Do you know that indoor and outdoor potted plants can outgrow their planter? Do you know that its roots can fill up the whole volume affecting plant growth and soil nutrients level? This is called root bound conditions and triggers many problems in plants that might be confused with other more serious issues.
In general, the most common root bound symptoms are 1) roots coming out of the drainage holes or soil surface 2) soil draining quickly 3) slow growth 4) early flowering 5) yellow and wilted leaves. The only way understands if a plant is root bound is to extract it from the pot.
Here is the good news
Root bound is hardly ever a problem that will force you to toss your plant. Indeed, once you are sure that your plant is root bound, you just need to take a few steps. However, if some mistakes can make the whole process way harder. Here is what you should (and should not) do.
Table of Contents
- 1 What is Root Bound?
- 2 Why Root Bound?
- 3 What are The Symptoms of Root Bound?
- 4 How Do You Know if Your Plant is Root Bound?
- 5 How To Fix a Root Bound Plant? Tools and Technique
- 6 Further Questions
Roots are the “channels” your plant uses to take minerals, water, hormones, and gases. These are the three critical components needed for its survival (with the energy from the sun). Roots also provide the anchorage your plant needs to stay upright and not fall under its weight.
During its natural development, your plant, promotes growth. In this case, the roots will start pushing against the container walls, and (as they cannot break it) will grow around them, creating a robust web (or ball) of roots. This is the root bound.
During its development, your plant wants to grow, producing more leaves and stems. For this purpose, it needs more “nutrients” (well, the minerals to produce them). These minerals do not come from thin air (the air is full of them, like Nitrogen, but evolution did not give plants such superpower). They need this mineral from the soil. Hence, they need to reach more soil.
And here is where the problem is.
Once the plant reaches all the volume of the pot, it does not have any further soil to reach. Hence, it does not have any additional source of nutrients to produce extra leaves and stems. In a desperate act to reach the “missing nutrients,” the plant develops even more roots as it does not “realize” to be “bounded in a pot.”
Yes, as crazy as it sounds, fewer nutrients are available, more roots your plant will develop. Although there is no final evidence (as this depends on countless factors) this conference study as well this other study from Beijing University stated this positive correlation.
The two highest nutrient treatments, indicating that nutrient deficiency promotes root growthUniversity of Beijing
Lack of watering and nutritional shortage are the most common symptoms of root bound. This can manifest in a large variety of ways, such as dry leaves, brown patches, and even yellowing, followed by dropping. Although root bound per se is not bad, the consequences of having way more roots in a relatively small amount of soil are.
Curling leaves, stunted growth, leggy plants, leaves yellowing, browning, scorching, and even dropping are the most common symptoms of root bound triggered by water shortage.
This is one of the first symptoms of root bound. Indeed, even if you pour an adequate (proportional to the pot size) amount of water, your plant will end up always thirsty. Why? With so many roots, the water drains faster (a bit like adding perlite to soil), and more importantly, your plant needs more water compared to what you might expect from the little pot it is in.
Underdeveloped and leggy plants, with small leaves, are one of the clearest symptoms of lack of nutrients, the second most relevant consequence of root bound. Very likely that roots have exhausted all the nutrients in the containers for a while.
This is due to the fact that a root bound plant might have more roots than soil. How is this possible?
The potting mix you use for your herbs and indoor plants is composed of organic matter that, over time, is broken down and absorbed by the plant. Hence, the soil is literally eaten by the plant. Good quality potting mix (as this one I use quite often, the FoxFarm here on Amazon) has up to a third of organic material. As a consequence, the soil over time disappears (a third of it), also justifying why you need to replace it. For more on soil, a replacement checks this article.
Here is something to remember.
The symptoms mentioned are not exclusively root bound. Indeed, curly leaves or scorched might simply be due to you forgetting to water your herb exposed to the scorching summer sun. The same applies to nutrients deficiencies. Did you apply the fertilizer to your herbs (here a guide on how to do it).
Two Preliminary Checks
To understand if your herb or houseplant is root bound check if:
- Roots coming out from the drainage holes?
- Roots on the surface (or just a few millimeters below it)?
If one of the previous gave a positive outcome, then chances are that your herb is root bound. To clearly identify whether your plant (or herb) is root bound is just to look at its roots. How? Here 3 steps
- Before: Let the soil dry a bit (without killing the plant, of course). Tip: this, although this is not essential, it will make your life easier;
- Location: if you do not have a garden where to bring your plant I would suggest working on the floor after placing some cardboard just to collect debris that will eventually come out;
- Technique: if the planter is in plastic, just squeeze it gently with your hand on the border. This will allow to “unstick” the roots from the container walls. If you have a ceramic container, then just gently hit on the border and then extract the plant by placing the container sideways on the cardboard and gently pulling the plant from the stem closest to the soil level.
