Tuesday, March 30, 2010

Sub-Irrigated Chicago Rooftop Garden: New Approaches for 2010

We're making a few changes this year, large and small, to speed multiple SIP planting and help preserve diminishing peat bogs.

Using a large rubber band to secure the 5-gal SIP shower cap
Sounds obvious, but in the past we've used string or the more expensive zip ties. We'll see if rubber bands hold up under all that UV, though the position of these under the bucket lip should mean the sun won't bake them to smithereens. You need nimble fingers to use them, though.

(And kudos to the marketing person who named these rubber bands.)

Potting Mix: peat+perlite vs. coir+perlite

We want to move away from peat moss, which develops over millenia and, when harvested, releases massive amounts of carbon dioxide into the atmosphere.

We're going to make this experiment as exacting as possible, planting two peppers, two tomatoes, and two sets of greens side-by-side, one each in coir/perlite and the other in our old peat/perlite mix (of undetermined exact specifications).

Bruce's recipe is: 70% (by reconstituted volume) coir and 30% perlite.

We found a relatively inexpensive (including shipping) source for large blocks of coir at Rolanka. We've been buying the 5:1 compressed blocks. Four come bundled together, costing $58 delivered to Chicago. Each of the blocks, reconstituted with 6 gallons of water and combined with 3 gallons of perlite (from Anton's Nursery in Evanston, $20 for a 4 cubic foot/30 gallon bag or at Home Depot for $2/gallon), makes enough potting mix to fill three 5-gallon bucket planters (3 cubic feet of mix).

All those numbers can be summed up in one sentence: The coir/perlite mix is $5.50/cubic foot, about the same price as the peat based potting mix we've been using.

Cutting out exact-sized plastic rounds for the "shower caps
Sounds minor, but I formerly used an old form to score garbage bags and cut out shower cap circles. They were a little large and I always ended up trimming the extra skirt from the top of my SIPs. And yes the results looked raggedy.

I discovered the 16" diameter recycled Olive Garden salad bowl (garbage picking at that graduation party last year was a boon) creates a perfectly sized round for the 5-gal bucket SIP. You can cut a plastic circle out of anything waterproof--a soil bag, whatever. I like garbage bags because they're thin and flexible.

Water fill tubes
One of our local readers last year brought us a roll of polyethylene drip irrigation tubing, which we'll cut and use for fill tubes on the new SIP run this year. Generous person whose name we have misplaced: thank you!

We'll keep you updated on the results of our changes. If you're making any, let us know.


Jonathan said...

Glad to provide the water tubing, it seemed a reasonable deal at Menards. I built one SIP, currently at a friend's patio - but the wind demolished my black cherry tomato. As I'm still without a roof or sunny space, SIPs are like a carrot on a stick for me. Any chance you need any help assistance with your rooftop setups? Would love to learn more by doing.

H2 said...

Thanks again, Jonathan. Would love to have you come up and help ... maybe when we plant the warm-weather starts toward end of May?

art and chel said...

I'm getting ready to finish up 20 sips! They've been a long time coming (ever since the first time I read your blog to be exact.)

I was excited to see pvc tubing cut into lengths perfect for the sip at HD. That saved me a lot of cuts.

One question. I could potentially have enough of the original bucket lids to cover each sip. I've noticed that some people use them. My concern is that if the plant blew around enough in the wind, the sharp edge of the cut-out could decapitate it? Not sure if have experience with the plastic lids or not.

I didn't pay much attention to the exact size of feed tube hole that I drilled and realized I cut 3/4" holes and got 3/4" tubes instead of the recommended 1". I'm sure that won't be a big deal. The bigger deal is going to be trying to figure out how to water the things.

See you soon!


et cetera said...

I really enjoy your blog. Were you able to calculate a cost per bucket (not including the plant)? I'm curious to know what a setup like this would run. Also, where did you get those awesome buckets???

Best regards,

H2 said...

Hey art and chel: I'm disinclined to use the hard plastic lids for the very reasons you mention. Also, some flexibility is required (at least by me) in settling the plants in and I like the soft plastic for that. Please keep us updated on your SIP garden.

etc...haven't calculated cost per bucket, but since we re-use the potting medium every year + the buckets too, the cost drops with each season. Plastic never dies!

Each week we pick up a couple buckets donated by Chicago's Vienna Beef (their kosher pickles are packed in the yellow ones) and donate some while using others for our garden. Check your local deli or grocery bakery (icky frosting comes in foodgrade buckets).

