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The Internet's Best Guide to Growing Plants in Water

In the world of houseplants, it's a fairly common knowledge that putting a cutting of nearly any plant in water is likely to result in root growth and propagation. As cool as that is, we feel pretty strongly that the real magic happens when you leave that plant in water and watch it grow. 


Here at Modern Botanical, we spend a lot of time testing and growing various house plants in water. For one, it's fun. But also that we realized there's not a ton of information out there on the subject. We'd like to fill that void.  We have plants in our homes that have been growing in glass grow vases for years. A lot of them actually. We've even spoken with friends that have monsteras that have survived and grown in water for decades. 


One of the big benefits from an ease of care perspective is that you no longer need to nail watering cycles for your plants. Simply refresh the water on a semi-regular basis and you're set. 


There's nothing like having a plant sitting in water, maybe a few drops of nutrients but maybe not, and watching roots develop. And then, one day, a new leaf starts to form and your mind is blown. It really seems like magic. 


We're here to teach you how to grow happy, healthy plants in water. Healthy plants that will grow new leaves, develop healthy roots, and even bloom flowers when the time and lighting is right. And the best part, it's damn easy. 


Like, really really easy. 


With all that being said, we're here to share all our tips and tricks to growing happy healthy plants in water. Here's what we'll be covering. 

How are some plants able to grow in water?

For plants to grow, their roots need access to water, nutrients, oxygen, and structural support. Growing in water handles the bulk of these and, interestingly, the glass vase or container offers the structural support. Great, we hit the checklist, but how does it actually work?


Not all plants can grow in water. However, a lot of houseplants that we're so familiar with come from tropical climates with high humidity, high rainfall, and generally mild to warm weather. Lots of trees to provide great structure for plants to vine up and shade to keep plants from getting hit with direct light. A lot of these plants adapted to large amounts of rainfall and developed the ability to grow roots to adapt to them. 


And that's basically our answer here. The how that makes growing plants in water possible is that plants that can live in water, do so by growing water roots that are adapted to utilizing the oxygen and nutrients directly in water instead of from soil. The roots are both visibly and structurally different than roots that are grown for soil. 

How to grow plants in water

As we write this, our intent is to be thorough and to share as much knowledge as we have on the topic. But don't let the length of this fool you. Sometimes it really feels as simple as placing a plant in water and watching it grow from there. There are a number of factors that do matter that we can go over. Here's the short list: 

  1. Watering: Refill the water in your glass every 1 to 2 weeks and replace with fresh water every 2-4 weeks. This will replenish oxygen in the water so the plant roots can continue to breath
  2. Lighting: Lighting needs can vary based on the plant, but most plants in water prefer medium to bright indirect sunlight
  3. Nutrients: a few drops of liquid nutrients every month will help support new root and leaf growth once the plant propagates
  4. Temperature: 55-75 degrees Fahrenheit is ideal for most houseplants. A good rule of thumb is that if you're comfortable, your plants are comfortable too

Of course, this is just the surface of care information we've collected over the years. If you want to learn more with in-depth care details, just keep on reading or click or jump to a specific section in the table of contents above!

Watering

Yes, you’re not out of watering entirely but the overwatering is impossible now and the underwatering is obvious when you look at the water. It’s foolproof...well, almost. Plants need oxygen to grow. So, as your plant sits in water, it utilizes the oxygen molecules that are held within the water molecules. So watering - or at least replacing the water - is still required, but the window to replace that water without hurting or damaging your plant is large. 


We generally recommend replacing water every 2 to 4 weeks in our standard grow vases BUT I've been known to replace water every few months at times. It's not ideal for the plants, but I can't recall a time that doing so has been a problem. No potted tropical plant is going to do a full recovery after 2 months without watering. 


Replacing water keeps off root rot which will kill your plant. The primary cause of this for plants in water is the roots suffocating due to a lack of oxygen, so playing it safe and refresh that water! 


What water should I use? 

We use tap water here in San Diego, but the optimal water to use would be mineral or reverse osmosis water remove the chlorine and fluoride that comes in with most municipal supplies. 


Does water temperature matter?

Yes temperature is important, but who’s really boiling their plants like a cup of noodles? Water temperature matters when the temperatures are too hot or cold because that can shock the plant. A good rule of thumb is staying within 5 degrees above or below over room temperature. The easiest way to do that is leaving the water out for 10 minutes before placing your plant back into its vase.


