Green Weed Control

Green Weed Control

Part of Ep. 1702 Think Green

Dr. Astrid Newenhouse, UW-Madison horticulturist shares green weeding solutions you can find in your own kitchen - dish soap, vinegar, boiling water, corn gluten meal. Other safe solutions include a propane tank flame thrower and BurnOut, an herbicide made with natural ingredients.

Premiere date: Apr 29, 2009

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
Every gardener knows weeds.  Every gardener hates weeds.  So we're going to look at some green solutions to weeds.  I'm with Dr. Astrid Newenhouse, horticulturist in the Madison area.  And you've got green solutions.  What are they? 

Astrid:
I do, Shelley.  And I think of these as a replacement for Round-Up, which is an effective weed killer, but it's a toxic poison which we didn't realize was as unsafe as it actually is now. 

Shelley:
So it's a little worse than we really thought. 

Astrid:
Yes, it's showing up in the ground water. 

Shelley:
So Round-Up can be used, but it shouldn't be used as freely as were using it. 

Astrid:
Time to find alternatives. 

Shelley:
And you've got something that we can try first. 

Astrid:
You probably have it just in your own kitchen. 

Shelley:
Oh, really, okay. 

Astrid:
The first one is dish soap.  A 20% solution of dish soap. 

Astrid:
Just the kind we use to wash our dishes? 

Shelley:
Yep, it'll dry up weeds. 

Astrid:
Any kind of soap will do.  Research has shown that Dawn is especially effective for some reason. 

Shelley:
Nobody knows why? 

Astrid:
It dries up the weeds.  And so, what I've done, is I've taken one part dish soap and four parts water. 

Shelley:
That's a 20% solution.  I'll let you do the math! 

Astrid:
And you just spray your weeds. 

Shelley:
Now, it looks like you're spraying small weeds.  So this is something we do early in the year before they've gotten too large. 

Astrid:
Yes.  These techniques only work on very small, like two-leaf stage weeds.  Another one to use is household vinegar.  When you just go to the store and buy vinegar, that is a 5% solution. 

Shelley:
Whether it's the white vinegar or apple cider vinegar? 

Astrid:
Any kind of vinegar.  Now, there's a horticultural vinegar you can buy that is stronger, that's 20%.  But if you just want to use what you have at home, you can put some of this in a spray bottle. 

Shelley:
Are we diluting this? 

Astrid:
No, straight up. 

Shelley:
Okay. 

Astrid:
And spray your weeds.  Squirt them again.  And it will dry it right out. 

Shelley:
It'll be more effective if we got the 20%, but you're saying the 5% will work fine. 

Astrid:
It'll work on very small weeds, the two-leaf stage.  This is my all-time favorite weed control method, boiling water. 

Shelley:
You're kidding? 

Astrid:
Cook the plant.  Watch that die. 

Shelley:
Wow!

Astrid:
And what I like to do, Shelley, is when I have cooked like sweet corn or pasta, I just take that leftover boiling water and dump it on my driveway or sidewalk cracks and kill the weeds. 

Shelley:
You see, that's a wonderful idea, because I'm always feeling like I'm wasting water when I cook pasta.  I'm always wondering what to do with it.  How big a weed will the boiling water work on? 

Astrid:
Boiling water works on the two-leaf stage, so young weeds.  Also, on a little bit taller, maybe like this tall. 

Shelley:
Oh, excellent. 

Astrid:
And it just cooks them. 

Shelley:
See, that's the best idea I've heard yet.  However, in my yard, there are some that are even bigger than that.  Do you have any solutions for that? 

Astrid:
Yes, there's other approaches we can take for those. 

Shelley:
Let's go look at them. 

Astrid:
Shelley, I wanted to show you this.  This is corn gluten meal.  And it's a natural weed and feed product. 

Shelley:
Made from corn? 

Astrid:
It's a byproduct of the corn milling process.  And it's used as an animal feed, so you know it's safe.  Your dog could eat it. 

Shelley:
Really?  So it's safe for kids and pets then. 

Astrid:
And it's used in your lawn to kill newly sprouting weed seeds. 

Shelley:
So pre-emergent. 

Astrid:
Pre-emergent.  If you have dandelions or creeping Charlie that's already there, if you can see it, this won't touch it. 

Shelley:
Okay, so this is something we're doing early in the spring. 

Astrid:
Early in the spring, in April, there's a two-week window when the soil temperature is just right for this to work.  And you know when that is, because that's when the forsythia blooms. 

Shelley:
Oh, okay, so when we see that yellow shrub blooming, that's when we get out there.  This is something that we apply that will leave the lawn okay, and just kill those weeds. 

Astrid:
Yes, early-emergent seeds. 

Shelley:
And you've got a big bag of it. 

Astrid:
You buy a big bag.  It also provides 9% nitrogen by weight, that's why the weed and feed.  So you get yourself a spreader, a regular lawn spreader, and spread away.  Twelve to 20 pounds per 1000 square foot of lawn. 

Shelley:
And just like with any fertilizer, you read the instructions on the bag for this, too.  Okay, so this is something early in the spring.  Do you have something, well, you mentioned something like a little more violent for the weeds. 

Astrid:
Oh, yes, we have a flame thrower! 

Shelley:
Perfect!  There's a few weeds I really want to hurt. 

Astrid:
This works really well, just by cooking the weeds.  It's a propane tank with a wand.  You give it some gas, turn it on.  Cook the weeds.  It literally cooks them. 

Shelley:
Now, roots and all? 

Astrid:
On very small weeds.  So, like in garlic mustard, in the two-leaf stage, this does a great job on that and small weeds.  If you have a stream bed or a creek that is getting overrun with garlic mustard, this is the perfect tool for that.  And some people just like to use tools. 

Shelley:
Oh, yeah, and play with fire, too!  Now, unfortunately, I don't always get to all of my weeds early in the spring.  Sometimes, things get away from me. 

Astrid:
Yes. 

Shelley:
Is there anything that's safe to use later in the year? 

Astrid:
There are new herbicides out that are made with natural ingredients.  Here's one called BurnOut.  But what you're looking for is the combination of horticultural vinegar, that's the 20% vinegar, really strong, plus a plant extract such as clove oil. 

Shelley:
Is that what I'm smelling? 

Astrid:
Yes, this is vinegar and clove oil. 

Shelley:
Okay, so these are essential oils. 

Astrid:
And it burns the plant.  It will also burn your skin, so be aware this is the very strong vinegar, plus the clove oil, and you need to wear gloves.  Don't get this on your skin. 

Shelley:
Basically, like the flame thrower.  It'll burn your skin, too. 

Astrid:
But Shelley, look at how it killed this garlic mustard. 

Shelley:
Look at that!

Astrid:
And that's the two-year-old stage.  My friend used this BurnOut, the clove oil and the vinegar and sprayed his garlic mustard, and it killed it. 

Shelley:
It literally burned it.  So there are lots of choices whether weeds are large or small. 

Astrid:
Yes, I'm so happy to have these choices. 

Shelley:
This is great.  We have some alternative that anybody can use.  Thanks, Astrid. 

Astrid:

You're welcome, Shelley. 

EPISODE SEGMENTS+
EPISODE RESOURCES+

Buy DVD »

Funding for The Wisconsin Gardener is provided, in part, by The Wisconsin Master Gardener Association.