Plant owners are often faced with the dilemma of leaving roots in the soil after a plant has died. It is easy to discard the soil with the roots but there are some benefits of reusing the soil because of the nutrients it still contains.
Here we discuss whether or not you should leave the roots in the soil depending on your gardening situation.
The Quick answer –
Roots should not be left in the soil that is to be reused as a potting medium in a plant pot because they will hamper the growth of new plants. In other cases such as open gardens and raised bed gardens roots can be left in the soil if the previous plants did not die because of a known disease.
In this article we are going to elaborate further and explain why you should and shouldnt use soil that has roots in it, depending on the type of gardening you are doing.
If you are going to repot your plant, there are many good soil options out there but I have found this potting soil made by Miracle-Gro from amazon to be most affordable and effective in keeping my plants healthy long after repotting.
You can find it by clicking here.
What if the Roots are Allowed to Remain in the Soil?
Can You Reuse the Soil With Roots in it?
You can reuse soil that still has roots in it depending on whether it is in an open garden, raised bed garden or a plant pot.
Soil has good bacteria and also sometimes termites which will aid in the breakdown of the roots. But this will take a long time. Time can be utilized growing new plants and crops.
Soil in Raised Bed Gardens-
This is particularly so for plants that are planted in an open garden or raised bed system where insects and bacteria can have open access to the soil and old roots to help the decomposition process.
Soil in Plant Potters –
In the case of soil in potted plants, the soil will not have such luxury as having additional bacteria and other beneficial insects to remove the old roots.
You should remove the old roots from potting soil as this can definitely become an issue when new plants are planted in the same limited space as the old plant.
If you are going to plant new plants in an open garden or raised bed garden that has other plants planted before, you should locate areas where there is vacant space so that old roots will not become a problem for the new root system.
In cases where there were plants previously planted. There are some things that need to be considered before planting new plants in soil that havent been prepared properly.
Factors Affecting Soil with Old Roots –
- Diseases Affecting Previous Plants
Firstly you will need to identify if the root has any lingering diseases such as damping off.
Damping off is a horticultural disease or condition, caused by several different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions (source)
If you have prior knowledge that the plants died of some type of disease rather than just neglect, then you should remove the roots from the soil.
- Soil Compaction
Soil compaction is an issue which may arise as a result of high density of roots in the same soil. The plants that were previously there may have a large fibrous network of roots and these will cause a compaction problem.
If new plants are sown in the same space the roots will have to compete for space with the old roots if it wasnt fully decomposed or removed.
Additionally, the roots which bind the soil closely together can lead to other problems such as drainage and soil aeration which we will discuss next.
- Soil drainage
Stemming out of soil being compacted by the old root system, drainage will become a problem as the space between soil particles will be small restricting water movement out of the soil.
This can lead to the soil becoming waterlogged after watering which also can lead to additional problems of its own such as root rot for the new plants in the garden or pot.
- Soil Aeration
A ripple effect of waterlogging is lack of aeration. This can be easily caused when the water totally fills up the available space within the soil preventing little air from reaching the roots where it is needed by the plants.
Roots of plants also respire and the rate of respiration can differ between plant species. Restricting a plants ability to respire can eventually lead to its demise.
Benefits of Removing Roots from the Soil
- More nutrients available for New plants
Removing old roots from the soil can allow for more nutrients for new plants.
Old roots, even if the plants are removed, may remain alive and still be drawing nutrients from the soil. In some cases, new plants may even shoot up as the roots are still alive.
This creates a nutrient defiant environment for the new plants as you will be feeding nutrient requirements for the new plant and not for additional nutrient sucking roots hidden beneath the soil.
Additionally, you will have the opportunity to add more nutrient rich soil additives to the new soil mix. The new soil mix can also be amended to suit the specific plant needs that is going to be planted in the soil or plant potter.
- Better Soil Aeration
When old roots are removed from the soil, you can add soil amendments such as perlite and vermiculite.
