The short answer is no. Fertilizer does not go bad.
Most lawn fertilizers are a combination of nitrogen, phosphorus, and potassium (N.P.K) These minerals stay active and do not change over time or lose their effectiveness. Some fertilizers also include many other micronutrients that are helpful for a lawn like calcium and iron and these will also not break down over time.
Be aware that if you are choosing a more all-natural or even organic fertilizer approach or using a liquid fertilizer that the shelf life may not last forever.
If choosing a product that is made of bat guano, sea kelp, earthworm castings, humic acid, and mycorrhizae fungi they will have a period of time that they are the most effective for. After the expiration date listed on these products they may still work, but they also may not be as good as a fresh source would be.
The all-natural choices are an excellent option if you have kids and pets playing in your lawn and garden and you do not want to apply a general chemical fertilizer. However, after a year or two you will be best served to get a new batch.
Granular Fertilizers Never Go Bad
Granular lawn fertilizers do not go bad.
You can feel confident unwrapping that 50lbs. bag in the back shed that you have had for years and fill up your fertilizer spreader and go to work. They literally will never go bad as they are just pure nitrogen, phosphorus and potassium.
You may notice that the granules inside the bag will clump up together and become “cakey” with age. This poses no problem though for use. Simply break up the material before putting it in your drop or broadcast spreader with a stick or your hands. Wear some gloves if you are going to do this by hand.
It is important that you keep bag of granular fertilizer dry for it to be usable over the long periods. If moisture gets in the bag it can damage it. High humidity is the reason that granular fertilizers can become “cakey” and require being broken up in order to be used again.
Liquid Fertilizer Can Go Bad
All liquid fertilizers do tend to have a most effective date or expiration date on the products. Check the products that you have prior to applying to make sure that they are still within the best by date.
Solutions made from organic materials will break down quicker than the chemical varieties. However, both organic liquid fertilizers and chemical liquid fertilizers are known to settle over time.
It is wise to shake the bottle well prior to using otherwise you will just apply the liquid in the bottle and all the good stuff will be left behind in the bottle defeating the purpose of fertilizing.
How to Store Fertilizers so They Don’t Go Bad
Always keep your fertilizers in their original bags or bottles. This is important so that it is easy to remember what product you have, and you can reference the instructions for how much to apply. You don’t want to spread a fertilizer out on the lawn and then realize that you just spread a preemergent herbicide or something else you are using in your lawn care.
Buy a plastic tote with a secure lid to place all your open but unused fertilizers. This will keep it away from little kids or pets from getting into it and will also help keep it dry to last the longest. Label the bin so it is easy to find in your garage or shed when it comes time to caring for your lawn.
Which Fertilizers is Best for You?
While it may seem that most homeowners should just buy a huge bag of granular fertilizer or pick up every half open bag, they can find at estate sales because they last forever. However, this may not be the best for you.
Liquid fertilizers are very effective and my preferred method for controlling a lawn fertilization strategy for maximum grass greening and growth.
Liquid and Granular Fertilizers Used in Tandem
If you apply granular fertilizer you need a rain to happen not just be in the forecast.
So many homeowners apply granular fertilizers in anticipation of a rain event and then when that rain doesn’t materialize or is very light, they forget to water the fertilizer in. This leaves the granules in the grass just sitting there. This can be harmful to small children, pets, and animals that may accidentally consume the fertilizer.
I recommend using a 50% application of granular fertilizer. Use half the recommended amount to spread on your turf lawn. Then apply a 50% reduced recommended amount via a liquid fertilizer.
By doing this in tandem you can guarantee that the granular fertilizer will be broken down and get into the soil and you get the best of both worlds.
If you aren’t doing a soil test which is 95% of households across the country, consider a broad spectrum fertilizer is recommended.
Many liquid fertilizers are a broad spectrum and so by doing a 50-50 split between granular and liquid you are ensuring that your grass is receiving all the macro and micro nutrients it needs to grow well and maintain that bright green color that you are seeking
Timing the Application of Liquid or Granular Fertilizer
The only way to eliminate the biggest variable of whether your lawn fertilizer is getting applied is by using a liquid fertilizer. Granular relies on the rain and even if it is in the forecast it doesn’t mean that you will get the rain you need to fully apply the fertilizer.
A liquid fertilizer gives you that complete control to apply it exactly when it needs to go down. When it is my lawn, I look for a window in the weather where it has just rained for two days and then will be sunny afterwards. After the rain has stopped and the forecast is clear, get out there and apply your liquid fertilizer. The grass will rapidly absorb the nutrients and you will see incredible growth and color with this timing.
Wrapping Things Up
The fertilizer you have will not go bad, but it is a good idea to keep it relatively fresh.
Get a new bag or bottle each season to avoid any of the problems with “cakey” granular fertilizer or liquid fertilizers that have settled at the bottom of the bottle. Plan your fertilization strategy to maximize the effectiveness of lawn care program.
I recommend home owners should plan on purchasing smaller quantities and use both a granular fertilizer and a liquid fertilizer rather than purchasing in bulk one over the other.
Develop a consistent irrigation and fertilization strategy for your lawn care for the full year and stick to it. After a season or two you will be able to gauge exactly how much product you need for the season. Then buy what you need for that season and avoid having to store lots of fertilizers in your garage or shed every year.
Your lawn will appreciate getting fresh fertilizer and you get to avoid any of the headaches of dealing with cakey granules that need to be broken up or wasting half a bottle of liquid fertilizer that becomes unusable after sitting for 6 months.