How to Collect & Clean Rainwater for an Orchid

Orchids do best in conditions that mirror their natural habitats. So, what if you feed your orchid rainwater? Is that better or worse than using tap water, and if so, why?

Can you feed an orchid with rainwater? Rain water is safe so long as you clean it of debris, and ensure that it’s not full of fungal growths or bacteria. You can collect rainwater with a water butt attached to your drainpipes. You can then filter it and clean it with additives if necessary, but the water doesn’t need to be as clean as it would be if you were drinking it. I recommend adding in orchid food, as rainwater is soft water, meaning it doesn’t contain any minerals. Allow the water to reach room temperature, but water as normal by bathing or showering your orchid. You can also use rainwater for misting. Overall, I don’t think using rainwater for orchids is worth the effort compared to tap water, filtered or not.

The guide below first gives a quick overview of how you water an orchid with rainwater. It then looks at how you collect rainwater hygienically, how you store it and how long rainwater stays fresh, how to clean it if it’s full of debris or pathogens, and how to use it to water orchids. We’ll finish by looking at whether it’s worth watering orchids with rainwater at all.

How Do You Water Orchids with Rainwater?

If you want to use rainwater to water your orchid, there are four steps you have to take. These ensure that the water is both safe and suitable for your orchid. The reason you have to take each of these steps is that while many growers recommend rainwater, there are numerous drawbacks associated with its use, and if you don’t account for them then you’re doing your orchid more harm than good. Here are the four steps we recommend:

  • Collect it cleanly. You must ensure that the container you collect the rainwater in is sterile. You must also ensure that there’s no way for debris to get into the container as you collect the water. If done correctly, you can store the water for a long time.
  • Check that it’s clean before use. Even with your best efforts, it’s possible that the rainwater isn’t completely clean. It could contain debris, bacteria or fungal growths, and if it does, I wouldn’t recommend using it.
  • Add in minerals through orchid food. Rainwater is perfectly clean and distilled, which is both good and bad. Because it’s distilled, it doesn’t contain any minerals. If you water your orchid’s potting mix with mineral-less water, the minerals in the mix will be leached out and lost. You therefore have to add in minerals by mixing in orchid food.
  • Water as normal. You can then follow guidelines on safe watering, which ideally should be how you water your orchids anyway.

I personally don’t think that watering orchids with rainwater makes a big difference, but some growers think it’s best. It doesn’t seem to be worth the effort to me, but if you already collect rainwater, then I would say go for it!

How to Collect Rainwater for an Orchid

There are a few ways to collect water. The most common is to set up a water butt in the garden. A water butt is basically a large barrel that’s connected to one of the drainpipes on your home. Water is collected in the guttering of your roof and directed to the water butt, and stored for later use.

It might sound dirty, the idea of collecting water from your drainpipes, but people around the world do it. So long as you do your best to collect and store it hygienically, and then ensure that it’s clean before use, it’s not a problem.

What to Store Rainwater In

You have a few choices when it comes to storing your rainwater. The BBC detailed the four most common ways:

  • Standard water butt: Holds between 100 to 300 litres, is a barrel or square shape and has a tap near the base.
  • Ornamental tank: Designed to fit in with your garden (shaped like boulders etc). Capacity is between 30 and 300 litres.
  • Large above-ground tank: Holds up to 2000 litres, and is a big rectangular shape, that needs to be sited on a flat firm base.
  • Large underground tank: Can store several thousand litres of water and requires a pump.

Talk to somebody at a hardware store, or a contractor, to assess your options. If you’re going to collect rainwater, and you live somewhere dry where you experience hosepipe bans or other water control measures, then you may as well install a large tank. You can then connect the tank to your plumbing system for flushing your toilet, running your washing machine, and all sorts of other things.

It’s a lot of effort to go to if you just want to water your orchids. But if you were going to do it anyway, then go for it.

Is It Legal to Collect Rainwater?

It’s legal in most U.S. states to collect rainwater, although some states have regulations regarding doing so. You should check up on the rules and regulations in your state to make sure it’s legal for you to do this. The reasoning often given is that some states have precious little water, so it’s better to allow it to run into reservoirs after it rains rather than be collected on private property. Remember though that just because you read something online, doesn’t make it true—websites like this one are written by regular people. I’d therefore encourage you to do some research on your own and maybe make some calls to relevant authorities just to make sure you’re in the clear.

