WEEDS, WEED PREVENTION AND WEED CONTROL

A few weeds in the garden are unsightly but of no real consequence. They are a problem in that they have the potential to take over and to out-compete the garden plants for moisture, nutrients, sun, and space. They are a particular problem in agriculture because weeds add so much to the expense of the farming operation. The presence of weeds interferes in the growing of a crop efficiently and the presence of weeds or weed seed devalues the finished product. 8 out of every 10 pounds of pesticide used by American farmers is a herbicide and the use of such huge quantities has a major impact on the environment.

This session is about weeds, their characteristics, and the various ways weeds can be prevented or controlled without the use of herbicides.

WEEDS

Gardeners know that the often heard definition of weeds as "plants growing out of place" misses the point. There are some super- vigorous plants that seem intent to take over and that once they become really established that they are nearly impossible to remove. They simply don't behave like other plants and it's more than just as issue of location. This segment is about that quality that makes a plant to be considered as a weed.

the nature of "weedness"

Mrs. Getty, one of the characters in Celia Thaxter's "An Island Garden", challenges the definition of weeds as "plants growing out of place" and says that the "essence of weed character is the innate disposition to GET into the wrong place" - she then adds, that this is also the character of men. " If you glance through your botanical books you will see often added to certain names, 'a troublesome weed'. It is not being venomous or ugly, but its being impertinent - thrusting itself where it has no business and hindering other people's business [that makes a plant into a weed]".

Hugh Johnson's "The Principles of Gardening" says, that weeds are " a race of super-plants of unfair vigour and tenacity".

The U.S. Bureau of Land Management, while not as poetic, defines weeds as "non-native plants that have adapted to a new area". Their thesis is that when these plants were growing in their native area, they were well behaved because they were held in check by the various indigenous organisms. Moving these plants to a different location then separated them from their natural control agents. In essence, saying that weeds are a problem BECAUSE they are out of place.

The New York Times cited an incident involving a "sea weed", native to the waters of the Pacific, that was accidently introduced into the Mediterranean, "Caulterpa taxiflora now occupies 8000 acres in the Mediterranean - and for the last three years, it has tripled annually." They then quote Antoni Grau, head of the Marine Resources in Mallorca, "Where this seaweed grows, everything else disappears. There are no more sea anemones, starfish, crabs, shrimp - and very few fish".

characteristics and control of annual weeds

Annual weeds are plants that grow from seed to adult plants that are able to produce seed within a single season. The adult plant dies after it has set the seed. Spotted spurge is an example of an annual weed. It grows aggressively in hot weather, sets huge quantities of seeds in Summer and early Fall, and then dies out in the Winter. The seeds germinate as it starts to warm up in early Spring.

This annual growth habit is the key to the control. Because annual weeds are going to die at season's end and because they only generate new plants from seed, you don't have to worry about getting all the bits and pieces in the weeding operation, you simply need to catch them before they have a chance to set seed.

characteristics and control of perennial weeds

Perennial weeds are plants that put on flowers and seeds from the same root structure in consecutive seasons. They spread by wind- blown seeds and by putting on new growth from buds on the roots. Dandelion is an example of a perennial weed. It grows from a deep, fleshy tap root, flowers in Spring and Fall, growth falls off in the Winter and then moves back into aggressive growth the following Spring. The cycle can go on for a number of years.

While catching perennial weeds before they have had a chance to set seed is helpful in preventing the spread, major control of perennials is by controlling the roots and this is a challenge. Any remaining bit or piece of bulb, tuber, stolon, crown or taproot of the perennial weeds carrying a single, growth bud is capable of generating a whole new plant. Getting the bulk of the perennial weed but leaving multiple pieces of the root system still in the soil can create an even greater and/or stronger weed presence.

Control perennial weeds in two stages:

  1. Cut off the top growth and dig up as much of the bulb, tuber, rhizome, stolon, crown or tap root as possible
  2. Let the remnant root structure pieces send up new growth and cut it off . . . the plant energy to generate new growth is stored in the root, continually cutting off new top growth eventually depletes the stored energy and eventually the root system dies.

WEED PREVENTION

It is infinitely easier and considerably more labor efficient to work at keeping weeds out of the garden than it is to work at their removal. The use of a clean, generous layer of compost or composted manure as a mulch is the single best way to keep weeds from happening. Black plastic landscape fabric, gravel, decorative bark also work as an effective mulch to keep weeds from happening but compost and composted manure offer the advantage of also being a source of organic material and nutrients for the garden. This particular segment is about the ways compost or composted manures used as a mulch keep weeds out of the garden, how these materials can be used, and the ways to avoid the problems associated with the use of compost or composted manure.

WEED CONTROL

Gardens Alive markets an organic herbicide that is derived from corn. (I have no personal experience with this material nor have I seen any reports on it's effectiveness) All of the commercial herbicides, including the product derived from corn, are prohibited for use on certified organic crops by the majority of the various certifying agencies. Herbicides, as a group, have a very poor environmental record and should be avoided.

ASSIGNED READING