You’ve heard of Neem oil but “What the heck is a neem cake?” There’s a specific tree that’s gone from the source of Ayurvedic folk medicine to one of the most important crops in horticulture.
This tree’s name is Azadirachta indica, but you might know it better as the neem tree or Indian lilac.
What’s made this tree famous is a chemical it naturally produces called Azadirachtin. It’s been used for thousands of years in natural pest management.
You’ve likely used neem oil extracted from all parts of the plant in healthcare or garden products.
However, did you know that neem oil isn’t the only beneficial product to come from these trees?
Welcome to the world of an underrated block of gardening natural products gold: the Neem Cake.
What Are Neem Cakes?
Neem oil, in its purest form, is created by cold-pressing parts of the neem tree.
The seeds and leaves produce more oil, but any part is usable.
After pressing, the solids leftover are compacted into neem cakes and sold in either cake form or further processed into granules, powder, or added to existing fertilizers or manures.
What’s in a Neem Cake?
While most of the oil in the extraction process comes from the solids, neem cakes still contain a small amount.
This means trace amounts of Omega fatty acids, Azadirachtin, and all the other goodies that make neem oil work so well. More on How Neem works on plant pests.
There are no additional ingredients in a neem cake in most cases, making it a form of all-natural manure or compost.
What are the Benefits of Using Neem Cakes?
Unlike many other types of natural fertilizers, neem cakes don’t rely on any additives to work.
Neem cakes are an excellent NPK fertilizer with a natural timed-release capability.
This “organic fertilizer” includes a wide range of vital plant nutrients, including:
- Calcium (0.5% to 3.0%)
- Copper (4 ppm to 20 ppm)
- Iron (500 ppm to 1200 ppm)
- Magnesium (0.3% to 1.0%)
- Manganese (20 ppm to 60 ppm)
- Nitrogen (2.0% to 5.0%)
- Phosphorus (0.5% to 1.0%)
- Potassium (1.0% to 2.0%)
- Sulphur (0.2% to 3.0%)
- Zinc (15 ppm to 60 ppm)
Also, the trace amounts of neem oil remaining give the cakes natural pesticidal, antifungal, and antibacterial properties.
The cakes even help reduce soil pH naturally by producing organic acids.
How Do You Use Neem Cakes On Plants?
Because neem plants are an NPK-style fertilizer, it isn’t always the perfect answer.
However, it works well when used as a soil amendment in three areas:
- Soil restoration
- Plant food
- Plant health
Using Neem to Restore Soil
You can use neem cakes in fallow ground to restore the natural nutrients when paired up with restorative crops (such as peanuts) or other fertilizers.
As the cake breaks down and releases its nutrients, it also reduces the amount of nitrates being released by soil bacteria.
This process can boost the performance of most fertilizers while also adding their nutrients to the soil structure.
While studies have not been made to determine the efficacy of using neem cakes on their own in fallow soil, they can be quite effective when combined with other methods.
How To Use Organic Neem Cakes as Plant Food
Neem cakes have a relatively low NPK ratio, with most cakes rating 4-1-2 and the higher-end ones rating 6-1-2.
The cakes are broken into powder or chunks and added to the soil.
For fields and gardens, add the cakes to the soil as an amendment during tilling at a rate of 1 pound per 20 square feet, mixing to a depth of 6″ inches, and watering well.
Wait a few weeks before planting for the best results.
For potted plants, it’s a little complicated.
As a general rule, you should only add about 1% percent neem cake concentration to any commercial potting mix before a transplant, especially when dealing with young plants.
Even though neem is beneficial, young plants are susceptible to chemical burns from fertilizers and pesticides if there’s too much organic content present.
It can also slow early root development if applied too heavily.
You can blend 2 to 2.5 tablespoons of neem cake with one quart of water to make a periodical plant fertilizer for older plants.
Let the mixture sit for 2 to 3 days in a cool dark place, then pour one cup into each plant’s soil.
Apply as often as directed by the cake’s packaging or following your plant’s needs.
Using Neem Cakes for Plant Health
Of course, the biggest benefit of using a neem cake is in the name.
Neem cakes contain nortriterpenoids and isoprenoids, which help keep nematode populations under control.
The trace chemicals kill lawn grubs and other forms of ground pest.
It can also slow and sometimes even stop fungal root rot, some bacteria, and other harmful plant pathogens.
Best of all, it’s harmless to earthworms, vital garden workers that provide soil aeration and leave behind additional nutrients.