June 22, 2021
Source: My Tasteful Space
Unsplash, Severin Candrian
What is root pruning? And, have you ever heard of this term before? Root pruning is the trimming of indoor plants’ roots. That’s right! Pruning of the roots, not of the stems! It sounds terrifying, right? It is mostly done to contain the growth of indoor trees, tall indoor plants, terrarium plants and bonsai. When a plant becomes root bound, (its roots have outgrown its container and start growing outside of it), its health starts to deteriorate. Root bound plants have a very compact and crammed rootball that basically “strangle” the plant, not allowing proper nutrients, water or air circulation. When this happens, the plant needs to either be moved to a larger pot, OR, to be root pruned. Root pruning is not as common as repotting a plant into a bigger container. There are instances in which, repotting a plant into a bigger container is not an option anymore. For example, if you have an indoor tree that is already planted inside a 14″ pot and you don’t want the plant to grow any taller, (or you’ll have to move out yourself!), you can contain its growth by root pruning it and repotting it in the same container. I had this same issue with my Fiddle Leaf Fig. After 14 years of growth and repotting into bigger pots every time, I decided that it was time for my Ficus Lyrata to slow down a bit!
(I sound all cocky and confident now, but trust me, it was a nerve-wracking decision to make. It takes serious guts to finally decide to root prune your 14 years old plant! You feel like a murderer when you are in the process of cutting the roots like you were slicing a loaf of bread with a knife!) WHY ROOT PRUNING? Root pruning is a great way to contain plants’ growth. When you repot your plant into a bigger pot, you give the roots more room to expand, and by doing that, your plant will grow bigger.
The more you upsize your plant’s pots, the bigger the plant will continue to grow. When you can’t upsize your plant container any longer, or when you want to maintain the size of your plant the way it is, because your plant is inside a terrarium, or it is a bonsai, root pruning is the answer.
Root pruning is also a great way to maintain your plant’s roots healthy. In-fact, pruning off decaying roots is a great way to divert the plant’s energy into new, healthier growths. Even though it sounds and it appears barbaric, it is actually a healthy intervention for plants, (provided that is done right and at the right time!). WHEN IS THE RIGHT TIME FOR ROOT PRUNING? Many sources indicate that the best time to root prune plants is when they are root bound. Sure! That is true, BUT WAIT A MINUTE! If you realize that your plant is root bound in the middle of Winter, it doesn’t mean it’s the right time to root prune it!
All “invasive plant procedures” such as; repotting, pruning and root pruning need to be done in Spring, (Summer is OK too).
There are two reasons for this:
Many plants go dormant during the winter months, (many plants stop growing during the Winter months), and a major procedure such as root pruning, can totally shock their system and eventually kill them.
Plants, whether they go dormant or not, drastically slow their growth process down during the Winter, so their roots are not going to grow any longer anyway.
Just wait until the Spring to root prune your plants!
Season aside, what are the clear signs telling you that your plant is root bound and that it either needs repotting into a bigger pot or root pruning?
Its roots are growing out of its pot’s drainage holes
when you pull it out of its pot you see more roots than soil
HOW ROOT PRUNING IS DONE!
Now that you know WHY and WHEN root pruning is done, it’s time to get into the nitty gritty of it!!
How to root prune your plants.
It is actually easier than you think.
Roots are not as delicate as we think they are!
But before we dig in, (and we focus on the step by step), I just want to clarify with you that you should never root prune more than 1/3 of the root mass of your plant.
So when I get into the details of root pruning the bottom and the sides of your plant, make sure that the TOTAL of what you prune does not exceed 1/3 of your plant’s roots!!
Ready for this?
Let’s dig in!!
STEP #1 - GATHER TOOLS & SUPPLIES
I always recommend to gather all the tools and supplies you’ll need for the entire “operation” before you even start.
Personally, I can’t stand being stuck in the middle of a delicate procedure, completely covered in dirt, and realizing I need a tool! (Or to blow my nose!!!)
I am sure you’d dislike that too! That’s why we get ready ahead of time!!
Here’s what you’ll need;
Pruning saw, (for pruning trees), or a serrated knife, (to slice bread! 😂).
Scissors.
Potting mix suitable for the plant you are root pruning.
Perlite, (I add it to my potting mix to improve the soil’s drainage).
Bucket to mix soil and perlite.
Hand trowel.
Gardening gloves.