The same applies to other countries around the world. It may not be legal where you live, again for the sake of preserving water for everyone rather than an individual.

How to Store Rainwater for an Orchid

Rainwater collection is absolutely pointless if the rainwater isn’t stored correctly.

Is Rainwater Clean?

Unclean storage conditions will render it unfit for use, even for watering plants, let alone drinking. It could be full of bacteria and fungal growths, turn brown, and stink to high heaven.

If the rainwater reaches the water butt through clean pipes, and the water butt itself is clean, the water should keep for several months. You can also consider adding some additives to it, like you would add small amounts of chlorine to a pool, to make sure it doesn’t go bad in the meantime.

Keep the Storage Unit Away from Sunlight

This is a basic mistake that you might make when collecting rainwater for any purpose. You should keep the storage unit out of sunlight, especially if it’s see-through, because the warmth and energy provided by the light encourages both bacteria and fungal growth. This would make the water unsuitable for use.

The same applies to the material that the storage unit is made from. It’s better to use a unit with opaque sides, as this means that the light won’t access the inside, whereas it would if it was see-through plastic. I would also recommend a bright color like white, as this would reflect sunlight rather than absorbing it and warming up the water inside. But keeping it out of reach of sunlight means that this wouldn’t be as much of a problem.

How Long Does Rainwater Stay Fresh?

How long rainwater stays fresh depends on whether it’s stored in a hygienic container.

Let’s say hypothetically that you fill up a completely sterile water bottle with completely sterile water. That water could have been boiled in a sterile environment, or it could be perfectly clean rainwater—it doesn’t matter. If you seal that water away, then there’s no way that bacteria can enter it. It could, again hypothetically, stay sterile forever.

The problem is that it’s very difficult to create a perfectly sterile environment for your rainwater. The storage vessel itself may not be completely clean, for example. And if you’re thinking of collecting water from the drains, then forget about it being sterile, or even vaguely clean!

If your rainwater was collected from a drain, it will start off dirty, and get dirtier and dirtier. Any debris in the water, whether it’s a leaf or a twig, will provide the ‘starter culture’ for all sorts of algae and bacteria within a month. But if you keep your drains clean and have a filter for water entering the water butt, it could stay fresh for a year.

How to Clean Rainwater for an Orchid

You don’t need to clean your rainwater as much as you would if you intended on drinking it. It’s very common for stored rainwater to have small amounts of debris in it, whether because the tank wasn’t entirely clean when you started using it, or because some debris fell in there after you set it up. This would normally mean that the water isn’t potable, i.e. drinkable. But your orchid doesn’t need the water to be as clean as you would need it to be, so filtering and sterilization aren’t strictly necessary.

That being said, it is possible that the water has become very dirty, and is chock-full of bacteria, fungal growths, old dead leaves and so on. If that’s the case, you should clean it before using it—or if I were you, just use something else. The section below addresses how you might want to clean the water before you use it.

Is Rainwater Sterile & Safe for Orchids?

You don’t necessarily need to clean the rainwater you provide for your orchid. That’s because rainwater, as it falls, is sterile. The water evaporates into the air to form clouds, and as it evaporates any pathogens (like bacteria, viruses and so on) are left behind. This is the same process that’s behind distillation, except we boil the water to make it evaporate quicker as steam.

However, sterile water doesn’t stay sterile forever. The rainwater, which is sterile at first, could be contaminated by what it falls on or what it’s stored in. That’s why we set out exactly how to store it in a hygienic way above. As such, unless you’re using the rainwater immediately, there’s a chance that there could be fungal or bacterial growth in the water.

The problem with dirty water is that it encourages rot. Your orchid’s potting mix will have some bacteria and perhaps some fungus in it as a matter of course, and there’s nothing wrong with that. But adding to that load with dirty water is not a good idea.

All that being said, it’s highly unlikely that the water will be so dirty that it’s beyond use. If there is visible growth of bacteria, I would recommend not using it. But if it still looks clean, with a minimum of debris in the water or growth on the water surface, it’s probably fine.

Filtering Rainwater for Orchids

Depending on your rain-catching setup, there could be all sorts of debris in there. There could be dead leaves, old twigs, even dead birds or rats in there—if the water butt is connected to the drain pipes, then anything could be in there. As such, the first step towards using it is to ensure that there’s nothing big and dead floating in it.

