Yep—a lot of people lose their minds about the idea of getting water in the crowns of phalaenopsis because it’s “commonly understood” that it will cause rot. That’s not 100% accurate though; bacteria and fungal infections are what cause leaf and crown rot, not water. There is a relationship between pathogens and water though, and a plant’s susceptibility to those pathogens is largely based on it’s health; a calcium-deficient orchid is an open-door for crown rot. To better understand this let’s explore: calcium and it’s role in orchids, how water can aid infection, how we can avoid it, and why it’s still in our best interest to get the leaves of our plants wet on purpose.
Calcium Deficiency Notorious for Orchid Rot
Before I jump into the talk about bacteria, fungus and water…let me ask you, do you dose your plants with Calcium? If the answer is no, then an existing issue with crown rot may have been staring you right in the face and you’ve wrongly assumed it’s related to water on your plant. Calcium is ever-present in the biological and geological cycles; it moves through every living organism and plants are no exception. Calcium is used to build cell walls (and orchids of all plants are especially “robust bodied” plants – they need a lot of calcium. You might be wondering, “In nature, there isn’t a fairy dropping little pills of Caltrate in the rainforest canopy…so where does all of this calcium come from?” and I’m glad you asked. Like I said, every living creature uses calcium, including plants, mosses, fungi, bacteria, animals and so on; and guess what? Birds poop…lizards poop…crickets poop… and everything that dies and decays releases Caclium! Everything that lives in the upper canopy of the forest is leaving behind bits of calcium every day. Hurrah for Calcium!
Here’s the thing, calcium is immobile in plants; that means once the plant pulls the calcium in through its roots and uses it within a cell, it can’t move it later on (like some other minerals can be). That means plants need a constant supply of calcium in order to build new cell tissue. In our homes, we need to add it or make it available to the plants or they suffer. If you’re using alkaline tap water, you can get calcium by acidifying your water but alkaline water has calcium bound up as “Calcium Carbonate” and without actively breaking that bond with an acid, the calcium is not freely available for your plants. If your water is neutral or acidic, odds are you need to add calcium because most fertilizers don’t have enough of it.
If you want to know more about calcium and it’s well-documented relationship to plants and orchids, follow these two links from the St. Augustine Orchid Society: Calcium Supplements for Orchids & Calcium Deficiencies in Cattleyas.
Calcium in a plant can be low for many reasons: maybe you haven’t been supplying it, maybe the plant has very few roots, maybe your pH is too low or too high, or maybe you’re just not keeping your plant hydrated enough. Regardless of HOW a calcium deficiency happens, it’s affect on a plant is often: poor vigor, leaf rot, black spots, and of course infections caused by low resistance to pathogens. If you’re experiencing crown rot, consider reading up on Calcium. If you want to become an Calcium expert, read this post from the NOFA.
On Watering Day – I DRENCH my phals
And look how well they progress…Want to see more? Watch this video of how I water my phals
How Orchids Get Leaf and Crown Rot
Pathogens (bad fungus and bacteria) germinate and spread in standing pools of water. Wet leaves (in theory) give bacteria and fungus the opportunity to enter the plant. Further, if a surface is dry, the spore or bacteria cell will have a difficult time germinating or spreading on the plant. That would mean, the easiest way to avoid infection is to keep our plants dry, right? Well, that’s not ideal either. Orchids need water to survive (duh), so we can’t treat them like precious cubes of sugar that melt under water. We have to keep them hydrated if we expect them to thrive. The good news is, there is a “Goldilocks zone” (not too wet, not too dry, but JUST RIGHT) where we can water our plants AND not deal with a constant onslaught of infection.
Avoiding Orchid Crown, Leaf (and likely Root Rot Too)
I have found the key to preventing crown and leaf rot is to ensure any residual water is dry within about 4 hours; this means your humidity can’t be too high AND you need good airflow. Pathogens seem less able to infect a plant when they’re not given long-term wet conditions. The evaporation speed of water will depend on the humidity where you grow (and this is vital to understand). Also, make sure your plant has ample calcium; there are many ways to get calcium to your orchids, from adding dolomitic lime to the potting mix, to dosing with “CalMag” (a calcium supplement). If you have hard water… buy a pH test kit and start acidifying your water. You want to target around 5.5-6.5pH.
If you live in a humid climate (75%+ RH), residual water can hang out for a while (possibly even days/weeks). This is especially true if you don’t have good air flow. If this is your growing conditions, then don’t get the crown wet (or consider getting a fan and increase your air movement which will help improve evaporation).
For the rest of us who grow in drier climates (60% RH or lower), when we spray the WHOLE plant, we gain an advantage of temporarily increasing humidity around our plants and we don’t have to worry about residual water because it easily dries within 4 hours–win win! Plus (and here’s the most important part) we are giving our plant an additional surface to absorb water and nutrients!
The Benefits of Watering THE WHOLE ORCHID:
- Orchids are foliar feeders which means they can take micronutrients through their leaves. Watering the leaves gives them a two-vector opportunity to take in both nutrients (yes, I use fertilizer water for this) AND water,
- Plant growth and root production respond better to wet/dry cycles,
- You’ll beat the crap out of any spidermites that are hanging out on your leaves, and
- After a few weeks of watering your plant with tap water you’ll start to make it very difficult for pathogens to take hold because you keep flushing them down the drain and bathing them in chlorinated tap water.
Look to Nature for Validation
Still not convinced eh? I get it, it took me YEARS before I tried this method as per the recommendation of a friend. I’ll leave you with this consideration…we both know there isn’t a little Bounty fairy fluttering around the rain forest dabbing water off the leaves and crown of orchids after each rainfall, so why would we be scared of wet leaves in our home? I encourage you to go look at photos of wild orchids. It’s true, you will find them angled with their leaves dangling down away from the tree and the crown basically upside down, but you’ll also see that their leaves are often wet–VERY wet. Water is your orchid’s friend.
The Proof is in the Pudding (My Anecdotal Truths)
This is how I water ALL of my orchids except one. My only orchid (of my over 200+ collection) that’s ever gotten crown rot was a new acquisition, Paphiopedilum lowii–within the first week that I owned it, I saw a brown spot start on the leaf. I later learned that this pathogen is very common in paphs and virtually impossible to get rid of–I’m still battling it even though I don’t get the crown or leaves wet. More importantly, of my 80+ phals, I’ve never had crown rot. I have all different types too — summer blooming “warm-growers”, winter blooming “cool-growers”, complex hybrids, novelty hybrids, NOIDs, you name it — I’ve never seen crown rot on any of them. My phals look very healthy too–here are a few photos of my plants for proof:
Still too scare you to try this? If going against the grain of common knowledge makes you nervous (or you don’t want to risk losing your favourite orchid) then don’t do it. Don’t get water on the crown of your orchids. Do what feels right to you. If you’ve been having troubles getting your phalaenopsis to grow or you think that there’s something odd about the concept of keeping a plant’s leaves dry (because they’re plants after all and grow outdoors) then give it a try; pick your least favourite couple of orchids and try it. You might be surprised at the response you see in your plants…