Weed Control: Herbicides 101, What Plants They Kill

Herbicides are chemicals used to control unwanted plants. All conventional or "organic" herbicides work by somehow interfering with plant growth. They may block photosynthesis and protein production, dry out the leaves, or destroy or inhibit root formation. Because different plant groups have different biochemical pathways, some herbicides can kill only one group and leave other groups unaffected. Other herbicides will kill a wider range of plants.

This means that you might be able to get rid of some plants and not kill the plants you want to keep.  But it also means you have to take the time to find the right herbicide, read labels and apply the herbicide correctly.

WARNING: If something will kill "weeds", it might also kill "flowers", "lawns", "vegetables", "shrubs", "trees", "animals", and you.

Read the labels before you buy a product or open the container. Follow the instructions. What has been sprayed can't be unsprayed.

READ THE LABELS: Yes, that means YOU!

A typical herbicide label has several pages of cautions and warnings and instructions.  The label will tell you how to safely handle the product, what plants to use the product on, and just as important, what not to use it on. You can read the labels online while you are deciding which product you need.

Label from typical lawn weed killer.
They tell you what NOT to apply it to because it will kill those plants.

There is also a long list of weeds it has been tested against that it will kill
if you apply it according to the package directions.

What are you killing, and for how long do you want it dead?

Classified by results, herbicides can be thought of as soil sterilizers, broad spectrum herbicides, broad-leaf herbicides, grass herbicides, and pre-emergent herbicides.  So your first step is to decide what effects you need, and identify the plants you want to kill. Then you can select which product of that class will work best for you.

Soil Sterilizer
A soil sterilizer prevents seed sprouting and regrowth from roots for a long period, months to years.  It usually kills existing plants as well.  This is the equivalent of "nuke it from orbit" for a gardener, and should be very carefully researched.

This is not the product you want to apply to clear the weeds from where you plan to put a lawn or vegetable garden.

Broad Spectrum Herbicide
Affects almost every plant you spray, but will not prevent seeds from sprouting, or only has a short effect on seed sprouting. These are useful for killing off everything and replanting with the desired species. With care they can be used around established plants without harming them.

Glyphosate is in this class, as is horticultural (20%) vinegar, and that stupid mix of salt, vinegar and dish soap. 

Broad-Leaf Herbicide
Affects most plants with two seed leaves, also known as broad-leaf plants, but does not affect plants with one seed leaf, such as grass and corn. This is what you get in the herbicides to kill weeds in lawns.


TIP: Not all plants with grass-like leaves are immune to this class of herbicide.  Some are not botanically a "grass" and others are just delicate varieties of a grass.

Grass Herbicide

This affect plants with one seed leaf or thin leaves, such as grass and corn, but does not affect plants with two seed leaves. These are useful for killing grass in your shrubbery and rose beds or an orchard.

Pre-Emergent Herbicide
This is often sold as a "weed preventer" because it sounds more appealing than "pre-emergent herbicide".  However it is labelled, it will prevent most seeds from germinating, so don't try to use it to keep weeds from sprouting in the vegetable bed or lawn you just seeded.


TIP:Timing is everything with pre-emergents. Applied too early or if there is too much rain and the herbicide might be washed below the level where the seeds are germinating. Applied too late and the weeds can be too mature to be affected.

On-Line References

https://en.wikipedia.org/wiki/Herbicide

http://extension.psu.edu/pests/weeds/control/introduction-to-weeds-and-herbicides/safe-herbicide-use 

http://extension.psu.edu/pests/weeds/control/introduction-to-weeds-and-herbicides/herbicides

http://www.ocregister.com/articles/plants-80501-weed-herbicides.html  Read more!

Watching Grass Grow: What I Should Have Done for Buffalo 2.0

This is another "Oops, should have thought a bit longer" post. I realized too late that there was a slower but less work way to get the front yard growing.

I should have established the grass and wildflowers over 2 or 3 years, not just one spring, to make weed control easier.

1. Water well, lure out and kill annual weeds by any means possible between November and May.  Flames, herbicides, tilling ... total war on weeds.
2. Plant the buffalo and grama grass in May, with the jute erosion control mesh.  The seeds would sprout faster in the warmer weather.
3. Get the grasses established the first summer, weeding and using herbicides as needed. Anything that is not a grass is the enemy at this time.
4. If the weed pressure is low, plant wildflower seeds that fall and following spring. 
5. If there are still a bazillion weeds, use a pre-emergent or  broad-leaf herbicide another year before planting wildflowers.

But, I was in a hurry, so I planted the buffalo and wildflower seeds in early spring, and the weeds took advantage of the water. They were well-sprouted before the grass even broke dormancy.

On the bright side, I have acquired excellent experience in hand-weeding large areas and recognizing weed versus wildflower seedlings.
Read more!

Weed Control Methods: Herbicides Series

I will be publishing a series of posts on herbicides for weed control, explaining in a non-technical manner how to select the correct one for your problem and use it effectively.

It's a bit more complicated than grabbing a bottle of "weed killer" and spraying the yard.

