I am sometimes shown a plant and asked, “Is this a weed?” The answer depends on your perspective.
A weed is just a plant that we do not want growing where it is. It is out of place, useless, harmful or unattractive and undesirable where it is. Some plants are almost always weeds — like crabgrass and nut sedge. No one wants crabgrass or nut sedge in their lawn.
However, these two plants can make good wildlife food. The hunter or birder would perhaps like to have this in the field behind their house. It all depends on where the plant is located.
Even good plants can become weeds. Bermuda grass makes a great lawn, but once it grows into the flower bed – it’s a weed. It may be only a few inches between your lawn and your flower bed. The difference of a few inches in where a plant is located can make the difference between it being a weed or a “good plant.”
What about this small weed with the seeds on the bottom of the leaves? This plant is called niruri, chamberbitter or Phyllanthus. There are two types. One has smaller leaflets than the other. They look like little mimosa trees with compound leaves and lots of little leaflets. The seeds grow directly on the bottom of the leaves.
This weed is small, but hard to control. The seeds require light to germinate. Keep a thick mulch around your plants so the seed will not come up. If the niruri is still coming up in mulched beds, the mulch may be too thin or not evenly spread. Sunlight is somehow getting to the soil. Make sure the mulch is evenly spread and is 2-4 inches deep.
Once it comes up in a bed, pull it up or spray it with Round Up. Keep Round Up off all desirable plants and do not soak the soil with the chemical.
In the lawn, the best weed control is a healthy lawn. Find out what kind of grass you have and care for it properly. Every lawn grass has its own specific care requirements.
If chamberbitter is a problem in the lawn, you can use one or both of these two approaches. Prevent niruri with applications of atrazine in mid-February and again 45 days later. The latter application will be important in late season weed control. Do not use atrazine on green Bermuda lawns.
Once the weed comes up, use Weed Be Gon, 33 Plus, Trimec or other similar herbicide mixes to kill it. It may take more than one application. Read and follow all label directions when using any pesticide.
“Can I still kill poison ivy and kudzu now?” you ask. There are several perennial plants that can be weeds. These include kudzu, poison ivy, bamboo, wisteria and several of the trees. The term perennial means that the plant lives year to year and does not have to be replanted.
Perennials store food in their roots, trunk and stems. This is what they use to begin growth the next year. This makes them very hard to control because any method we use must deal with this stored energy and ability to re-grow.
Typically I recommend cutting the plant off as low as possible. To slow re-growth, you can paint the freshly cut stump with an herbicide like Brush Be Gon or Round Up. Contact us for specific details on mixing the herbicide for this special use. You can also spray the top of the plant to kill it. For woody plants we often use Brush Be Gon.
No matter the method you use to control the weed, the key is persistence. You must re-treat the weed whenever it re-grows. Check it every four weeks and re-cut or retreat the weed. Keep doing this and you should finally kill the plant. Be patient. This may take years.
To kill crabgrass in a lawn, use Poast, Vantage or other chemicals that also contain sethoxydim on centipede lawns. Use MSMS on Bermuda and zoysia lawns. Do not use these on lawns that are not listed on the label.
For more information, call the Bryan County Extension Office at 912-653-2231 or email us at firstname.lastname@example.org.