Gardeners Guide To Soil (Indoor and Outdoors)

Gardeners Guide To Soil (Indoor and Outdoors)

Last Updated On: June 6, 2022

One of the most important pieces of any good garden is the soil. Good soil is essential to healthy plants, and using poor soil is a quick way to kill your garden. Soil is, after all, where plants get all their nutrients. Today we’ll look at what makes up soil, and how you can tell where your soil sits. We’ll also look at some quick tips to improve your soil if it’s not quite where you’d like it.

What is Soil?

Soil is a mixture of mineral and organic matter that plants require to grow. Good soil is rich in nutrients, and encourages healthy plant growth. Good soil is a key for plant growth as it helps keep your plants fed. Bad soil on the other hand can kill your plants, as it lacks things like nutrients or proper drainage.

What makes soil good for plants can get really complex, but for most of us it comes down to two things. That is, its ability to hold nutrients, and it’s drainage. You’ll see that different types of soils do both of these differently, and understanding how your soil behaves is important to achieving optimal plant growth. Different types of plants require different soil, so it’s also important to match your soil with the plants you plan to grow.

Soil Vs Dirt

In a lot of cases you’ll probably hear dirt and soil used interchangeably, but there is a technical difference. While soil is a great medium to grow plants in due to the aspects mentioned above, dirt is not.

Dirt, in a gardening sense, is referring to a medium that is devoid of nutrients; dirt is dead. It’s possible that overtime soil can turn into dirt once it’s lost all its nutrients. This is most likely to happen in a closed environment such as a pot where there is no natural processes replenishing used nutrients. That’s why it’s important to change the soil in your pots as we’ll see later.

This may seem a bit nitpicky, but it’s important to understand the difference and it’s a neat little trivia point.

Soil Nutrients (N-P-K)

If you’ve ever looked at fertilizer you’ve probably seen something like 10-10-10 on the side. This is the concentration of the three most important nutrients for plant growth; nitrogen, phosphorus, and potassium. While there are other nutrients that are used by plants, these are by far the most important for plant growth. This is important as healthy soil that’s good for growing will be rich in these three nutrients.

Nitrogen: Primarily used for leaf growth

Phosphorus: Used for root and flower/fruit development

Potassium: Promotes overall healthy growth in the plant

Understanding how these values interact can help you pick fertilizers that match your goals. For example, for beautiful blooming flowers you might want to go with a phosphorus rich fertilizer to promote flower blooms. Before doing that though, it’s always a good idea to get your soil tested to get a baseline. We’ll talk about that a bit later in this guide after we go over some other important characteristics of your soil.

In addition to the three mentioned above there are a number of other nutrients that are helpful in trace amounts. You might see these listed, but know that the three above are by far the most important for plant growth.

There are also certain elements that may be harmful to certain plants. This is why doing a test is important to not only figure out the good but also the bad in your soil.

Soil PH and How It Affects Plants

Another aspect of soil quality is the PH level. PH level is a measure of how acidic or alkaline your soil is. This score ranges from 0-14; a score of 7 is neutral, with less than 7 being acidic and more alkaline.

PH is important for your soil as it has an effect on how good bacteria and fertilizer work. Most fertilizers for example work best in a relatively narrow PH range. Outside of this range they are likely to perform poorly or be ineffective. If your efforts with fertilizer don’t appear to be working, your soil’s PH level might be the problem.

In general, a PH level of 5.5 to 7 is ideal for most plants, although some do grow outside this range. The further you get from it, the more likely you are to have issues with plant growth and fertilizer effectiveness.

We’ll talk at the end of this guide about getting a soil test, one of the things it will test is your PH. If you find that your soil is too far to one end then there are steps you can take to correct it. Be warned though, that some areas may naturally tend to move away from neutral based on environmental factors. If this is the case it may be difficult or impossible to make a long lasting change to the soil PH level and it might be easier to simply grow plants more suited to the environment.

Buying Soil at The Store

For many home gardeners, we get a good deal of our soil at the hardware store. This is a great way to get specially treated soil, but it’s important to understand the differences. Reading the package goes a long way.

For example, my local hardware store sells maybe two dozen different types of soil, and some are specially made for pots while others for outdoor planting. This has a lot to do with the drainage, but suffice to say using an outdoor potting mix in a pot is a good way to get your plants killed. Other soils come with varying amounts of organic matter, which is usually good except if you’re trying to grow seedlings. If you’re confused read the package, most manufacturers do well in describing which situations their soil is made for.

The great thing about pre-bought soil is it generally has correct nutrient level for growing. That takes a lot of the guess work out of gardening, and removes the need to actually test your soil.

Using Soil In pots and Indoors

Buying soil for pots and indoor use is completely different than for outdoors. There are two main problems with potting soil that can end up hurting your plants.

For one, there is no recycling of nutrients. While outdoors you have the constant breakdown of organic matter, in a pot you don’t have this same natural process. This means that eventually your soil will lack the nutrients necessary for plants to grow. Plants in pots need to be regularly fed and their soil’s nutrients replenished.

The next problem is that over time the soil in pots tends to compact. This leads to soil being too compact for nutrients and water to flow through it. Even with proper feeding eventually the soil will choke out the plant. This means that potted plants should have their soil switched out periodically. This should be done roughly once every 2-4 years depending on the plant and how fast it’s growing.

It should also be noted that using soil designed to be used in pots is a must. This type of soil is specially designed to be used in containers, and comes with the proper drainage and nutrients, which are different from outdoors.