Would an air stone and air pump be helpful to replenish oxygen?

Yes! Air stones and pumps are a great way to replenish oxygen in the water and reduce the need to replace water as often. For aesthetic purposes of our plant walls, it's not something we've integrated, but they're quite common in hydroponic agriculture setups. Keep in mind that you will need to replace the water from time to time to replenish nutrients in the water and avoid nutrient lockout. 

Lighting

Second to watering, lighting is going to play the biggest role in the health of your plant.


When growing plants in water, optimal lighting tends to err towards lower light intensity. This is because too much direct light on the vase can bring up the water temperature and that too much light intensity shining into a glass vase will trigger algae to grow which is ideal to avoid. 


As a rule of thumb, aim for moderate indirect light for most houseplants in water. What does that mean? No direct sun-rays and bright enough natural light that you don’t need to use your lights for most of the day in that room. 


Can I use light bulbs to replace sunlight to grow my plants?

Yes! We can't wait to write another content piece on this topic alone, but the TLDR is that a variety of bulbs off the light spectrum necessary for plant growth. LEDs are your low-cost + low-electricity option. 

Nutrients

Yes, growing plants in water isn’t entirely magic. Usually, plants early on in their life are healthy just in the water they’re living in. But as the plant matures, it will need access to nutrients. 


There is a lot of science that goes into finding the right nutrients for your plants. We'll save that for its own article. A few things that you might want to keep in mind: 

  • Nutrients are generally in either powder or liquid form. Liquid form generally means you're paying for water BUT it can make using nutrients much much easier when doing small but frequent doses. It's never a bad idea for the committed plant parent to mix their own nutrients to keep on hand - both saving on money and reducing unnecessary packaging. 
  • The primary nutrients for plants is signified by NPK ratios but plants have needs for other micro nutrients not listed in just that NPK ratio. Not all nutrients are created equal.
  • When growing plants in water, it's best to find formulations meant for hydroponic plant growth to ensure the formulations and bioavailability are optimal for your plants. 
  • Nutrient density is generally measured in PPM (parts per million) or EC (electrical conductivity)

If the bullets above are making your head spin, don't worry. We've solved it for you and have a Hydroponic Nutrient Solution available that is as easy as it gets. We generally recommend adding 2 to 5 drops per refill of water. 

Temperature

Let's make this one easy for ya - keep your indoor water growing plants indoors. 


Plants growing in water are more susceptible to temperature fluctuations than plants in water due to the thermal conductivity of water. Soil acts as a bit of a buffer to temperature change. Too hot or too cold can kill or really damage your plant. 


Try to keep your plants in moderate climates between 55 and 75 degrees Fahrenheit - basically indoors. Don’t worry, a 95 degree day here in there won’t likely hurt your plants. But, repeated days in a 100 degree room will likely to do some damage to a number of plant species. 

Plant Care Checklist

If you're a checklist person, we have your back. Here's a quick list thats easy to print out and keep a healthy pulse on your plant health. 

Common plant issues when growing in water

Algae Growth

What to look for: 

Identifying algae growth in the water is about as easy as it gets. Look for green water! Sometimes algae will attach to plant roots or glass vase first, but there's an undeniable green that you're looking out for. 


About Algae Growth: 

Algae isn't generally the end of the world for plants, but it can expedite the process of root rot if you're not careful. Both your plant and the algae need oxygen in the water to grow in thrive, so the two end up competing for it, ultimately reducing the window of time you can go without replacing water for your plants. Also green water is just a bit unsightly - if you're plants are up on the wall to be beautiful as living art, having clean, clear water is a part of that. 


How to Treat Algae Growth: 

Treating algae in water is a two part process - managing and eliminating the variables that created the algae in the first place, and cleaning out the algae that has grown. 


The best way to stop algae growth is by managing lighting, specifically light intensity. When using a glass vase, bright, direct light promotes algae so your best bet is to simply move your plant to a less lit area. Sometimes even a couple feet in either direction can make a world of difference. Also it's worth being aware of the different light patterns through the seasons - what's bright now might be fine through the winter. With that in mind, your second tool for managing algae and lighting is by reducing the amount of time between replacing water. If you're dealing with algae showing up on week 4, then try replacing the water on week 3 and stay ahead of it all! 