Thanks for the good words!

Jabberstream said...

Wow! This is what I call an innovative way to garden. I love the idea. I too have an amazing method growing tomatoes and that is Upside down tomato growing. :)

Bruce said...

Mr. Jabbystream/Topo Turvy,

Your product makes a terrific infomercial, why do you want to sell it on our blog?

It's cute, but it uses too much water and you need to hang it from a sturdy trellis instead of resting the container on the ground.

Anonymous said...

Hi!! I've been incredibly inspired by your blog, so much so that I now have ten of what I'm calling my earth-buckets in my tiny yard! The dream is realized! I told my Dad about the idea and he loved it, so now he has ten as well! We live in Tucson, AZ so this seems really ideal for a place that has really difficult soil (we have caliche = nature's cement), and I'm really excited about conserving water.

A couple of questions for ya if you don't mind:
1) we had an innovation of using irrigation tubing and directly sticking it into the bottom of the buckets. So, no watering tube, PVC or otherwise. I've looked all over and heard anyone else mention this idea. The best part about it is the ease of watering. Do you think that there are potential pitfalls with this that we haven't considered?
2) Also, For my lids I've been using white garbage bags (we don't need the extra heat here!!) and also I have used 2 grocery bags for each lid on a few. They fit really well with no cutting involved! Probably temporary, but good for now.
I've noticed that there is moisture condensing on the plastic from beneath. I'm a little concerned that there might be TOO much water going into the soil, is that possible?

You guys have really lit a fire under me and I'm so thankful.

H2 said...

Hey Thea:
Congratulations! Your set-up (and your dad's) is inspiring.

I'll let Bruce comment on your irrigation tube innovation--he's got more experience in playing with alternatives to watering SIPs than I do.

Can't imagine in Tucson that too much water in the soil would be a problem. Since I've never peeked under my "shower caps" I'm not sure how much condensation is under there.

Do you tie the white garbage bag off under the SIP lip (what we're using rubber bands to do)? If not, maybe this has something to do with the condensation.

Thanks for all the good words. Keep us updated and please send pictures when you have them.

Bruce said...

Hi Theahlilea,

Innovations are good, thanks for sharing. It's also very gratifying to know that other people find our blog helpful. Thanks for the kind words.

It sounds like a good idea. If I understand you correctly, you are drilling a small hole in the side of your planter and putting the supply line straight into the water reservoir of each SIP. I'm curious how you make the connection watertight between the drip irrigation tubing and the side of the bucket/container. Some kind of bulkhead fitting? A series of washers and gaskets? Silicone?

What happens if you want to tip the bucket over to empty the contents/clean out any excess roots at the end of the season? Are you prevented from doing so by the fact that your planter is connected to a relatively fixed water supply line?

I've been trying to find a cheap, reliable way to put a 1/4" drip irrigation line directly into the side of a SIP water reservoir. One that, unlike silicone, lets me take it apart and put it back together if I need to do some kind of annual maintenance. It sounds like you may have figured it out for me.

Anonymous said...

Hi Bruce and H2, thanks for writing me back so soon!

The way we have the watering set up is this: we drilled 3 of the 1/4 inch holes at the over-flow line, and use one of them for the irrigation tube. I glued 3 nuts on there at the tip of the tube, just to weigh it down so it lays more or less flat in the water reservoir. The beautiful thing is that no silicone or fancy attachment is needed, the tube fits very snugly in the hole when you feed it through! We attached that shorter line to the main water tube using a rubber connector thing, sorry, I don't know the correct lingo. I feed all of the buckets to that same main line. It kind of reminds me of how cherry tomatoes look in the clumps. :)
I don't do any drip-irrigation, I just turn the water on until I see the water over-flow for each of the buckets. The only negative is that some of the buckets seem to fill faster than others (slightly different elevations perhaps?) so a small amount of water is wasted but I think it's worth it.

Tipping the buckets will not be hindered by the watering line as it can be unplugged from the main line easily at the rubber connector spot. It just pops in and out of place!!

Phew, it's a bit tough to explain... I do have photos, how might be the best way to get them to you?


Anonymous said...

