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Indoor house plants in water

  • Subject: Indoor house plants in water
  • From: "Dawber, Ken" <Ken.Dawber@getronics.com>
  • Date: Fri, 28 Jun 2002 10:54:55 -0500 (CDT)
  • Content-class: urn:content-classes:message

Low Maintenance Indoor plants Emersed in Water.
For the last couple of years I have had an interest in low maintenance indoor plants growing emersed in water.  This interest came about due to my disgust at the large number of people who have given up on using living breathing plants and gone over to the pretend plastic etc.   My objective was to create indoor living plant displays that would survive the non green thumb.
Yes, you too can have live indoor plants … and a life.    Come home after a month or so away and find the indoor plants alive without having had other people enter your house.  No concerns about killing plants by over watering.  When a big glass jar is low on water its very obvious.
Note that many of best plants (from the NASA study) for cleaning air are Aroids.
I have spent a lot of time researching (internet etc) other peoples experiences with keeping indoor plants with the roots kept emersed in water.  I have found it very hard to get reliable information.  Much of the information I have gleaned I am placing below for comment.  I am not qualified in Horticulture and much of the information I have picked up is from people who have even less knowledge.  I welcome criticism as well as wanting more information
My interest was to keep the plants with the roots emersed in just water in a jar (generally a glass vase).  In some cases I include a layer of pretty stones at the bottom.  There are similar concepts that are often labeled water culture where the roots stay immersed in water plus an inert medium.  I expect most of the concepts to be the same but with the inert material you don't get to see the roots and they don't show the level of water as easy unless they have a water level indicator added to them.
The last of the 3 links above on air quality is a site with a lot of information on this water plus inert material type of hydro culture.
First my objectives needs to be specified.
1) A healthy looking display.  I do not have the objective for the plant to grow as in expand in size.  Considering the costs of good glass vases it's often an advantage if it just grows very slowly.
2) Lack of need of expertise once set up. 
3) As close to zero work as possible once set up
4) They must survive in low light conditions (ie indoors)
5) Plants that are known to survive gas-heating, air conditioning and similar.
Some of these objectives require me to look at terrestrial plants that most would not think of as water plants.
Things I have found are as follows:
A)  Plants that can survive with their roots emersed are called Hydrophytes.  Some Terrestrial plants are hydrophytes, others aren't.  The most common methods for plants to acclimatize to root emersion is to either change the roots to being aerenchymous or grow new roots that are aerenchymous.  These are roots that have air channels in them that bring Oxygen etc  from above the water line down to the root systems.  Doing a search on the internet for the word aerenchymous will show a lot of detailed information on this.
In the way that I am setting up the plants the water is still.  I believe that the water should be thought of as anaerobic (that is, without oxygen).
Some plants are better at acclimatizing than others.  One study of a plant (Rumex Spp.) that could acclimatize showed that plants of this species that came from low-lying areas did a better job (i.e. grew longer aerenchymous roots ) of acclimatizing than those of the same species that came from drier habitats.
B)  Just because a plant is known to get root rot in wet soil doesn't mean that it will get root rot when the roots are emmersed in water without soil.  I often get told by a nursery that such and such a plant will rot in wet soil yet when I ignore that advice I find no problems in keeping it in water.  Of course I would only do this if I knew that it was one of the plants that gets mentioned as a plant to keep in water or closely related to one.  A couple of possible reasons why they don't get root rot  (ie theories of mine but I'm not exactly expert enough to know if I'm correct) are as follows:
Theory One
Root rot is caused by various soil born fungus  (In some places it gets defined as "soil born")  While these organisms love a wet environment maybe they still require soil. 
Theory Two
With clean roots inside a glass jar with this inside a house or office, maybe the water and roots never gets infected with any spores to start the root rot attack
A corollary to this is the advice that you will probably get better results if the environment has no soil.  I try to clean the roots as best I can before putting them in the vase or jar.
Going by much of the literature on hydroponics etc it would seem that the lack of soil will also be advantageous in stopping a whole host of other problems that are common with normal soil based agriculture.
By the way, I'm not saying that it can't get root rot or vice versa.  This is something I would like to know.  Just that many of the plants that are known to survive in clean water are plants that are known to get root rot in wet soil.
It is also interesting that in the aquarium literature several truly aquatic (ie. Used in aquariums ) aroids are susceptible to something called root rot.  This occurs in most species of Cryptocoryne and some Acorus.  In Cryptocoryne it is caused by incorrect water chemistry (particulary iron and CO2) or sudden changes in water chemistry.   I would expect that regardless of the name and appearance of this being called root rot, it probably is totally different in concept and cause to the soil born fungus root rot in normal soil agriculture.
Anyway, the problem generally isn't so much root rot but the ability of the plant to survive without the roots getting oxygen.
