Soil depth for onions in containers?
I posted this on the Vegetable forum and got one answer but thought people in this forum might have more experience in container growing than those of us who grub around in garden soil.
Here's the post:
Since I have heavy red clay, I've been planning to grow onions to full maturity in ProMix in some large bins so they have nice loose soil to expand in. I am however clueless about how deep the growing medium ought to be.
I haven't been able to find anything about a recommended depth of soil for onions other than at the link below. And it doesn't actually recommend a soil depth. It just notes that in the varieties of onions they observed, the roots reach as deep as 39 inches! Whether it's relevant or not, it appears that onion roots for the most part spread laterally rather than vertically, so I'm wondering how important vertical space is for them. No way can I grow onions in ProMix that's 39 inches deep since my bins aren't that deep!
If you've grown onions to maturity in containers, what depth soil have you provided for them -- and did they grow well?
Someone commented that most root crops require 6-8 inches of soil for their root systems. I thought that might be fine for a raised bed but didn't sound like enough growing medium for onions in a container. If it is, that's great, but I wanted to check it out.
Here is a link that might be useful: Onion Roots