Proper way to apply preen weedpreventer/fertilizer granules?

[theskyisthelimit99]

Over the years I've used preen.. it works ok, however.. I never really fully understood a few things on application.

Is it necessary to wait until the plants are 2" tall before sprinkling it around them?
There should be no issue on transplants from pots right away that are 5"+ correct?

I thought I read somewhere it could be applied after seeds were in the ground, but before they came out of the ground and reached that 2" height, unsure?

Does anyone know, have some experience with it?

Thanks

[imafan26]

Preen inhibits seed germination in the top 2 inches of the soil. So, if the roots are below that like in established plants and after seeds have emerged; true leaves have appeared; and the plants are at least two inches tall. (and assuming the roots have established) it should be safe to use. Preen contains corn gluten which inhibits seed germination. It does not kill existing weeds or any weed roots left behind. If you break the barrier by adding transplants or cultivating below the top few inches, Preen won't work as well. Transplants should be put in and be established before you use Preen. Preen is active for about 4 weeks then it will need to be applied. It can be used in combination with mulch to help control weeds.
In other words your plants should all be put in an established before you use Preen. Once the corn gluten is in place it keeps in the top two inches of soil from sprouting as long as the barrier is intact for about a month. The corn gluten needs water to activate it. It works by drying out the emerging seeds. It is important that you don't water for a few days after that so that the weed seeds can dry out.

https://eartheasy.com/article_corn_gluten.htm

[theskyisthelimit99]

Preen inhibits seed germination in the top 2 inches of the soil. So, if the roots are below that like in established plants and after seeds have emerged; true leaves have appeared; and the plants are at least two inches tall. (and assuming the roots have established) it should be safe to use. Preen contains corn gluten which inhibits seed germination. It does not kill existing weeds or any weed roots left behind. If you break the barrier by adding transplants or cultivating below the top few inches, Preen won't work as well. Transplants should be put in and be established before you use Preen. Preen is active for about 4 weeks then it will need to be applied. It can be used in combination with mulch to help control weeds.
In other words your plants should all be put in an established before you use Preen. Once the corn gluten is in place it keeps in the top two inches of soil from sprouting as long as the barrier is intact for about a month. The corn gluten needs water to activate it. It works by drying out the emerging seeds. It is important that you don't water for a few days after that so that the weed seeds can dry out.

https://eartheasy.com/article_corn_gluten.htmseeds

Thanks for the reply.. so on my transplanted zuchini for instance.. I should maybe wait till they are a little taller and have more than 2 leaves each right? I think the tomatoes are plenty tall, maybe 6".

Then for the rest I just wait for them to pop up and get to 2".

I thought I read though, in some cases you can mix it in the soil before putting seeds in, like for peas (I didnt do this, all my seeds are in at this point, no preen added anywhere yet, transplants in).

[imafan26]

Preen can be incorporated into the top 1-2 inches of soil for some vegetables listed on the label. It cannot be applied to flower seeds and only after seedlings and transplants have established on other vegetables like cucurbits. Preen looks like it can be applied to the soil before seeding carrots, brassicas, legumes, and radishes.

See page 4 on product label on "for use on vegetable gardens". Remember that the label is the law. If you have any questions about a product where the label seems confusing, you can always call the help number listed on the label. I have called them and basically they will tell you what is already on the label. So if you call them about a plant that is not on the label like herbs they will tell you if the plant is not listed it was not tested and technically should not be used.

I grow a lot of herbs. It is a good thing that most herbs are pest repellents because there are very few things for which herbs are listed.
https://www.preen.com/labels/2463793.pdf

[rainbowgardener]

Preen does not contain corn gluten (or if it does, it doesn't list it on the label). It's active ingredient is trifluralin.

Just so you know what you are using, here is some information about it:

Class and Uses: Trifluralin is a selective, pre-emergent dinitroaniline herbicide that must be applied before target weeds sprout. It prevents seeds from sprouting. It is one of the most widely used herbicides used for the control of annual grasses and broadleaf weeds in nut, grain, vegetable and fruit crops.

Human Toxicity: EPA considers trifluralin to be a possible human carcinogen. Trifluralin is an endocrine-disrupting chemical, according to both the UK Environment Agency and the World Wide Fund for Nature. These chemicals have adverse, "gender-bender" effects [such as gynecomastia] by interfering with the body's hormones, or chemical messengers, and are active at even miniscule level. Contact with it can be irritating to the skin and eyes and can cause a rash. High or repeated exposure can affect the liver and kidneys.

Animal Toxicity: Trifluralin has been banned in the European Union since March 2008, primarily due to its high toxicity to fish and other aquatic life. It is very highly toxic to cold and warm water fish, amphibians, and other aquatic organisms. It is moderately toxic to honeybees and earthworms

Fate in the Environment: Trifluralin is not readily biodegradable and persists in the soil. Germination of crops can be impacted for up to a year after use, especially in arid conditions. It is nearly insoluble in water, but persists in aquatic environments due to its strong bonding with sediments and particulates in the water column. Trifluralin has been detected in nearly 1% of the wells tested. It is highly bioaccumulative, that is persisting in animal tissues and concentrating up the food chain. Trifluralin residues in the atmosphere of remote, non-use regions have been reported, suggesting its potential for long-range transport. Scientists found traces of trifluralin in the Canadian Arctic. Since it bonds so strongly with particulates, it is carried long distances in dust and air and is transported via sediment particles in ocean currents.

