You chose a great pot for your houseplant, but do you need rocks in the bottom of the pot as well? You’ve heard that may be a necessity for some indoor plants, but admittedly, you’re not sure. Besides, won’t adding rocks to the pot impact water drainage? What should you do?
Should I put rocks in the bottom of my pot? It’s not recommended to put rocks in the bottom of your houseplant’s pot. You can’t fill the pot with as much soil if it already has rocks in there, giving your plant less room. The water also cannot exit the drainage holes in the pot, as they’re blocked up by the rocks. This can cause waterlogging and lead to root rot, killing your houseplant.
In this article, we’ll explain in even more detail why you should avoid adding rocks in your houseplant’s pot. We’ll also discuss whether gravel or pebbles are better alternatives. If you’ve fallen victim to the fable that you need rocks in your pot, then you’re not going to want to miss this article.
Rocks in the Bottom of Your Pot: Yes or No?
Among gardeners, adding rocks to the bottom of your houseplant’s pot is considered a myth these days, but that wasn’t always the case. For many years, this faulty advice was pushed as fact, even getting publication in various gardening books and magazines. People believed it, and so they did it, sometimes killing their plants in the process.
It’s okay if you thought once upon a time that rocks were supposed to go in your indoor plant’s pot. You’re about to learn differently as we explain all the ways rocks can hinder rather than help your poor plant.
Rocks Impact Drainage
The drainage holes at the bottom of your pot are very important, as that’s where water escapes from. Without that, the water can sit and saturate in the pot. More so, all that water can “drown” your houseplant, so to speak. Imagine if you got a lot of water poured on you with no chance to breathe. Pretty scary, right? The same can happen to plants if there’s not enough oxygen and too much water.
So yes, it’s clear that a pot’s drainage holes serve a crucial purpose. It’s okay if a bit of soil gets in the way of the drainage holes since soil is relatively malleable. Water can certainly erode it somewhat, making a pathway to exit the pot. You know what water can’t erode? A giant rock. Well, maybe with many years, but you don’t have that kind of time.
That brings us back to our current predicament. If you happen to block up your drainage holes with a rock, that water is not going anywhere. It’s trapped within the pot. Your houseplant, lacking oxygen, can wither and die.
Rocks Don’t Give Your Houseplant Much Room
The main selling point to adding rocks to your houseplant pot was that you didn’t need as much soil. We can understand why this might appeal to some gardeners, especially if they use somewhat pricier specialty soil.
Okay so, for argument’s sake, let’s say you did add a couple of sizable chunks of rock to your houseplant’s pot. Maybe about a quarter of the pot is filled with rocks, perhaps about halfway. The other half (or slightly more) has the potting soil. This doesn’t help your sad houseplant at all. It’s like you took half its house away.
When you shopped for a pot for your houseplant, you made a precise pick that could accommodate your plant at its current size. You made sure the pot wasn’t super small, of course. Now, even though you have an appropriately sized pot, you shrunk the space your houseplant has to grow.
Will this necessarily kill your houseplant? No, but it can severely limit its size potential. Plants are smart in that they grow around the environment they have, but in this case, that environment is not enough.
Rocks Could Cause Root Rot
There’s another little side effect that occurs when you fill your houseplant pot with rocks. As we just talked about, space in the pot is already very limited since you have rocks taking up a good amount of room. What do you think happens when you add water to such a setup?
Earlier, we mentioned how water can’t travel through the drainage holes as readily—if at all—because the rocks are blocking those holes. So where does it go? Well, you know how gravity works when watering a houseplant. The water travels downwards towards the plant’s roots, nourishing them.
The water still travels down with a pot of rocks, but now it’s got this hard, impenetrable wall. It can’t go down to the bottom of the pot, so the water just sits and pools where the rock layer starts. The soil gets soggy, then wet, perhaps even waterlogged with time.
Now, remember that your indoor plant’s roots haven’t gone as deep because of the rocks. They’re sitting there amongst all that excess water that has no room to drain. That’s the perfect recipe for root rot, which can kill many a houseplant.
Rocks Make Your Pot Really Heavy
Admittedly, this one doesn’t really affect your plant at all, but should you try to carry a pot with rocks in it from one room of your home to another, it’s not going to be easy. The pot can get quite heavy depending on how many rocks you added!
