Dave, would you say ANY amount of compost(finished) is bad in a container? For instance, if it was something like 5 parts sphagnum pm, 5 parts perlite and 1 part finished compost.

Most commercial organic potting mix has compost in it.. and it seems to work fine. It may be low in nutrition without continued breakdown by a soil food web, but for seed starting you don't need much. I think what Dave is saying is that for growing full size plants containers, it isn't going to do the job to feed your plants.

Right. I definitely know it needs supplemental feeding, especially being in a container. I was just wondering for the consistency of the mix.

Thank you all for your replies. To be safe and provide the best nutrients to my plants, I am not going to reuse the compost from last year. I'm going add it to my own compost pile and leave it to decompose further.

"Dave, would you say ANY amount of compost(finished) is bad in a
container? For instance, if it was something like 5 parts sphagnum pm, 5
parts perlite and 1 part finished compost."

What I am saying is it won't be a source of nutrients for the plants. Organic soil mixes get around the problem by using water soluble ingredients like humus, manures, and meals.

Otherwise compost's use in containers depends on the amount used relevant to the other ingredients. Compost on its own or in very large amounts can compact, drain poorly and suffocate roots, and create water table problems in containers.

Don't get me wrong I am a big composter and use truckloads on my soil gardens annually. But its use in containers is a totally different animal, especially when expecting it to provide nutrients for the plants. Compost as a source of nutrients is a two-stage process, which is why it is primarily a soil amendment, not a 'fertilizer'. Part 2 of the process is present in garden soil but can't survive in containers.

Dave

I understand what you mean, and even if compost was a source of nutrients in a container, it would only be temporary. Would still need to feed the plant something else over time.

True. Which is one reason why many container growers who wish to grow organically recommend using organic liquid supplements, not compost, for nutrient sources.

If you think about it, even in the garden where it can be a low-dose nutrient source, compost continues to decompose and compact and has to be replaced/refreshed on a regular basis. So common sense says that is even more true in a container.

Plus container grown plants, be they organic or synthetically grown, have always required more frequent applications of nutrients just because those nutrients leach out of the container every time you water.

Dave

leaf mold has a lot of micro organisms. i like combining compost with leaf mold in containers.

not all compost is bad. I always mix soil in mine (in part to extend it, in part to offer cover to the earthworms who are doing the real work). It is cold throughout, and it does have spores for micro-flora. Hot compost is the worst of course, having been pasteurized.

"leaf mold has a lot of micro organisms. i like combining compost with leaf mold in containers."

I agree. The problem is they don't survive for long in the contained environment so have to be frequently replaced. And you still have the compaction and drainage problems associated with compost and/or soil in a container.

The bigger the container the less problems and the longer lived the micros. 1/2 whiskey barrel or 25 gallon containers, depending on the plant, can work almost as well as in ground. But given the overly small 1-5 gallon containers so many try to use, especially new growers, they are setting themselves up for problems and poor plant performance that can be greatly reduced simply by switching mediums and using liquid organic supplements that are already pre-digested. Not that I advocate growing much of anything in a container that small to begin with.

Dave