rule would be no chemicals never, no how, no way. Yet such an uncompromising rule is just not always practical. There are two situations where I feel that herbicides are worth the poison that they introduce to the environment.
When a natural garden is being planted where a turf grass lawn now exists, there are a number of ways to 'prepare the bed' for the new native plants. One is to dig up the sod with a sod cutter. If you are going to carry the sod away, off your property, this is a horrible idea. Top soil is a precious resource so why would you give it away? If you have somewhere to compost the sod on your property, this is a fast way to prepare the bed, but should never be used if the sod is going to be hauled off property.
The ideal way to prepare the bed is to cover the turf grass with waste paper such as newspaper, then cover that with mulch and wait several months for the paper to soften and decompose. Then you can move away the mulch, plant the garden, and redistribute the mulch. This is the most environmentally friendly way to plant into turf grass.
However, in many cases, we do not have the luxury of leaving a mulched bed unplanted for so long. A garden on a commercial property or park or church or even in a residential front yard are areas where such a method might cause complaints. In these cases, spraying the turf area with a glysophate herbicide will kill the grass all the way to the roots. When the grass is dead, which takes about 10 days to 2 weeks, you can plant directly into the dead turf, then mulch over it when the planting is complete. The dead turf biodegrades to improve the soil and the dead roots keep the soil stabilized while the new plants fill in.
The other situation where herbicide use is mare valuable than the harm it does is in natural landscaping maintenance to keep invasive woodies out. In a woodland garden, undesired tree and shrub (woody) species such as boxelder, buckthorn, Norway maple, burning bush, and honeysuckle may seed in, threatening to overtake the native trees and shrubs and wildflowers. In a prairie, any woody plant is probably undesired, including those above as well as mulberries, multifora rose, even walnuts or sumac. In these situations, the maintenance burns will keep most of the woodies out, but if you cannot burn or do not burn often enough, you will need to remove them by hand. Once the woody is cut to the ground with a lopper or hand pruner, that stump will resprout, often with several shoots. You can recut them year after year for a number of years before the roots will be starved and the plant finally killed. Or you can spray a tiny amount of an undiluted glysophate herbicide directly onto the cut surface and prevent most resprouting. The labor saved by this careful and minimal herbicide use can mean the difference between a manageable natural landscape and one that ends up abandoned back to traditional landscaping. This is especially true in an area such as a restoration or park or church where precious volunteer labor is being used to keep the woody weeds out. Of course, responsible decisions about use must be made. The glysophate herbicides need a few hours of dry weather to soak in and a few hours of sunlight to be broken down into harmless substances, so never use them just before a rain is predicted, and do use them when sunlight is predicted. Store them carefully to prevent spillage and waste, wear rubber gloves when handling, use with care to prevent spillage on site, wash hands and gloves and bottles in appropriate places, and dispose of gloves and bottles responsibly.

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