Cleaning the algae out is pretty straight forward but can take a bit of time to fully get it cleared out! Here's the process: 

Cleaning Algae from your Plants: pretty much anytime your water has turned green, your plants' roots will also have a bit of algae that has affixed to them. Removing this without disrupting your roots is a bit of an art and can take a day or two to complete. To start, get a cup or tub and fill it with room temp water, then take your plant and dip your roots in it and swirl it around slowly to encourage any loose algae to fall loose. Replace the water if necessary and repeat. Then follow the cleaning instructions for your glass vase below, then add your plant back into it. If there is still visible algae on the roots, add 1 part hydrogen peroxide to 20 parts water in your glass vase and let it sit overnight. After 24 hours, replace the hydrogen peroxide solution with your standard water and nutrient solution and you're all set! 

Cleaning Algae from your Glass Vase: Cleaning your glass vase is a really important step and it's necessary to remove all of the algae when doing so, otherwise it will just regrow. Running them in the dishwasher is a fail proof way to get your glasses algae free. If you're not patient enough for this, a bit of soap, warm water, and a Long Cleaning Brush similar to this one is a great way to ensure a clean glass vase! 

Root Rot

What to look for: 

Root rot can be a real issue when diagnosed too late - even fatal for the plant. The great thing about growing in water and in clear vases is that diagnosing it early on, before its effecting leaves or the core plant health, is pretty simple. The most common thing to look out for is a dark colored discoloration of the root, usually starting at the tip. It's important to not use the browning as a diagnosis, but a flag to look into it further. If you think your plant might be experiencing Root Rot - the best confirmation is to simply take your plant out of water and touch the part of the root that you believe is rotting. Root rot is literally part of the plant disintegrating, and that's very obvious when you touch it because it will just start falling apart. 


Another sign of root rot is a funky smell coming from the water which is the organic materials of the plant beginning to decompose. Just another clue as you keep an eye out for your plant's health. 


About Root Rot:

Root rot is the most notorious of plant ailments that don't involve pests. Aptly so because left untreated it will kill your plants - but what is the cause of it? Root rot is more of a sympton of poor plant health and/or environments that the plant can't sustain itself in. If a plant gets no sunlight, it will eventually rot and die. If it's roots drown or suffocate, again, root rot. Late stage nutrient toxicity will also express itself as root rot, eventually. So in a lot of ways, it's a convenient catch-all. 


In this context though, its helpful to look at root rot from the context of ailments that start from poor root health first - not lack of light or other such aggravators. And when it comes to root health, 19 out or 20 cases of root rot are watering related. In the case of soil based plants, overwatering causes this by drowning the roots which were grown to utilize oxygen from within the soil and not from water. A lack of access to oxygen is also the problem in the case of plants grown in water - if water goes unchanged for too long and all the oxygen gets depleted, the roots suffocate and begin to rot as well. 


The other thing to keep an eye out for to avoid root rot is avoiding extreme temperatures. Both temperatures that are too hot or too cold can induce root rot and, unfortunately, usually effects more of the root faster than roots that are suffocated.   


How to Treat Root Rot:

Tackling root rot is a two part process - prevention and treatment. Here we go! 

How to Prevent Root Rot:Prevention of root rot when growing plants in water really comes down to just 3 easy things.

1. Treat and remove algae that shows up in your water early and often

2. Replace water for your plants no less than once a month

3. Keep your plants away from areas that greatly fluctuate in temperature and out of direct light. Windows and heaters can be major culprits here, so watch out!  


How to Treat Root Rot:Root rot can be easily treated by following these three simple steps. First start by cutting off any diseased roots using a sterile cutting tool like a knife or scissors. You want to make sure that you’re cutting off the roots that are black and mushy, all the way up to about 1/4 of an inch into the healthy root. After you’ve cut off any dead roots, you should give the roots a quick dip in a hydrogen peroxide bath. We recommend soaking them in an 90:10 solution of water to hydrogen peroxide for about a minute. Give your glass a thorough clean, then add your room temperature filtered water. Carefully put your plant back into the planter by guiding the roots with your hands to avoid disrupting the root system. 

Yellowing leaves

What to look for: 

Yellowing of the leaves can come in a lot of ways. Sometimes it takes over the leaf quickly, other times it's just a few spots that show up. It all means different things on different plants. 


