Perlite is a common additive used by gardeners and indoor plant enthusiasts to improve soil drainage and aeration. But figuring out exactly how much perlite to add per gallon of soil can be tricky. Use too little and you won’t see the benefits. Use too much, and you could hurt your plants. So what’s the right amount? Here’s a guide to help you get the perfect perlite to soil ratio.
What is Perlite?
Perlite is a volcanic rock that has been superheated causing it to expand into lightweight white granules. These granules are porous and have excellent water retention abilities while still promoting drainage.
Adding perlite to soil provides the following benefits:
- Improves aeration
- Increases drainage
- Retains moisture
- Lightens heavy soils
- Provides anchor for roots
It’s an ideal amendment for both outdoor gardens and indoor potted plants.
How Much to Add to Potting Mixes
Most experts recommend adding perlite so it makes up 10-50% of the total volume of your potting soil or seed starting mix. A good general rule is to use:
-
10-20% perlite for seed starting mixes and general potting soil. This provides moderate drainage without drying out too quickly.
-
20-30% for succulents, cacti and plants that require very good drainage.
-
Up to 50% for orchids air plants and plants that thrive in an airy, light mix.
You can also use perlite to lighten up heavy garden soils at a ratio of 1:4 perlite to native soil.
Perlite Ratio for Specific Uses
Here are some more specific perlite ratio recommendations based on use:
-
Seed starting: 1 part perlite to 1 part potting soil. This gives maximum drainage and air circulation for delicate seeds.
-
Rooting cuttings: 1:1 perlite to soil. The extra perlite prevents wet conditions.
-
Cacti & succulents: Up to 1:1 perlite to soil. These plants need exceptional drainage.
-
Orchids: Up to 50% perlite mixed with bark chips and sphagnum moss provides an airy, moist growing medium.
-
Hydroponics: 30-50% perlite is ideal for hydroponic media like flood and drain or aggregate systems.
-
Indoor plants: 10-30% perlite mixed into a quality potting soil helps prevent soggy soil.
-
Vegetable gardens: Mix in up to 30% perlite if you have heavy, compacted soil.
-
Raised beds: Add up to 20% perlite to improve drainage and create a loose, friable soil texture.
How to Mix Perlite into Soil
Adding perlite to your potting mixes or garden beds is easy. Here are some tips:
-
Measure out your soil and perlite in a wheelbarrow or large bucket first.
-
Start by mixing just the perlite into an equal amount of soil until well blended.
-
Then gradually add in more soil a bit at a time, mixing thoroughly between additions.
-
Use your hands to break up any clumps and distribute the perlite evenly.
-
When potting plants, put a bit of soil in the bottom of the container, then place the plant and fill around it with your perlite/soil mix.
Follow these guidelines to get the ideal perlite to soil ratio for your gardening needs. Proper mixing will give your plants an improved growing medium that’s loose, well-drained and abundant in air pockets for healthy roots.
Vegetable and Flower Gardens
- For gardens or new lawns, till the ground to a depth of 150–300 mm (6–12 inches) by hand or with a rototiller.
- A thick layer of a mix of half perlite and half peat moss or compost should be put down, and it should be mixed into the soil. (If the soil has a lot of organic matter already, you may not need to add the peat or compost.) ).
- If the garden is very big, the person gardening at home may only prepare the rows or areas where plants will go. If the process is kept up for two to three years, the whole garden will be in good shape.
- In dry parts of the Middle East, putting a layer of perlite under new sod has been shown to cut down on irrigation by up to half.
- Applying perlite to lawns that don’t get enough air flow or are prone to drought can make them better. Plugs should be used to open up the lawn, and perlite should be raked into the holes or worked in with irrigation water. It might take as much as 50 L/m2 (1 gallon/sq ft) to get the job done. Apply a few smaller amounts over several seasons to get the concentration you want.
Perlite is a valuable component of growing media used for container growing and patio planters. Planters with a mix of perlite and soil are light, even when they’re full of water. This makes them easier to move or rearrange to protect plants from bad weather.
- One third should be perlite, one third should be peat moss, and one third should be composted wood products like bark or shavings.
- Although perlite doesn’t hold as much water as other materials, it helps garden planters and raised beds keep water longer and supply just the right amount of water for plant growth.
ADVANTAGES FOR LAWNS AND GARDENS:
- Conditions the soil: makes it easier for plant roots to get into the soil and improves air flow and drainage
- It makes the soil better at holding water, so it doesn’t pond or crust over, and it lets water from irrigation and rain get deep into the roots.
- Keeps soil from compacting by lowering bulk density.
- Neutral and pH-balanced: won’t change the chemistry of the soil or the way nutrients are taken up.
- Clean, sterile and free of weeds and pathogens.
- Safe, lightweight, and easy to handle.
- Durable, long-lasting, and retains structure when mixed into soil.
- Insulates soil from extreme temperature variations.
HOW MUCH PERLITE DO YOU MIX INTO POTTING SOIL? DOES PERLITE CAUSE BROWN TIPS? A SOIL SCIENTIST VIEW
FAQ
What is the ratio of perlite to soil?
Can you put too much perlite in soil?
What are the disadvantages of perlite?
Should I mix perlite with soil?