If you have an indoor plant that needs full sunlight some of the day but indirect light the rest of the day, shifting your rock-filled pot across the room could leave you with an achy back. Luckily, it’s completely avoidable by not putting rocks in your houseplant’s pot in the first place.
Rocks vs. Gravel: Are They the Same Thing?
Alright, so we already established why rocks in the bottom of your indoor plant’s pot are a no-no. Perhaps you figured you would try gravel instead. For definition’s sake, gravel is simply smaller stones and rocks, often fragmented pieces of the latter.
Since it’s not nearly as big, gravel won’t get in the way of your pot’s drainage holes, right? Well, maybe, but without seeing the gravel personally, it’s hard to confirm that. Some gravel can be pretty chunky, in which case, you could still have drainage hole blockage.
Even if the single pieces of gravel were small enough that they could pass through the holes in your houseplant pot, that doesn’t make using gravel a good idea. By the handful, gravel is no better than a large rock or three. It could still interrupt drainage. Gravel certainly limits how much soil goes in the pot, making your houseplant’s home squished. It could also contribute to root rot and make your pot feel heavier than necessary.
While rocks and gravel aren’t quite the same thing (even if they both come from the same source), they do operate pretty much identically in a houseplant pot. They’re both something you want to avoid using if you want to see your indoor plant live a long, healthy, happy life.
What about Using Pebbles?
Rocks, gravel, pebbles: aren’t they all the same thing? Yes, but we’re not advocating for putting pebbles in your pot this time. Instead, what some gardeners do is make what’s known as a pebble tray. This is something we’ve talked about several times on this blog.
Pebble trays go under the pot, not inside of it. You’d still fill the pot with the soil your houseplant needs, no rocks included. What the tray does is contribute to your indoor plant’s humidity.
How? Good question! Since you add water to the pebbles and then put your pot atop the tray, your pot’s base stays over the recommended water level. This lends more humidity to your plant once the water begins evaporating.
If you’re interested in making your own pebble tray for your houseplant, we first recommend checking the humidity requirements of the indoor plant you’re growing. If it needs more humidity than the average plant, then here’s what you do.
First, you want to find a tray that outsizes the base of your houseplant’s pot. Then add some pebbles. River rocks work just as well, and even decorative beads can do the trick. No matter which medium you choose, make sure the tray is filled halfway with water. Then shift the stones and create some room for your plant.
This means of generating humidity is more reliable than misting your plant all the time. You just have to make sure to replace the water every now and again, since it will eventually fully evaporate.
Can you put Styrofoam in the bottom of a planter?
Okay, first, we have to be clear: a pot and a planter are not the same. Planters are large boxes or containers that you can place indoors or outdoors to grow your plants. They’re often much larger than a pot to the point where you can have an excess of soil.
The houseplant doesn’t need all the soil, but you can’t exactly leave the bottom of the planter empty, now can you? That’s why gardeners advocate for filling the bottom of a planter with something besides soil.
Yes, Styrofoam does work for such a purpose. The same goes for terracotta pot pieces, ceramic shards, concrete chunks, gravel, smashed bricks, and rocks. One more time for clarity’s sake: you should only add these things to a planter, not a houseplant pot.
Can plants grow in pots without holes?
Getting back to growing plants in pots, what if your pot happens to lack drainage holes? What would happen? Your indoor plant might survive for a few days, but with nowhere for the water to drain, you’re soon going to have a major problem on your hands. Your plant may begin developing root rot within its first week or two in the pot.
If, by chance, your houseplant survives to the point where you fertilize it, you only compound the problem then. At that point, the salt in the fertilizer gets logged into the soil with no way to get it out.
Yes, it’s true that drainage holes are kind of an eyesore, especially if you bought a pretty pot for your houseplant. However, they’re a necessity, so please don’t make your plant go without them for long.
Are lava rocks good for drainage?
We want to talk about yet one more kind of rock in relation to houseplants. That’s the lava rock.
Since they’re so porous, lava rocks have a much better drainage capacity than your average rock. Some gardeners even opt to grow their indoor plants on the lava rock itself. Certain grasses, succulents, and the Tillandsia do especially well on these rocks.
All that said, if you’re wondering if you should add lava rocks to your pot, we’d still say no.