Oh, and as for the plastic coverings, I used clearing packing tape for the garbage bags, and less for the grocery bags. I found that the grocery bags fit quite snugly on their own. They will probably have to be replaced soon but I was in a hurry to come up with something as their was the threat of rain. I'm pretty pleased with it! I think white plastic is important for Tucson since the problem I will likely face will be too much heat soon.

Bruce said...


Now I understand what you're doing. I think it should work well for you.

It's very similar to how H2 and Art have set things up--except you're going through an overflow hole instead of down the fill tube--in that you need to physically turn the water off and on. Either by hand or with a timer of some sort.

I was asking questions about the connections thinking that you wanted a completely automatic system. One where you don't need to do anything once you've set it up at the beginning of the growing season. For that I think it needs to be pressurized or to make use of siphons.

Anonymous said...

Yes, I guess my system is not that complex. The best thing about is avoiding the whole "to PVC or not to PVC" quandry altogether. I hope to put it on a timer system if I go out of town during the summer.

I think that my earth bucket SIPs will face unique challenges here in the Sonoran desert. For example, I'm not adding lime because I'm told our water is very hard and full of minerals. I'm concerned about the heat and sun they'll be getting in the coming months, though that would be true for any plants and at least these buckets can be shifted around slightly in response.
Another potential difficulty will be keeping the water from soaking them too much when the monsoons happen....

The upside is, we should have a really long growing season if I can get them to survive the summer, and we'll save lots of water!

I'll keep you updated if you like. How would you recommend I send you photos? I'm not very familiar with blogging.

Bruce said...


If you have a photo storage account, like Flickr or Picasa, you can upload your photos to it and send us the link to your photos. The nice thing about this option is that you can pass the link on to others as well.

It sounds like you've got an amazing project going. Maybe you'd want to start a blog? I didn't have much experience with computers prior to beginning our blog and found the process relatively easy. Either Blogger or Wordpress are good places to start.

If you don't want to do that, you can send us photos, attached to an email, to - greenroofgrowers [at] gmail [dot] com

H2 said...

Thea--You might want to check the earthbox discussion forum.

Look for Donald1800, who I think also uses SIPs in the desert. He's a great resource.

uli said...

Dear H2, dear Bruce,
I'm starting a small farm of 60 SIPs in Berlin, Germany this spring, mainly because I'm very interested in old vegetable varieties. They are very hard to find in shops and markets around here, but I found seeds.
This is my first time gardening and i want to get as much as possible right from the beginning. I have been googeling for weeks now to figure out which methods to use, and your block has been a huge inspiration for me.
So at the moment my seedlings grow bigger and bigger every day, the buckets are in good progress, but I still couldn't figure out the growing medium. I want to try to avoid peat completely. Luckily I found affordable sources for coir and perlite, and I want to try the 70% coir / 30% perlite mixture that you mentioned in your post. I was wondering if you figured out how to fertilize this mixture and if you think that there should be any other substances mixed into it. I read, for example, that coir is less acidic than peat ( mine is around 5.8 ), so one should use gypsum instead of lime as a source of calcium. Then again, Berlin has very hard water, so i might not need extra calcium.
It would be great if we could exchange recipes and experiences for growing in coir. I'm documenting everything and hopefully find time to post some pictures online soon. Anyway, thanks a lot for blogging so much about your gardens, it is very valuable knowledge and i really appreciate it.
Best, Uli

H2 said...

I need to dive into work right now, so just quickly: DON'T use 70%coir-30%perlite. I don't think it wicks water well at all.

I'll post on this on the blog soon. The collards in 70%peat-30%perlite are just hanging on.

With that said, both Bruce and we are indeed mixing in a good amount of coir into our pre-used peat.

All for now. Thanks for the great words. We're excited about your big SIP farm. Bruce can let you know what his ratios of coir-peat-perlite are.

ps: I'd love to know what varieties you're growing!

Bruce said...

Hi Uli,

It sounds like you are working on an amazing project, good luck!

We, too, are experimenting with coir. I'm doing a small test in 4 rubbermaid tub SIPs, with a control group of greens. Each of the planters has a different % of coir, ranging from 0% to 70% (the rest is either peat based potting mix or perlite), and while all the plants have been going well for a couple of weeks, it is too soon to know what the best blend is. Heidi's (aka H2) test bucket planter using coir isn't doing as well. I'm not willing to rule out the 70/30 coir/perlite just yet.

