Marin Master Gardeners
University of California
Marin Master Gardeners

Managing Weeds

dandelion
Problems With Weeds

  • Nuisance
  • Detract from the overall appearance of the garden
  • Rob the soil of precious water and nutrients
  • Serve as hosts for insect pests and pathogens
  • Provide cover for rodents
  • Allergens to many people (think hay fever or poison oak)

What is a Weed

Weeds, simply put, are plants growing where they aren’t wanted. Almost any plant – from grasses to trees to shrubs, under the right conditions, can be considered a weed. They come in a myriad of shapes, colors, sizes, and degrees of tenacity...some are pretty easy to control, while others, like bindweed, seem to withstand and almost thrive on significant abuse. Common weeds (both grasses and broadleaf plants) that plague our gardens are annuals like bluegrass, crabgrass, mallows, purslane and spotted surge, and perennial types – bermudagrass, bindweed, dandelions, nutsedge and oxalis. 

Weed Management

An overall weed management program involves preventive and removal methods. Preventing weeds from sprouting will make your life a whole lot simpler, especially given how prolific some types are in producing seeds. Purslane, for example, can generate over fifty thousand seeds from one plant! Prevention generally focuses on some type of weed suppression through garden design, habitat modification or horticultural controls. 

Weed Prevention

  • A designed part of your garden with no water or soil (driveways, paths, patios) would eliminate the elements necessary for the plant to grow
  • Reducing the available water (using drip irrigation)
  • Reducing sunlight (adding mulch) would make life difficult for weeds to germinate and sustain growth
  • Crowding of plants to reduce the available space for weeds to grow, or planting types that have some level of inhibition for seed germination

Removal Methods

  • Hand pulling or hoeing
  • Heat, in the form of soil solarization, is also an effective eradicant, especially when planting a new bed. Clear plastic sheeting placed over the area to be treated for a period of four to six weeks during the warm summer months can kill both existing weeds and their seeds.
  • Chemical treatment is a last resort as it requires an understanding of the lifecycle of the weeds to be eliminated, soil characteristics, weather and location as well as the multitude of product choices - pre-or post emergent, contact or systemic, selective or non-selective, and the pros and cons of each type. No single product will do the entire job of controlling all weeds.

Caution

Safety should always be a priority when using an herbicide, both for people, pets and other garden creatures as well as other plants. Many ornamental plants are extraordinarily sensitive to broad-leaf weed killers and even the slightest amount of drift can cause stunted, twisted, cupped, curled, chlorotic foliage and even death to your plants. Damage from the popular non-selective herbicide glyphosate (Roundup) is commonly mistaken for disease or insect damage, and symptoms may not appear until the season following accidental exposure.

For more information on weed management, click here.

Adapted from article by Nanette Londeree, Marin Master Gardener
Photo courtesy UC IPM website.

Webmaster Email: banielsen@ucanr.edu