How To Use Perlite To Improve Soil And Stimulate Plant Growth
What is perlite† “Air for the soil” is what it means, and it is the second best way to compost and improve soil structure. Get practical tips on how to perlite effective can use in your garden.
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How perlite in the garden to use
Perlite is often used in potting soil and soilless mixes (especially for seed starting indoors) to soil structure loose and well permeable without risk of compaction over time.
You can share equal perlite, vermiculite and peat moss (or coconut fiber) combine for a clean, simple seed starter mix that supports healthy seedling development and reduces disease damping.
You can also use it to propagate plant cuttings. instead of you cutting just root in water, you can root it in a small pot filled with moist perlite.
The same goes for seeds: start them only in moistened perlite, or test the germination of older seeds in bags filled with moistened perlite (as an alternative to the coffee filter method of starting seeds).
In raised beds or in-ground garden beds that have problems with cakey clay soil, you can improve drainage by raking a 2 inch layer of perlite into the top 6 to 12 inches of soil, while amending the soil with compost and other nutrients at the same time .
Because it won't break, a single application of perlite can keep the planting bed light and loose for several years! It was my "secret ingredient" during my years of gardening in Southern California, when I needed something more than just compost to break up all the hard clods in our beds.
Some (but not all) bagged pot and garden soils also benefit from adding more perlite to the mix.
This is especially beneficial for deep-rooted plants that are more productive when the roots don't need to penetrate dense, compacted soil (think root vegetables like carrots and daikon – you'll see how my previous clay soil was notorious for crazy, upturned roots).
I also like adding extra perlite to my garlic planting beds in the fall as the perlite helps prevent bulbs from getting wet in winter and spring. Perlite also helps the soil dry out in the weeks or two before your garlic crop is ready for harvest.
Perlite is an essential soil conditioner that I always have on hand, and I buy several bags every year because I always find a use for it.
Keep in mind that smaller varieties of perlite, and in some cases cheap perlite with little quality control, can get dusty (especially if you get to the bottom of a bag).
If you are sensitive to fine airborne particles, wear a dust mask and goggles when working with perlite. (I like to keep both items in my gardening toolkit. See my Resources linked below for stylish reusable mask options I own for working with dusty garden products.)
Types or sizes of perlite
Perlite is generally available in four grades or grain sizes, which correspond to the coarseness levels.
Grain size type of perlite quality
Super Coarse Perlite #4 1 inch
Coarse Perlite #3 1/2 inches
Medium Perlite #2 1/4 inch to 3/8 inch
Fine Perlite #1 1/8 inch
Super Coarse and Coarse Perlite: This type of perlite is often used to amend raised beds and garden beds, or dense soils with a high water holding capacity (clay). Size #4 perlite is a whopper of a particle that should only be used for extremely heavy soils.
Medium-sized perlite: You usually see medium-quality perlite in commercial potting soil. It is a good all round size for potted plants, window boxes and general garden use.
Fine Perlite: These smaller particles are ideal for starting seeds or rooting cuttings. Fine perlite is hard to find in this size as a standalone product, so I tend to go with fine pumice, which is usually labeled for planting bonsai or succulents.
Benefits of Using Perlite in the Garden
Perlite is a very useful part of gardening for many reasons:
It is physically stable and keeps its shape even in heavy or saturated soil.
It does not decompose, so it is ideal for use in potting mixes for plants that are not often repotted (such as succulents and other houseplants).
It has a neutral pH, making it suitable for any container or garden bed.
It contains no toxic chemicals or additives; when you buy a bag labeled as perlite, that's exactly what you get.
It can absorb some water and let the rest flow out freely.
It provides excellent aeration. Plants take up 98 percent of their oxygen through the roots, so proper aeration is crucial for healthy root development. Good airflow also supports earthworms, beneficial nematodes and other good stuff in the soil food web, which in turn supports plant life.
Because of these properties, perlite is also popular in mixes of orchids, cacti and succulents that like to be on the drier side, and in hydroponic setups as a standalone growing medium.
Does perlite cause fluorine burn in plants?
Rumor has it that perlite is responsible for fluoride burns
nding in houseplants, appearing as brown leaf spots or scorched leaf tips in sensitive plants such as dracaena, spider plants and Easter lilies.
However, if you use a commercial potting soil that contains perlite, the chances of that happening are very slim.
Fluoride poisoning can be caused by many things, including fluoridated water, superphosphate fertilizers, low soil pH, and other environmental factors that have little to do with potting soil containing regular perlite.
Where to buy perlite
The most convenient source of perlite is your local independent garden center or nursery with large boxes. When buying perlite, make sure you are buying 100 percent perlite and not soil or soilless blend.
I've also linked my favorite brands of perlite (below) in different sizes, which you can easily buy online.
If you can't find local perlite, pumice is a good substitute because it has similar properties. Sometimes you can use vermiculite in a pinch (especially as a seed starting medium), but keep in mind that it holds more moisture than perlite.
When it comes down to it, perlite is still the best soil improvement choice if you want moderate water retention, excellent aeration and drainage, and long-term benefits.
