Treflan pre-emergent

I was told by an experienced nursery owner that Treflan herbicide granules can be used around fruit trees and in the garden to prevent certain weedy grasses and forbs. He also said it can be applied on top of mulch and watered in.
When I check the label, it doesn’t list fruit trees at all. It lists some vegetables, but not all. I always try to follow label directions of course. Anyone have input on why this wouldn’t be safe around fruit trees? Or a recommendation for an affordable pre-emergent for a backyard grower?

Unless I’m mistaken, it’s the same active ingredient as PREEN…(trifluralin)…the yellow tubs at the ‘big box’ stores in the garden department.

I don’t always read and follow labels…so you’ll have to read and use your best judgment.

But, I have used PREEN on just about everything from Black-eyed-susans
to cherry and apple and maple and holly trees…

In my 22+ years, I don’t think I’ve killed anything by using it. (But I don’t guarantee you won’t).

What it will do is keep about 99% of weed seeds from sprouting…that still means a few dandelions and other things in your flower beds or orchard will sprout.

If you have flowers (or vegetables) that ‘volunteer’, or if you plan to sow seeds intentionally in a given area be they flowers, veggies, or other seeds, this herbicide does not discriminate. Your seeds won’t germinate.
It does, after about 3 months, lose it’s effectiveness, however!

Hope you find that helpful.


I added compost (which contains millions of weed seeds) to most all of my tree mounds last year. I put about 3"+ wood chip mulch over the compost and I still had some annual grasses and forbs pushing up through the wood chips. I weeded each tree mound 3x and some more than that, which is at least 2x more than I want to do over the course of the summer since it is very time consuming. I am thinking a pre-emergent should help with this, if it works as advertised. Just don’t know why it wouldn’t list fruit trees on the label.
Most of the problem weeds are all annual, but everything is coming up from seed in the compost regardless of whether it is annual or perennial. Lambs quarters, buffalo bur, burdock; crabgrass, windmill grass, goose grass, etc.
I also had thought to put the pre-emergent down in between rows of plants in my garden to cut back on the crabgrass, purslane, sunflower, and other weeds. I could use a break on the weeding this year! I mulch in the garden too, but the weeds are persistant.
Thanks for the info!

Do you have to water-in Treflan and Preen to activate them?

I don’t. I guess that makes the answer “no”. :slight_smile:
But it might make it work a little quicker.

1 Like

Blueberry is right. Trifluralin is the active ingredient in Treflan. The liquid form (emulisfiable concentrate) has a pre-emergent label for all new stone fruit trees, except cherry. In doing a little internet search, I found at least one granule formulation of Treflan also includes stone fruits, again except cherry.

The problem with Trefluralin is that it photo degrades very easily. Half life is pretty short in sunlight. That’s why the label indicates incorporation of the herbicide in the soil within 24 hrs.

Still, I don’t doubt Blueberries success with the product without incorporation. Some of these herbicides work really well, even at small amounts. Once trefluralin is in the soil, it lasts a long time. The pre-plant interval for some the crops is as long as 18 months, depending on the amount of rainfall.

If you didn’t want to incorporate trefluralin, I’d probably suggest trying to put it down as close as possible before a good rain. Or water it in with irrigation. That will help get it into the soil profile before it has time to degrade.


Thanks for the extra information @Olpea. Interesting about it not being listed for cherries with the other stone fruits…
I think I could rake back the wood chip mulch, sprinkle the Treflan granules on the soil and rake it in a bit. Water it in, or apply before an expected rain.
I would like to try it in my blackberry and raspberry rows too. I will have to check labels for those as well. Have you used a pre-emergent in your blackberry rows?

Yes. We typically use Sinbar on the blackberries. It is very expensive, but does a good job.

I plan to use Trifluralin as a pre-emergent for tomatoes this year.

