Soil Additives

There are many different products that you may choose to add to your houseplant soil mix.  What products you choose and how much you add really depends on your houseplant’s individual needs.  This article isn’t going to be a thorough guide on soil for each individual plant, but it will overview some of the additions out there and why you might choose to have them in your houseplant mix. 

First and foremost – why add anything at all?  Well, houseplant soil, typically, just isn’t very good.  Looking at almost every major brand, the soil simply does not provide adequate drainage for your houseplants – leading to root rot.  It is always important to adjust your soil and give your houseplant its best possible home.  The most important additives to know about are the ones that add drainage while still keeping your tropical houseplant adequately moist.   


Perlite is a puffed volcanic stone that creates air pockets in your soil.  These air pockets allow the roots of your houseplant to get the oxygen they need while also helping with water drainage.  You don’t ever want your roots to sit in compacted or wet soil because that causes rot; this aeration is really crucial.  Many houseplant soil mixes do come with perlite in them, but not nearly enough.  Adding more can help boost your soils aeration and keep your roots happy. 


Pumice is a type of volcanic rock.  It can be used in the exact same way as perlite.  One benefit of pumice is that it won’t ever float to the top of your soil – as perlite can tend to do because of its light weight.  Pumice adds some very nice and reliable drainage to your soil.

Orchid Bark

Orchid bark is just what it sounds like it is– chunks of bark.  These bits of bark are sold for use in potting orchids, but they are also extremely useful in other houseplant mixes.  The bark adds additional drainage while also holding moisture.  It can also help to mimic the natural home of epiphytic houseplants (plants that would grow on trees in nature). 

Horticultural Charcoal

Horticultural charcoal is a type of activated charcoal that can be added into houseplant soil in order to improve the drainage while also cleansing the soil.  The charcoal acts as a Ph balancer and guards against rot, bacteria, mold, and fungus.  It also helps to absorb any bad odors – keeping your houseplant smelling as nice as a houseplant can smell. 


LECA is a type of puffed clay ball often used as a substrate in semi-hydroponic systems.  You can, however, also add it to your houseplant soil.  LECA can act in a similar way to pumice or perlite.  While it isn’t as common or popular, if it is all you have on hand it can be used in a pinch. 

Sphagnum Moss

Sphagnum moss is a sponge like moss that grown on the top on peat bogs.  It is often used to mount houseplant onto boards, to create climbing poles, or to propagate cuttings in.  It is also used to add to houseplant soil as a means of retaining moisture.  The moss allows the roots to access oxygen while providing them with ample moisture. 


Vermiculite is made up of a group of hydrated laminar minerals that looks similar to mica.  Vermiculite can boost water and nutrient retention in the soil, while again, adding drainage.  You can never have too much drainage.  Vermiculite is often added to houseplant soil as a means of keeping the plant moist for a longer duration without the roots becoming wet or compacted.

Coconut Coir

Coconut coir, or coco coir is a finely ground substrate made from the fibre of a coconut husk.  It is often used as a substitute for peat moss in houseplant soil.  The coir acts as a sponge of sorts, holding moisture.  It doesn’t, however, carry any nutrients.  So, if used as a base substrate, natural fertilizers need to be added.

Coconut Husk

Chunks of coconut husk are sometimes used as a means of creating a chunkier, more aerated houseplant soil.  These bits of coconut are often used in the same way orchid bark would be. 

Worm Castings

Worm castings are worm poop. They act as a wonderful source of nutrients for your plants without the risk of burn from chemical fertilizers. Worm castings are often added to homemade soil mixes as a source of compost and nutrient booster.

Houseplant soil isn’t an exact science.  But generally speaking, houseplant soil should be well draining, airy, and full of nutrients.  You want the soil to breath and dry out, but to hold moisture long enough for your plant to take in what it needs.  Using additives can make your houseplant mix a much better home for your houseplants and greatly improve your chances of success.