It is this that generally differentiates what I am doing from hydroponics and similar.  With almost all hydroponics the water is cycled on and off so that plants get plenty of air on the roots.  I'm just dropping the roots in water and leaving them there
I often leave the water levels to go down nearly to the bottom before refilling (ie over a month or so)  I expect that the plants getting air on some of the roots for various periods would be beneficial.  This is meant to imitate a plant going through various levels of flooding.
One thing I do not know is how to tell if a plant dies due to lack of oxygen to the roots or due to some other cause.  Can anyone tell me if there are any specific symptoms associated with lack of oxygen to the roots?
C)  In converting to water most people who succeed seem to cut the roots back.  (A heavy trim)
D)  Those that succeed either do not fertilize or fertilize with a minute fraction of what you would expect.
My initial theory as to why this was so is that these terrestrial plants only become hydrophytes as a means to survive floods.  In this situation that are not in their optimum growing situation.  It's a bit like winter when you feed less, only more so.  In this situation plants don't seem to like more fertilizer than they need.  If this is true then a problem that this implies it that most plants won't flower in this situation so you have to chose plants that look attractive without flowers /inflorescence.   Most of my water culture plants were picked for their leaves rather than there flowers..
A problem with the above theory is that some of my plants have lush growth.  This includes ones that have roots  emersed without ever having any added fertilizer.
The second possible reason for this is that when you put fertilizer on a plant in soil, most of it washes through or remains in the soil.  Only a small proportion gets caught by the plant roots in the soil.  When you put fertilizer in the water of the emersed plant, the fertilizer remains there.
The aspect of what mix to use for plant food is something that I need more information on.  There is a reasonable amount of information on feeding of aquarium plants, some of which probably applies but other information that doesn't apply.  In the aquarium situation the fish droppings (after processing by bacteria), excess food and filter residues give the plants plenty of Nitrates and Phosphates.  The special aquarium plant foods are designed around this, and probably would not be suited to a root emersed plant without fish.
I expect that when the terrestrial plants are in their hydrophyte mode that the relative quantities of the different components would be different to normal.  I don't know which elements they need less of and which they need more of so at present I am just giving some of them a few standard slow release fertilizer pallets and other's nothing.  The slow release pallets seem to take months to dissolve in the motionless water.
From aquarium literature apparently aquarium plants often have a problem getting enough iron and may need more in their fertilizer.    The aquarium fertilizer advertising suggest that minerals in normal fertilizers are in a form that would oxidize if added to the water of an aquarium and then not be in a form suitable for the plant to get.  I doubt if this is true as most normal fertilizers are designed to allow their use with water. 
Also from aquarium literature, they often need or do better with extra Carbon Dioxide.  Water hardness should be greater than 50 ppm but less than 150 ppm.  Salinity should be kept below 440 ppm.  The p.h.  should be between 6.0 and 7.5.
If the water is simply topped up when the water level goes down then the water may build up high concentrations of salts or other minerals.  Apparently, if the plant doesn't want as much salt or other mineral as is in the water then it can leave it in the water while taking the water that it was in.  I presume that the plant must take the mineral/salt laden water into its roots then later excrete the unwanted salts and minerals.
Apparently, the level of salt can be tested by testing the electrical resistance of the water.  Unfortunately the level of resistance also changes with the addition of fertilizer.  More on this is in the following link:
For those that have difficulty with keeping plants emersed in water where other people have no problem, I would look closely at water quality.  Water quality issues for plants in soil pots is dealt with well at the following link
I would expect most of the issues in this to apply only probably more so.
I have seen lists of plants that are meant to not like having high levels of fluoride.  I notice that many of the plants in these lists are plants that are known to be able to be a hydrophyte.  Obviously, these plants need a particularly low level of fluoride in the water when grown emersed.
Putting fertilizer in the water has a further disadvantage in that it increases Algae.  This alone makes it well worth trying to grow the plants without fertilizer.
E)  Algae is one of the major problems with growing plants in this manner.  I think that that the major reason so many people who do it keep changing the water at regular intervals is the fact that the algae is unsightly, not that the water needs to be changed.  In fact I have seen the theory expressed that the algae on the plant roots is actually advantageous for the plant in its oxygen exchange.  I would like to get more information on this.
Possible things that can be done to reduce algae are as follows:
1) Try to deny the water any light.  With glass vases try to shade the vase from as much light as possible.  In a modern house/display you can use food dyes to color the water.
2)  Snails may be useful.  I have yet to try this.
3) There are algae eating aquarium fish but I believe that you would need a very big aquarium and a lot of plants before you could support one small fish in a self-sustaining environment.  (I would love to get figures on just how large it would need to be).
F)  Choice of plant is one of the most critical things.  Aspects that I use are as follows:
(i) Plants mentioned in books or on the internet that someone has done this with.  This will often only mention a family or genera not an exact species so if the first attempt doesn't work it doesn't hurt to try a different species of the family..  Typical lists on the internet are as follows:
Note: I use to have quite a few bookmarks on this but I seem to have lost them.  If anyone can give me some others please do so.
