Soil Amendments: How to Amend Soil for Your Houseplants

Kassi Kuppinger
Jan 11, 2023
6 min read

Updated: Sep 26, 2023

One of the keys to being a successful plant parent is knowing what your plants need so that you can take care of them appropriately, and the soil they are growing in is one of the first and most important things to take into consideration. Every plant has different needs and grows natively in different areas that have different soil types and compositions. So, planting every plant you own in the same "all-purpose" potting soil likely will not cut it for many of your plants. Even if you have planted all of your various plants using the same all-purpose potting soil and they seem to be doing just fine, well, they might be. But do you really want to settle for "just fine," when they could be thriving in a potting mix that is tailored to their needs? And while there is not a ready-to-go bag of potting soil for each individual plant, there is an easy and affordable way to tailor your soil to the needs of each individual plant with the use of soil amendments!

What Are Soil Amendments?

Soil amendments are different materials that are added to your soil to improve or change different physical properties such as moisture retention, drainage, soil pH, and the like. Many "all-purpose" potting soils often come with some soil amendments in them already, such as perlite, sand, or peat moss, however, this is not always enough for some plants, and it is recommended to know what your plants need in order to be able to amend your soil appropriately. But before we get into that, let's look at the most common soil amendments and their uses.

1. Perlite

Perlite is perhaps one of the most common soil amendments. It comes in nearly all potting mixes and its main function is to improve drainage. It has high permeability and low water retention, making it a great amendment for plants that are susceptible to overwatering or root rot.

2. Lava Rock

Lava rock is also very popular for amending soil when it comes to cacti, succulents, and other plants that are accustomed to more rocky, desert-like environments. It is extremely permeable and holds on to very little water. One type of cactus potting mix in particular, called Crump, is comprised almost only of lava rock and is fantastic for avoiding any overwatering situations with desert plants.

3. Sand

Sand is pretty straightforward. It is, more or less, what you would find at the lake or on a beach and is highly permeable with low water retention. It is also great for plants that are accustomed to more desert-like environments and can be useful in improving drainage for plants that are sensitive to overwatering.

4. Vermiculite

Vermiculite is a bit more obscure. It is a naturally occurring mineral that looks similar to mica, having a slight shine to it. It is lightweight and highly permeable, though it also has high water retention. These qualities make it great for plants that like the illusive "moist but not soggy" soil condition.

5. Peat Moss

Peat moss is a fibrous material that is great for moisture retention. It is not very permeable, which is what makes it good at holding on to moisture. Peat moss can also be used for certain plants that like more acidic soils or can be used to reduce the pH levels of alkaline soils.

6. Wood Chips

Wood chips are another soil amendment that is commonly used. Wood or bark chips have high permeability and medium-low water retention, making them useful for holding on to limited water while letting the rest drain freely.

Why Is Amending Soil Important?

Amending soil is important because, while many potting soils market themselves as "all-purpose", this does not necessarily mean that it is ideal for every situation. All-purpose potting soils can be used in many, if not all situations, but it is often the bare minimum for many plants. This does not mean that all-purpose soils are bad, it just means that they aren't great to use on their own. All-purpose potting soils are intended as a good starting point, but should not be relied upon solely to provide your various houseplants with what they need. Soil amendments allow you to take your all-purpose potting soil and turn it into a specialized and unique mix formulated to meet the specific needs of your plants! And while it may sound complicated, it really is quite simple. Let's walk through some steps on how to amend soil so that you can give your plants the best growing medium possible!

How To Amend Soil for Your Houseplants

The first thing to know about how to amend soil for houseplants is that amending soil is not an exact science. There are many different materials, ratios, and personal preferences, and any one of them could be just as effective as the next. Our one suggestion is to not get too hung up on finding the perfect recipe. Your houseplants will not necessarily know the difference between a 1:4 ratio and a 1:3 ratio. Much of amending soil for houseplants also involves being aware and observing how your houseplant reacts to the soil mixture you've planted it in. If leaves are turning brown and crispy and you have to water a certain plant every other day, chances are the mix you used drains a little too freely. Or if you seem to have plants that are struggling with overwatering even though you barely water your plants, this is possibly a sign that your soil mixture needs to include more perlite or other elements that don't retain water. Here are a few tips to help you find success in amending soil for your houseplants:

Know Your Plants

Knowing your plants is the first and most important part of amending your soil. If you know your plant's needs, this automatically takes a lot of the guesswork out of it. Cacti and succulents are native to desert environments and grow best in a soil mixture that drains freely and does not hold onto a lot of water. Certain tropical houseplants such as Dracaenas are sensitive to root rot and overwatering, so they like to grow in soil that drains and drys out quickly, but holds onto enough water to keep the plant hydrated. Other tropical plants like Calatheas do not like to dry out at all and require that their soil remains moist, but not soggy. Some plants are more particular than others, so just be sure to do your research when you buy a new houseplant so you know how to properly repot it when the time comes!

Know Soil Amendment Qualities/Uses

Knowing different soil amendments and their uses is also very important. You will not know how to use your soil amendments properly if you do not know their functions and benefits. Here is a table that will help you know which soil amendments to use to achieve different soil properties:

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AMENDMENT PERMEABILITY WATER RETENTION -------------------------------------------------------------------------------------------------------------------------------------------

Peat Moss Low-Medium Very High

Wood Chips High Low-Medium

Vermiculite High High

Perlite High Low

Lava Rock Very High Low

Sand High Low -------------------------------------------------------------------------------------------------------------------------------------------

Mixing Ratios

Ratios for mixing your soil amendments with your potting mix will depend on the plant you are mixing soil for. If you are mixing additional perlite into your soil to help with drainage, generally 2 parts soil to 1 part perlite is adequate. If you are mixing soil for a plant that needs consistent moisture, 1 part soil to 1 part peat moss to 1 part bark chips will work great. For your succulents and cactus, you can mix 1 part soil with 2 parts lava rock.

Amending Soil for Houseplants

As we said above, there is no exact science behind amending soil for houseplants. Do your research, get other people's opinions, create your own mixtures based on your plant's needs, where they are located, and other factors, and then see how your plants react! Give your plants some time to adjust after repotting them. Repotting plants can shock them and it can take several weeks for them to really adjust. If your plant does not seem to be thriving, consider changing up the soil recipe the next time it needs to be repotted (for more info on repotting houseplants, click here!). If you have any questions or want to talk to one of our plant professionals, give us a call, fill out a contact form, or come into Bath Garden Center! We are here to help you grow better and we love getting to answer all of your houseplant questions. We also have a video that may help to answer some of your questions, so check it out!