Thursday, April 14, 2011

Spring Cleaning Your Sub Irrigated Planters (SIPs)

In the back of my mind after four summers of growing vegetables in our sub irrigated planters (we began in 2007), I've wondered about the integrity of the potting mix. Could pathogens survive winter and affect the plants in subsequent years?
Aug 2008

Earthbox says you can re-use potting mix for five growing seasons. We remove the mix from all our SIPs each fall and dry it out in the sun. The SIPs themselves get a swipe with a stiff brush...

...but stubborn attachments remain.

I was inspired after reading this post at Love Apple Farm (on growing potatoes in containers) to disinfect all our SIPs. I used their approach: a 10-to-1 water to bleach solution. If you click through, you'll see a happy worker twirling a potato bucket in its dilute bleach bath. 

If life were so easy.

I spent parts of the last three days on the roof, scrubbing away every last scrap of anything that was attached to our grow buckets. Art set me up with a nice hot-water hose run from the laundry room (because our last frost date is May 15, we don't have the full watering set-up on the roof going yet) and a mortar mixing tub. 

On the first day, I used rubber gloves and all kinds of bleach water got in and and made my hands raw.  On the second day, I used packing tape to seal the gloves where they met the skin on my arms (nice look, Pippi). 

Better, but today Art came home with these babies. Exceptional gloves.

I scrubbed everything, including the fill tubes, and let the sun do the drying.

In the middle of all this, Bruce emailed to say: as long as you're bleach-washing...we need 200 clean grower cups to transplant the eggplant, tomato, and peppers into. I was all over it. Disinfecting and reusing these cups year after year is a way to keep plastic out of the waste stream.

There they are. I'm glad it's done.

I'm still not sure about pathogens in potting mix. Love Apple Farm uses fresh mix every year to grow its container potatoes. That would be a deal-breaker for us. Let's hope all this bleach scrubbing leads to a glorious season of clean growing.


Alison said...

Those mortar mixing tubs come in handy for so many things! What a chore you had--glad it's behind you.

Debbie said...

Talk about spring cleaning! That was quite a task. You're ready for 5 more years?

H2 said...

All set...

Brandy said...

I am new here, just found your great site...I have an in-ground garden, but small, so always looking for new expansion ideas! I was thinking about your sterilization techniques...

I think the scrubbing of the containers is a great idea, but for re-using the soil, I think your best bet would be eventually to institute a rotation system--plant pathogens are generally host specific, and the tomato and potato diseases shouln't bother beans, peas, lettuce, if you swapped dirt around?

I have a tomato container that I reuse each year, but I never grow tomatoes in the same dirt twice in a row. I don't bleach it, I drop a clear plastic sheet over it and let the sun cook it, then re-fill with fresh dirt. Works so far(3 years)! :)

I can't wait to read the rest of your urban gardening!


H2 said...

Right and fine idea, Brandy. We have done that with our potting mix. After baking the mix in the sun in autumn, the soil from tomatoes goes into primary position, to be used first for planting greens the following spring.

Ben Czajkowski said...

I agree with Brandy. If you grow tomatoes in potting mix one year, it's another two before I use it again for tomatoes. It can be a headache to remember what soil was used for tomatoes though.

Generally, soil borne diseases don't last the winter, with the exception of the nasty tomato killers (I know nothing about tater diseases). So, you should be okay to reuse, as long as you refresh a little. I generally add about 1/4 to 1/3 new mix and some fresh worm poop and/or composting.

I also have some soil that I am particularly worried about from one container. I'm probably being paranoid, but it is sitting out the entire summer (and might go into rotation for peas in the fall). I don't want to just dispose of it. I could add it to my compost bin in hopes that any baddies are destroyed in there, but I keep forgetting.

Hope this is helpful!

I need to clean my SIPs too! Hopefully this provides the motivation I need to get it done!!

Ben Czajkowski said...

Oh! Another thing you may want to do is have the pH level checked in some random samplings. Since your set up is exposed to potential acid rain, you may need to throw in something to bring the pH back to neutral (for most of what you grow). Your local extension office should be able to provide tests, if you're interested.

Neeli said...

I've been a container gardener for a few years and I can't seem to figure out the best system (what to do with all that soil!) I can't seem to separate them so I do leave them out (through winter) and mix in new compost. Tried the lasagna layering technique in a raised bed (in NC) and it worked fine, although everything grew much more slowly.
Your SIP containers have been on my list for a few years for when I have some more tools. That's a helluva lot of work - I stuck my old small pots in the dishwasher. Keeps you busy in the winter, right?

H2 said...

You're right, Neeli, that SIPs involve some work, but the payoff in clean food is well worth it.

Plus, without adequate sun anywhere for growing, it's our only option.