You can easily see this difference by feeling the soil. Soil made for containers will feel much lighter and fluffier than traditional garden soil. If you pick up a bag of each, the potting soil will feel significantly lighter. This is done on purpose as it encourages proper drainage in your plant’s container.

As noted above, read the packaging and select the right soil.

Getting Your Soil Tested

The quickest and easiest way to test your soil is through at home soil test kits. These small kits come with everything you need to test your soil, and instructions on what the results mean.

These kits usually give a variety of information including the makeup of nutrients and the PH level. If you have a large garden space, it might be a good idea to get several kits, and perform and independent test in different areas. It’s not uncommon for the makeup of the soil to change, even over relatively short distances.

It’s also a good idea to re-test your soil every once in a while to make sure that your strategy shouldn’t change. You can also run a test after preparing your soil with fertilizer to see if you’ve reached the desired results.

As noted above, this is really only applicable to outdoor gardening. If you’re using pots, or even using store-bought soil outdoors, you probably don’t need to test it.

Quick Ways To Improve Your Soil

We’ve learned a lot about what makes good soil; and by now you might be wondering how you can improve your own soil. While there’s certainly a lot you can do, it really depends on where your current soil is at and what your goals are. With that in mind, here’s a few tips that are universally applicable to most soil and garden types.

Get Fertilizer

Probably the easiest and most popular way is to add fertilizer or feed to your soil. This is a great way to add extra nutrients to your soil without much effort. Having an idea of your goals is important though as not all fertilizers are made the same as noted above. Test your soil before using, and make sure to buy a fertilizer that fixes the issues you find.


For those looking for a more natural way to add nutrients to your soil composting is a great option. This allows you to recycle old material that you might otherwise throw away and add it to your soil. The idea is that when many organic items decompose they release the exact nutrients that plants are looking for. For more info, check out our guide to getting started with composting.

Don’t walk on it

Something that a lot of people do without noticing is walking on their flower beds. This might seem harmless, but it can actually harm your plants. When you walk on your soil it actually compacts it down, which in turn can hamper water and nutrient flow. Now, don’t freak out and tiptoe around your flower beds, a little bit of walking won’t ruin them, But, make sure to limit the times you do and you’ll be rewarded with airy, well draining soil.

Use Mulch

Mulching is another great way that doesn’t necessarily improve your soil quality, but makes it more accessible to your plants. The main purpose of mulching is to prevent weeds from sprouting up. Weeds are not only unsightly, but suck up all the nutrients your plants needs. Using mulch can help stop the spread of weeds, which in turn leads more nutrients for the plants you do want growing. Mulch will also naturally decompose over time, which will add nutrients back into the soil.

A Simple Homemade Potting soil

While store bought soil is great, making your own can be a huge cost saver. This is especially the case for larger gardens where you need a lot of soil. A good homemade soil only has a couple of ingredients, and is quite easy to make. Here’s a sample recipe, feel free to adjust the numbers to match how much you need to make.

Of these items, the peat moss and perlite are probably the least common that non-gardeners might not know about. Peat moss acts as a base that provides volume and weight to your mix. It drains fairly well, and this helps provide the bulk of your soil. Perlite also helps with drainage and moisture retention.

As these items have little nutrient value, I like to add a handful of slow release fertilizer pellets to the mix. This helps provide a lot of key nutrients, and turns the soil into a great home for my plants. The other great thing about the slow release pellets is it’s generally difficult to over fertilize with them, making it easy to add them to the mix with little risk.

Different Kinds of Soil

Lastly, I wanted to briefly touch on the different types of soils and the key characteristics of each. This will help you understand your soil, which in turn will help you take better care of your plants. For example, if you have sandy, fast draining soil then you may need to water more often and provide more nutrients for your plants.

Certain soils are also better suited to grow different types of plants. If you find plants difficult to grow try cross checking your soil type with suggest plants and see if that makes a difference. Some soils also hold nutrients better; another important thing to keep in mind.

Soil is typically grouped into one of the following 6 categories:


Clay feels lumpy and sticky when wet, but will quickly harden up when dry. It’s difficult to work with, but with improved drainage will grow plants well due to its ability to hold nutrients. Without improved drainage though it may retain too much water subjecting your plants to root rot.


Sandy soils are a fast draining, gritty feeling soil. They’re very easy to work with, but will often wash away nutrients very quickly. You may hear sandy soils referred to as “hungry” because of this. If you have sandy soil you may need to fertilize more frequently.


Silty soil is smooth to the touch with almost a “Soapy” feel. Silty soil is usually very well draining but still good at retaining nutrients. This makes it an overall good soil if tended to well.


Peaty soil is usually very dark and retains a lot of moisture. It may require drainage and fertilizer, but if properly used it is a decent soil for plant growth.


Chalky soil is usually slightly alkaline and may contain rocks or small stones. Due to lack of certain minerals, plants here will often develop yellowing leaves without proper fertilization.


Loam is seen as the perfect soil and what every gardener hopes for. It is well draining, but won’t dry out too quickly while still maintaining a good amount of nutrients. Loam is also very good at recycling minerals and will likely require minimal fertilizer.

All About Soil

Hopefully after reading this you’ve come away with a bit better of an understanding of what makes up soil. With all of that said, it’s important to know that soil (and gardening in general) is extremely complex. There’s a lot more that goes into it, so don’t get discouraged if it doesn’t go right the first time.

Most importantly, get out there, get gardening, and have fun! As always, check back here often for new articles, and consider signing up to our mailing list to get notified as we publish new content.

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