Houseplant Soil 101: Necessary Ingredients and DIY Recipe

Houseplant soil is very different to the soil that your outdoor plants are growing in. Because your plants are living in pots, they need an open mix that can hold some moisture but is also free draining. Here’s all you need to know and an easy do-it-yourself recipe.

When it comes to growing lush and healthy houseplants, the soil that you use is of the utmost importance. Because your plants are growing in pots, their soil requirements are far different to those plants growing outside in the ground. The roots of your houseplants are confined to just the soil in the pot, and garden soil does not have the right structure for roots grown in a confined space. Plus, the soil in your garden can easily become compacted when it dries out too much.

In order for your houseplants to thrive, you have to use a good quality potting mix. You can either purchase a ready-made mix from your local garden centre or you can easily make your own if you’re keen.

The Necessary Ingredients in a Quality Potting Mix

A quality potting mix needs to be open, friable and lightweight. For healthy roots, the soil that they grow in has to have air pockets. This is because roots need air as well as water and nutrients. If the soil becomes too compacted, the roots of your plants will suffocate.

Your potting mix also needs to have a little water retention so it doesn’t dry out too quickly but it also has to be free draining. If the soil becomes waterlogged and doesn’t drain freely, the roots will also suffocate due to lack of air. Plus, most roots will rot if they sit in water for too long.

A good potting mix should have a combination of the following ingredients.

• Compost. This could be compost made from vegetative materials such as vegetable scraps, grass clippings, dry leaves and composted bark. Many commercial mixes also use peat moss or coconut coir. However, in recent years, it’s become apparent that peat moss is not sustainable and the peat bogs that it’s harvested from are slowly diminishing.

For this reason, it’s far more advisable to use coconut coir which is a sustainable and renewable product with similar qualities. Coconut coir is a by-product of the coconut industry and is made from coconut husks.

Other ingredients that are used in the compost part of the mix are animal manures and worm castings. This compost provides your plants with their initial nutrient requirements.

• Perlite or vermiculite. These two ingredients help to aerate the mix and to retain moisture. They’re derived from mined minerals and volcanic glass. They help to keep the mix both light and friable. Most commercial mixes will use one or the other and you can do the same if you’re making your own mix.

• Sand. This helps to improve the drainage of the mix. Coarse builder’s sand is the type of sand that is commonly used. The larger sand particles open up the mix, to create air pockets for the water to flow through and drain away easily.

• Fertilizer. Although the compost does contain many nutrients, these will quickly be used up by the roots of the plant. That’s why a lot of commercial potting mixes also add a slow-release fertilizer. These slow-release granules will release their nutrients as the plant needs them.

How to Make Your Own Potting MIX

If you have many houseplants and you’re repotting often, you might like to make your own mix. It’s really simple and ensures that the mix contains all the necessary ingredients for healthy plant growth. Here’s a simple basic recipe to get you started.

All these ingredients can be purchased from your local garden center. When measuring out your ingredients, it’s important to measure them by volume rather than by weight. This is because some ingredients have a greater mass weight than others.

Once you’ve measured out your ingredients, it’s just a case of mixing them together really well. You can do this in a wheelbarrow, a garden cart, a large plastic bin or even on a groundsheet.

Store any mix that you don’t use immediately in a sealed plastic bag or a garbage bin with a sealed lid. You want to ensure that no critters get into the mix while it’s stored. Therefore, make sure you keep it in a cool, dry spot out of direct sunlight.

This mix is ideally suited to most houseplants. However, if you’re growing succulents or orchids, you will need a different mix. This is because succulents prefer a much drier mix or one that will dry out quickly. Orchids, on the other hand, are epiphytes and don’t need compost in their mix.

Final Thoughts

Hopefully, you now understand the basic soil requirements of your houseplants and why you should never use garden soil in your pots. The mix that you grow your plants in has to provide them with all the water and nutrients that are necessary for healthy and lush growth.

The potting mix needs to be open to allow for air pockets and free drainage. It also needs to be light so that the roots can easily access all the water and nutrients that they need.

In addition, the mix has to have some water holding capacity so that it doesn’t dry out completely. Remember that plants growing in pots indoors will have different water requirements to those that grow outdoors in the ground.

When selecting a commercial potting mix, make sure that you check the ingredients on the packaging and buy the best quality that you can afford. Or, you can save yourself some money and easily make your own mix using the easy recipe above.