From this thread on garden poisons: viewtopic.php?f=11&t=57653

Corn gluten meal is a weed preventer that is completely harmless and breaks down to add nitrogen to the soil, which could be used instead. In my garden, the proper way to apply Preen is never.

[theskyisthelimit99]

Preen does not contain corn gluten (or if it does, it doesn't list it on the label). It's active ingredient is trifluralin.

Just so you know what you are using, here is some information about it:

Class and Uses: Trifluralin is a selective, pre-emergent dinitroaniline herbicide that must be applied before target weeds sprout. It prevents seeds from sprouting. It is one of the most widely used herbicides used for the control of annual grasses and broadleaf weeds in nut, grain, vegetable and fruit crops.

Human Toxicity: EPA considers trifluralin to be a possible human carcinogen. Trifluralin is an endocrine-disrupting chemical, according to both the UK Environment Agency and the World Wide Fund for Nature. These chemicals have adverse, "gender-bender" effects [such as gynecomastia] by interfering with the body's hormones, or chemical messengers, and are active at even miniscule level. Contact with it can be irritating to the skin and eyes and can cause a rash. High or repeated exposure can affect the liver and kidneys.

Animal Toxicity: Trifluralin has been banned in the European Union since March 2008, primarily due to its high toxicity to fish and other aquatic life. It is very highly toxic to cold and warm water fish, amphibians, and other aquatic organisms. It is moderately toxic to honeybees and earthworms

Fate in the Environment: Trifluralin is not readily biodegradable and persists in the soil. Germination of crops can be impacted for up to a year after use, especially in arid conditions. It is nearly insoluble in water, but persists in aquatic environments due to its strong bonding with sediments and particulates in the water column. Trifluralin has been detected in nearly 1% of the wells tested. It is highly bioaccumulative, that is persisting in animal tissues and concentrating up the food chain. Trifluralin residues in the atmosphere of remote, non-use regions have been reported, suggesting its potential for long-range transport. Scientists found traces of trifluralin in the Canadian Arctic. Since it bonds so strongly with particulates, it is carried long distances in dust and air and is transported via sediment particles in ocean currents.

From this thread on garden poisons: viewtopic.php?f=11&t=57653

Corn gluten meal is a weed preventer that is completely harmless and breaks down to add nitrogen to the soil, which could be used instead. In my garden, the proper way to apply Preen is never.

I wonder on the human toxicity, if it is only toxic if touched.. ie: having it on the ground being ok, just so long as you don't handle it?

For the corn gluten.. what alternative product would suffice? Looking briefly at amazon, seems reviews on this is mixed.

[told2b]

Ingredients of Preen
Preen herbicides target lawn and garden weeds.

The Preen brand refers to a line of garden, yard and turf weed-control products for the home. Except for Preen Vegetable Garden Organic Weed Preventer, which contains 100 percent corn gluten meal, the products contain herbicidal chemicals in varying combinations and strengths. Preen's weed and feed product also includes fertilizer

[applestar]

Ooooh, then we need to know which Preen brand product the OP has/intends to purchase and use....

[theskyisthelimit99]

Ooooh, then we need to know which Preen brand product the OP has/intends to purchase and use....

I currently have/unopened preen (non organic) which can be returned.. but I don't see very good reviews on the organic.. most say it doesnt work.

This still doesnt answer the science of the question, having the regular preen on the ground.. can it cause any harmful effects via the plants.. it sounded more like a skin/breathing contact issue than anything. I wouldnt put it near things like beets or other inground/ dirt based plants though.

[rainbowgardener]

having the regular preen on the ground.. can it cause any harmful effects via the plants.. it sounded more like a skin/breathing contact issue than anything. I wouldnt put it near things like beets or other inground/ dirt based plants though.

I doubt it is taken up by the plants and agree that it would be more an issue of contact. Anyway it sounds like the human toxicity issues are more related to repeat and chronic exposures.

[imafan26]

I put the wrong label in the link. This is the one for the organic Preen.

https://www.preen.com/labels/2463774.pdf

I have also read that studies showed that corn gluten was effective only on weeds listed but not on others. It does not work well in wet soils, and so it does have its limitations. It needs to be wet to germinate the weed seeds but since it is a dessicant, it cannot be wet or get rain for a few days after so the newly sprouted seed can dry out. It isn't cheap and since it has to be reapplied every 4 weeks it can get expensive.

[rainbowgardener]

I did try corn gluten meal once on a patch of weedy lawn. It didn't help much, but then the stuff was expensive, so I put it on way thinner than recommended. So I can't say it wouldn't work used as recommended.