Ask A Master Gardener – Summer Days & Weed Control

Authored by Carol Shirk

Summer has arrived and we are enjoying the best of it.  The sun is shining, ample rain has fallen, grass is growing, flowers are blooming, and unfortunately, weeds are popping.  The idea of putting in a garden, planting seeds, transplanting tender seedlings, and then setting back to enjoy the fruits of your labor is a great idea, but gardening requires maintenance.  So, let’s talk weeds.

Dealing with weeds does not need to be labor intensive, expensive, nor fraught with mind-bending chemical application.  Weeds fall into several broad categories: annual and perennial; and monocot and dicot.  Each category has rogues that cause trouble and make life challenging, but for the most part weeds can be easily handled.  However, it is important to know what category the weed falls into when considering how to control it.

By definition, a weed is a plant out of place.  To one person a dandelion is a weed.  To another, it is an early pollinator plant for bees.  Weeds compete with desirable plants for nutrition, sun, water, and space.  They are also prolific seed producers, and if not kept in check will dominate the area.  They lack aesthetic appeal, can be toxic, can survive in harsh environments, and their seeds can lay dormant for years.

Annual weeds complete their life cycle in one year and reproduce primarily from seeds.  Examples include:  lamb’s quarter, velvet leaf, pigweed, and giant foxtail.  Biennials need two years to complete their life cycle and include Queen Anne’s lace and bull thistle.  Perennial weeds like dandelion, quack grass, and Canada thistle, live for two years or longer.  They reproduce either by seed or by vegetative growth.

Monocot weeds are grass-like and can be either annual or perennial.  Crab grass is an annual monocot while quack grass is a perennial monocot.  Dicot weeds are broadleaf and can also be annual or perennial.  Creeping Charlie is a perennial broadleaf while common and giant ragweed are annual dicots.

There are three ways to control weeds: culturally, mechanically, and chemically.  Rather than make chemicals your go-to method, try the other two methods first.

Culturally practices include keeping your turf healthy and dense to prevent weeds from getting started.  Mowing at the proper height will go a long way to keeping your grass healthy.  In landscape beds, keep your plants healthy and planted closely enough to shade out competing weeds.  Use mulch in landscape and vegetable gardens to smother weeds and prevent invading weed seeds from germinating.

Mechanical weed control includes simply removing the weeds by hand.  Sever annual weeds at ground level with a hoe.  However, perennial weeds need to be pulled out by the root to prevent them from returning.

If cultural and mechanical methods have failed you—or if you have a particularly persistent weed—use chemical means.  However, it is important to know the classification of the weed.  Pre-emergent herbicides are applied to the soil before seeds germinate.  They are used on annual grass and broadleaf weeds, but will not kill already emerged weeds.

Post-emergent targeted (or selective) herbicides will kill either broadleaf weeds or grasses, depending on the product.  Read the label carefully.  The danger is that there may be some drift and they may also kill a non-target plant.  Post-emergent non-selective herbicides will kill everything they contact.  Again, drift can be a problem with unintended consequences.

Finally, with any chemical usage, read and follow label directions carefully and use proper personal protection equipment.


Carol Shirk

Certified Master Gardener

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