(ii) Plants that are known to root in water.
(iii) Plants that are known to like or put up with a wet soil environment are more likely to survive emersed.  Regardless of that many desert plants also work.
(iv) Known aquatic plants.  Most plants used fully immersed in aquariums are actually grown by the aquarium suppliers as root emersed plants.  Of all the aquarium plants the only ones that seem to be known as good in low light conditions are the Anubias and Cryptocoryne (both of which are aroids)  plus a number of aquatic ferns.
(v) Most climbing plants seem to have this ability.
(vi) The cheaper the plant and more common the plant is,  (ie commonly sold in Woolworths, K-mart, supermarket etc) the more likely it is that it has this sort of feature.  That is, easily grown plants that are often resilient to the masses are more likely candidates. 
(vii)  A very high proportion of the plants mentioned are in the Aroid family (Family Aracea).  Almost all the main terrestrial genera of the aroid family seem to be there.  In particular
Philodendrons.  Some references are more specific and say the vining Philodendrons species within this Genus.  I'm not sure about the self heading Philodendron species other than Monstera
Monstera. (Split leaf Philodendron)   Even if it hadn't been mentioned I would have expected it based on its ease to root in water.
Spathiphyllum (Peace Lilies).  There is a tradition of keeping these with roots in emersed in gold fish bowls.  There is a controversy on this in that the fish (typically a male Beta fish) are sometimes sold as if the fish could survive without being fed.  In nature the Beta lives on a diet that consists predominantly of insects and insect larvae.  When starved of this they appear to hold off starvation by nibbling on the roots.  They often can end up surviving several months, just long enough for people to think that the problem is something in the water.  As far as I know the controversy is purely with the fish.  The Peace Lily in water works fine and is often used as an emersed plant coming out of an aquarium.  There are a number of species in this family.  Some probably a lot better than others.  It would good if we could get of listing of the most likely and least likely species within these larger genera.
Zantedeschia (Calla Lilies)
Aglaonema (Chinese Evergreen)
Dieffenbachia (Dumb Cane).  I haven't tried this but it is interesting that it keeps being mentioned as it is also a plant that is always described as being very easy to get root rot.
Scindapsus Aureus (Pothos, Devils Ivy)
Pothos and Philodendrons may even have some use as Aquarium plants:  See
I'd take this last comment with some caution as I have seen references to other people who have tried and failed.  Many of the terrestrial plants that are known be hydrophytes get themselves on the false aquatic plants lists.  These are cheaper plants that some aquariums try to pass off as aquatic plants and when fully immersed last just long enough to fool some people that it's their fault that they died.  See
and  http://faq.thekrib.com/plant-list.html

Anthuriums aren't normally listed but the following link shows a picture of an Anthurium growing in water culture with an inert medium. (along with a number of other water culture plants)
Non Aroids
Some plants that will grow in water are quite surprising.  Although orchids aren't listed very often as suitable plants the following link give full information on their culture this way:
The absolute best plant I have found for growing in water is a non aroid called: Dracaena Sanderiana  (particularly D.S. Virescens).  Its many common names include Lucky Bamboo (its not a bamboo but looks a little like a bamboo or corn plant) and Chinese water bamboo.  Its use growing emersed in water has a long Oriental history which I understand features in both Buddhism and Feng Shui.
Clean all dirt off the roots.  Trim the roots and place in water.  Apparently in Buddhism you are not meant to feed it or change the water.  Just replenish the water when it gets low.  With a reasonable sized jar it takes a couple of months before you even have to top the water up.
Instructions similar to the above were apparently given by Quan Yin (The Goddess of Mercy) when giving this plant to Buddha.     Actually, I don't know whether it was Quan Yin that gave it to Buddha or the other way around.  Maybe some kind reader of this will correct me or give me a reference on this.
This plant kept in water is also meant to be particularly good by Feng Shui.  By Feng Shui the best place to place to keep it is just inside a doorway.   It will give increased prosperity/happiness etc if the jar contains either 3 or 4 plants (i.e. depending on the Feng Shui Text) 
Like almost all plants in this category it looks best with the roots on display in a glass Vase.   This also makes it obvious when the water gets low.  At home with a reasonable amount of light on the Vase the water gets just a little dirty after a few months.  That's enough for my wife to run off and change the water.  At my office with the same plant the water remains clear enough for my likes and I haven't changed it in over a year.  Actually, its been surprising how clear the water is as other plants in the same area have their water going green.  I have wondered whether this plant had something in it to suppress algae.
A related plant Dracaena fragans  (Common names: Corn Plant or Prosperity plant) also works well but in this case you are recommended to fill the bottom of the glass jar with pebbles.   It's amazing how quick this plant's roots burrow into the pebbles.
I hope some people can help me with my questions and I welcome all to correct my errors
Ken Dawber
   Melbourne Australia
   ph 0409 790 802
   Best Email:   ken@mira.net

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