Greensand, also called glauconite, is an incredible organic soil amendment for your organic garden.
It’s a mineral that formed in prehistoric times in anaerobic ocean environments. Deposits of iron, potassium, lime, silicates, and 30+ other trace minerals at the bottom of stagnant pools of water eventually compressed to form the rock known as greensand, which is mined up and processed for use in the garden. It’s easily crumbled, thus the name greensand stuck due to both the texture and color of the mineral.
Glauconite greensand is a popular amendment for your raised beds, boosting growth due to a variety of benefits it accrues in your soil.
Best Organic Greensand: Espoma GS7 Greensand Soil Conditioner
Benefits of Greensand
Unlike actual sand, greensand holds on to both water and nutrients. It’s estimated that it holds around 1/3rd of its weight in water, making it a fantastic remedy for soils heavy in clay or sand.
- Improves your soil’s ability to hold both moisture and nutrients
- Improves soil structure by increasing cation exchange capacity (CEC)
- Eventually breaks down and becomes bioavailable, specifically a good source of potassium as it has an NPK value of 0-0-3
How to Use Greensand
Greensand is best applied in spring, as the slow-release potash within it takes time to become bioavailable. For all applications, mix into the top 3-6″ of soil.
- Trees – Work 1-2 cups of greensand into the soil around the base of the tree
- Lawns – Apply 10-20 pounds per 1,000 square feet
- Flowers and Vegetables – Apply 25-30 pounds per 1,000 square feet
- Container Plants – 2-3 tablespoons per gallon of high-quality potting soil
- Broadcasting – Heavy applications of 50-100 pounds per 1,000 square feet for poor soil
After the first year of amendment, you should use less. Around 1-2 pounds per 100 sq. ft. is a good recommendation, provided your soil needs amending at all.
Don’t be afraid to over-apply greensand, as it isn’t “hot” and will not cause nutrient burn. This makes it a great choice for plants that are sensitive to synthetic fertilizers.
While application of greensand to your potted plants is possible, it’s only useful to improve soil condition, as its slow-release nature won’t break down quick enough to boost potassium in your houseplant gardens. You can also add coconut coir, perlite, or vermiculite to improve your potting soil instead of greensand and have similar effects.
Texas Greensand vs. Lava Sand vs. Glauconite
There’s a bit of confusion out there about these three soil amendments, so let’s clear it up:
- Texas greensand is different from the glauconite type and has an NPK ratio of 0-2-5
- Lava sand is crushed up scoria, which is a type of reddish-brown volcanic rock
Is It Safe For Your Garden?
You’ll be happy to know that greensand fertilizer is completely safe to use for both yourself and your garden. You don’t need to use gardening gloves when working with it, and it is not toxic to animals or children. This is one of the few soil amendments you don’t have to worry about, which is a huge relief!
Equally important, glauconite greensand doesn’t harm or disrupt the beneficial microorganisms in your soil that are working to break down minerals and nutrients and make them bio-available for your garden. As a “beyond organic” gardener, my plants and soils are treated with the utmost respect, so adding a synthetic fertilizer to my garden is a big no-no.
I don’t want to mess with the natural soil food web within my garden, so greensand fertilizer to improve moisture and nutrient retention is a fantastic solution. Now, get to planting an epic plant and search for green sand at your local garden center or favorite online store!