"Over-potting" is a term that arises from a lack of basic knowledge about the 3-way relationship between plant material/ soil composition/ container size, which together logically determine appropriate container size(s).

It's often parroted that you should only move up 1 size in containers when "potting-up". The reasoning is that the soil will remain wet too long and cause root rot issues. Of course, that's true if you're growing in a heavy, inappropriate soil, but it can be remedied by changing the soil to one that drains freely.

The size/mass of the material and soil type/composition determine both the upper & lower limits of appropriate container size. Plants grown in slow soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil. This (smaller soil volumes) will cause plants to both extend branches and gain o/a mass much more slowly. Rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that trees necessarily rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers with a soil that is too slow.

We know that there is an inverse relationship between soil particle size and the height of the PWT in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (saturated).

If you wish to grow in a large container - please do. Just be certain that your soil supports no, or very little perched water. You have all the tools you need to make an excellent soil. Now all you need is the confidence and the materials. ;o)

Al

Thanks, Al. Isn't it late where you are? Your dedication to us is amazing!

Hey, so I have been meaning to ask you, if composted redwood bark could be used as the "bark fines" component of your mix?

I'm thinking of mixing 2(ish) parts of my organic potting mix I mentioned previously, with 5 parts of the composted redwood (from Greenall), and 1 part of perlite. Does that sound like a good mix?

And I've been meaning to ask (because I'm a little neurotic about this stuff), are there any toxicity/poison issues (to humans, I mean) by growing food items in composted wood bark?

I just discovered a new independent nursery and the owner has all his blueberries in 100% composted redwood bark. Nothing else. They were exceptionally large plants, lush and covered with blossoms. What do you think of that?

I'm thinking of copying his recipe for my blueberries... and then doing your mix (well, my variations as I described above) for the citrus.

Thanks!

Isn't it late where you are?

It was just before 12, and I'd just finished chatting with a neighbor of yours, a friend from CA, so I thought I'd send you an answer. It was mostly a copy/paste thing from a reply I'd left somewhere else, so it only took a sec. ;o) It's pretty normal for me to be busy doing something or other until 12 or so.

I have been meaning to ask you, if composted redwood bark could be used as the "bark fines" component of your mix?

Yes, I have a friend that grows LOTS of citrus near you (I hope I have your location correct - aren't you near SF?) and she grows in either a mix of perlite/composted redwood bark, or 2/3 Turface:1/3 fir bark she buys from OSH (I think those are the right initials. The name of the place is Orchard Supply Hardware or Orchard Hardware Supply)

... are there any toxicity/poison issues (to humans, I mean) by growing food items in composted wood bark?

Well, there is prolly no way to offer absolutes in an answer, but I would say with a fair degree of certainty 'NO'. Many/most of the bagged soils you buy have some level of 'composted forest products' in them, which is just ground up and composted forest duff, slashings, tree tops, etc.

I just discovered a new independent nursery and the owner has all his blueberries in 100% composted redwood bark. Nothing else. They were exceptionally large plants, lush and covered with blossoms. What do you think of that?

I think the lushness is prolly more attributable to the fact that he knows his stuff when it comes to nutritional wants/needs and the fact that he can use the redwood exclusively comes from the fact that he pots up as the plants grow quickly & then sells them before soil collapse. My guess is that if he had to grow them on in containers for extended periods, his choice of soil would be quite different. Your call, though.

Al

Hey Al,
Do you know why your friend in Fremont leaves out the Granite?

Also, where does she get her Turface?

thanks,
kristi

She has a busy & erratic schedule & has difficulty finding the time to water. She needs the aeration provided by the Turface and also to maximize water retention, so she leaves out the granite.

Lolol on the Turface. I'm the one who found it for her, but that was a couple of years ago and I can't remember where. I'll ask later when I get the chance & get back to you.

Al

Don't worry, I found it at Ewing's.

I think I'm going to put my citrus in the turface/bark mix, I think. Maybe. LOL. It's such a strange concept for me to plant in a non-soil. But I'm learning.

I just potted my 4 blueberries in the composted redwood (5-6ish parts), 2 parts potting mix, and 1 part perlite. I'm so proud of myself.

I was shocked at how quickly it drained. I hope we'll see lots of blueberries this summer!