Much like the flavors of spices and seasonings in your pantry diminish over time, the effectiveness of garden chemicals can do likewise. But just how long do garden chemicals, whether synthetic or organic, actually remain effective? Or said another way, do they have a finite shelf life? Well, it depends on who you ask and the product in question.

And unfortunately, three of the major manufacturers of garden chemicals have different takes on the subject.

Scotts (which also produces Ortho products) says its products should be used within three years, although granular fertilizers with no additives such as herbicides should keep indefinitely. Chemical giant Bayer claims its products will keep indefinitely. And Bonide, which makes a number of synthetic and organic chemicals, says its liquid products have a shelf life of between three and 10 years.

However, the one thing all three companies agree on is that the effectiveness of their products can be greatly affected by how they’re stored. Specifically, they acknowledge that the shelf life will likely be reduced if the chemicals are stored where they’re exposed to extreme temperatures, as in above 90 or below 32 degrees Fahrenheit, or in areas of high humidity. And my guess is that at least one of those conditions probably can be found where you store your chemicals, such as a garden shed or the garage. All three can be found in my shed depending on the time of year.

What’s more, the Big Three generally agree that once opened, the active ingredient in their products may change chemically and begin to break down, thereby decreasing its concentration and effectiveness. The product may also begin to form flakes, crystals, or sludge, making it impossible to mix or use in sprayers. Powders are especially prone to caking.

So what’s a gardener to do? Well, I do believe that granular fertilizers that don’t contain any herbicides should keep indefinitely, although organic fertilizers and soil amendments that contain beneficial fungi such as mycorrhizae should be used shortly after purchase. Most liquid formulations – whether fertilizers or pesticides – should be used within two or three years, especially once they’ve been opened.

That’s why I strongly suggest you check your inventory of lawn and garden chemicals and regularly replace any old products with new ones. And just how do you get rid of unwanted garden chemicals? Well don’t pour them down the drain or throw them in the trash! Instead, take them to the City of Tulsa’s Household Pollutant Disposal Facility. For details, go to:

Tulsa residents can drop-off for free by showing a drivers license or City of Tulsa utility bill.

Residents living in Bixby, Broken Arrow, Claremore, Collinsville, Coweta, Glenpool, Jenks, Owasso, Sand Springs, City of Wagoner, and unincorporated Tulsa County can obtain a voucher from the Metropolitan Environmental Trust (918) 584-0584, to drop-off the first 45 lbs. of pollutants free of charge. If the weight is over 45 lbs, there will be a disposal fee of $1.37/lb.. Residents of these communities must obtain a voucher number before dropping off pollutants.

We maintain an extensive inventory of organic and synthetic insecticides, fungicides, herbicides, fertilizers and other essential gardening products. So when it comes time to restock your supply, drop by our Solution Center or shop online.