Rosemary is notorious for becoming root bound when grown in pots but is that a bad thing or does it actually like it? That is a question I have often been asked and often seen people ask online, so I decided to write this article to answer it once and for all.
Rosemary does not like to be root bound since it causes the plant to grow slower and eventually stop growing entirely. While the plant will survive being root bound for some time, it will eventually die unless the problem is solved.
I have had to deal with this problem many times, but it is luckily not so difficult. If you want to learn why it is so bad for rosemary to be root bound as well as which signs to look out for and what to do when it happens, I recommend reading the rest of this article as I will explain it all.
Why Rosemary Should Never Be Root Bound
When a plant is root bound it means, as the term indicates, that the roots have run out of room to grow and are bound by some kind of barrier, typically a pot, which prevents them from growing further.
Some plants don’t mind this much but rosemary absolutely does not like it.
Rosemary should never be root bound since it prevents it from obtaining nutrients and water from the soil efficiently enough, which leads to stunted growth. If a potted rosemary plant is showing signs of being root bound, repotting it into a larger pot or pruning its roots are the two best solutions.
I enjoy growing most of my rosemary in pots since it allows me to move the plants around, although it also means that I have had to deal with my plants being root bound several times.
Because of this, I have talked to a gardener from a nearby garden center who is an expert in the field of growing Mediterranean herbs. He gave me some excellent tips for identifying and dealing with the problem that I share in this article.
3 Signs Your Rosemary Is Root Bound and Needs Help
Potted rosemary can become root bound quite easily but it can be tricky to identify the issue early. That’s why it is important to know the signs to look out for so you can react before it is too late.
These are the four most common and easily noticeable signs to look for.
- Stunted growth
- Wilting
- Leaves turning yellow and brown
- Roots filling up the entire pot
Rosemary can stop growing, wilt, or turn yellow or brown for several reasons, so the only certain way to tell if your plant is root bound is to carefully lift it out of its pot and look at the roots like I did in this photo.
If the roots look like the ones in this photo, your rosemary is definitely root bound and needs a helping hand. I have two easy methods for this, which I share now.
What to Do When Rosemary Is Root Bound (2 Easy Options)
What you should do if your rosemary is root bound depends on your goals with the plant. I have two great methods for dealing with the problem.
The first method is useful if you want your plant to grow bigger. The second method is best if you don’t want your rosemary to get much larger but prefer to keep it more contained.
Method 1: Repotting or transplanting for continued growth
The first method I want to share is to repot your rosemary into a larger pot or transplant it into the ground.
I have written a full step-by-step guide for repotting rosemary with photos of me doing each of the steps in the process to make it as easy as possible for you.
The point of doing that is to give your plant’s roots more room. This will allow them to continue to obtain enough nutrients and water to continue to grow.
Keep in mind that transplanting is not risk-free. You can read more about the risks of transplanting rosemary here if you are interested.
I have read a lot of recommendations saying that you should repot your rosemary into a pot that is 1-2 inches (2.5-5 cm) or “one size” wider and deeper.
While this is sufficient for a while, my experience says that the plant will outgrow its new pot relatively quickly, so I recommend considering a pot that is several inches wider and deeper than the one your plant is currently in so you don’t have to repot it as often. I often go with a 12-inch pot. Alternatively, you can just put your rosemary in the ground which I also have a guide for.
It can be beneficial to carefully massage the root system to loosen the roots up a bit before replanting it. It can make it easier for the roots to spread and grow afterward, but if you are not gentle enough, you can damage them.
If you transplant your rosemary into the ground, you will most likely never have to deal with it being root bound again since it almost certainly has plenty of room for its roots.
If your plant is severely root bound, you should repot it immediately but if it is not that urgent, you can wait until the best time of the year to do it. I have another article where I cover the best time to transplant rosemary.
Method 2: Root pruning for limited growth
This method is ideal if you want to keep your rosemary happy but also don’t want it to get much larger.
Root pruning essentially means that you cut a portion of a plant’s roots as I do in this photo.
I have used this method a handful of times but not nearly as much as repotting which I explained above. I wanted to be sure I included all relevant information, so I reached out to an employee at a nearby garden center who is a true expert in growing Mediterranean herbs such as rosemary.
He shared some excellent info about root pruning.
When you prune your rosemary’s roots, you can add new soil to the bottom of the pot and put your (now smaller) plant back into it. That way the roots will have room to grow again.
Make sure you add an amount of soil equivalent to the chunk of soil and roots you removed from the plant. The surface of the soil and the base of the plant should be at the same level as before you pruned the roots.
I found that the easiest tool for cutting through the roots is a serrated knife, although you might have to also use some pruning shears to cut through thicker roots.
The expert I talked to recommended to never remove more than about a third of the roots at the same time. This would be approximately as much as I cut in the photo above.
You can remove more, and I have done that before, but if you do that, the plant is forced to focus on growing roots for a while, which means that it won’t grow new foliage as fast.
This plus the fact that there really isn’t more room for roots than before once they grow out means that your rosemary will not get much larger. Sure it will still grow some, but not nearly as much as if you repot it into a bigger pot without pruning the roots.
I have written a complete guide on root pruning rosemary. In that guide, I explain the best and easiest way to do it, the best time to do it, how to tell if it is necessary, and a lot more.