About Yellowing Leaves 

Plants express many issues in their leaves and unfortunately for us, a lot of times that looks the same. Thus our catch-all here of yellowing leaves. A yellow leaf is always good to pay attention to but not necessarily stress over. In a most benign case, sometime plants simply move on from old leaves. This is pretty common for Monsteras in early growth stages of when they've maxed out the available root space for their growth. Other times it can be an expression of a lack of nutrients, temperature extremes, or unoptimized lighting. Rather than trying to diagnose based on the yellowing - not an easy task - we've found it's best to take leaf yellowing as a sign to pay attention to the plant. Every environment is different - take into account what might be off in your environment and make any adjustments necessary to lighting, nutrients, temperatures, or water. 


At the end of the day, more often than not, a yellowing leaf is not an issue at all and just the natural progression and life of a plant. Pour yourself a glass of wine and sit back. 


How to Remove Yellowing Leaves: 

Perfect! Now that we're not stressing about the yellowing leaf, now let's address how to treat it. And by treat it I mean removing it in the best manner possible for your plant. We generally recommend letting the leaf remain on your plant until it's fully yellowed and looks ready to fall off. At this point, sometimes the leaf will do exactly that, fall off upon a light touch. If so, great! If not but you're ready for it to go, take a sharp knife and simply remove the leaf as close to the stem as you can. That's it, you're all set! 

How to optimize your plant's growth

Want to go the extra mile to ensure extra healthy, happy plants? Here's a list of a few things you can look into to really maximize your plants' growth! 

supplement with exra humidity

Walk into a plant shop and the majority of those houseplants are going hail from some tropical environment. Pamper them with some extra humidity and they'll love you and reward you with beautiful leaves. 


Humidity is generally measured as a percentage out of 100%, where at 100% the moisture in the air will begin to turn into water. Most houseplants will be happy to be in about the 50% range, though some exotic anthurium varieties will want you to push that up into the 70% or so range. Humidity can be supplemented with a humidifier. Another great trick is simply putting your humidity preferring plants in your bathroom so it can enjoy that extra moisture from your showers! 

Maximize oxygen

Plant roots need access to oxygen to support plant growth. More oxygen means happier plants and more rapid leaf development. Our recommendation of replacing water in our vases at least once a month is very much indexing towards convenience. If your goal is to maximize plant growth, consider replacing water weekly. Also, if your vessel allows for it, consider adding a water stone and air pump into your plant reservoir.  

Give your plants something to climb

Many draping and viney houseplants are actually climbers. They want to latch onto things and climb up towards, presumably, better lighting. Philodendrons, monsteras, and pothos all fall into this category! As these plants vine, they are actually looking for something to attach to, when they do they will try to climb up it. If successful, they'll actually begin to release a hormone in the leaves that allows them to grow larger. Look into adding a pole for your plants to get support, like a moss pole or totem for extra large leaves! 

Optimize your water's ph

PH is used to measure alkaline to acidity - generally water is at or around 7.0 on the PH scale. Right in the middle. Adding nutrients often brings the PH down to the 6.0 range which is often a great spot for most plants and helps make certain macro-nutrients more available to the plant. We're not going to pretend to be botanists here - every plant has it's own sweet spot for PH and we simply don't worry about this on our end too much. We just trust the RO water we use to be in the right range. If you'd like to dive into the rabbit hold, we'd recommend getting PH testing drops to measure alkalinity. Readers are an option as well, but tend to be inaccurate until you get into more expensive models. Think $150+ range. 

Optimize nutrient density

Similar to PH, nutrient density is another area that can be optimized for many plants. I generally measure this in PPMs (parts per million) and have a little hand ready for this. Do I check the PPMs of my plants often? Absolutely not. Once upon a time I measured this to get a healthy recommended range of drops of nutrients to go into our glass vases. A good target range of PPMs for most houseplants growing in water is 300 to 600 ppms of nutrients (starting from about zero in reverse osmosis water, tap water will have PPMs by default). Of course, each plant will have a preferred range, so if this is something you plan on optimizing on, please do your research!

Hopefully you walk away with a great foundation of info on growing plants in water if you've made it this far down the page. We did our best to put the bulk of our knowledge into one place for you to dive into growing in water plant care if that was your interest! 


For more ongoing plant care conversations and inspiration, we recommend joining our Facebook Plant Community to share, participate, and learn from one another! 


Happy growing! 


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