Controlling Weeds

Perhaps the biggest challenge with gardening is weed control.  There is no way to garden completely weed free, but there are methods and ways to control or manage weeds.

What is a weed?

Each area of the country seems to have specific weeds that are a constant struggle. Here in New Harmony, Utah white top and morning glory are some of our biggest challenges but there are many others.   

To help develop a strategy you must first understand your enemies. I have heard people say that a plant out of place is a weed so a tomato in a flower bed would be a weed.  

I disagree with that definition.  Weeds have specific characteristic that make them a consistent reoccurring problem in cultivation practices.  Weeds have short life cycles but in that time are prolific reproducers.  The can have more than one seed cycle and can propagate vegetatively as well.  Their abundant seeds can remain dormant in soils for years. All these factors make weeds a challenge for any type of gardening.

Annual Weeds

Annual weeds spread through your garden by seed.  The seeds can be brought into your garden from animals, birds, or even by sticking to your shoes and clothes.

Examples of annual weeds include crabgrass, lambs quarter, pigweed, spurge, purple dead nettle and bur buttercup.

There are cool season and warm season annual weeds.  Cool season weeds will make their appearance in early spring, disappear in warmer weather, but may return in the fall.

Warm season annual weeds will emerge and remain throughout the growing season.

Bur Buttercup which is toxic to livestock

Perrienial Weeds

These culprits are by far the hardest to eradicate.  They spread by seeds and through aggressive vegetative structures such as stolons and rhizomes.  Stolons and rhizomes are underground and have buds that produce new plants which is why tilling does not kill these weeds.

Examples include bindweed, white top, quack grass, and thistle.

There are two prime times to apply herbicides to perennial weeds.

  1.  The first critical time is spring before flowers open.  At this time root reserves are depleted so the plant is sending sugars from the leaves down to the roots.  The herbicides will move with the sugars down to the roots.  
2.  Another critical time is in the fall when the plant is moving sugars down to the roots for storage for the winter.  Perennials are least susceptible to herbicides after flowering and during seed development.

Redstem Filaree or Cransebill

Plan of Attack

Discouraged?  Don't be.  Let's talk strategies for managing weeds.  

1. Prevention

• Be sure vegetable, flower, and woody plants you bring into your garden are weed free
• Clean your tools.  If you use a shovel outside the garden area be sure to clean it before using it in your garden
• Use weed free mulch and compost.  Often homemade compost does not reach high enough temperatures to kill weed seed.  I would use bagged compost in garden beds and in greenhouse.  Save homemade compost for fruit trees and large field gardens.
• Mowing unmaintained areas to prevent weeds from going to seed will help.  In my large field garden we till every couple weeks a path around the garden and mow from that path on out. You can mow around the outside of greenhouses and your garden
• Keep garden paths weeded.  I have found this is easier if you put down a heavy duty weed cloth and cover it with a synthetic bark.  If that is not feasible use a hula hoe every week to weed the paths.  
• Disturbing the soil is as good as planting weed seed.  Do not disturb an area you are not going to use.  You can mow the area but do not till.
• Regularly monitor for weeds

Mullien

2. Mechanic Control

• Striking at the right time!  Weeding is import the first 6 weeks of spring to control early annuals and perennials.  The first 6 weeks of summer are also a vital time to weed to get emerging warm annuals.
• Hoe when dry: hand pull when wet.  Hoe when the soil is dry especially in paths the sun will then shrivel up the exposed roots.  If you hoe when its wet the weeds can and will reroot.  Hand pull weeds in garden beds and rows when the soil is wet so you can get all the roots.
• "One years seeding mean seven years weeding"  Do not allow weeds to flower and seed.  If you have neglected weeding attack those ready to flower and already flowering.
• Mulch, mulch, & mulch  after you weed an area cover it with at least 2" of mulch
• Lop off their heads.  Cutting off the flower heads of weeds you can't pull will buy you time.  This is also helpful with hard weeds like bindweed (morning glory).  Consistently pulling any bindweed prevents reseeding and forces the plant to use up food reserves in the roots.
• Flaming small emerging weeds is very effective.  In preparing a garden in open ground you can till or work in your compost, wait two or three weeks and flame any emerging weeds.  Be sure to plan ahead so you aren't late planting
• Weed whacking 
• Brush mower 

Dandelion

3.  Pre-Emergent Weed Controls

• Products containing corn gluten prevent germination of seeds
• I use a pre-emergent on my lawn to control dandelions.  Apply it in a broadcast spreader when the forsythia blooms because this is when seed will start to germinate
• Pre-emergents weed control does not kill existing weeds.

4.  Herbicides

• Herbicides are designed to kills plants.  They can be non-selective meaning they will kill all vegetation.  There are also selective herbicides.  These herbicides are divided into 2
  groups broad leaf  or grass selective.  Broadleaf herbicides kill broadleaf weeds while grasses are unharmed. Grass selective does the opposite.
• The growth stage of a plant will affect the performance of all herbicides.  Seedlings are more susceptible to herbicides than mature weeds that are not actively growing but instead focusing energy on seed production.   Most weeds are less susceptible to herbicides after flowering
• Organic herbicides are non-selective and kill or damage all plants.  I use one that contains clove and d-limenol oil.  On my roads and fence lines I use an agricultural 30% strength vinegar. (Burn out herbicide certified for organic use)
• Herbicides in my experience need to be used while weeds are small and in some cases repeatedly

Here's a link to USU Landscape and Garden Weed Identification Guide:

Common Weeds of the Yard and Garden

White Top