I asked about this at the AHS convention. Ortho had a speaker there. Preen is not an Ortho product, but Ortho now has a product that is the same active ingredient.

Preen's job is to keep weed seeds from germinating. So, if you have a weed that's a creeper, it will not work on them. I don't believe it works on tree seedlings either.

Pretty pic! I have some preen that I plan to try for the first time. I am thinling I should put it down late winter/early spring...? Hope it works b/c it sure will make my life easier!

I've used Preen in my flowerbeds for a number of years and think it's quite effective in preventing seeds from germinating. I've used it around my hostas and have never noticed any negative results. I put down two applications throughout the growing season- one in spring and another in mid-summer. Preen does not work, however, on weeds that are already growing.

You can buy a 16# bucket at Sam's Club, but I've found Preen to be the cheapest when purchased in a large 30# bag at Lowes or Menards. The bag doesn't come with a scoop, so save your scoop from the bucket if you have one.

Preen website

The active ingredient in Preen, made by Dow AgroSciences, is Treflan. If you want to save even more money, you could buy generic Preen, in either liquid or granular form. A couple pre-emergent products that are cheaper than Preen include Barricade and Snapshot. These, or similar products, could be found at a farm supply store such as Wilbur-Ellis or United Ag Products.

I used it this year for the first time and found it to be highly effective. (The occasion for its use was an invasion of garlic mustard from a neighbor's unkempt yard.) I pulled back mulch before applying, watered it in, then restored and renewed the mulch.

The only adverse effect on hosta I observed was, one leaf of Princess Anastasia was wet and touching the ground. The tip of that leaf yellowed where it came into contact with a few granules of Preen but the rest if the leaf was ok. On second application, I was very very careful to keep the Preen clear of the hosta leaves.

I am a Preen fan. I usually put some down just when things are coming up in early spring (March-ish) and in the areas that I plant some impatiens, I put it down after I plant those. It has definitely been effective for me.

WARNING: non- scientific explanation ...

with proper application .. it creates a chemical barrier to germination .... each fleck needing to be a small distance from all the others ...

if the barrier becomes broken.. the effectiveness of the product will be reduced ...

so if you walk thru your beds.. its effectiveness will be greatly reduced ...you... the cat.. the dog.. the deer.. etc ....

also .... the generics are MUCH CHEAPER .. and sold in much bigger quantities .... like 50# bags ...

the scope of my garden.. made it extremely cost INeffective ...

ken

I'm glad this question was asked... I thought about purchasing some back during the growing season but wasn't sure if it would affect the plants.

I know what I'll be applying in the spring! :-)

Love that chair.

Is it too early to apply Preen? I'm sure it is but I'm dying to do something in the flower beds!! We've been in the 70's but our winter will kick back in this week... they're projecting in the mid to upper 30's.

Hmmn, wondering if it works on Rose of Sharon???

Rookie.... Stay outta your beds!
It's too wet to be in them and winter isn't over yet!
Preen only works for 3 months, so you're going to have to do another application regardless.