WARNING: If something will kill "weeds", it might also kill "flowers", "lawns", "vegetables", "shrubs", "trees", "animals", and you.

Read the labels before you buy a product or open the container. Follow the instructions. What has been sprayed can't be unsprayed.

As I complete the posts, I'll update this, or click on the tag "herbicide" to see them and any other posts on herbicides. Read more!

Four Cheap, Effective Fertilizers

For Occasional Use by a Lazy Gardener

I seldom use fertilizers, but if I have to, I use the simplest ones that will do the job.  I am reluctant to use combination fertilizer and weed killer or pest killer. If landscaping has weeds or pests, I'll buy the right single-purpose product. I am also reluctant to apply "time-release" products because in my experience, they are timed for the typical Eastern lawn and garden with more rainfall.

1914 Fertilizer Brochure Cover

If a landscape that I'm responsible for needs fertilizer, one of these four fertilizers will be applied: ammonium nitrate, ammonium sulfate, ammonium phosphate, or soil sulfur. In keeping with my gardening philosophy, they are the simplest, cheapest fertilizers you can buy.
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Weed Control Methods: Flame Throwers and Weed Burners

Flame Throwers and Weed Burners

Weed burners or flamers are blowtorches adapted to deliver flames to ground level.  They do not have to burn the plants to ash as long as the heat cooks the leaves.  Flamers work best on small weeds with a high moisture content because the plant doesn't have the resources to regrow after the leaves are dead.

Too big for most of us, but a very striking photo from www.lpg-apps.org. 
Flaming the weeds on a large field before planting the crop.

Read more!

Manual Weed Control Methods: Hand Pulling and V-Weeders

There is something deeply satisfying about grabbing a fistful of weeds and yanking them out, roots and all. However, you have to make sure you aren't just pulling the leaves off because the weeds will regrow.  The soil should be damp, either from a heavy rain or recent watering.  If it's too wet you will yank out huge clumps of dirt with the weeds, and if it's too dry the roots are locked into the dry dirt.

Best Technique:  Grasp the entire plant at the base, holding all the leaves in your hand and rotate it as you pull up.  If things go right, you should pull out an intact tap root.  If you are just breaking the tops off, water the area and try again in a couple of days, or use a V-weeder.

NOTE: Most annual plants have a growth point at the base of the leaves that can regenerate leaves. Slice below this point or the weed has a chance of growing again. 

Growth point: be sure to get this and the top inch of the roots.

Read more!

Weed Control: Know the Enemy

It's not the weeds you see that are the problem, it's the ones hiding in the dirt, waiting to grow.

Weeds in Rye
By Agronom (Own work)
[CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)],
via Wikimedia Commons

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Dealing with Weed Seeds in Compost

This accidentally turned into a nice demonstration because the various leafy greens germinated in their soil blocks at different times and were planted out at intervals of a few days.

My compost method is known as "slow" or "cold" composting.  This pile it and forget it method doesn't produce enough heat to reliably kill weed seeds.  Some will die of old age before the compost is used, but others will survive.

That means my just-filled raised beds were filled with unsprouted weed seeds. They sprouted as soon as they got  light and moisture, leaving me with a weedy mess of a vegetable bed like this. 

 

Weedy mess and transplanted chard seedlings

It will get worse every day unless ...
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How to Kill Bermuda Grass in 10 Easy Steps

In its proper place, Bermuda grass (Cynodon dactylon) makes a good lawn or good pasture. Unfortunately it doesn't stay in its proper place. The underground roots and the above ground runners spread everywhere. Soon you have Bermuda grass erupting from your flower beds, creeping through your cactus, tangling in your shrubs and even invading your garden shed.

Killing Bermuda grass is not difficult, but it's not going to happen overnight. I'm a desert landscaper. I spend a lot of time killing lawns, especially Bermuda grass lawns, to replace them groundcovers that use less water. I have learned that no matter what the herbicide package says, it will take at least a month and several applications of herbicide to kill 90 to 95% of the Bermuda grass, then several months of spot application on surviving sprigs to get the remainder. It's a tough plant. It's so tough that it grows in the cracks of the concrete medians in the middle of a Phoenix freeway.

Bermuda Grass with seed heads
By Harry Rose from South West Rocks, Australia via Wikimedia Commons

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Gimme Shelter! Queen's Wreath (Antigonon leptopus)

We needed shade for the west wall of the house to keep the electric bills down, so we built an arbor. Then came the discussion of what to grow on it.

• We wanted pretty flowers, if possible.
• We wanted native plants if possible.
• We needed a thornless vine
• We needed heat loving vines that would cover the arbor for the summer.
• We wanted a perennial vine to come back every year.
• We needed a drought tolerant vine in case we slacked on the watering.

TAH DAH!!!!  The winner was Queen's Wreath Vine (Antigonon leptopus), an  incredibly hardy, fast-growing, flamboyantly blooming native from the lower parts of the Sonoran desert.