STEP #2 - CUT-OFF THE ROOTS GROWING OUT OF THE POT! Cut-off the roots creeping out of the drainage hole. It will make your life much easier when you’ll have to pull the plant out of its pot! STEP #3 - PULL THE PLANT OUT OF ITS POT This part may require a bit of muscles, or two people, depending on the size of the plant. You need to be gentle at the same time as you don’t want to rip the roots. We are here to root prune, not to root rip! If you have a big plant, you may want to lay it on its side first. If your plant is in a plastic pot, you can put pressure all around the pot to loosen up the rootball and pull the plant out. If your plant is in a terracotta or ceramic pot, you may need to use your long serrated knife to scrape along the edges of the pot and loosening up the soil. STEP #4 - LOOSEN UP AS MUCH SOIL AND ROOTS AS POSSIBLE (IF POSSIBLE) Once you’ve pulled your plant out of its pot, loosen up and remove as much soil as possible, if possible. Some plants have such crammed roots that there is next to no soil left in the rootball. If that’s the case, move to the next step. If there is some soil, try to loosen it up with your fingers, or by gently tapping the back of your knife/saw on the rootball. As you can see in the picture below, I was able to remove some of the soil and to loosen up just the bottom roots. The side roots, all around the pot’s wall, are a solid block impossible to loosen up. STEP #5 - PRUNE THE BOTTOM ROOTS Start by slicing off the bottom 1/2 to 1″ of the rootball with your saw or serrated knife. For an indoor tree or any other large plant that you don’t want to grow any more, cut-off even more, as long as you don’t remove more than 1/3 of its root mass!!! PRO TIP! Every plant has two types of roots; Tap Roots and Thread Roots. Tap Roots are the main ones, the biggest ones, while the Thread Roots are the smaller ones growing off of the Tap Roots! When root pruning, (whether you are pruning the bottom or all around the sides), it’s really important you only prune the the Thread Roots. Avoid cutting Tap Roots! And remember! Don’t remove more than 1/3 of Thread Roots! Here above you can see a Tap Root, which is clearly thicker than the other Thread Roots around it. When cutting a slice of roots, whether you are cutting the bottom or the sides, you’ll be able to fill the Tap Roots with your knife. Try to work around them, living them intact.STEP #6 - PRUNE THE
SIDE ROOTS Now slice off the side roots all around the rootball, making sure to leave the Tap Roots alone! If you find Tap Roots while root pruning your plant, and find it difficult to cut around it with a knife, just switch to scissors. STEP #7 - LOOSEN UP SOIL AND ROOTS Now that you’ve pruned a good portion of your roots, try to loosen up even more soil and roots. It’s good to loosen up the roots to face down, so that they can grow in that direction, rather than
circling around the pot again.
It’s also advantageous to remove as much of the nutrients depleted soil as possible. This soil is also saturated with excess mineral salts.
STEP #8 - MIX SOIL & PERLITE Mix your plant’s specific soil with perlite before your start repotting your root pruned plant! I like to mix perlite to all my potting mixes because it adds drainage to the soil, and drainage is oh! so important for the health of your plants! I generally add 2 parts perlite to 5 parts of soil. STEP #9 - REPOT YOUR PLANT After root pruning the bottom and sides of your plant, (for a TOTAL of no more than 1/3 of its rootball), there should be plenty of room for the pruned roots to grow back into its old pot. Place a layer of fresh potting mix at the bottom of your pot and then place your plant in it! STEP #10 - WATER YOUR PLANT Once your plant is happily repotted inside its old pot, give it a good drink!
STEP #11 - CLEAN YOUR PLANT'S LEAVES, (OPTIONAL, BUT WHY NOT?) Before you move your plant, put everything away and clean up your space, I recommend you give your plant’s leaves a good wipe too!
I always take advantage of these “operations” to pamper my plants and do everything I need to do to care for them, before I move onto the next plant or the next project. Cleaning houseplants leaves is not just for the look!
Removing dust from their leaves helps your plants to process photosynthesis more effectively, and keeping them healthier.
Check out this blog article for more details on How to Clean Houseplants Leaves and for a home made, natural leaf cleaning product recipe. I use a Norwex mitt to dust my plant’s leaves…It is just easier than wiping them with a cloth. STEP #12 - LET YOUR PLANT REST Now that your plant has been root pruned, watered and even leaf polished, it’s time to let it rest. If your plant is usually sitting in a medium to low light area, you can go ahead and put it back in its original space.
However, if the plant you’ve root pruned is a plant that normally sits in a lot of direct or indirect light, you’ll need to give it a week or two break in an area with partial shade, before returning it to its original location. Plants too need to heal after “major interventions”! And that is it! You now have all the tools you need to root prune your plant! I know it can be an intimidating process, but trust merit works!
What plants do you grow in containers? What plants do you grow indoors? How has this article helped you?
Create your own Rain Garden: Find Out How. Have you tested your soil? What type of soil do you have? Is it appropriate for what you are growing? Do you need to amend your soil? How do you need to amend it?
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