Steps to identify a weed

by Stephanie Suesan Smith on May 4, 2011

One of the things I spend a lot of time doing every spring and summer is identifying weeds for people.  Now, a weed is just a plant that is growing where it is not wanted.  Sometimes, though, it has to go, and until you know what it is, you do not know how to get rid of it.

Eliminating weeds is important when growing vegetables.  Weeds take up nutrients the vegetables need as well as scarce water.  They shade your vegetables and sometimes produce soil toxins to keep the plants around them from growing so the weeds can steal all the nutrients available.  Finally, weeds such as nettle make harvesting your vegetables a misery.

Weeds in the garden are not usually shrubs or trees, and vines overlap several categories, so I am going to discuss the three most common categories of weeds and how to tell them apart.  In the days ahead, I will cover how to get rid of them so your garden has a chance to grow the plants you want it to grow.

To identify a weed, first try to find one that has flowers on it.  Pull the weed up roots and all if you want to remove it, or at least examine it from head to toe. Try to answer these questions.  You may not be able to answer them all, but each gives clues to finding the plants identity.

  • What do the leaves look like? How are they arranged on the stem?
  • What does the stem look like?
  • Is it woody or green and soft?
  • What do the flowers look like?
  • Is there one flower, or a cluster, or dozens?
  • What color are they?
  • Is there fruit, berries, or other seed pods?
  • What do they look like?  How many per plant?
  • What do the seeds look like?

Once you have all your data, you can classify the plant into one of three broad categories:

  • Grasses — this seems like a no brainer, but consider that grasses range from bamboo to bermuda grass, and that a popular “grass” is actually a broadleaf plant.  Grasses have hollow, jointed stems and long leaves with the vein running the length of the leaf.  Flowers are usually small and hard to see.
  • Broadleaf weeds –Saint Augustine “grass” is actually a broad leaf plant.  Most other weeds fit in this category, too.  They have showy flowers, leaves with veins that run throughout the plant, and the stems are often pithy.
  • Sedges and Nutgrass — the stems of sedges are triangular in shape and have leaves coming from all three sides.  These plants are hard to kill.

If all you want to do is kill it, that is generally close enough.  If you actually want to know what it is, now you begin to refine your search.  The National Agricultural Library, maintained by the United States Department of Agriculture,has a page of resources to help you identify plants.  Aggie Turfgrass has a nice section on identifying lawn weeds that will help you identify weeds in your garden, as well.

One thing that should be noted is that many herbicide products that are labeled for lawn use are not allowed in the vegetable garden.  Because you are going to eat the produce, the products have to meet a higher safety threshold to be used around your vegetable plants.  Always read and follow product labels before using.  You do not want to end up poisoning yourself and your family in an attempt to kill the weeds.

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Available in print or ebook from or other retailers, this book walks you from choosing the site of your garden all the way through what to do after the harvest. Buy a copy for yourself or a friend today!

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