Potting soil lasts longer than ordinary soil, but it’s not indestructible. Over time, gardeners in all climates find that their potting soil loses its ability to nurture plants properly, and they’re left wondering how long does potting soil last and how to know when it’s time to buy new potting soil to replace the old stuff.
Here are some tips and tricks you can use to get more out of your potting soil so that you don’t have to spend money on new potting soil when you don’t need to.
Potting Soil Preparation
Potting soil is typically made of two types of ingredients: compost, which is a rich mixture of rotted organic matter (including manure and decomposing leaves) that creates excellent growing conditions for plants; and perlite, which creates lightweight but aerated pots and mix.
Achieving the correct moisture content in potting soil can make or break your success as a gardener. To measure the necessary moisture content, dig down about 2 inches into the top layer of your potting mix with a ruler.
If it feels slightly moist but not wet or clumpy, it’s just right for planting. If it feels dry to the touch (anywhere from bone-dry to dusty), water thoroughly before planting.
The other way to test if your potting soil has the right amount of moisture is by squeezing a handful and releasing it slowly; if you feel any moisture on your fingers when you release the soil, then it’s time to water. If you don’t, then your potting soil is too wet and will begin to break down once planted.
What Happens if You Use Old Potting Soil?
While it’s tempting to repurpose old potting soil, old and dry potting soil is unable to retain the proper moisture and nutrients.
You’ll notice that using old, dry potting soil can be really hard on plants that require lots of water because the dryness of the dirt will suck all the moisture out of them.
Adding a wetting agent or watering more frequently can reduce this effect but it’s a good idea to get fresh new dirt anyways. You should know that using old, damp or wet potting mix also has its pitfalls as well!
Is Dried Out Potting Soil Still Good?
Dried out potting soil is still good! Yes, as a matter of fact, it can be better because it’s more aerated and moist. Potting mix in the bag starts out dry and doesn’t change over time – whether sealed or not.
This is because it’s sterilized to eliminate mold and fungus that might otherwise form over time in the container. Since they’re both sterile, there’s really no difference between using fresh or dried out potting mix.
The main concern should be how deep you need to plant, as planting too deep will cause roots to grow only along the surface which isn’t good for your plants.
How To Store Potting Soil
Potting Soil is often touted as a miracle product for providing the nutritional plants need to thrive and survive. It’s no wonder, then, that so many homeowners use it on a regular basis in their own homes.
The downside to using potting soil regularly is the question of how often do you need to change it? The answer really depends on how much your potting soil is exposed to the elements.
Generally speaking, if you leave the bag outside or keep it near an open window for long periods of time, then it won’t take nearly as long to break down and lose its original properties than if you store it indoors with little contact with natural light or air flow.
Does Potting Soil Need To Be Sterilized?
Potting soil does not need to be sterilized, but it will start losing its nitrogen over time. The overall composition of the potting soil is almost 100% organic matter (from peat moss and wood chips), with a little bit of sand, bark mulch, and perlite.
The air-filled perlite provides aeration to the mixture while the sand provides drainage. Aeration and drainage are essential for promoting healthy plant growth.
As soon as you have finished mixing your container full of potting soil together it begins to decompose, meaning that eventually it’s going to lose its nitrogen which is one of the most important fertilizers in plants.
Potting Soil Shelf Life
Potting soil in bags typically have a one-year shelf life. Manufacturers are not required to include a use by date, but should provide some indication of the time that has elapsed since the product was packaged.
Old potting soil can have lower nutrient content and not hold moisture as well. Plants may look wilted or will develop brown edges, either from too much water or too little water.
Do I need to add fertilizer to potting mix?
Potting mix that is not containing fertilizer should be replenished every year, or when the mix starts to look depleted.
The potting mix will start to deteriorate when it reaches a certain level of compaction from being in pots for too long.
Any parts of the potting mix with bacteria will start to spoil and release ethylene gas. If you can’t determine how old your potting mix is, adding fertilizer is a good bet to add some freshness and sustainability back into the mix.
How do I make sure potting soil doesn’t have bugs?
Keeping potting soil free of bugs is key to its longevity. When buying potting soil from a store, you should always take a quick look and smell for insects or other signs of contamination.
If there are no bugs, pour a small amount into the palm of your hand and make sure it has a fresh, earthy smell before purchasing it.
Potted plants should be moved into fresh potting soil regularly, as using old soil can result in plant death due to insect infestation or disease.
There are many types of potting soils on the market so it’s important to find the right type for your plants needs.
What is potting mix vs potting soil?
Potting soil is an all-purpose gardening mix that is suitable for containers or raised beds. It can be mixed with sand, gravel, manure and water to make a moist soil, which then becomes potting mix.
Plants are planted in pots of potting mix and watered until they have soaked up enough water to maintain the correct moisture levels.
Over time, potting soil will slowly decompose and lose its nutrient levels, but it should still have some life left after a year of use.
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How to Revive Old Potting Soil
It’s easy to store unused pots of potting soil away for a future planting. The problem is what to do when the next season rolls around and you open the container to find its contents have turned to clay.
It may be impossible to tell how old your potting soil is but rest assured, you are not alone!
Gardeners who are green-thumbed veterans know that over time, wet, peaty compost mixes can clump together and can turn hard and powdery on top as a result of prolonged exposure to air.
How To Tell If Potting Soil Has Gone Bad
When you want to be sure your potting soil has gone bad, here are a few signs.
- The mulch may seem too course and no longer easy to break apart.
- The color is the wrong shade of brown. If it’s turned a greenish brown, then it is time to get new mulch.
- If the texture has been reduced to grains or small pellets, this means that the organic matter has decomposed and the fertilizer level has been depleted.
- The appearance of mycelium tells you that mold is present in your mulch, which might not be safe for plants as its spores will grow on roots and cause disease when plants are growing under humid conditions in close proximity of each other.
A smell can also indicate that your potting soil has gone bad. Mulch should have a fresh earthy smell; if it smells sour or stinky, throw it out!
- You can tell if your mulch is ready to use by squeezing some between your fingers; if there’s lots of moisture and wetness but the fibers don’t come apart easily, than you should buy new mulch.
Should Potting Soil Be Replaced Each Year?
A common question about potting soil is how often should it be replaced. Soil composition can vary, so it depends on the type of soil you are using.
If you use a commercial potting mix from a garden center or nursery that is intended for use within two years, then you should not need to replace the potting mix more than every two years.
However, if you buy a cheaper bag of home-made compost that is mainly composed of high-nitrogen materials like cow manure, food scraps and shredded leaves, then this soil may need to be replaced every year because compost contains nutrients that will decompose quickly and may become nitrogen-rich after only one year.
Final Verdict on How long does potting soil last
How long potting soil lasts largely depends on the brand and composition of the soil. In general, you can typically expect your bag of potting soil to start getting dry after two or three years in storage.
However, if you store your pots indoors with plenty of light exposure it can slow down that process by a year or two. Avoid storing potting soil outside where its subject to sun, rain, wind, and fluctuating temperatures as this will accelerate the drying process.
Even under perfect conditions though, potting soil only has an expected shelf life of 3-5 years before it needs to be replaced. That said, there are lots of factors that can affect how quickly potting soil dries out including sunlight, water usage, and proximity to heat sources.
Plus many people mix their own potting soils at home for a fresher product so they won’t need to buy new ones every few years.
Meet Tomas Clayton, a seasoned plant gardener who has been passionate about horticulture since he was a child. Tomas John developed a love for the natural world and a strong appreciation for the beauty of plants while growing up on a farm.