Sunday, January 31, 2010

mobile garden on Track for Chicago

Good news in our inbox this morning: CTA has given the mobile garden project a green light to move forward.

What is mobile garden?

A garden on a Chicago Transit Authority (CTA) flatcar
that will travel
with the train as part of regular service.

We can scarcely think of anything cooler.

mobile garden creator+artist Joe Baldwin visited the roof this summer and told Green Roof Growers about his concept, which germinated in a sustainability and design graduate seminar class at University of Illinois Chicago.

We urged him to consider sub-irrigating the train car and hope he'll call on us to help. We'd also love to see him plant some hardy vegetables, which we can start from seed for him if he wants.

Today we congratulate him on his tenacity in keeping the project alive. Way to go, Joe!

(Thanks to Inside Urban Green for alerting us to mobile garden. Sometimes it takes a village...)

Friday, January 22, 2010

Rat-Proof Composting + Compost Tea for SIPs

Today I'm interviewing my partner Art on his rat-proof composter, which he also designed to produce compost tea to feed the SIPs.

Here are 333,000 ideas on how to keep rats out of your compost. And here is Art's:
What motivated you to build the rat-proof composter?
Apple cores and various vegetable remains sitting on the exhaust manifold under the sheltered hood of my truck. Rats would take from our open compost heap and go picnic in peace.

After we decided to ditch our open heap 5 years ago (H2: we had an open heap for 15 years), I purchased a commercially produced, heavy-duty plastic compost bin to keep the rats out.

Here's what happened to it.
In other words, plastic doesn't deter rodents.

Do you have more rats now than you did 20 years ago?
More rat activity anyway. Over the last few years massive rehab and tear-downs were occurring in our neighborhood. This is extremely disruptive to rat patterns, sending rodents out of their hidey holes into a newly gentrified world. Our street has also become a sort of club+restaurant row, with 6 new restos in the past 5 years.

What got you thinking about this raised composter?
I had a couple of steel plaster tubs I'd purchased at a construction auction a while back and decided to put them to alternate use. I positioned the composter off the ground both to discourage the rats a little (though they're capable climbers) and because I wanted it to produce compost tea.

Most people don't add compost to the growing medium for SIPs (at least we don't--they seem to require a non-organic mix to maintain their wicking capability), but you can add liquid compost tea to the water reservoir for the plant roots to take up.

So how did you approach the project?
I put the two plaster tubs together in a clamshell arrangement using a piano hinge and set the composter in a stand 3 feet off the ground, with one end about 4 inches lower than the other to facilitate gravity flow of rainwater passing through the compost. I coated the interior of the bottom tub with linseed oil to prevent rust.

Then I built a frame (with 4x4 leg posts) to sit it in and drilled a series of quarter-inch holes along the low underside of the bottom tub, where the liquid would gather and drip through.

Lined up with the holes on the bottom tub, I attached a rain gutter that's pitched toward a compost tea reservoir sitting on the ground. It's made from a kitty litter container I found on the street.

How does the compost get oxygen?
I put a handle on the top plaster tub and also cut an access door into the end where we add kitchen scraps (H2: no meat, bones, or fat--maybe we have vegan rats). The hole is a little larger than the old tupperware bin we keep near the sink to collect compost bits.

We open the composter to turn the heap and also when it rains, so the moisture can get to the contents. When it's not raining, we leave it open to dry and oxygenate the heap. We close the lid at night, when rats feed.

How hot does it get in there?
Last summer temps got as high as 120F. I painted the exterior of the tubs black to enhance the heating and drilled a hole in the lid through which we slide a thermometer.

What about that handsome wood surround you made?
Mainly aesthetics and to create a semi-enclosed area underneath for storing buckets of unfiltered compost tea. The amount we get depends on how much rain we have.

Tell us how you manage the compost tea
It's a gravity feed system that drains into the kitty litter container, to which I attached a valve and a clear piece of tubing so I can tell when it's time to empty the container into the back-up buckets.
To get tea, we position the container on a higher spot and drain it into a 5-gal bucket, using a sieve to remove any large bits.
Then the filtered tea goes back into the container and we use a funnel to send it into recycled two-liter bottles, which we transport in buckets (we use a lot of buckets around here) to the roof.

Last season H2 gave compost tea our large 6-gal in 7-gal SIPs, which grow tomatoes and eggplant, delivering one two-liter bottle per SIP via the fill tube. Since it was a wet summer, we had enough tea to provide three doses, one each in June, July, and August.

H2 doesn't give straight tea--she sets down a two-liter bottle next to each SIP and adds it over several days to the water already in the reservoir. Here's an eggplant diggin' the tea.

What do you do with the compost?
H2 shovels it out onto our small in-ground bed that gets sun enough to grow things. It's a richly endowed garden bed, with about 5 inches of compost applied each fall. Here's a shot from last spring.
So did you stop the picnicking rats?
Yes! There was no evidence of rat buffets under the hood of my truck last summer. I'm not naive enough to think I can ever completely outsmart Chicago's Norway rats. Even though the link says they can gnaw through cinderblock, we'll see about steel.

H2 final note: Art has set up a trapline around the courtyard. Don't let him fool you--he will never stop trying.

Saturday, January 9, 2010

Results in Roof Growing 2009: Emptying Your Sub-Irrigated Planter

In this link, we show you how to make a two-bucket SIP, or sub-irrigated planter. But what happens when the growing season ends?

You pull the top bucket out and get to view plant behavior underground. In this photo, the lefthand bucket grew greens with shallow roots. On the right, a tomato.

Note the tomato roots have plunged all the way down
to the wicking cup
and out its slits into the water reservoir.
This year we tried something new with buckets. While a majority of our SIPs are made from 5-gal in 5-gal recycled food-grade buckets, last spring Art ordered a bunch of 6-gal and 7-gal food-grade buckets to make sets with larger reservoirs.

Click the photo to see the height of the overflow hole
in these 5-gal SIP sets.

Now check the height of the overflow hole
in this 6-gal in 7-gal set.

We haven't measured exactly how much more water the larger bucket set holds, but it's considerable. You don't need a larger bucket set. It just cuts down on the frequency of watering at the height of summer, especially for the heavy drinkers, tomatoes and eggplant among them.

We also wondered if these same veggies might benefit from the extra space for growing medium--obviously more potting mix fits in a 6-gal bucket than in a 5-gal bucket. I'm not sure we saw any difference, but summer weather was very odd this year so it's tough to compare.

I thought you'd be curious to see the root system in the larger buckets. To make the wicking cups for the larger SIPs sets, we used recycled two-liter pop bottles with the top cut off and slits downs the side.

Look at the density of eggplant roots
in the two-liter wicking cup.

These ropey eggplant roots
know where to head for water.

A long view.

The Official Earthbox™ Planting Guide says you can re-use potting mix year after year without emptying the boxes, but I don't do that with my two adopted earthboxes. I believe any type of SIP needs emptying, airing, and drying out to limit the chance for disease.

With bucket SIPs, because the plants so completely occupy the growing space, you need to extract the roots at season's end and toss them away to compost somewhere. Your goal is to pull out as much of the organic matter as possible.

Pulled root mass with potting mix
shaken off for re-use.
We combine used potting mix with fresh mix in a large bin and use it again to plant the following spring. Our blend contains mostly peat and perlite with a little coir. Mea culpa: we're going to try to use less peat next season and boost the coir--coconut fiber that's vastly more renewable than peat.