How to Tell if Your Potting Soil Has Gone Bad

Your plants need a home, and it is up to you to provide them with the best potting soil.

You want your plants healthy and happy, but where do you start? What is the difference between all these different potting soil types out there? How do I know which one will be best for my plant type? Does potting soil go bad? What are the signs?

What is potting soil, and what does it do?

First of all, you need to know what potting soil is. Whether you’re dealing with bagged potting soil or your recipe, the basics are the same.

Potting soil, or potting mix, is made of composted bark, peat moss, sand, or perlite; it also usually contains chemicals like fertilizer and water-soluble charcoal (to help filter the water). Potting soils are specially formulated for use with potted plants grown in containers.

Why you should use potting soil

There are several reasons you should use potting soil when starting your potted plants.

For starters, it is designed specifically for the growing needs of container-grown plants, so it contains everything your plant needs to thrive. It also doesn’t have any large particles that could harm your delicate new seedlings or more tender container plants, and it will stay fluffy and loose in the container allowing air to reach the plant’s roots. Common ingredients like peat moss and perlite are added to the mixture to help ensure proper drainage.

How to tell if your potting soil has gone bad

Does potting soil go bad? For those new to gardening, this isn’t such an uncommon question. Potting soil will generally last a good long while before it becomes unusable.

Here’s how to tell if your potting soil has started to go bad:

• Bad potting soil may be showing signs of decay like mold or fungus. This is usually an indicator that it has also become home to insects and other pests, so don’t use it in your containers!
• If the potting soil looks wet and crumbly, this can lead to drainage problems, which will affect your plant’s health.
• If you find any clumps or lumps in the potting soil, there is too much clay content; this potting mix isn’t good for starting seeds because there won’t be enough space for the roots to grow.
• Old potting soil may have lost its nutrients, so check it before using it if you are planting seedlings or young plants.

If your potting soil is looking funky in any way, don’t use it on your plants! Throw it out, give it away, and start fresh with some new potting soil.

Common issues with old potting soil

Here are some of the most common causes of issues with old potting soil:

• Unused potting soil left in the elements
• Using garden soil as potting soil
• Moldy potting soil
• Fungus gnats
• Using old potting mix for new containers
• Expired potting mix
• Lack of an airtight storage container

These issues can cause potting soil fresh out of the bag to go bad. Check the dates on any potting soil you’re getting from a garden center. Don’t reuse potting soil or re-pot with used potting soil. It’s very likely that used potting soil lacks nutrients and needs more amendments at the very least.

Used potting soil can harbor fungus gnats larvae, blight, and mold. It’s your best bet to skip the old potting soil and get yourself a new bag of good-quality potting soil each gardening season. You can also mix up your potting soil with peat moss, perlite, and some other ingredients. We have included our seed starting mix recipe below.

The best types of potting soil for different plants

Potting soils come in a variety of types. Be sure you find something that will work best with the type of plant you want to grow to get optimal results.

For growing vegetables

The organic mix will be what you want for growing vegetables. This potting soil is often black and contains mulch, which helps water retention. It contains natural fertilizers, so you won’t have to feed your plants too often.

For young plants from the nursery

Use all-purpose potting soil. This kind of potting soil is not super fancy, but it works well for a majority of small potted plants because it contains composted bark and other safe ingredients that won’t make them sick when they start to grow.

For ornamental plants like flowers and shrubs

Look for a readymade potting mix that is light in texture that also contains vermiculite, perlite or sphagnum peat moss. These kinds of soils are perfect for adding water-retaining organic layers to the soil mix, without sinking too fast.

For seed starting

When planting seeds, use a coarse potting mix that is made of mostly composted bark and other safe items your plants won’t object to having around them as they grow. You can also make your own seed starting medium by mixing up equal parts shredded paper (easy for drainage), composted bark, vermiculite, and perlite.

Potting soil is easy to find at any garden center or home improvement store near you, but if you want to try something different, don’t hesitate to experiment with mixing your own seed starting mix.

Create your own basic seed-starting potting soil.

Here are the basic materials needed to create a seed-starting potting soil:

• 2 parts quality composted bark
• 3 parts sphagnum peat moss or coir
• 1 part perlite or vermiculite

Follow these instructions to craft your seed-starting potting soil:

1. Mix the ingredients well enough to distribute them evenly, but do not over-mix as this can damage the soil structure.
2. Add water slowly and mix it into the potting mix gently.
3. Keep adding water until the potting mix is moist with no dry lumps. Make sure you let all of your plants drain properly! If they sit in too much water, they’ll die. 

There are many different kinds of potting mix on the market, so if you aren’t sure which one will work best for your plant, then go ahead and ask someone at the garden center what kind of soil you should use.

Storing tips to prevent potting soil from drying out or getting moldy

When pots dry out or get moldy, it can kill your plants, so keep them moist at all times!

Here’s how:

• Always water your plants from the bottom to ensure they drain properly. Pots without a watering tray need something to sit in for bottom watering. Pots don’t sit well without them, and drainage holes get blocked. If you pour too much water into them, it will pool and make a mess + potentially drown your plants.
• Cover pots with plastic, and poke holes into the plastic for drainage. This will prevent plastic from sticking to the container.
• You can also store empty pots in water (but not ones with a growing medium as roots grow poorly underwater), which prevents them from drying out and dying.
• If your plants are inside the house, put them near a window where they’ll get plenty of light without getting too hot or cold. Direct sunlight can burn leaves and cause leaf loss or browning, so it’s a good idea to keep your seedlings away from windows that receive direct sun until they have grown larger and adapted to become stronger growers!
• Finally, don’t forget to check on your seedlings/plants every once in a while! Plants require attention just like any other living thing

So, does potting soil go bad?

The answer is yes, potting soil does go bad, but it takes a considerable amount of time and with the proper poor conditions.

We hope this gives you a great idea of whether or not your potting soil has gone off the deep end. Make sure you change out any potting soil you used in the previous season if you had any blight or pest issues, as it might still be in the soil.

If your soil looks questionable at all, it may be best to use something fresh for the best results. It’s not worth spending time cultivating a plant in soil that’s working against you. Remember, life’s short, do what you can to make your gardening experience enjoyable.