It can be difficult to know exactly when the time is right to repot your favorite houseplant, especially taking into consideration that some need more room than others. When it comes to ZZ Plants (Zamiifolia Zamioculcas) you may be wondering, “Do ZZs like to be rootbound?” and “When is the right time to transplant them?”
ZZ Plants do not like to be rootbound. They grow large underground rhizomes that take up a lot of space inside a planter. When too many rhizomes are forced to live in a small pot, the odds of root rot and fungus increase. ZZs should be replanted every two years into a pot that is one size larger than the one is previously lived in.
While trimming back roots may work for other houseplants, ZZs have rhizomes, which look similar to bulbs or tubers, under the surface. That means that in order to expand, your ZZ must have room to grow. A good rule of thumb is to repot your plant every two years into a container one size larger than its previous home, but there are a few more things you should know. Read on!
Before We Get Started, Let’s Talk About Rhizomes
ZZ Plants differ from many of our other favorite houseplants because of what’s going on underground: rhizomes. Not to be confused with bulbs or tubers, ZZ rhizomes are typically round, white, and grow just under the soil. They store the water and nutrients that ZZs need.
The rhizomes under your ZZ spread out underground and need room to grow as the plant ages and expands. In fact, when new growth appears in the form of a new upshoot stem, there should already be a rhizome beneath the soil at the base of this new growth.
When too many rhizomes are present in a container, your ZZ Plant will be more susceptible to root rot. These rhizomes need room to spread out and the more airy the soil, the less likely you are to see rot.
Because these plants take up so much room underground, they do need to have adequate room in their containers. However, ZZ plants are slow growers, so while they will need to be repotted eventually, you should be fine to only do so every two years.
If you have more questions about rhizomes or want to further explore the differences between rhizomes, bulbs and tubers, read this article.
What Does Rootbound Mean? Why Does it Happen?
Now that we’ve got that out of the way, let’s move onto the bigger questions like, “What does it even mean to say a plant is ‘rootbound’ and what causes this to happen to houseplants?”
A plant that is rootbound (or potbound) is one where the roots have become larger than what the current container can accommodate. Signs that your plant needs more space are: roots growing out the drainage hole in your container or large roots spiraling at the bottom of the container to create a dense coil.
Rootbound plants often become hard and will slide out of their containers easily, retaining the shape of the pot. When this happens, the large amount of roots have replaced much of the soil in the container, meaning the plant cannot get access to the nutrients, air and water it needs. This can stress your ZZ Plant and keep it from growing.
In nature, plants are able to grow as they please, stretching out their roots in all directions. But when we bring those same plants indoors and place them in containers, we put restrictions on how and to what extent the roots can grow. Healthy plants are plants that are allowed room to grow, more like they would in their natural habitat.
The main reason a plant becomes rootbound has to do with the size of the container it is planted in. A container that is too small will not allow enough room for roots to grow. When a container is mostly filled with roots, there is not enough soil present to provide the plant with what it needs to grow and be healthy.
What To Do If Your ZZ Plant is Rootbound
Before I get into the specifics, let’s talk a little about toxicity in ZZ Plants. ZZ Plants produce a compound called calcium oxalate that can cause irritation if it gets onto your hands or face. This compound is mostly found in the sap of the plant, which resides inside the stem. If you’ve been handling the stem or roots of your ZZ, there is a chance that you’ve been exposed to this compound.
READ OUR EBOOK
Keep Your ZZ Happy With Our Guide
ZZ Plants are tough. They can survive a range of conditions and require little input from us. But if you want your ZZ to thrive, you'll need to know a thing or two about what they need and love. Get our 80+ page care guide and you'll be on your way to a very healthy houseplant.
GET YOUR COPY NOW
To minimize the chance of irritation to your skin, you should always wash your hands after touching your ZZ Plant and avoid touching your face. If you have sensitive skin, you should consider wearing gloves while handling your ZZ leaves, stems, roots, or rhizomes.
Repotting ZZs: If your ZZ is rootbound, there is a simple solution: transplant the ZZ into a larger pot. The larger pot will give the ZZ room to spread its roots and rhizomes out, which will in turn allow it to continue growing taller and wider and eventually become a large plant (ZZs can reach up to 2-3’ in height).
