The Ultimate Guide to Milorganite and When to Use it on Your Lawn

Milorganite is an all natural, slow releasing lawn fertilizer that’s been made for decades right in Milwaukee, WI.

We take a look at how it’s made, how and when to apply it, and how often use it on your lawn.

a lawn with milorganite fertilizer
When should you consider applying Milorganite to YOUR Lawn?

What is Milorganite Made of?

milorganite being made in a water treatment facility
A typical water treatment facility

Milorganite is a specific brand of lawn fertilizer, manufactured in Milwaukee, Wisconsin.

According to the company’s website, it is one of the oldest brands of fertilizers available on the mare today. It is one of the oldest .

Milorganite is composed of heat dried microbes that have digested the organic matter in wastewater.



a bag of Milorganite
Click to check price on Amazon.

The microbes absorb the nutrients found in the wastewater, and then the cleaned water is returned to Lake Michigan while the microbes are kiln-dried into small pellets and then made available as fertilizer.


What Does Milorganite do for Grass?

a lawn with milorganite fertilizer
Milorganite is a healthy, all natural way to green up your lawn throughout the entire year.

Milorganite is an all-natural, slow release fertilizer that provides much needed nitrogen and other nutrients to your lawn.

Major brand name commercial fertilizers sold in the big box stores are like a “sugar rush” of nitrogen to your lawn, and not much else.

They are known for making your grass grow quickly and turn very green, very fast.

Which is why they sell so well.

The downside is that nitrogen rush quickly wears off and leaves your grass stressed and susceptible to disease.

Compare it to your own diet:

Imagine if you ate one giant bowl of sugary cereal first thing Monday morning and then nothing else the rest of the week.

You’d feel great for about 30 minutes and then pretty awful the rest of the week!

But if you had a small steady diet of protein, vegetables, fruit, and grains, taken in small doses throughout the entire week,…well you get the point.

Slow release natural fertilizers like milorganite provide that smaller, steady stream of nutrients to your grass.

Similar to slow releasing lawn lime, this release takes place over a period of about 10 weeks, depending on how much rain you get, before it will be time to make the next application.




When to Apply Milorganite

When to put down Milorganite on your lawn depends on whether you have warm season of cool season grass.

In general, warm season grasses are found growing in southern states and cool season grasses are found in northern states.

If you aren’t sure what you have, you can ask a knowledgeable neighbor, a local landscaper or take a sample into your LOCAL lawn care store to ask.

(Don’t bother trying to ask anyone at a big box store).

Here is a list of common grass types in each category for you to determine when to use Milorganite:


Warm Season Grasses:

warm season grass
You can first apply Milorganite earlier in the year if you live a warm climate.
  • Bahia
  • Bermuda Grass
  • Centipede
  • St. Augustine
  • Zoysia

If you live in a southern state with warm season grass, you can make your first application of milorganite after the last frost of the year and once the grass has started actively growing.

Temperatures should be consistently in the 70’s (degrees F) during the day.


Cool Season Grasses

cool season grasses in a northern farm
Bluegrass and Fescue are the most common cool season grasses found in the northern and midwestern states.
  • Kentucky Bluegrass
  • Ryegrass
  • Fescue

If you live in a northern state with cool season grass, you can make also your first application of milorganite after the last frost of the year and once the grass has started actively growing.

Temperatures should be consistently in the 60’s (degrees F) during the day.


How Often to Apply Milorganite

According to the folks at Milorganite, the fertilizer should be applied:

4 times per year at a rate of 32 lbs per 2500 sq. ft of lawn.

You will want to check with your local and state websites for any local ordinances related to fertilizer blackout dates and allowed rates of fertilizer application.


How Often to Apply Milorganite in Warm Season Zones

Four times a year generally during the following times:

  • Easter
  • Memorial Day
  • Labor Day
  • Early October

Avoid fertilizing warm season grasses late in the fall when they are trying to go dormant.

Your grass is naturally trying to stop growing and adding fertilizer counteracts this and can cause stress to your lawn.


How Often to Apply Milorganite in Cool Season Zones

Four times a year generally during the following times:

  • Memorial Day
  • July 4th
  • Labor Day
  • Thanksgiving

Avoid fertilizing too early in the year when the grass has not started growing yet.

However, unlike with warm season grasses, when fertilizing cool season grasses you should lay down your last dose of Milorganite as late in the season as possible.

Preferably just before the first freeze or snow fall.

Unlike warm season grasses, cool season grasses love to absorb fertilizer when they going dormant as this helps them to come back even stranger in the spring.



How to Apply Milorganite

To apply you Milorganite correctly, you will need a good spreader. Either a drop or broadcast spreader will work fine.

Set your spreader to about ¾ open.


How Much Milorganite do you Need to Put on your Lawn?

Calculate how much Milorganite you will need to spread based on the advised ratio of:

32 lbs per 2500 sq. ft.

Don’t be alarmed by the amount of Milorganite you may need for a larger lawn.

Remember, this is an all-natural, slow releasing fertilizer compared to the highly concentrated mass market fertilizers you may be used to purchasing.


How to Put Down Milorganite

Before applying the Milorganite, make sure to mow your lawn, and avoid spreading it on a windy day or right before a rainstorm.

Walk in at a steady pace and try to evenly distribute the calculated amount of Milorganite evenly around your lawn.

We recommend walking in predetermined straight lines back and forth across your lawn with a small amount of overlap. Take note of how far to the right and left your milorganite lands if you are using a broadcast spreader.


How Long does Milorganite Take to Work on a Lawn?

a bunny eating weeds in a green lawn
When it comes to healthy lawn fertilization, it’s better NOT to be the Hare.

According to the folks who make it, Milorganite’s slow release formula will provide nitrogen and other beneficial nutrients to your lawn over a period of about 10 weeks, hence the four application a year schedule.

This slow release is critical to maintaining a healthy, stable, green lawn that can grow deep roots and stand up to disease and drought.

You won’t see that immediate “pop of green” you get with mass market chemically concentrated fertilizers that give your lawn the aforementioned “sugar rush.”

But your grass was never meant to need anything from a lab in order to stay healthy and green. Grass just needs water, sunlight, and soil with a healthy and steady balance of nutrients.

So have a little patience, but know that the Milorganite is not only working to green up your lawn, but setting it up to STAY healthy and green throughout the entire season and beyond.


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