In researching this post, I did the same as a presume my readers would: I googled "how to repot houseplants." But then I read through pages and pages of results. I was delighted that the most sensible advice had risen to the top of the list, from HGTV. What I liked most about the HGTV article is that it explains the repotting procedure simply and clearly, without any unnecessary steps or unneeded materials, while at the same time answering many of the most common questions about repotting. These are just a few questions that they missed:
How often do houseplants need to be repotted?/How large will my houseplant eventually get? How quickly a plant grows, thus requiring repotting, depends on the plant. Different plants grow at different rates. Even two identical plants can grow at different rates if one gets more sunlight and fertilizer than the other.
How large a houseplant will inevitably become depends on you. I mean, will you still be caring for this plant in 20 years? If so, bravo! However, I suspect that most people don't keep their plants for nearly that long, especially if they move to a new home. Most moving services won't accept the liability of potentially damaging your houseplants.
You can find estimates for how large a specific houseplant is expected to grow in a good houseplant book or online. Keep in mind that these are estimates and not prophecy. And a plant grown "in captivity" of a pot will never grow as large as a plant grown in its native environment.
Can't I just buy a big pot now and not have to worry about repotting? No, because a pot that is too large puts your plant at risk for overwatering. Potting soil behaves like a sponge; it absorbs and holds on to water. A larger pot full of soil holds on to more water than a smaller pot, taking longer to dry out between waterings. A small plant in a too-large pot is most certainly in danger of root rot. This is why it's advised to incrementally increase the size of a pot as a plant grows, potting up to just a couple of inches larger.
How can I tell that my houseplant needs to be repotted? Here are three things to look for: Do you see roots circling the surface of the soil or poking through the drainage hole? When you water the plant, does the water run through instantly because there's more roots than soil to absorb the water? Or does your plant seem like it's no longer growing any larger (and it should be) because the pot is constricting its roots and therefore it cannot support more leaf growth? If you answered "yes" to any of these questions, it's time to repot.
Do I need to put anything at the bottom of the pot? Nope. No layer of rocks. No layer of charcoal. No shards from broken pots. Your potted plants need nothing else but potting soil.
The idea that containers require a drainage layer is one of those pervasive gardening myths that continues to get repeated, despite ample evidence to the contrary. Soil scientists demonstrated that the drainage layer does not work more than 100 years ago. But if black and white photographs aren't your thing, check out YouTube:
If you are doing your repotting indoors (I don't have the space for a backyard potting bench either), you could use a biodegradable paper coffee filter at the bottom of the pot to keep the soil from falling through the hole during the repotting process. However, you could just as easily spread a few sheets of newspaper across your work surface, as it's only a small amount of soil that ever falls through the drainage hole. Once soil is moistened by watering the plant, soil sticks to itself and won't fall through the drainage hole any longer. Personally, I can never repot a plant without getting soil all over everywhere, including all over myself, so I'm never concerned about that tiny bit of soil that falls though the drainage hole. I always keep a dustpan and brush nearby for cleanup.
Does my pot need a hole in the bottom? Yup. That's the only way the water will come out. Unless you are growing aquatic plants, you want the water to come out.
Pots made without drainage holes are cachepots, decorative cover pots intended to conceal the unattractive plastic pot that you purchased your plant in. If you must plant directly into a non-draining pot, then you must drill a drainage hole in it first.