Need for a composter?

Houston, TX(Zone 9a)

For 2010, and probably for 2011 as well, I am container gardening only. (May make a foray into raised-bed gardening later).

Do I have a need for composting? I'm using tapla's 5-1-1 mix for my containers (using either pine bark or coco coir). On the one hand I don't see a need, but on the other hand it's good for the earth, and there may be uses for compost in containers that I'm not aware of. Or maybe I could store it for a couple of years? (That may garner a Yay or a Yuck, I don't know. :-)

Comments anyone?

Bay City, MI(Zone 6a)

I limit peat and compost to small fractions of the soil when using bark, and I prefer not to use coir. As you can see by the 5:1:1 mix that peat is limited to 1/7 or about 15% of the mix. You could substitute compost, but I would limit compost and peat combined to the same 15% fraction. I've never had good results using coir under any circumstances, and you should be aware that if you do use it in a significant amount in homemade soils, the pH is so high that you shouldn't use lime as a Ca/Mg source.

Storing your compost for later use in gardens/beds is a good idea. It will keep indefinitely if it's dry.

Al

Houston, TX(Zone 9a)

Well, it should be an interesting experiment. I hope it doesn't get too much more expensive. Thanks for the warnings, Tapla. I've got coir on the way, so I'm going to give it a good try. But I'm beginning to realize just how much of a by-guess-and-by-golly activity gardening really is.

Methinks somebody just slapped this newbie with a clue-by-four. :-)

Bay City, MI(Zone 6a)

Don't be frightened by the things I say. Just keep them in the back of your mind. When you think about container soils, think about aeration and durability of the soil - especially of plants fail or exhibit poor vitality. You CAN grow nice plants in soils like MG and other peat-based soils, it's just more difficult - and the margin for error is diminished considerably, compared to growing in the bark-based soils.

Al

Tonasket, WA(Zone 5a)

Al, I don't understand why it isn't a good idea to use homemade compost with pine fines bark. I thought it was a good idea to use lots of compost. I usually have volunteers, tomatoes, melons, etc grow in my compost bins and they do beautifully.

Donna

Bay City, MI(Zone 6a)

The reason that bark-based soils work so well is because they are highly aerated. Using large fractions of fine ingredients like compost/peat/coir, destroys that aeration. Imagine a quart jar filled to the top with BBs (representing the bark). You can add a pint of sand (representing the compost/peat/coir) which simply filters into the air spaces, driving air out and allowing a layer of perched water (PWT) at the bottom of the container.

If you start with fine, water-retentive ingredients like compost/peat/coir, you cannot amend them to change the drainage characteristics or the level of the PWT unless you reach about 60% of a coarser material. E,g., adding a handful of perlite to pudding isn't going to make the pudding drain, and adding a handful of perlite to a quart of compost won't make it drain any better and it won't change the height of the PWT. It WILL reduce the volume of water in the PWT, but that is only a step in the right direction and still leaves the height of the PWT and lack of aeration to deal with.

Container soils are all about structure and little about 'nutrition'. You get very little nutrition from compost when used in containers, so little you might as well consider it negligible. To my way of thinking, compost/peat/coir are only convenient as an amendment to help increase water retention a little so you don't have to water so frequently.

FWIW - I've been helping growers improve their container growing skills for many years, and in nearly every case, the most significant reason for improvement was a change from the heavy, water-retentive soils from a bag to a more open, airy and durable soil.

As I think I said, it's not that you can't grow in compost/peat/coir-based soils, it's just that it's much more difficult, and the decisions you make as far as fertilizing and watering are far more critical. Easily, better than 75% of the problems I help people with regarding container culture are directly or indirectly related to soil choice. that is very significant and very telling.

Remember too, Donna, that the physics of how water behaves in containers is much different than how it behaves in a compost bin. You have the entire earth to act as a wick to 'pull' excess water from the compost in your bins, but in a container, finished compost can support as much as 6" of totally saturated soil at the bottom of a container, which is decidedly a bad thing.

Al

This message was edited Mar 19, 2010 1:51 PM

Edmonton, AB(Zone 3a)

Al
Thanks for the detailed explanation as I get so much information from your expertise.
I have gone from using garden soil in my containers to straight Container soil that I can buy in 4 cubic ft bags that really isn't soil as it's soil less. I have had a lot of sucess with the Promix brand. Do you know that one? Any comments? We don't seem to have the pine bark fines in Edmonton so availability is difficult.

Thanks again for the tips.
Ann

Tonasket, WA(Zone 5a)

Thanks so much Al, I do understand now about the growth being easier for plants in the compost bin. I just worry that the GreensMix Bark Mulch that I bought is too fine. I just went outside in the cold 25 degrees and took a picture. I will send it next. Thanks again for all your informative help. Donna

Tonasket, WA(Zone 5a)

Tapla, here is the photo of the GreensMix bark Mulch, with a dime . Donna

Thumbnail by rutholive
Bay City, MI(Zone 6a)

Perfect!

If I had found such nice bark I would definitely have stocked up by buying a whole pallet. ;o)

Al

Tonasket, WA(Zone 5a)

Thanks, I don't know how soon I can get back to Wenatchee,(nearest Lowe's where I got the two sacks) when I do I will take the pickup and get what I can. I is 130 miles away.

Donna

Houston, TX(Zone 9a)

That looks just about like what I get when I take the regular pine bark and sift it through a screen. I guess I'm on the right track. Thank you, Donna (RuthOlive) for posting your picture!

Tonasket, WA(Zone 5a)

My youngest son and I went to Wenatchee Tuesday, and I got 20 sacks of the Greensmix bark mulch. So I don't need to worry about running out of it very soon. I just finished transplanting my tomatoes. I potted them into the 5-1-1 ratio that Tapla has been explaining to us. One thing it is a little difficult to get the mix evenly moist. I know it would probably be best to moisten the bark first the mix the three together, but I had to get the transplanting done.

donna

Bay City, MI(Zone 6a)

Donna - I put the peat on a tarp first, then the bark, then the perlite. I wet the perlite and bark, then mix. Allowing the soil to remain on the tarp and covered over night allows the moisture to diffuse into dry bark and peat particles, breaking the tendency toward hydrophobia (water repellent) when moisture content is below about 30%.

Al

Tonasket, WA(Zone 5a)

Thanks All, will try that method.

Pittsford, NY(Zone 6a)

great information everyone.

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