Most of the time at
MONSTERA, before seeing off a customer, we give advice about watering their plants. Not all indoor plants have the same needs, of course, and not all nurseries use the same soils (our’s included). So some quick pointers can’t hurt.
I always start with the general rule, which is a thirsty plant’s a happy plant, assuming it doesn’t die of thirst. 😊 Then I point out which of their plants make it easy by allowing themselves to essentially dry out before needing water. And then there are those plant trouble-makers that get their unwatered feet hurt and won’t forgive (such as button ferns and fittonias). These we don’t recommend.
Telling the customer any more than this is asking for trouble. This is because once you go down the rabbit hole of ‘advice on plant watering’ you can never really come back. So reader be warned, stop here if you’re (dirt) wise and just follow this one simple rule: water the plants when they’re parched, and I mean pretty well parched, and those that don’t make it, well they never would’ve survived anyway. This is such a good rule because it’s the best prophylactic against the great cause of nearly all plant disaster: over-watering.
So, before heading down the rabbit hole — where plants, soil, and roots all hang together (in Part II) — let’s first consider the why in ‘why we over-water our plants.’
The Psychology of Over-watering
Everything about watering plants seems counter-intuitive. Consider the example that some nursery soils are hydrophobic. As the meaning of the word suggests — hydro (water) + phobic (fear) — this makes no sense. Maybe the soil doesn’t actually fear water, but the fact that it repels it is bad enough. But it’s true, such soil exists. Most often this occurs because there is peat in the soil mix. When peat loses its hydration, it becomes as oxymoronic as a dry sponge: water resistant. The result is that, when you attempt to introduce water to the soil, it runneth over. Now how fun is that!
But I digress. The present topic is not soil mechanics, but rather human behaviour: why do we over-water? The answer, you won’t be surprised, is not so simple.
Let’s begin with the assumptions many people make. We are neither botanists nor soil scientists, so when we’re confronted with the simple task of watering our plants we use common sense. As humans we get thirsty and being thirsty is no fun at all. Plus we know that, whether thirsty or not, having an extra drink of clean water never hurt anyone. Applied to plants, we thus arrive at the following, better-safe-than-sorry approach: when in doubt, pour it out.
Getting on the right side of the watering problem thus requires us to condition our minds differently. It is common, horticultural knowledge that most plants prefer a regular wet-dry cycle, as that’s the natural conditions under which they evolved. So what is really better-safe-than-sorry is not to water willy nilly, but to forgo watering whenever there are any signs of water still in the soil. Let it be. Remember, plants are much tougher than we are.
If the plant’s in a plastic pot, moreover, you can pick it up on occasion, prior to watering. Like us humans, nearly all the weight of the soil is actually water, so if it’s hefty, don’t even think of watering it. One example are anthuriums. With their thick, waxy leaves and fibrous roots, they can survive in soil that’s akin to baked earth. When you pick up a small one of these, it can weigh next to nothing and still be smiling back at you (so if you see brown tips, you’ve overwatered).
This brings us to another bit of psychology: at home, we’re lazy. Put differently, how much work are you really willing to do to determine the exact watering needs at any moment for each individual plant. Even the sentence describing this is too long! Easier therefore, when meandering around with the watering can, to retreat to the usual bad habit: wet and forget. I know people who have wall-to-wall plants and do much the same thing, with one exception: they wait until the plants are crying out for water.
In fact, the psychology here is more complicated that just being impatient and forgetful. It is my belief that that primary reason for over-watering is that watering (vs not) makes us feel better, or at least, at ease. This stems from one of the nightmare aspects of watering a house full of plants, that it’s an ever-recurring task, often messy, full of uncertainty, and with little immediate feedback. If, with each plant we are confronted with a complex array of assessment issues, it’s much easier to just throw water at the problem to make it all go away. There, done that, my guilt’s been assuaged. Now I don’t have to worry about watering for at least another week, whew!
Unless — oh my god! — you suddenly find you have plants turning their toes up. Leaves yellowing and falling off, tips browning… we’ve all been there. Whatever you do, don’t make the serial-plant-killer mistake of adding insult to injury… rushing in to water your already over-watered plants.
You can’t blame a person for thinking that a wilting plant needs watering, it’s intuitive. But a failure of hydration (and hydraulics) in the foliage by itself tells you nothing about the state of the roots. If there’s a time for picking a plant up and feeling it’s weight, or even popping off its container, it’s when it looks unhappy.
Some find pleasure in doing the dirty work of carefully assessing how dry the soil is for each individual plant prior to watering. But if this isn’t you, stick to the golden rule: a thirsty plant loves to drink. Plants shouldn’t be a burden of extra work. So wait a bit longer to water and when most are clearly nice and dry, give’m a drink.
When and How
Of course the problem isn’t just when to water, there’s also how and how much. These issues become pressing when you’re having to troubleshoot plant issues, such as flaccid foliage, browning tips, or yellowing and falling leaves. My suggestion, when asked questions along these lines, is for a person to ask themselves what’s more likely: over- or under-watering. As noted above, both can damage roots and cause similar plant woes. When forced to choose between these two, the answer is usually clear. Either the plant was totally forgotten about recently, and passed its tipping point, or more likely, it’s been chronically over-watered.
Cases of under-watering are not uncommon, of course. Sometimes you’ve gone and watered an already miserable plant, only to ride the pendulum to the other extreme of never watering it again. Other times this involves another facet of watering, which is how you go about it.
MONSTERA we encourage people to not repot their plants into formal, decorative pots, even if those pots have drainage. If there’s no drainage, it’s highly likely the plant will be set for a prolonged swim; then it’s only a matter of time before irreversible root rot sets in. Even when there is drainage, however, there’s still the issue of where’s the water going to go?