Some storage tanks have filters in them already. If that’s the case with yours, then this should take care of the biggest bits. But if you want to make absolutely sure that there’s no debris in there, you can always run it through a Brita filter or something similar.

Sterilizing Rain Water with Additives

If you can’t be sure that the water is safe to use, I would recommend cleaning it with an additive. There are additives you can add to water which won’t be harmful to your orchid (or to you), but which will take care of any pathogens.

The most common kinds that are added are chlorine and iodine. That’s why chlorine is added in minute amounts to drinking water—while it may have drawbacks, it’s also a highly effective disinfectant at very low concentrations. The same applies to iodine. There are tables and powders that contain chlorine and iodine that you can add to water to make it drinkable. One amazing powder, invented by P&G, can both disinfect the water and remove debris, which is doubly effective. Tools like these are commonly used by people on camping trips, and are one of the many ways people in third world countries clean their water before drinking it.

If you’re worried about the chlorine in the water being bad for your plants, that’s easily avoided. You can leave the water to sit for several hours, and the chlorine in it will evaporate. That’s because chlorine is a gas at room temperature, and it’s a ‘volatile solute’, meaning that these gas molecules will eventually escape from the water into the air. You can also boil water to speed up this process.

How to Water Orchids with Rainwater

So long as the water is clean, you can use it as you would use any other water. That means you can either bathe your orchid, or shower it in the water—whichever works best for you. However, there are a couple of things you should do first.

Is Rainwater Hard or Soft Water?

Rainwater is soft water, so it doesn’t have any minerals in it. As such, if you feed it to your orchid, it will absorb and wash away some of the minerals in your orchid’s potting mix. If you spray and water your orchid with nothing but rainwater, then, it may not have access to all the minerals it needs.

This is both a good thing and a bad thing. It’s a good thing because if you add in the minerals it needs, then you’ll give your orchid what it needs and nothing more. Orchid food like Baby Bio contains everything that orchids are proven to need, so by adding in a suitable amount, you make the water better than regular tap water, be it hard or soft, because it’s exactly what orchids like.

Bring The Water Inside

It may be a good idea to get some of the water from your storage unit, and to bring it indoors. That’s especially the case if it’s winter. That’s because it may be a little too cold for your orchid’s preference.

As such, take a little water from the storage unit in whatever way is easiest. Most water butts and similar structures have a small tap towards their bottom end that you can use to drain them. Fill up your jug that you’re going to water your orchids with. You can take this opportunity to see if the water is clean, so use a jug or container with sides that you can see through. If it looks clear, and doesn’t smell, then it’s probably fine.

You can then leave it for however long it takes to reach room temperature. I’ve personally never had a problem using water that’s straight from the cold tap, although I wouldn’t use it if it were winter and I was watering my orchids late at night. I also wouldn’t use rainwater that’s sat outside all winter without letting it warm up first, though, as that would be even colder.

Bathing & Showering

There are two main ways that people water their orchids. These are bathing and showering, and their names are fairly self explanatory.

Bathing is where you fill your orchid’s outer pot with water, and leave your orchid in there to stew for about ten to fifteen minutes. This is enough time for the roots and mix to absorb all the water they need. The excess can then be drained away. Showering is where you shower the orchid with water (surprise!) You can either shower the whole orchid, or just its roots.

You can use either of these methods with your rain water. I recommend bathing, as that’s the way that works for me, but other people prefer showering for one reason or another. If you do want to shower your orchid with rain water, I would recommend avoiding getting any on your orchid’s crown; or if you do, at least dabbing it away. Good air circulation and accurate humidity levels can help this water evaporate, but I think it’s better to be safe than sorry, since crown rot is such a killer.

Is Rainwater Good for Orchids?

I would say it’s not quite worth all the effort you’d have to go to.

If you already have a water butt, and you already collect rainwater, then there’s nothing wrong with using it to water your orchids. But if you would have to set one up, learn how to filter and clean it, learn how to sterilize the inside of your storage unit, and all of these things… Then no, I don’t think the arguable benefits are worth all the time you would put in.

I personally use regular tap water to water my orchids. I live somewhere that has hard water, and the tap water here is actually quite nice and drinkable, so that’s not a problem for me. If that’s not the case where you live, I would recommend filtering the water or boiling it (whichever is necessary) to water your orchids as this would still be considerably less effort.