Weeds

Every garden will have its weeds.  They can be a nuisance and compete with desirable crops.  They can turn a beautiful garden into an unsightly mess, creating a headache for years to come.  Even though weeds have the admirable qualities of being strong and tenacious, they are not welcome in many landscapes.  With a little information and prevention, you can be more successful than your weeds!

 

Cultural Controls, or changing the garden to make it less hospitable for weeds.

  • Weeding—Catch them when they are small!  Done early and often, either by hand or with a hoe, cutting down weeds will help keep their numbers down.
  • Bed Planting—A high density of plants will out-compete and out-shade weeds.  Also, once a bed is established, there is less digging and turning over of the soil, and therefore less weeds.
  • Transplants—Using a transplant start instead of planting seeds gives them a head start against germinating weed seeds and will out-compete many weeds.
  • Mulches—If used effectively mulches reduce weeds significantly.  When bare soil is covered, many weed seeds won’t germinate or can’t grow through mulch.  Place mulch twice a year, in the fall and spring.
  • Water Management—When water is directed only to desired plants, such as with drip irrigation, much of the garden stays dry and weeds have a harder time germinating.
  • Competitive Planting—Eliminate bare areas under trees and shrubs by planting them with groundcovers or herbaceous perennials.
  • Cover Crops—Grown in winter on annual or vegetable beds, the cover crop smothers many winter weeds, and often returns nutrients to the soil.
  • Weed Barrier Landscape Fabric—Prevents weeds from growing, yet allows water through.

 

Chemical Controls  are herbicides that kill or alter the normal growth of weeds.

Always read all instruction before using any chemical product!

  • Selective Herbicide—these affect only certain plants and not others.  For example, most lawn herbicides kill broadleaf plants such as dandelions without damaging the grass.
  • Non-selective Herbicide—these can damage any type of plant.  Some last a long time, others do not.  Examples are Round-Up and Citric Acid.
  • Systemic Herbicide—these are absorbed throughout the entire plant, traveling from roots to stem and vice versa.  An example is Roundup.
  • Non Systemic Herbicide—these are contact herbicides and affect only the part of the plant they touch.  One example is citric acid or vinegar.
  • Pre-Emergent Herbicide—these stop weed seeds from germinating when applied before the weeds sprout.  Corn gluten is an example.
  • Post-Emergent Herbicide—these are used to kill weeds after they have sprouted.

 

Herbicides can be influenced by several factors.  The type of leaf (a smooth leaf will absorb more herbicide than a hairy leaf), temperature, wind drift and moisture or rainfall.  Always read and follow the directions on the label!

 

Some common Herbicides

Organic—Naturally derived such as corn gluten or citric acid.

  • Blackberry Brush Block is a non-selective citric acid herbicide.  It suppresses undesirable woody plants.  Spray directly on new foliage in early spring and drench soil to seep down to the root system.  It will lower the pH of the soil and cause the taproots to dry up.  Use for blackberries, scotch broom, horsetail, dandelions, deep-rooted weeds, star thistle, morning glory, bindweed, grasses and more.
  • Dr. Earth Final Stop Weed and Grass Killer is a non-selective herbicide, killing grasses and broadleaf weeds.  It contains citric acid as well as cinnamon, clove and soybean oils.
  • Concern Weed Prevention Plus—A pre-emergent non-selective herbicide with corn gluten as well as a slow release fertilizer.
  • Corn Gluten inhibits the growth of seeds and causes weed seedlings to die.  It poses no health risks to people or animals, but does take time to get established as an effective weed c0ntrol.  If used regularly, by the fourth year weed control will be very good.  It also fertilizes the lawn.  It has a short window of effectiveness, apply twice a year, in early spring and early fall.  Do not apply if rain is in the forecast.  After initial watering, it is more effective followed by a dry spell.Not for grass that has been recently seeded, but can be applied after the first mowing.
  • Burn-Out—Citric acid herbicide.

 

Synthetic—Synthetically produced such as Roundup.

  • Bonide Weed Beater complete
  • Bonide Weed Beater Ultra—Performs in both warm and cool weather
  • Kleen-up Grass and Weed Killer—The  primary component of this is glyphosate, similar to Roundup.  Good to use as a spot treatment along sidewalks, fences, driveways and patios.  It kills tough weeds in 1-2 weeks, roots and all.

 

A Special Mention of Horsetail

Resources

Sustainable Gardening, The Oregon-Washington Master Gardener Handbook.  OregonState University.2008

http://www.kingcounty.gov/environment/animalsand plants/noxious-weeds

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