What Is Winterizer Fertilizer?
There’s a lot of confusion out there surrounding winterizer fertilizer. What is it and do you really need it? How is it different than other fertilizers, and when should you apply winterizer fertilizer?
The truth is ‘Winterizer’ is really just a marketing term the fertilizer companies came up with for the last fertilizer application of the season.
There’s really nothing special about that bag of fertilizer labeled ‘Winterizer’. It’s actually just fertilizer that is higher percentages of of a specific macronutrient.
For cool season lawns the important macronutrient heading into winter is nitrogen (the first number on your fertilizer label). For warm season lawns it’s potassium(the third number). There’s no special compound or chemical other than what’s typically found in fertilizer.
When fertilizer companies market their fertilizer as a winterizer, they’re simply acknowledging it’s a good fertilizer to apply during the end of the year because it contains the macronutrient you need to give your lawn depending on your location (north or south). But the truth is any bag of fertilizer containing the correct macronutrients will do. It does not have to be labeled winterizer.
Now, it’s important not to trust these marketers. You may see bags of fertilizer that say something like “Winterizes all grass types”. That’s really impossible given the different needs that cool season and warm season grasses have.
Understanding those three numbers on your bag of fertlizer (N-P-K) are important. But for now, the biggest takeaway should be that for cool season lawns you want nigtrogen (N) heading into winter. For warm season lawns you want potassium (K).
Since cool season and warm season lawns need to be treated differently during the winter, let’s break them down separately:
Cool Season Lawn- Last Fertilizer Treatment
What Does the Last Fertilizer Treatment Do?
If your timing is right, the last fertilizer treatment of the year shouldn’t do anything for your lawn until the following spring.
The idea is to apply your final fertilizer application after your last mow of the season. At this point the lawn should be done growing for the year. The lawn is not yet dormant though, it is just preparing for dormancy. This is the time to fertilize!
In preparation for winter dormancy, your lawn will respond to the fertilizer treatment by taking in the nitrogen and storing it over the winter. It will use the stored nitrogen in early spring while coming out of dormancy. This is what gives you a nice head start in the spring.
It’s usually easy to spot the people who did this correctly when driving through a neighborhood in early spring.
What Fertilizer Is Best for Last Treatment?
We’ve already established that you don’t necessarily need a fertilizer labeled as ‘Winterizer’, just a fertilizer that contains mostly nitrogen.
The great thing is you can shop around for deals. Since it’s the end of the season, big box stores have fertilizers on clearance. The only fertilizer that is actually still marked up are the ones labeled winterizer. Save yourself some money.
Something like Scotts Turf Builder is usually on clearance around the end of fall. The breakdown is 32-0-4. That means the bag contains 32% nitrogen. That’s a great choice for a last application. Any other synthetic fertilizer containing mostly nitrogen is fine to use.
Notice how I just recommended synthetic fertilizers for the last treatment. For most of the year I’m a big fan of organic fertilizers. Check out my 3 product lawn care program where I talk about all the benefits of organic fertilizers.
But for the last treatment a quick release nitrogen is more beneficial. In some areas, especially up north, the weather can get real cold, fast. You want to make sure the fertilizer has enough time to be absorbed before the ground freezes and enters dormancy. Synthetic fertilizer usually reacts quicker than organic fertilizers. Typically the slow release of the organic fertilizers is a plus, but for this last treatment speed is actually a plus.
Not to contradict myself, but if you insist on staying organic with your fertilizer, or perhaps you have some left over that you want to use up, then by all means go organic for your last treatment. In most cases it will have plenty of time to be absorbed. We’re only talking about a weeks difference.
How Much to Apply
Apply 1 pound of nitrogen per 1000 s/f for your last fertilizer application of the season. You could apply a little less, but don’t exceed a pound, especially with synthetic fertilizers since they are more susceptible to burn, even during the winter.
If you’re wondering how figure 1l/b of nitrogen per 1000 s/f check out my post on : How to fertilize your lawn. I explain how to figure application rates and how spreader settings really don’t mean anything.
Warm Season Lawn- Last Fertilizer Treatment
What Does the Last Fertilizer Treatment Do?
Winter lawn care for warm season lawns is very different then cool season lawns. Unlike cool season lawns, warm season lawns go dormant on top but the soil stays active. Soil temps usually remain warm enough so there is still activity going on in the root system of your lawn.
This is a period of high stress for warm season lawns. The last thing you want to do is add nitrogen to your stressed out lawn during this period. Conditions are not ideal for pushing blade growth, so don’t try and force it by using nitrogen. This will cause more stress.
Instead, what you want to do is apply a treatment of straight potassium (K). Without getting too nerdy, potassium helps lawns by maintaining turgor pressure in the cells of the lawn. This helps it during periods of cold, drought, or disease. All you need to know is that potassium helps lawns in times of stress. For warm season lawns winter is the most stressful time. For cool season lawns it’s summer.
Before getting into recommending a high potassium fertilizer for warm season lawns, we can’t ignore the fact fall is a great time to apply pre-emergents.
Once soil temps head back down to the 70 degree mark after the hot summer months, weed seeds germinate. For cool season lawns this is in late summer. That’s why I recommend applying pre-emergents during this time for cool season lawns in addition to the spring applications of pre-emergents.
For those with warm season lawns, your soil temps don’t head back down to 70 degrees until later in the season (early-mid fall). Applying pre-emergents during this time will help prevent weeds such as Poa Annua, henbit, hairy bittercress, chickweed and other broadleaf weeds.
What Fertilizer Is Best for Last Treatment?
Now that we know we want to treat warm season lawns with a fall application of potassium as well as a pre-emergent we can start to talk about recommended products. Of course it’s always fine to apply potassium and a pre-emergent separately but there are a couple of products that have the two combined for one simple application.
My favorite product is by Yard Mastery. It is a 0-0-7 with Dithiopyr. This a fantastic pre-emergent and this product will give you some potassium as well. This product is sold online and it’s priced competitively. Stick to the application rates recommended on the label and in the online description.
Another great product is Lesco 0-0-7. This product contains the pre-emergent Pendimethalin. If you are in a state where you can’t purchase Dithiopyr, than this product is what you want. Also, this product might be available at your local big box store or hardware store. Again, stick to the recommended application rates per the label.
My third recommendation for winterizing warm season lawns is a product that is straight Potassium with no pre-emergent. It’s Yard Mastery’s Sulfate Of Potash. This will allow you to apply potassium at a higher rate since there is no pre-emergent mixed in. Remember, when there is pre-emergent we have to stick to the recommended application rate since we certainly don’t want to over apply pre-emergent herbicides. But there are no pre-emergent herbicides in Yard Mastery’s Sulfate of Potash so you can apply up to 1 lb. of Potassium per 1000 s/f. That’s much higher than the other two recommended products.
Lastly, you can use a combined approach. That would mean using one of the fertilizer/pre-emergent combos and also applying a lighter feeding of Sulfate of Potash. This would allow you to have optimal weed protection as well as a higher dose of potassium.
In the end, you just want to make sure you don’t exceed 1 lb. of Potassium per 1000 s/f for a single application. For a better understanding of application rates and the breakdown of the math check out How to Fertilizer Your Lawn.
With warm season lawns continue to irrigate all winter. It doesn’t have to be as often as during the summer months but don’t forget your lawns root system is still active. It seems unnatural to irrigate a lawn that looks dormant on top but it’s important to remember the roots still need water. Remember, your warm season lawn is stressed during the winter months, irrigating will help reduce stress.
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