Why And When Change the Soil of Your Potted Herbs?


No doubt, growing herbs in pots is more practical and can be done by everyone as you do not need a large garden or fantastic weather conditions. However, there are still a few essential aspects you need to take care of, like watering and providing the right light conditions. However, very few talks about the soil? Do you know that you need to change the soil to keep your potted herbs healthy? If not, this article walks you through everything you need to know to maintain a supportive, nurturing home for your potted herbs.

Hence, why and when should you change the soil for your potted herbs? Over time the chemical and physical property of the soil tends to degrade. It loses nutrients affecting herb growth. Its airy structure is also affected by compromising aeration and drainage. Professionals recommend changing the soil in potted herbs every 1-2 years in spring or summer when growth is at its peak.

How do you know when to change the soil of your herbs? How do you do it to make sure you don’t harm them during the process? Read on to find out more.

Why Do You Need to Change the Soil Of Your Potted Herbs?

Fresh soil is one of the most critical elements for vigorous plants and plentiful herb yields. The soil is the principal source of essential nutrients, micro-organisms, and moisture for your herbs. Without these, they will wither and die. The soil also needs to be well aerated, that is, to have enough space around the roots to allow air to flow and the roots to grow. As discussed in this article, well-aerated soil is light and fluffy.

The problem with the soil in pots is that as it ages, the level of nutrients and micro-organisms decline. This causes the soil to compact, reducing the space and air available to the roots. This problem is made worse by watering the plant, as the water, little by little push the soil down. As the soil becomes more compact, any excess water can’t drain as well as it should, and so the roots of your herb get sodden, increasing the risk of root rot and mold.

Old soil will not provide the physical and chemical properties that your herbs need to fully develop – Photo by Markus Spiske on Unsplash

The soil degrades slower in outside gardens because of the constant nutrients intake from the breakdown of leaves, twigs, bacteria, and insects. However, in the constrained environment of a pot, this natural process does not occur. Over time the nutrient level in the soil of potted plants diminishes, stunting more and more the development of your favorite herbs.

So it is essential to replace old soil, but how do you know when this is gonna happen?

When Do You Need to Replace the Soil?

One look in your pots is sufficient to understand whether the soil has become aged and lost its ability to support the growth of strong and healthy herbs. The soil will look dull, and when pressed at the top, it will feel hard and compact. This is a sure sign that the soil may affect the growth of your herbs. If left unchanged, this might slowly damage your herbs from a lack of nutrition, air, and moisture.

However, if you keep your eyes on your herbs, this can be avoided! Indeed, your herbs send early-warning signs. The University of Illinois suggests to keep an eye out for the following messages from your herbs that they might benefit from some fresh soil:

the herbs are wilting more often between waterings – this shows that the soil is not retaining moisture well any more and there is little available hydration for your herb.

when the rate of the plant’s growth has slowed, the leaves become smaller or discoloured, or there is a complete lack of new growth – this indicates a lack of nutrition for the plant to support continued development.

The University of Illinois

Even if all is looking well with your herbs, it is a great idea to refresh the soil before problems arise. My recommendation, as well as of many professionals gardeners, is to change the soil at least every two years. This, ideally, should be best done in spring or summer when your herbs need nutrients from the soil to support them through the growing seasons.

How Do You Replace the Potted Soil?

Like any action on a potted herb, the key is to be gentle and well prepared. Transplant shock, discussed here, is a real danger to your plant and results from any sudden change in the environment. So make sure you handle the herb very gently.

It is crucial to have a clean container to replace the plant into. If you are reusing the same pot, then before filling with fresh soil, you will need to wash it with soapy water and bleach to kill any diseases or pathogens. If you are using a new pot, it is recommended that you have it ready prepared with fresh soil, and watered to minimize the time that the plant spends away from soil and moisture.

Using a clean container is important especially if you are aware that the previous plant suffered some kind of disease of pest infestation

Use this opportunity to undertake some root maintenance. The rule here is that approximately ¼ to ⅓ of the existing root mass can be trimmed away. Make sure you also take some time to very gently pull apart any roots that have been wound up together. Also, spend some time inspecting your herbs for any issues such as insects or disease, and remove any dead, decaying or yellowing foliage. For more information, you can have a read to this article.