If you proceed well, the plant should come out of the container almost effortlessly. Then check the roots. Are roots bound?
Here you can see three examples of root bound. Not all root bounds are equal. In the same case, it is extreme, while in other cases, it is moderate.
In the case of moderate root bound, you will still have a fair amount of soil (more than half of the container space is soil). In this case, the root bound is not that serious, and, in case you are not ready yet, you can wait without any major issue a bit longer.
In the case of extreme root bound (photo below), the roots occupy the majority of the container. The plant stopped for a while its healthy growth, and it is at serious risk. Is this your case? Hence you cannot wait more.
You quickly need to check if you have everything in place to proceed and then apply the right technique.
What do you need?
After checking if your plant is affected by root bound, you need to first to have ready the following:
- A new larger plant container: Ideally you need a container that is 2-4 inches larger than the current one. A too-large container (as discussed in this article for basil) can trigger watering issues (overwatering problems can get more common).
Which container to choose? In my case, especially if I deal with herbs I go for self-watering like this one on Amazon, relatively cheap, sturdy, and durable.
More elegant version: For a few dollars more, you can find a more elegant version that suits quite well in the living room like this one on Amazon made of ceramic (go for the white version). Remember to pick up the 10-inch version (ok for the majority of houseplants except for succulent).
If you plan to use an old plant container, it is ok. However, wash it first. Indeed, old soil residue might carry bacteria or pests that can damage the plant.
- Good quality potting mix: there are quite a few potting mixes, however, the one that I enjoyed the most and gave me the most results is the FoxFarm. Check it on Amazon, pretty sure you will also find good reviews. The amount of potting mix strictly depends on the amount and size of pots, however below, you can find some indicative numbers.
- Gardening gloves: these are optional, but it will protect you (and the plant) from eventual pathogen you might
- Clean and sharp pruning shears: make sure this pruning shear (here the Gardenite I am using, on Amazon, quite good for the price) is cleaned if they have been recently used on other plants.
As you will see later, you need to cut some roots. If the shears are not clean, you will risk transmitting pathogens (lying on the blades of the shear) straight to the circulatory system of the plant through the wound. This might kill the plant.
Soil Required approximately
3 gallons (11 liter – 0.45 cu. ft.)
5 (19 liter – 0.78 cu. ft.)
7 (26 liter – 1 cu. ft.)
10 (38 liter – 1.6 cu. ft.)
How To Fix the Root Bound: the Right Technique
Then you have to proceed to the repotting. Nothing complicated, just 4 steps
1 – Extract the plant from the original container as detailed before
2 – Place a bit of fresh new soil (a few inches) at the bottom of the new container. Check if the plant, with such amount of soil, will stay at the same level compared to the container.
3 – Cut the external layer of the roots: in order to fix the root bound problem, before repotting the plant, you need to cut the roots in the outer layer (those that were touching the inner wall of the container). You can use your shears.
Indeed, experts agree that this root pruning will improve your plant health as it stimulates the growth of “higher quality roots”. These are the roots with tiny hair on them that have the highest capability to absorb nutrients and gases.
Tip: for those large roots making circles, try to straighten first and then proceed with cutting. If you do not do that very likely they will keep growing in circles.
Tip: you can safely cut up to 30% of the roots without issues. In some special cases, professional gardeners can easily cut most o them (check this YouTube video for bonsai) without issues.
Do not be scared of pruning your roots. Indeed, this is a practice used for decades (centuries) to create bonsai (in an extreme way, up to 60% of the root removed). Curious? Watch the YouTube video here.
How to cut the roots of your plant? Gently pull the roots around the planter with your hands (wear gardener gloves if you can). Once they are loosely cut, the long ones that were traveling in a circle with your shear. Another technique is just to slice, like butter, the outer layer of the plant roots. Both are ok.
4 – Place the plant in a new container: once the roots are loose, place the plant in the prefilled new container. Add the remaining potting mix so as to cover the plant.
5 – Pro tip #1: cut some leaves, especially the old ones. Why? The plant has fewer roots and has to focus its energy on recovering and growing new ones. This stress requires energy that cannot be focused on maintaining all the leaves it has
6 – Pro tip #2: water the soil to keep the soil moist but not soaked (of course, different applies to succulents).
Then, you just need to wait. In a month or so, your plant (especially if it is an herb) will start new shootings and be ready for its new home!
Are there plants that prefer to be root bound? Quite a few houseplants prefer to be roots bound such as peace lily and spider plant, asparagus fern, and spider lily
Will a root bounded plant die? The chances of a plant death if left for too long in a root bound condition are quite high. The only way to avoid/delay this even is to provide a constant supply of water and fertilizer to compensate for the lack of soil and space.
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