Planting Subway Grates: Step by Step Instruction





Introduction: Planting Subway Grates: Step by Step Instruction

The premise of this project is to start a conversation about the potential for plants to filter the air flow from underground networks that exist in our cities. The spaces in between subway tunnels and the sidewalk/street surface can be metaphorically perceived as membranes within our city, and some would argue that they are under-utilized. This particular experiment is situated in New York City.

Step 1: Materials for Prototype

These are the materials needed for the following how-to guide.

Step 2: Steps 1-9: Preparing the Fabric

The above images introduce the folding methods needed for creating a burlap circle. 

Step 3: Steps 10-18: 'Sewing' the Fabric

Take the burlap circle and begin to puncture holes 2 inches into the circle, 2 inches apart. Although we used a zip-tie in this example, a single hole puncher is recommended (see last slide for further details).

Then, take the nylon twine and begin to ‘sew’ through each hole until the entire circle is complete.

Use your hand to hold the base of the circle down while pulling the excess nylon to create a sac.

Step 4: Steps 19-25: Inserting Into the Subway Grate

In preparation for inserting the burlap sac into the subway grate, fold carefully and squeeze through one grate cell until the sac opens up underneath.

Keep a hold of the nylon while pouring soil. Then, squeeze the small plant through, add more soil, and some water. Lastly, tie the nylon to the grate.

Make note that several changes have been incorporated into the procedure for making and inserting this prototype. See next set of images for details.

Step 5: Changes to Prototype Preparation and Insertion

Preparing the Burlap Sac: After producing several prototypes as depicted in previous slides, we decided to incorporate some changes that would make the burlap sac more efficient and durable.

1. The first change was to create a double fold of burlap around the outer edge by folding 1 inch in, then another. To keep this double fold in place, we used small amounts of glue. Once secured, we proceeded to use a single hole puncher to make holes for the nylon to go through, at 2 inch intervals.

2. We further realized that it might be useful to have a double lining at the base of the sac to retain water more efficiently. We cut small plastic circles and punctured holes to allow some water to permeate.

Securing the Burlap Sac: The initial prototype insertion revealed a setback in securing the prototype for adding the soil and small plant. Rather than allow the burlap sac to simply hang loosely and swing around underneath the grate while attempting to pour soil and insert the plant, we decided to use wire to create hooks that serve to temporarily raise the prototype along it’s nylon twine edge.



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    33 Discussions

    really cool. Was there a particular reason for your choice of plant? What sort of conditions are said plants going to experience?

    3 replies

    We choose the spiderplant because it is really easy to propagate-the pic below shows our nursery. As the grates are really narrow you need small plants or branches for a start. (And it survives in a student flat.)
    If you would start such an intervention in spring it might be possible to start with seeds in the soil-if you have the time to keep it moist at the beginning.

    About the conditions: pretty rough, dark but at least with warm air flowing from the subway station every now and than. Let's see how long they will make it. If you have an idea for subway grate suitable plant-let us know ...


    As someone else pointed out, I am sure subway maintenance loves this. The point of the most grates is for storm water run off. If that plant does manage to live and grow it will block or at least restrict the water flow. Not being an expert, but having worked at a Civil engineering firm as a drafter I can tell you that drainage systems are usually designed/calculated to handle certain amounts of drainage per the amount of ground above/ between them. Now granted trash does fall in them but it does not grow larger than the grate they have fallen through. Nor does most trash take root, clinging to the small cracks in the concrete therefor can usually be flushed away in the case of heavy rain. When it comes to urban design most things are done for a reason. An empty lot is one thing, but when messing with potentially safety issues please check with your city first. I would hate to see someone get a ticket or fine over this instructable, or worse.

    All that Flyinseamnky said, and any plant chucked down a storm drain, subway grate etc. will eventually get removed with the rest of the trash that finds it's way down there.

    Spider plants and Pothos (which is a genus of plants, not 'pathos' which in an emotion) are tropical plants, they would never survive the winter.  But if they did somehow manage to survive, and they were looked over by the cleaning crew, then there are pests and diseases to worry about -  subway grates and storm drains are not exactly noted for being clean, healthy places.  So not only is the plant exposed to pests and diseases, but it also becomes a carrier for these things, spreading to other plants nearby.

    Bottom line, there are much better places to put plants, and they'll still filter the air, only much more effectively since they are both alive and disease free.

    Okay, so the conversation: What evidence do you have that a small amount of biomatter will act as an effective filtration system in subway ventilation systems? How would this compare to a more traditional carbon or even HEPA filter? What are you trying to filter using these plants? Heavy metals? Benzenes? Formaldehyde? Small particulates? CO2? I know people have experimented with this concept before and the results have not been supportive - most of these tests were in indoor settings with more sedate airflow that the massive blasts you get from subway trains. So it's an interesting concept and probably looks pretty neat but do you have any evidence to support the air cleaning capabilities? Especially any evidence that refutes the studies under taken in the late 80s? Please note: I'm not saying that the idea has no merit but it may be impractical as a filtration system in high volume/velocity situations as envisioned. I think it may have a lot more merit as a way to introduce more green 'spaces' in crowded cities.

    Pathos will grow most anywhere... even in a closet, if you open the door once in a while. DON'T throw Kudzu down there!!! it might end up eating the commuters!

    3 replies

    I agree Pathos will grow happily in warm, moist, shady conditions. If you build in a 'break point' on the rope used to hold the plant in place, it will let go the plant once it is too large/heavy or if the waterflow drag coefficient becomes too great, or if the rope itself degrades enough; then the plant becomes so much debris that will wash away.

    eating the commuters might definitely be a problem. although nyc commuters during rush hour can be quite ferocious themselves =)

    Yes, I've ridden those rails enough years to know how we are, but I also spent a couple of years in the southeast, and have seen what kudzu can do to a whole forest!!

    @GreatestGrates; Hi! This reminds me of the other Instructable to put self-contained plant grenades in empty lots. Just add rain. My curiosity is totally hooked at the idea of "planting plant bombs to go green." Is there a risk of clogging rather than filtering air flow?

    Cheers! :)

    3 replies

    plant grenades? wow, never heard of it described that way! and that's an excellent question...we paid careful attention to the density of insertion and we've been using sensors to get data for how much blocking of air these little guys are contributing to. as they exist right now, there is a lot of air that currently still passes through. this is most evident when the subway train is approaching and the sudden rise in air flow intensity makes them swing around frantically as they hang.

    Very neat Idea!
    I live in Seoul and I want some of em near my apartment. lol

    Fantastic. Love it. Once you've learned if the spider plants will survive, round two should consider perennial edibles that can provide food--urban permaculture.

    Be very, very careful about your plant choices.

    3 replies

    I'd be careful about edible plants, as many heavy metals (which would get into the air from the exhaust of the trains, the creosote and other chemicals on the rails, etc.) can be taken up by plants - so if you eat the plants, you could get dangerously high levels of heavy metals. Think of the plants merely as air purifiers. That does us lots and lots of good as well, right?

    I was wondering exactly how legal this is. Might be better to work with the subway people to access the area and place plants in pots. I know in Memphis this summer a fellow received a grant to plant wild flowers in the city owned vacant lots.

    The city for insurance reasons couldn't allow the guy access to the lots so the fellow made seed bombs and used an air compressor powered mortar.

    This spring we will have flowers everywhere.