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I have a balcony that gets about 4 hours 1 hour of direct sunlight a day (but several many hours of indirect sunlight bouncing off a building in front) that has an A/C unit where the water condensate drain line from the unit can only go into a bucket on the balcony. In Summer, this large 3 Gallon bucket fills in about 24 hours from having the A/C on 24 hours a day. The condensate drain line drips water into the bucket 24 hours a day, but at a faster rate during the day when it's warmer. So instead of having to empty the bucket every day, I'm looking for a plant that can be placed on the balcony that can consume a full bucket-load of water every 24 hours in Summer without dying from over-watering.

Do such plants exist?

If not, then what are the absolute most water-thirsty plants? Perhaps I can have several of them next to each other to absorb the full bucket-load of water every day.

Ideally, I'm looking for a plant that is ultra-thirsty when water is available, but very hardy when there is a lack of water (e.g. no A/C in winter) so it can survive for several years rather than just in Summer when the A/C is feeding it water.

I hoping nature can solve my problem!

  • The condensate is loaded with dissolved solutes and in general is not good for most plants. Yes, there are tough plants that can take the water quality but I'm not sure there is a plant that works the way you want... – kevinsky May 11 '15 at 18:04
  • @kevinsky: Although ideally I would prefer a plant that wouldn't die from the dissolved solutes, over-watering, and/or irregular watering throughout the year, if the plant just lasted the Summer, then that would still be better than having to empty a heavy bucket of water every single day for 3-4 months straight. I could also use more than one plant and spread the water between them as i mentioned in my OP. If the plants died by the end of the Summer, then I would just buy new ones the following Summer. Keeping that in mind, which plant(s) would be the best to accomplish this? – ProgrammerGirl May 11 '15 at 18:37
  • When you say a large bucket, how large exactly? 1 Gallon? 2? 5? – GardenerJ May 11 '15 at 18:46
  • @GardenerJ: About 3 Gallons. – ProgrammerGirl May 11 '15 at 19:44
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    Please tell us where in the world you're located and what the climate is like there. That knowledge will help us give you better recommendations. – Niall C. May 11 '15 at 20:20
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I think your best bet is to look into plants that are used in graywater garden design. Cattails are one very common one, as they don't mind standing in water, as are bulrush, canna lily and reed canary grass. They are all tough, and seem to grow well on graywater.

ETA: I looked up the calculation - you'll need about 1.25 square feet of wetland plants per gallon of water that you need to get rid of every day.

My two biggest concerns would be figuring out whether the size of garden you need to absorb 3 gallons a day would actually fit on your balcony, and figuring out whether your balcony can support the added weight of such a garden.

Good luck!

  • Thanks for your suggestion. I did more accurate calculations. The actual floor of the balcony only gets 1 hour of direct sunlight a day, although plenty of indirect sunlight from the building in front which is in the sun all afternoon long. I did very accurate measurements and the total area I have to play with on the balcony comes down to exactly 37 sqft. Would the sunlight and area be enough for your suggestion? If not, what about covering the entire 37 sqft with thirsty grass (e.g. Carpet Grass)? – ProgrammerGirl May 12 '15 at 18:36
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    All of these plants prefer full sun. With only 1 hour of full sun, any of them are going to struggle, but if you don't mind experimenting and possibly losing the plants after 1 year, it might still be worth it. The next thing you need to figure out is how much weight your balcony can safely support to see whether you can build the garden there. I know nothing about carpet grass, but it looks like it might be worth trying! – michelle May 13 '15 at 13:01
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I would say it isn't really workable, even ignoring the possibility of contamination from the water killing plants quite quickly. I have a balcony in London UK which is 5.5 feet wide by 12 feet long - it has large and medium pots and containers all round the outside edge. Its south facing, so in full sun all day, and summer temperatures here can be anything between 25 to 39 degrees C (roughly 75 - 90 degrees F), with relatively low precipitation, but usually high humidity. I should add that the temperature readout on the balcony itself frequently reaches 45 deg C or higher (100-110 deg F) during hot dry spells. Some of the pots are 3 feet deep by 18 inches wide, with large, permanent climbers and plants; when the weather is hot and dry, the medium and smaller containers may need watering daily, but the large ones every other day only. That means I'm using, at most, around 20 litres of water a day when its hot and the sun is out all day, but more usually 20 litres every other day max. Three gallons of water equals roughly 13.5 litres of water.

Your balcony is only 3 feet in width - that significantly reduces what size pots you can use, so you're stuck with small pots. The advantage with those is they need watering more often, the disadvantage is you can only grow smaller plants which drink less anyway. Even so, I'd be surprised if you managed to use anywhere near 3 gallons every day, given they're not in full sun. The other consideration is where the water from the pots ends up after its dripped through the drainage holes - you can't leave them standing in trays full of water or they'll die much faster, so where will the flow of water go once you've watered all the pots, and does it matter.

I'm not sure that its any easier to water several containers every day, whether they need it or not, to attempt to use up some of your three gallons of water, and then dispose of the rest though - the need to water several pots daily will quickly become quite tiresome (I speak from experience). It seems quicker and simpler to just dispose of the whole lot, particularly given its not 'clean' water.

If you don't mind replaceable plants, its probably best to go for 'summer bedding' type plants, which are usually cheaper to buy, particularly in trays or flats I think they're called in the USA, and not expected to last more than a couple of seasons, things like Dahlia, Snapdragon, Verbenas, Fuchsias and so on.

In terms of permanent plants which like a great deal of water, willows come to mind, but you're still heavily restricted as to which you can use because of container size. Alternatively, in larger pots, anything which produces fruits which are normally edible, tomatoes, blueberries, whatever. I wouldn't recommend you eat the fruits though, given what you're watering with.

  • Thanks for your detailed reply. I did more accurate calculations. The actual floor of the balcony only gets 1 hour of direct sunlight a day, although plenty of indirect sunlight from the building in front which is in the sun all afternoon long. I did very accurate measurements and the total area I have to play with on the balcony comes down to exactly 37 sqft. What if I covered the entire 37 sqft with the thirstiest grass (I read Carpet Grass is one of the thirstiest), would that be enough? – ProgrammerGirl May 12 '15 at 18:35
  • Bear in mind that grass, carpet or otherwise, is expecting to grow in soil - if you bought carpet grass as turf and just rolled it out, it wouldn't last long - its got nowhere to root into. – Bamboo May 12 '15 at 18:37
  • My apologies, I should have been clearer. I would use wooden planks as borders and screw/nail them together along the perimeter of the balcony, then use pond liner as the floor and sides and nail it to the borders, add a porous or drip irrigation system running along the inner perimeter and center and connect it to the condensation drain line, fill the 37 sqft area with soil, and plant the seeds of grass on the soil to be watered by the condensation drain line. Would something like that work? – ProgrammerGirl May 12 '15 at 19:44
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Absolutely. I would go with the wetland grasses route, these plants are hearty and can handle standing water. Your biggest problem is going to be sun, so you will want the tallest grasses possible, to take most advantage of that indirect light bounced off the neighboring building. Plants use water mostly for photosynthesis, the more photosynthesis they are doing (the more sun/light it gets) the more water they will use.

Make your bed as deep as possible (do required research on the weight!) in order to maintain as much water as possible. Also, a deeper bed will be taller, further raising your grasses and other wetland plants to fetch more sun and indirect light.

Finally I would recommend a polyculture. In 37 sqft you can plant mostly cattails, but leave room for a bush or two. More species will be more resilient to whatever contaminants you are adding via the A/C.

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