When choosing a new container for your ZZ, it’s important to only move up one size. While ZZs like room to stretch and grow, too much room actually causes the soil to dry out more slowly and can result in root rot and other problems from overly wet soil.
Transplanting ZZs is easy. To do so, gently remove your ZZ from its old container. The best way to do this is not yanking or pulling but rather flipping the entire plant and sliding it out once it is upside down. Discard the old soil and fill your new container about ⅓ of the way full with fresh soil. Place your plant in and put soil around the edges until your new container is filled.For more info on repottings ZZs, read this article.
Dividing ZZs: If your plant is becoming too large for you to maintain in your home, rather than sizing up to the next container you may want to divide your ZZ and replant.
To divide a ZZ, remove the plant from its container and wash off most of the old soil. This will give you a better view of the rhizomes as you will be making cuts to them.
If you’re lucky, you will have a couple of rhizomes that are well developed and only attached to the mother plant by a small amount of tissue. Ideally, you are looking for ones that already have a stem protruding from the rhizome. To divide, remove those rhizomes by making clean cuts with a sterile knife.
If your ZZ is large, you can cut the plant into halves of thirds. This requires cutting through the larger rhizomes but never fear, your ZZ can handle it. Divide your plant by making clean cuts (no sawing motions or serrated blades) through the rhizomes.
Allow divided ZZs to sit out for at least two hours (I prefer leaving them overnight) to dry over before replanting them into new soil. For a more extensive overview of dividing ZZs, read this article.
Replanting Is Best Done in Spring or Early Summer
ZZs have a reputation as slow growers, so they don’t need to be replanted very often. Transplanting up a pot-size once every two years is usually all these plants need from us.
I recommend waiting to repot your ZZs until the spring or early summer. This is because in the colder months of the year, your plant enters a dormant state and growth is slowed way down. I find that transplanting in the early spring will give your ZZ the room it needs to produce new growth once it is in it’s growing season again.
What Container Is Best For Your ZZ?
When it’s time to move your plant up a pot size, you’ll need to find a new container for your ZZ. And when it comes to ZZ containers, there are a few things you need to know.
First, it is important that you don’t choose a pot that is too big or too small. Pots that are too big will cause the soil to dry out more slowly, something your ZZ won’t appreciate. And pots that are too small won’t accommodate your plant to expand underground for the next two years.
I recommend always choosing a pot that is only 1-3” larger in diameter than the container your ZZ is currently residing in. This will give it room to grow, but not so much that it causes a problem.
Also, look for a container that has a drainage hole in the bottom. ZZ soil needs to dry out between waterings and in order to do so properly, excess water must be able to flow out from the bottom of the pot. Drainage holes in planters will also allow you to bottom water the plant by sitting it in a shallow dish of water, which is something I like to do to keep from overwatering my ZZ Plants.
What Soil Is Best for Repotting ZZs
When it comes to soil, drainage is key. Soils that are too heavy will keep the roots of your ZZ wet which can cause major problems like root rot and fungus.
A good rule of thumb for ZZ Plants is to transplant them into soil that is a mixture of half regular potting soil and half cactus or succulent blend soil. This will give your plant the right soil balance to drain quickly. To find out more about the best soils and containers for ZZ Plants, read this article.
Final Thoughts
I don’t think that any plant really “prefers” to be rootbound. Many people suggest cramping your plants in small containers to force them to bloom or produce growth more quickly, but I don’t think it’s what is best for any plant.
We see little to no evidence in the wild of plants restricting their own growth in order to thrive. In nature, plants are able to extend their roots out in all directions to firm up their foundations and access nutrients in the soil.
ZZ Plants need room to grow due to their large underground rhizomes that function as storage reservoirs for water and nutrients. If your plant has outgrown its old container, follow these simple instructions and either transplant it, or divide it to share with a friend.
Want more tips and tricks to keep your ZZ growing to its full potential? Grab a copy of our best-selling book Caring for ZZ Plants and learn all you need to know about your favorite houseplant.
