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How to Keep Weeds Out of Sweet Corn [5 Best Tips]

Sweet corn is a delicious crop, and nothing makes your backyard garden feel more like your own private farm than a corn patch. The biggest threat to your corn are invasive weeds. Weeds compete with corn for nitrogen and moisture, significantly reducing your sweet corn sprout survival rate and your eventual harvest. You’ve got to tackle the weeds to get the most out of your corn.

To keep weeds out of sweet corn, first, prepare your corn patch prior to planting. Either spray a non-selective weed killer or cover the area with black plastic to kill all existing weeds. Additionally, you can use a pre-emergent weed killer to stop weeds from sprouting. After planting, employ a selective weed killer and carefully spray weeds to keep your corn patch weed-free until your corn matures.

How to keep weeds out of sweet corn

5 Tips for Sweet Corn Weed Control

Use Non-Selective Weed Killer Before Planting

Because corn is a warm weather loving plant that dies in fall and requires warm soil to sprout in spring, corn patches are often overgrown with weeds and invasive grasses in fall, winter, or early spring. A weedy patch of ground must be prepared before planting corn if you want your plants to thrive.

The best option for complete weed control is a Glyphosate-based weed killer (such as RoundUp). It kills weeds and grasses down to the roots and washes out of the soil quickly. If you prefer all-natural weed control, a vinegar-based weed killer can be used. Perform the following steps:

  • 3–4 weeks before planting corn, spray the entire corn patch with your weed killer of choice.
  • Wait 1 week for weeds to die.
  • Rake away dead weeds.
  • For 1–2 weeks, water your corn patch as you would during the growing season. If any new weeds come up, repeat weed killer application.
  • If you till your soil after the first weed killer application, be especially vigilant, as tilling will bring additional weed seeds to the surface and may cause a new infestation. Plan to apply more weed killer 1–2 weeks after tilling.
  • Once weeds are eradicated, plant corn. As long as you plant 1–2 weeks after your last weed killer application, your corn will sprout

Cover Area with Plastic

For smaller corn patches, or corn planted in raised beds, an organic solution for weed control is to cover the ground with black plastic. This blocks sunlight and moisture from reaching the weeds, killing them. Follow these easy steps:

  • Perform any soil prep (such as tilling) before covering your corn patch. Tilling after ridding your soil of weeds will bring dormant weed seeds to the surface, undoing all your work.
  • Cover corn patch with black plastic 6–8 weeks before planting corn. Weigh down corners of plastic to keep it in place.
  • Remove plastic. Rake away dead weeds.
  • Plant corn.

Use Pre-Emergent Weed Killer Before Planting

Because corn loves warm weather, it is often planted after many varieties of weeds have already sprouted. This gives us the opportunity to apply pre-emergent herbicides at the time when weeds are coming up but you aren’t quite ready to seed your corn.

Pre-emergent herbicides prevent plants from sprouting. If used correctly, they’ll prevent weeds from appearing in your corn patch. To apply this method:

  • Prepare your corn patch (perform any necessary tilling).
  • 3 weeks prior to planting corn, apply a pre-emergent herbicide, such as Preen, to your corn patch.
  • Water corn patch as you would during the growing period.
  • Wait 3 weeks, then plant corn.

Selective Weed Killer After Planting

Weeds are stubborn. With all the different varieties and growth patterns of garden weeds, it’s not uncommon for a few weeds to crop up among your corn. Weeds are typically most dangerous during the early stages of corn growth. Young corn plants can be smothered by weeds. To kill weeds without harming your young corn, follow these steps:

  • Use a selective broadleaf weed killer containing 2,4 D on weeds in your corn patch.
  • Spray carefully, to apply as little herbicide to the corn as possible.
  • Spray when temperatures are between 40 and 95 degrees Fahrenheit, for best results.
  • Spray on dry, windless days. Windy or rainy conditions can negatively impact herbicide effectiveness, and wind can blow overspray onto your corn.
  • Apply herbicide only when corn plants are young. Never apply it when corn plants are 3 feet tall or higher.
  • Wait at least 45 days after herbicide application to harvest corn.

Hand-Weed Your Corn Patch After Planting

If you have properly prepared your corn patch by killing weeds with herbicides or by covering the ground with black plastic before planting, you should experience relatively little weed growth in your corn patch. In many cases, weed control in a corn patch can be accomplished by these methods:

  • Hand pull weeds growing close to young corn
  • Use a hoe or rake to kill weeds growing between cornrows
  • Use a tiller to kill weeds growing between cornrows in larger areas
  • Weed control should only be necessary during early stages of corn growth. Once corn is tall enough to shade the ground, it should prevent most weeds from sprouting.

Best Herbicide for Sweet Corn

Amazon product

Simple and effective, RoundUp weed and grass killer is our number 1 choice for clearing your corn patch of weeds before planting. The main ingredient in RoundUp is Glyphosate, which is a fast-acting chemical that destroys weeds and invasive graces, has low toxicity, and is washed out of the soil quickly. You can plant corn in as little as 2 weeks after applying RoundUp.

Weed Control for Sweet Corn

The trick to keeping weeds out of your sweet corn is to go all out with weed control methods in early spring, prior to planting. In large and medium-sized corn patches, use a Glyphosate or natural weed killer to wipe out weeds. In smaller areas, cover the ground with black plastic for 6–8 weeks before planting to prepare the ground. By killing weeds before planting, you make it simple to spot-treat weeds with 2,4 D herbicides or hand-weeding methods while your corn is young. Once your corn is tall enough, the shade it casts will keep new weeds from sprouting at its feet, resulting in your own beautiful, well-tended corn patch.

5 Best Tips on How to Keep Weeds Out of Sweet Corn both Before and After Planting Your Harvest
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