Since we started carrying the new 5oz “liquid” prodiamine late last year, one question I’m getting often now is “which is better, liquid or granular prodiamine?”
I’m going to give you a few different reasons why to consider each one, but the short answer is “the best choice is the one that you, the DIYer feel most comfortable applying,” or said another way “the one that you can get down across your lawn the most consistently is the best one to choose.”
I say that because prodiamine is a pre-emergent herbicide that stops crabgrass from appearing in the lawn. The way it works is that once you apply and water it in, a vapor barrier is created in the top portion of soil. This vapor barrier remains for several months and as crabgrass seeds germinate and grow the young (very young) plants encounter this vapor which disrupts cell division and effectively stops the the plant from growing. Science is pretty awesome!
Some of this below is going to get a little technical - I say that because many of you just want to “throw and go” and if that’s you, just get granular and spread it - that is how the majority of y’all will have the most success. Professional lawn companies across America use both liquid and granular. When it’s early in the season and there is still a chance for a freeze, they use granular, and when things warm up in later spring they switch to liquid. So both do fine, just know that much, but if you want to get into the details and understand the “why” behind my recommendations, keep reading...
How Prodiamine Works
Now just picture a vapor barrier across your lawn. That vapor has to be constant in order to be completely effective. If there are “holes” or spaces where you didn’t get the product down correctly, evenly, consistently; those areas will fail and crabgrass will get through. So first and foremost, choose a prodiamine product that you can apply consistently.
For many DIYers, this will mean granular is the best choice. That’s because the majority of your prefer granular application for everything else - fertilizer, insect control, disease control, all of it. You are comfortable using your spreader and you have gotten good at applying granular products to your land. If that is you, then granular is best.
What About Liquid Prodiamine?
Now, if you are someone who has experience using a pump sprayer or battery sprayer (battery sprayer preferred for consistent flow) then liquid does offer some advantages. First off, just picture the coverage you get with blanket spraying.
Let’s pretend there are no chems involved and you fill your pump sprayer with just water and spray it on your driveway. It will cover 100% of the driveway with water, like painting a wall. Can you picture that?
Now picture putting sand in your spreader and pushing that across the driveway. Sure, that sand will spread out nicely but if you get down and look close there will be space between the grains.
So this is the advantage to liquids - they do cover better/more thoroughly during application. In the case of the Prodiamine 65 WDG we have for liquid, it’s actually a “powder” of sorts know as a “water dispersible granule” which basically means you are created a very fine particle suspension in water. This is why it’s important to stir it up well upon initial mix and keep it agitated as you go - so the suspension remains consistent.
However, does this mean liquids are better than granular? No, they will both work the same if applied according to the label.
And that is the key: the rates on the label must be followed. They are important because math has been done to compensate for the variance in coverage between liquid and granular. In other words, granular prodiamine requires much more “pounds on the ground” in order to get the same results as the liquid.
Granular Prodiamine Make Up
The way granular is formulated is that prodiamine powder is bonded to the outside of filler material. In the case of the prodiamine we carry, it’s bonded to limestone and muriate of potash. (that’s why it has a 0-0-7 analysis from the potash)
Our blender, Sunniland, has a math formula they use to tell them how much prodiamine to bond to the grains based on the size and consistency of those grains and the desired application rate. Because I work with DIYers I have our product manufactured so that essentially, 1lb of product per 1,000 sq ft will give you one month of pre-emergence protection*. I do that so it’s simple.
So let’s stop right here and think a minute: 1 pound of grains that are coated in prodiamine are spread across 1,000 sq ft of lawn area. How does this compare to the liquid?
The liquid WDG formulation, also made for me by Sunniland, requires .183 oz/1000 sq ft. Photo
See how there are a whole lot more granulars/grains/prills needed to cover the 1,000 sq ft area? That is needed in order to ensure that when you water the application in, the powder is washed off the granules and is dispersed throughout the top layers of soil. With the liquid, you don’t need that because the water acts as the carrier and it’s much easier to cover evenly. However, with the liquid, the walking speed becomes much more important because if you coat the lawn “thin” by walking too fast you can have break through in those areas.
Now, we could get much much deeper here but I won’t. I could go into the actual amount of active ingredient in those stacks you see in the picture and compare those too because the prodiamine granular is .38% active meaning only .38% of the 45lb bag is actually prodiamine, the rest is filler and carrier. And the WDG formulation (water dispersible granule) to make liquid is 65% active. But I feel like that isn’t needed - for purposes of this post, I think I’ve gone deep enough in helping you understand the differences.
What About Prodiamine Cost?
One final angle to explore, and an important one, is the cost. This is an easier equation to figure out.
A 45lb bag of granular prodiamine is $49.99. That is by far the cheapest you will find it anywhere shipped directly to your door. That 45 lb bag covers 15,000 sq ft utilizing the rate I recommend is 3 lbs/1000. Each 3lbs/1000 application you make gives you 3 months of pre-emergence protection. I recommend two of these applications in spring, and one in fall (if you are not seeding).
A 5oz bottle of prodiamine WDG costs $20.48 including shipping. This is the only small bottle of prodiamine WDG found anywhere in the world lol. The 5oz bottle covers 27,000 sq ft utilizing the .183 oz/1000 rate I recommend. This rate gives you 3 months of pre-emergence protection. I recommend 2 of these applications in spring and another in fall (if you are not seeding)
45lb bag - $49.99 covers 15,000 sq ft
5 oz bottle - $20.48 covers 27,000 sq ft
And you are going to find this is the case with almost all lawn products. The liquid formulations are usually cheaper overall. Granular products are just bigger and bulkier so you have to pay for more material to start with, and on top of that, they are more expensive to move around.
Prodiamine DIY vs Hiring Lawn Company
Again, if you are more comfortable using the granular, then that is where you should stay with that because you are still not spending that much money when you compare what a professional would charge you.
If you have a 5,000 sq ft lawn, a professional lawn spray company will charge you anywhere between $40 and $50 to apply prodiamine one time for you. You can get an entire bag for $49.99 that would give your same 5,000 sq ft lawn 3 applications or an entire year of treatments. So for sure, even with granular, the DIY option is still much cheaper than hiring it out.
And lastly, have no fear with prodiamine. If you mess it up, you are not going to hurt anything. If you go too light, you may have some breakthrough and if you go too heavy, it isn’t going to burn your lawn. I don’t want you to go crazy with it on purpose but if you do make a mistake and over apply, non harm will come - you will just get much much longer pre-emergence protection than you need.
The key with all prodiamine is that it has to be watered in - use ½” or irrigation or rainfall as your guide and you’ll be well on your way to a crabgrass free season in 2021!
*I do not recommend trying to apply prodiamine granular at 1lb/1000. That low rate is nearly impossible to spread consistently. Never do an app of less than 3lbs/1000 sq ft.