Q: I buy a new fertilizer every spring just because I don’t know if what’s left over from the previous year still works. Is the fertilizer going bad, and if so, how long is the fertilizer good for?
A: How long does the fertilizer last? Almost forever, although there may be exceptions for types with short-lived additives like germs and weedkillers. For this reason, there are different answers to the questions, “Does the fertilizer expire?” and, “Does lawn fertilizer expire?”
If properly stored in cool, dry conditions, most types of fertilizer can be used until you run out and need to buy more.
RELATED: Solved! It’s time to fertilize the lawn
Synthetic granular fertilizer can last indefinitely if stored properly.
Does granular fertilizer degrade? No, it can technically last an indefinite time. In reality, of course, it can suck in moisture and grow mold, or rodents could chew holes in the bag. To keep granular fertilizer in the best possible condition, store it in buckets or airtight plastic boxes with lids inside a building (like a shed), rather than leaving it exposed outside. .
Does fertilizer deteriorate if it gets wet? If your granular fertilizer becomes lumpy when wet, you can simply crumble it again. Simply wear a protective mask to avoid inhaling dust or mold.
Organic granular fertilizer can last 1-5 years or more.
Although some cooperative extensions warn that the shelf life of granular organic fertilizers is only 5 years, it depends on the ingredients included in a given formula. As mentioned above, fertilizers containing microbes tend to be shorter-lived products.
According to a Request an extension expert, fertilizers with nitrogen-rich ingredients like blood meal can leach some of that nitrogen if they get too wet or lose it as gas if they get too hot. However, Espoma claims that its organic fertilizers will last indefinitely when kept dry and cool. You shouldn’t need to throw away organic granular fertilizer just because it’s old, but if you’d rather buy newer bags for your garden, add the old material to your compost pile.
Liquid synthetic fertilizer can last indefinitely unless it freezes.
Does liquid fertilizer degrade? Whether sold as a liquid or as crystals to be dissolved in water, this type of fertilizer also has a long shelf life. Miracle-Gro recommends that while its liquid plant food is best used within 3 years of purchase, it will remain effective for at least 8 years when properly stored, per “Living in Kentucky.”
For this reason, do not make the mistake of storing liquid fertilizer where it can freeze, as freezing can separate certain elements and decrease their effectiveness. Always shake liquid fertilizers before using them to make sure they are well mixed.
RELATED: Solved! Do grass seeds go bad?
Unopened liquid organic fertilizer can last indefinitely if stored properly.
The most common liquid organic fertilizers are fish and kelp emulsions. Neptune’s HarvestOrganic fertilizers “have an indefinite shelf life, until water is added”. The company warns, however, that the older the emulsions, the more you may need to shake them to properly mix them with water.
Just keep in mind that emulsions almost always have an unpleasant smell, whether old or fresh. So you’ll want to apply them very soon after mixing and wash your hands well afterwards, because what’s good for your plants isn’t necessarily good for your skin!
Weed and feed fertilizers can last about 1-4 years.
Does lawn fertilizer expire? As the name suggests, lawn care weed and feed products often contain herbicides in addition to nutrients. Because herbicides lose their effectiveness quite quickly (some within 1 or 2 years), these fertilizers generally have earlier expiration dates than those that do not contain herbicides.
However, that doesn’t necessarily mean that this type of lawn fertilizer goes bad, because the actual fertilizer component should still work even if the herbicide doesn’t. Miracle-Gro recommends using lawn fertilizer within a year of purchase, however, as it will become more difficult to apply with a fertilizer spreader if it begins to clump.
Microbial inoculants have the shortest fertilizer shelf life and should not be used after the expiration date on the package.
Often considered plant probiotics, microbial inoculants contain live microorganisms, so their shelf life can be as short as 6 months or as long as 2 years, depending on the product. Some inoculants require refrigeration and the packaging may warn against exposure to extreme temperatures.
Instructions for biofertilizers containing microbes often recommend that these fertilizers be used within 3 months. However, a study published inAgricultureindicates that these plant foods continue to contain large amounts of microbes for at least 4 months, whether stored in the dark or in direct sunlight.
RELATED: Homemade Fertilizer Makes Grass Ever Greener
5 tips for storing leftover fertilizer at home
- Place the fertilizer in an airtight, rodent-proof container.
- Keep the fertilizer off the ground, instead place it on a pallet or other elevated surface.
- Store fertilizer inside a building where it stays both cool and dry.
- Keep the fertilizer out of direct sunlight and away from windows.
- If you decide to throw away the original packaging of a fertilizer, clearly label its container and keep a copy of its instructions.
How to Properly Dispose of Unusable Fertilizers
The best way to get rid of fertilizer is to give the old, unwanted product to other gardeners who can still use it. If you can’t find anyone to take them, you can add organic fertilizers to your compost pile. However, for synthetic fertilizers, wait until your community’s next hazardous waste collection day and dispose of it properly then.