1 Like


@BlueBerry @Olpea
Do you either of you think that Treflan is OK to put down in soil around newly planted fruit trees? Or only around ‘established’ trees?
The label seems vague on this… it says
SHRUBS AND TREES: Use Hi-Yield® HERBICIDE GRANULES CONTAINING TREFLAN®**around most common varieties to prevent weeds throughout the growing season.
You can apply anytime of the year around
shrubs, trees and established plants

I just finished planting some peach trees and wanted to get this down before the rain. I checked the label one more time and now I am wondering if it is OK. I talked to product support and she was unable to help, as fruit trees aren’t specifically listed on this label, but as olpea noted above, there is another granular formulation that does include stone fruits.

I personally would use it…but not bigger dose than label recommends.

1 Like

I wouldn’t hesitate to use it once the dirt had settled around the new trees. The liquid form I have is label for use on new trees.

1 Like

Thank you both, @Olpea and @BlueBerry, for your replies. I am really looking forward to having even a semblance of weed control this summer.


@BlueBerry @Olpea I recently sprinkled some Treflan (Preen) around my Asian Pear trees before realizing that fruit bearing trees are not recommended for this product. Do you know why this stuff is not recommended for fruit bearing trees? Will it kill the tree? Destroy the fruits? Thanks!

Good question, and I’m not positive. Maybe someone else that is can chime in.
But it’s
a chance there might be uptake into the fruit of small amounts of the stuff that could be harmful if you ate enough of it. (Chlorine and Flouride they put in drinking water are deadly in large doses but they put it in.)
Or, often times, pesticides are EPA registered to get the ‘low hanging fruit’…and since each different plant needs testing and evidence to get “recommended” some things aren’t economical as they are not often used for such applications.

It also is recommended to have gloves on to use the stuff…and I don’t, I just wash after use. Have used it 3-5 days a year, for near 30 years.

Typically, it’s used for landscaping…not gardens for food. So, don’t make it practice to put on things you’re going to be eating .

But in this case it isn’t going to kill your pear tree.

And probably do no more harm if you eat the fruit than if you eat corn or cornmeal made from corn sprayed with Roundup (and most all commercial corn is sprayed). (And most corn on the cob gets sprayed or gmo
seed are used.)

1 Like

Never used a pre-emergent until 2019… when I broke down and used Prowl H20(pendamethalin) on middles between rows of CBD/floral hemp in the last 3 acres of 12 that we planted that year… I was fighting a losing battle against redroot pigweed, lambsquarters, smartweed, and foxtail in the early stuff we planted. It was a game-changer.
Used it last year in the vegetable garden… again, a game-changer… otherwise, it would have been a virtual forest of pigweed. Best garden I ever grew - and virtually NO hoeing, very little hand-weeding required.
Better believe I’ll use it again, when it quits raining long enough to get the garden planted.


BlueBerry gave you very good information. I can’t really add to that! I wouldn’t worry about it harming your tree or fruits after this application. Follow the label in the future, or search for a pre-emergent with fruit trees specifically on the label. Olpea mentioned above:

Might be best to find where you can purchase the liquid concentrate in your area (or order online) and use that one in the future.

1 Like

Thanks @KSprairie…the thing is, use your noggin. If the liquid is approved by EPA, and the granular isn’t…
it has a lot more to do with goverment red tape than safety.

Yes, I agree. That appears to be the case with several products…
Look at the options, make a decision based on the information you have available. Some, however, may feel more “safe” to have a product in hand whose label is clear, easy to follow, with the specific plants/trees listed on the label. For peace of mind, if nothing else! :wink: Not trying to push keropie3 one way or the other.

I’m not exactly sure either. I would note that the label of the Treflan 4L (what I’m using) does not include pome fruits. That label just includes stone fruits. It may be that pome fruits are less tolerant of Treflan than stone fruits. I don’t know.

In terms of pre-harvest interval. It has a 60 day pre-harvest interval for grapes. For transplanted tomatoes, I don’t see a pre-harvest interval at all.

My guess is that its probably got something to do with what Blueberry mentioned. Too many hoops to jump through to get a label for spraying the product on producing stone fruit crops.

There may be some other reason, but that’s the only reason I can think of, given the product is approved for use on producing vineyards, and that there is no pre-harvest interval for tomatoes (I would think tomatoes would have a greater uptake of the herbicide than stone fruits, since tomatoes are much shallower rooted.) But again, I am just guessing. I don’t really know.