No longer captured in the bottom of the pot, the water will come out the bottom. No problem, you say, put a shallow plate under the pot to catch the overflow. Theoretically, this is fine, but in reality, rarely do plant saucers or trays have the volume to catch the water that’s necessary. They look nice but are not fit for purpose. What often happens is this: we add an ample dose of water, it comes pouring out the bottom, and then it overflows the dish and makes a silly mess. Having learned this lesson, we hesitate thereafter to give an appropriate dose and thus, from this point forward, we never really water the plant properly.
We are nearing the edge of the rabbit hole here, but something still needs to be said about soil: think sponge.
Wet versus dry, a sponge moves between two states: absorbent and repellant. Soil is similar. If you lightly water a plant that has moist soil, that water will be absorbed and assimilated. However, if and when light (or forgotten) waterings allow parts of the soil-mass to dry out, the soil now acts like a dry sponge. Which is to say, future waterings will hydrate moist areas but dry areas will repel the water, perhaps getting even drier (if there are roots in these dry areas, these roots will die).
When water in the soil runs right past dry areas and out the bottom of the pot, that’s called channeling. To find the solution, consider what’s necessary to get a dry sponge wet. It has to be soaked. It’s the same for soil.
I once had a big agave outdoors in a massive, ceramic pot. After two months of drought and despite regular waterings, the soil had shrunk so much it had pulled away from the pot. The plant was still doing fine, but I decided it best to rehydrate the soil mass. Spraying water on the soil surface had not worked, so instead I set the hose up so it would release a constant drip. Amazingly, it was ten days before the entire soil mass was hydrated.
With this example in mind, if you pick up a plant and its lightweight because the soil is super dry, soak it. You may have to sit the plant in water overnight to get the soil fully hydrated. This brings us to another basic rule: whether a cactus, a bonsai, or a houseplant, when you water, don’t mess about — water thoroughly.
Much has been written about how some indoor plants drink more water than others, and thus need to be watered somehow differently. This is just an unnecessary complication to basic, best practice: water when dry and water thoroughly, regardless. There is no school of horticulture that embraces the practice of watering only some of the roots. So don’t water until it’s really necessary, and when you do, don’t be shy.
Hah!, I hear you say, wondering what exactly “water thoroughly” might mean for each and every plant you own. See what I mean, watering is a nightmare.
I do recognise there might be an apparent contradiction here, recommending we don’t water until the plants are dry, and then suggesting we really can’t water them at this point, because they’re too dry! The way out of this conundrum is to appreciate that, even when dirt-dry on the surface, the soil is probably not all that dry deep down under. If you really want to get dirty, pop a pot off and have a look. Meanwhile, it’s worth keeping in mind that, in some instances, soaking may be necessary.
The human tendency to over-water is so powerful I don’t hesitate to exaggerate. When I suggest waiting until the plants are really dry, I’m imagining there will still be enough moisture in the pot to avoid the problem of the dry sponge. Still, a caveat can’t be avoided: if you think the soil has gone hydrophobic, consider soaking it overnight.
Again, I digress — let’s get back to the choice of whether or not to pot in ceramic pots.
As much as I like the simplicity and refinement of a plant planted firmly in a decorative pot, the “cover pot” has I think more watering advantages. Instead of planting in a pot, you can place the plant and it’s plastic pot inside a larger, cover pot. The immediate benefits are several.
First, you can still pick up the plant to see how heavy it is. Large decorative pots are usually too heavy to easily pick up, plus the pot is so heavy that now it obscures the weight of the soil. With the cover pot, by contrast, we no longer have the mystery situation in which we don’t really know what’s going on in there.
Truth be told, I’ve had far more bad experiences with larger plants when they’re tucked into ceramic pots. With cover pots, somehow the plant seems to breathe easier.
Second, as suggested above, the cover pot avoids the water mess by catching excess water within. No need for a plate or bowl. This does raise a related problem, though, for now the plant might be sitting in water. To deal with this you can usually place a small saucer or bit of gravel inside the cover pot so the plant has breathing space.
No method is perfect, however, when it comes to watering indoors. You still have to periodically check to ensure the water hasn’t creeped up too high. If it has, or if you poured too much in, you can avoid a mess by simply lifting up the dripping plant and placing something temporarily underneath it. It will look odd, sitting proud of the cover pot, but this serves as a reminder to remove it later.
There is still much to be said about water as it relates to plants, soil, and roots (which I will explore in Part II, to come). But let me close with a few final basics:
if you have fungus flies about, try watering from the bottom of the pot; this allows the top surface to dry out, which is where the fungi live
if you can avoid it, don’t water centre-mass; the wettest area within the pot is always at the centre, so give the plant a break and water near the edges
water with rainwater if you can, but if you can’t, avoid putting water on the foliage — it leaves ‘water’ marks
misting plants is mostly a waste of time, and rarely a substitute for watering anything, including a cactus
don’t ask me how often to water! — only when considering the season, the aircon, the room’s natural lighting, and the humidity, can you really answer this question
going away? don’t trust your flatmates, family, or friends to water (the stories I’ve heard); instead, if possible, water them thoroughly the day before and then put them all in hiding somewhere (in a dark room or even closet); this should work for a few weeks, they’ll sleep it off
self watering pots are great, but not for plants that need drier conditions; assess individually
be Dirt Wise and double check that the water is really going into the soil; when watering from below, in a saucer, water needs to be high enough to be touching the soil to be absorbed 🙃