Place the new soil in the clean pot and replant the herb. It is recommended that you use an excellent quality potting mix (more in this article) to make sure your herbs get all the nutrients they need to grow well. Water the plant thoroughly to help the medium settle and feed the plant to help minimize the risk of transplant shock. For more information and tips on how to grow a prosperous plant, have a read to these 21 tips, applicable to basil and majority of indoor herbs.

Now your plant has a hospitable new home for the growing season. However, given the benefits of fresh soil to your plants, would change the soil more regularly than every 1-2 years be a good idea?

Can You Change The Soil More Regularly?

While, in theory, it sounds like a great idea to replace the soil for your herbs, in practice, there are real risks in doing it too frequently. Every time you transplant your herb, you need to cater to a transplant shock. Transplant shock impacts the plants’ ability to grow and protect itself from insects and diseases, affecting its long-term health. For this reason, continually repotting the herbs just to freshen the soil is not recommended and actually can do more harm than good.

Replacing the potting soil is not an operation to perform often

However, there are a few other ways you can boost the nutrition, air, and drainage of the soil of your potted herbs, without having to disrupt them. You can work some fresh soil or compost in from the top of the pot once a year.

Alternatively, every 2-3 months, you can cut out a 2.5cm (1 inch) wedge of soil from the edge of the pot and refill the space with fresh soil. This will slowly and progressively change the soil in the pot over the course of a year without having to remove the plant.

Can You Reuse The Same Potting Soil?

With the concern these days on minimizing waste, the question arises whether you can reuse old soil. The answer to this question is yes you can, but there are two key risks that you need to protect against when using old soil.

1. The presence of pathogens. These are organisms that might seriously affect plant growth and include viruses, fungi, and bacteria. To make sure pathogens in old soil don’t contaminate your new pot or plant:

  • Never reuse soil from plants that have had issues. It is safer to use fresh soil than to risk to lose future herbs also given how cheap it is generally a good quality potting soil.
  • Make sure the pot that you replant the herb into is completely clean. If the pot was hosting an herb with some kind of issue, then it is safer not to reuse that same pot (or to clean carefully with bleach and or soapy solution).
  • Pasteurize the soil to kill off harmful organisms. This is done by putting the soil into black plastic bags and baking the soil in the sun for several days. As the temperature rises in the bags, the pathogens will be killed off, making the soil safe to use again.

2. Used soil has lost many of the nutrients that your herbs require. These need to be replaced to ensure your herbs can grow strong and healthy. For this purpose you need to:

  • Fertilize the soil – either add in a slow-release fertilizer that lasts all-season or use a liquid fertilizer more frequently, such as every fortnight;
  • Add in some compost. The general rule is to use compost in a ratio of 1:4 with soil. This will add micro-organisms to the soil and assist with aeration and drainage;
  • Mix in some fresh potting soil. You can freshen up the old soil by mixing through some new potting soil. If the soil you are working with is several years old, then it is best to make a blend of ½ old and ½ new soil.

Having constant access to fresh herbs is a real joy, made even easier by growing them in pots inside your home. This article has shown you how you can make sure you are sustaining a happy, healthy home for your herbs for many years to come.

Related Questions

Where can you store the potting mix during the winter? To preserve as long as possible its physical and chemical features, potting mix should be stored in a dry and dark place, far away from any source of heat and light. Basement and garages are ideal locations

How long unused potting soil last? Usually, unused potting soil preserves its initial physical and chemical properties for around 6 months to 1 year. After this period of time, it can still be used but not with the same results in term of herb growth

Further Readings

21 Tips To Grow Massive Basil – https://yourindoorherbs.com/21-easy-tips-to-grow-massive-basil-indoor/

All You Need To Know On Potting Soil – https://yourindoorherbs.com/2-aspects-of-the-best-potting-soils-and-diy-recipe/

Best Potting Soil Around – https://yourindoorherbs.com/recommended-tools-lets-make-the-indoor-gardener-life-easy/best-potting-soil/

How To Keep Your Soil Loose and Light In Your Gardenhttps://www.denverpost.com/2017/03/31/garden-soil-loose-light

This article provides information on how to keep your garden soil well-aerated, and full of oxygen and organisms to give your plants life – https://extension.illinois.edu/blogs/good-growing/2016-04-06-give-little-tlc-your-houseplants

Andrea

A young Italian guy with a passion for growing edible herbs. After moving to the UK 6 years ago in a tiny flat, it was impossible to grow herbs outside. So I start my journey in growing indoor and so I decided to share my knowledge.

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