Leaving the old roots as previously discussed, can have the soil compacted so much that the plants roots will have a difficult time respiring due to a lack of aeration between soil particles.
Aeration is necessary for plants to respire and a lack or aeration can cause the entire plant to suffer and eventually die.
These soil amendments increase aeration and drainage properties of the soil, creating the perfect environment for plants to thrive.
- Better Soil Drainage
When it comes to drainage, an additional benefit of removing the roots is that you get an opportunity to make the soil even better than it was before.
Again, with respect to potted plants, when the old roots are removed by taking out the soil from the plant pot, you can enhance and reuse the old soil by adding new soil mix which will usually include particulates such as perlite and vermiculite.
This increases the soils drainage capacity to better suit the needs of the intended new plants.
Why You Should Reuse Potting Soil
You can definitely reuse potting soil because it will still contain all the nutrients that was previously used to feed the last plant that was in there. However, the soil must be treated before use if there were any known disease which may affect plant growth.
Potting soil usually has a limited supply of nutrients which is supplied by routine addition of fertilizer. As a result, the soil will contain various quantities of nitrogen, potassium, and phosphorus along with an array of nutrients, all beneficial to plants.
These nutrients will also be useful for other plants if the soil is reused and it will be somewhat of a missed opportunity if you choose to simply discard the potting soil from an old plant.
Additionally, the soil will also still contain beneficial micro-organisms which make up the ecosystem that made nutrients available for the previous plant to grow.
However, caution must be taken when there is any suspected disease in the soil. And proper sterilization will have to be used to bring back the soil to a safe reusable state.
In the case where there was root rot, you can reuse the soil because root rot is usually caused by overwatering conditions which creates a good environment for bacteria and fungus to thrive.
If you are interested in knowing how to control overwatering conditions and preventing root rot, we have written a detailed article explaining how to dry overwatered soil.
Treating the soil with fungicide is recommended once you identify the type of fungus that was attacking the roots before the previous plant had died.
How to Salvage Potted Soil from a Plant that has Died?
- Remove the Soil from the Plant Potter
Removing the soil from a plant potter can be tricky especially if you don’t want to cause any damage to the potter itself.
Firstly you should lightly moisten the soil by wetting it with water. You don’t want to over water the soil because it will cause a muddy mess when it’s time to remove the roots.
Next, Spread a netted material onto the floor which will be used to sift the roots out of the dirt. Gently turn over the plant potter onto the sifter and allow the dirt to spread unto the sifter.
- Remove the Roots
If the dirt is being held together by the old roots, and most likely it will, you can use a knife or a sharp object to cut through the larger roots which are holding up the soil.
Once the soil is broken up into smaller pieces you can start sifting out the smaller root system.
- Check for Diseases
Once the dirt is separated from the roots. Its time for inspection.
Old roots May contain diseases which may have contributed to the plants death in the first place.
In some cases, the roots may also still be alive and careful inspection will be necessary to ensure the right steps are taken to prevent any lingering disease from passing it onto the new plants if the dirt is to be reused.
One method of removing and suspected root disease is sterilizing. Which we will discuss next.
Salvaging Soil After Root Rot or Disease by Sterilizing
Sterilize with steam (mention other methods). Using steam is the most effective way to sterilize soil.
Steam is the gaseous form of water that exists as a gas at atmospheric pressure at 212F. This temperature is high enough to kill any lingering pathogens or fungus.
Using this method you will have to place the sifted soil on top of a pot of boiling water allowing the steam to sieve through the soil.
Additionally, if you have a steamer, you can use it to directly focus the steam onto the soil.
While killing bad pathogens is good the temperature extremes will also kill the good bacteria and microorganisms in the soil.
A good recommendation is to mix a well-rounded potting soil with the existing soil to reintroduce the beneficial bacteria and microorganisms in the soil.
Beneficial nitrifying bacteria and microorganisms helps plants absorb organic material from the soil by first breaking down organic matter into nutrients for the plants to use.