Container size and design is something to be careful about when potting a houseplant. It affects your plant in ways you might not realize.
A: The one on the left!
This monstera will grow huge and may eventually need a pot the size of the one on the right, but right now the smaller pot is the perfect size. Let us explain why...
You want to choose a pot that is the correct size for your plant. Ideally, this is a pot that fits the root ball comfortably, with one or two inches of substrate (potting media) in all directions for the roots to grow into. Even if you know that your plant is going to get much bigger over time, it’s important not to put it in a pot that is too big, too soon.
If you overpot, chances are that you might start seeing symptoms of overwatering with your plant. If there is too much substrate, it will stay saturated too long and could lead to root rot.
If you underpot, your plant will end up rootbound very quickly, which leads to symptoms of underwatering due to the roots getting in their own way of water absorption.
Don’t be afraid to take your plants out of the pot when you need to assess rootball size.
Q: When to repot?
The start of the growing season, which is early spring for most plants, is a great time to check on plants’ roots and size up pots as needed.
Another great time is 2-3 weeks after bringing a plant home from the nursery. It’s good to give them a few weeks to settle in to their new home, but after that you might want to get them out of the pot to see how the roots are doing.
If a plant has been growing quite vigorously during the growing season, then suddenly slows down, that can sometimes be the first sign that they need a bigger pot. If they are in a container that is flexible (like plastic,) you can squeeze the sides to test how tightly the roots are filling it. A pot with plenty of substrate often feels relatively soft when squeezed, whereas a rootbound plant will feel hard and tight.
You might want to consider repotting if you are seeing health issues with your plant that can’t be explained in other ways. Your plant might be rootbound or the substrate may be depleted of nutrients.
Is your plant rootbound?
Once you take your plant out of the pot, it’s easy to tell if it is rootbound. If your plant’s roots are looking smashed into the shape of the pot, growing tightly next to each other, growing directly against the side of the pot, winding around in circles, and/or there’s a lot more roots than substrate -- it’s rootbound. In that case, you’ll want to gently loosen the roots and see how big they are when they aren’t being squished. Then, find a pot that that is one to two inches larger in diameter. (Trimming the roots is a possibility, but do your research. It can cause parts of your plants to die.)
Refreshing the substrate
Repotting doesn’t always have to mean sizing up. You can repot your plant just by refreshing the substrate and returning it to the same pot if the size is still working well. Houseplants appreciate fresh substrate once a year or so.
Plastic pots hold in the most moisture, closely followed by sealed ceramic and painted terra cotta. Plain terra cotta and orchid pots let the substrate breathe quite a bit more.
Pots with drainage holes
Pots with drainage holes are almost always the most successful for growing houseplants.
Plastic and sealed ceramic pots are great for plants that like to stay moist. Any plant that wants to dry out between waterings will benefit from terra cotta. Orchid pots (and terra cotta) are appropriate for anything growing in bark.
You can grow a wide variety of plants in a wide variety of containers, but keep in mind that if you have a succulent in a sealed ceramic pot, for instance, you will need to be extra careful about how much water you give it.
You can also choose containers based on your watering habits. If you tend to overwater, try terra cotta. If you tend to underwater try plastic or sealed ceramic.
Pots with no drainage holes
The best way to use a pot with no drainage holes is as a cachepot, which is a decorative pot that a plastic liner fits inside of. In this way, if there is excess water draining out of the plastic liner, it can still be emptied from the cachepot so that your plant isn’t oversaturated.
Some people advocate for adding stones at the bottom of a non-draining pot to “add drainage.” This is inaccurate. Adding stones at the bottom of a closed pot is adding space for a water table. It can be helpful, in that a small amount of water can drain there if the plant is overwatered, but often it doesn’t ever have a chance to dry. Therefore, over time, the stagnant water table often moves up into the soil (or the soil collapses into the stones) creating an oversaturated situation.
For a better chance of it working well, you could separate the stone and soil layers with a screen and use a transparent container. That way you could effectively keep the substrate and water table apart, while also monitoring how high the water table is. Of course you can try this in an opaque container, just take care and go slow with watering.
Pots without drainage holes can also be drilled, therefore allowing them to become pots with holes! Cornell Farm will drill holes into any pots you buy from us for a small charge.