Contrary to what we've done in the past, and to what the official earthbox company recommends, I'm mixing fertilizer in the body of my planters and covering them with wood mulch rather than a plastic bag. Much as the Montreal Rooftop Garden Project is using their planters (pdf file here.) While there is a certain element of risk and uncertainty in doing so, I'm comfortable with it, others may not be willing to risk it.

Most of the recipes that I've found on places like GardenWeb (container forum) and the Earthbox forum have as a rough ratio 40% peat, 40% coir, 20% perlite/vermiculite. No compost, as it doesn't wick well. I have the feeling that will turn out to be the best blend, though at this point it's too soon to tell.

Search the Earthbox Forum for Donald 1800's comments on potting mix. Here's a good one.

When I have some results to post, I'll put them on the blog. I hope you'll let us know how your project develops.

uli said...

Hi Heidi & Bruce,

thanks so much for your quick reply and advice.
So far i bought 216 liters of coir and 100 liters of Perlite. I guess i will go search for additional peat and fertilizer at some nurseries tomorrow, make a couple of different mixes and see how they wick and work. My squash-plants are ready for transplanting, so they will be the guinny pigs.

Here is a bit about my project:
I'm doing this for various reasons: first of all i love fruit & vegetables, the way they taste and the way they look.
In 2006 i started photographing strange and deformed vegetables, that i found on local farmers markets. The collection kept growing up to this day. You can see parts of it here. It made me question a lot of things about the way food is produced and the way we perceive it. Why is it that we never see these shapes and forms in supermarkets, why does all the produce there look almost identical ? How and why is ( visual + genetic ) diversity of produce prevented from entering the market ? Why do we mistrust a fruit or vegetable that looks unusual ?
So this year i want to grow vegetables myself, to retrieve new specimens for my collection, to find out how they grow, and of course to eat them. I probably keep 14 SIPs in our apartment, 6 on the balcony and 8 indoors by a large window (facing south). The rest i can keep at a friends place who has a sunny backyard. I wish i had a roof like yours !
I started 180 seeds of these varieties: (on average five of each,148 made it)

Cucumbers / Gherkin:
Lemon Cucumber
Mexican Sour Gherkin
West Indian Burr Gherkin
Dragons Egg Cucumber
Boston Pickling
Suyo Long Chinese Cucumber
Miniature White Cucumber
Armenian Cucumber

Rosa Bianca Eggplant
Thai White Ribbed
Turkish Orange ( didn't make it )

Bishops Crown Pepper
+ 10 seeds from a mixed back of sweet pepper varieties

Reisetomate (Voyager Tomato)
Pink Accordion Tomato
Tlacolula Pink Tomato
Pink Pondarosa
+ 30 seeds from a mixed bag of these heirloom tomatoes:
Omars Lebanese
Golden Sunburst
Black Russian
Aunt Ruby's German Green
Djena Lee's Golden Girl
Black Prince
Early Cascade
Flame Orange
Garden Peach
Green Zebra
Lime Green Salad
Pink Ping Pong
Pink Oxheart
Prudens Purple
Silvery Fir Tree
Black Crim
Black from Tula
Cream Sausage
Brandywine Pink
Cherokee Purple

Prescott Fond Blanc Melon
Tiger Melon
Jelly Melon Kiwano ( African Horned Cucumber )
Common Foo Gwa ( didn't make it )
Swiss Chard ( Rainbow blend )
Miscellaneous Summer Squash mix
Turk's Turban

And because we love Mexian food, and these are hard to find in Germany:
Okra ( Long Pot Green )
Relleno Type Pepper

I chose most of these because they looked interesting, i guess i'll find out about their taste later.

I hope all works out and will keep you posted on how things develop. Who knows, maybe we can figure out a miracle potting mix for SIPs ! It would be great to find one that is based on locally sourced, recycled, or at least environmentally friendly materials. I have been looking into parboiled rice hulls as a substitute for perlite, but couldn't find a source for it yet. It is a byproduct, same as coir, and seems to be promising. The only problem with both is that they have to be shipped from far away places, but at least they are grown, renewable and not mined like peat and perlite.

Heidi, i hope your collards will make it !
Bruce, thanks for the links, i will read the pdf tonight.
The link to donald didn't work, but i did a search for him on the forum and found a lot.

Again, thanks a lot for your replies !

H2 said...

Your deformed vegetables are the best, Uli.

And that's a diverse list of veggies you're growing. We admire your tenacity in finding a satellite growing location at your friend's house. Keep us updated...

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