Unlike the "other native", Cat's Claw (Macfadyena unguis-cati), Queens wreath is frost-tender and dies back to the ground every winter.  It's a less aggressive grower and can be controlled with occasional pruning.

Except for the trees ... It goes from the arbor to the old orange tree and covers it like a hat. This doesn't appear to harm the tree, and the oranges ripen under the vine.  We pull the vine out when the oranges are ripe.

Queen's Wreath Covering Orange Tree
(the tree is the mound at the left)

Are Bees a Problem?

Queen's Wreath attracts bees, dozens of honey bees and wild alkali bees - it's a great way to attract pollinators to your garden all summer long. 

Because it's growing on an arbor, the flowers are all "up there" and so are the bees. You can sit under the arbor and listen to the bees, but they stay with the flowers.

Self-Seeding

This is a prolific seed-producer. The quail and other seed-eating birds forage under the arbor most of the year, gorging on seeds.  They don't find them all, and those that land in a moist spot will germinate.

They pop up all over the yard, but they are easy to recognize and pull up.

Volunteer Queen's Wreath Seedlings
(after a summer of unusually heavy rains)

Removing the Dead Vines

We need to remove the vines every year or they build up a heavy, ugly dead mess on the arbor. The stems tend to lie on top of an arbor instead of twining through the mesh. We left space between the top of the vertical mesh and the side of the top mesh to make vine removing easier, and there is a foot or so between the top mesh and the wall of the house.

Removing the old vines in early winter is easy. Don't let them get dry and brittle.

1. Trim off all dangling vines at the top and edges of the trellis or arbor.
2. Roll up any mat of vines that is on top of an arbor and toss it in the compost heap. A rake works well to get the mat going.
   You may need to clip a few stems, but Queen's Wreath is more of a sprawler than a clinging vine on a horizontal lattice or mesh.
3. If you have room, get behind the trellis and cut the stems that you can find passing behind the trellis.
4. If the trellis is large, cut the stems to divide the growth into vertical sections 3 or 4 feet wide.
5. Start pulling the vines down from the sunny side.  I use a rake and pull from the top down, rolling the vines as I pull.  This removes most of the growth. 
6. Cut the stems close to the roots.
7. That's it until next year.

Read more!

Dandelions and Clover Terrorizing Lawns Nationwide!

Through a chain of gardening blogs, I found Garden Rant's rant about the inability of Scotts Chemicals to comprehend that diversity in lawns is a good thing. To Scotts, the only good clover is dead clover, the only good dandelion is a dead dandelion, and the only good lawn is one that soaks up several hundred dollars of their product every year.

Dandelion For Sale In Seoul, Korea

Does this cute yellow flower look like it should be hunted down and poisoned to make a sterile monoculture that covers half of my property? Let's bring back the lawns of granny's time, when they were a vibrant mix of grasses, clover and a few volunteer wildflowers. Bees loved those lawns, birds loved them, children loved them, and they were easier to take care of.

Dandelion In October, White Mountains, AZ

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Watching Grass and Weeds Grow: Week 10

This week I have some comparison photos. I took these by standing at the edge of the patio, with the camera pointed straight down.

March 24, 2009 is really wimpy. It's a few days after planting.

April 27, 2009 is not much better, and the weeds are sprouting.

May 21, 2009 is starting to look like it might be a lawn. The runners are criss-crossing the bare patches and starting to root.

June 3, 2009 shows it's getting dense and almost needs mowing in this spot. Not all of the lawn is like this, but most of it looks at least like the previous picture. This is only 2 1/2 months after planting the plugs at the maximum recommended spacing. There are a few weeds, but it's choking most of them out.

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Watching Grass and Weeds Grow: Week 9

It's Memorial Day. I'm sitting in the shade with a beer! We had several cool, cloudy days with light rain, which is unusual for May, and now it's back to the usual hot and dry.

The Buffalo grass continues to spread, and weeding by hand is making slow progress. The grass is spreading and rooting under the spurge where the dirt is cooler and moist all day.

Pics are coming, I promise. Read more!

Watching Grass and Weeds Grow: Week 8

Not using a pre-emergent to prevent weed growth in a new lawn area is a major mistake, especially in Phoenix. The abundant water has encouraged astounding numbers of weeds to sprout. Arizona's warm-weather weeds are mostly waxy-leaved like spurge, or fuzzy-leaved desert plants, and herbicides aren't absorbed well. Most of the weeds barely slowed down when I sprayed them with a broad-leaf weedkiller.

Most broad-leaf weed killers can't be applied to turf grass when the temperatures are above 85°F, which happens really early in the morning in Phoenix. Some herbicides specify that the daily maximum temperature can't exceed 85, which makes them useless here.

I'm hand-weeding, which in a way is good, because in the course of pulling the broad-leaved weeds I find a lot of small surviving Bermuda grass clumps that are coming from the deep roots. Left alone, these would be huge and well-rooted in a couple of months.

The buffalograss is thriving despite the weeds. The plugs have turned into dense clumps the size of dessert plates, and there are only a few patches of dirt the runners haven't reached.
Read more!