You certainly can organically grow container plants. As I recall most of the artificial fertilizers also rely on soil microbes to make the elements available to plants. However, I believe less of a micro herd is required to deliver that nutrition than an organic program. The majority in the container forum seem to prefer using a synthetic nutrition program as that provides more consistent results.

The last time this topic was discussed there was a lot of flaming. I personally will stick to organically feeding my container plants.

Organic soil amendments do take the activity of soil biota to make them available in elemental form so that plants can absorb the nutrients. Cell walls are permeable to ions - sort of like tossing BBs at a chain link fence. Organic molecules are more like trying to push basketballs through the same fence.

Chemical fertilizers, like Miracle-Gro and others are immediately available to plants because they are soluble. Don't confuse fertilizers like fish emulsion and others carbon-based as being soluble - they are not. They form suspensions and need soil micro-organisms to break them down into usable forms.

Because containers by nature are usually inhospitable to micro-organisms, no matter how hard you try, nutrient delivery varies erratically with their populations - often boom/bust. This creates delivery issues and can impede our ability to troubleshoot because of delivery lags (carry-over).

There is room for both schools in the pursuit of our container culture goals. I have tried both methods extensively and can say that personally, from the perspective of results:effort and in gaging the ease/reliability of both methods, the chemical fertilizers and a well-aerated, free-draining soil win hands down.

Al

My answer is 'chemistry is chemistry'. Wishes do not change chemistry or physics.

What may benefit our forum is if someone were to do some side-by-sides and document in replicable form the methods and report the results.

On the other forum gurgler mentioned, someone did perform such tests over multiple seasons and reported their results (for fertigation in a greenhouse) and maybe a trusted voice not tied up in knowledge or academia can perform a test to show others.

Dan

Thank you very much for your helpful responses. As the plants belong to my upstairs neighbour, an old lady, I probably go for synthetic nutrition. I want those roses to perform really well this season. And I think the maintenace should be fool proof as the owner is enthusiastic but non too skilled. And I will sprinkle the organic fertilizer on the heavy feeders in my perennial border, keep mulching and slug-hunting manually :-)

cheers Lin

Some few garden writers have stated that potting soil would not have the bacterial activity that garden soil did because they never saw any earthworm activity in the pots. I have used compost as my potting soil for a number of years and the plants in those containers have grown better, and blossomed better, than some in containers with commercial potting soil. I see no reason to believe the bacteria would be less active in good compost in a pot than when that same compost is spread on a garden plot.

The reasons are: Too much/too little moisture - the conditions change rapidly, unfavorable pH - also changes rapidly, extreme temperature swings - changes rapidly, soil composition/compaction/aeration - compost-based soils can usually be counted on to compact badly, making anaerobic conditions ......... any one or combinations of several factors affect microbial populations in containers, and because they are tied together with nutrition organic soil supplements - nutrition as well.

Since bio-populations rise and fall dramatically in containers, it follows that nutrition availability follows the activity levels and population numbers of the critters. Add to that you often have no idea of what you're supplying (% of nutrients) and when they will eventually become available, you can easily see how a chemical nutrition program for containers could be easier, less worrisome, and more reliable than depending on soil amendments to deliver the goods.

That someone indicates his plants grew better in compost than commercial potting soil is no clarion call to hurry to a water-retentive medium as a solution to container culture problems. I grow in a bark/peat/perlite mix and it has been proven by many to be extremely productive, in large part because of its structural durability. The FIRST thing any container gardener should consider when it comes to soil is it's (structural) durability. The question should be asked, "Will it remain well-aerated for the intended life of the planting?" The bark based soils garner a resounding 'YES' while the compost-based soils get a weak "probably not".

If compost is in large enough pieces that it is appropriate as the basis for a container soil. it's not finished and will quickly break down and collapse, bringing N immobilization along the way. If it IS finished, particulate size is too small for it to be the basis for a container soil.

The chemistry and physics of container culture are often, if not usually, quite different than growing in the earth, and we often create more problems than we solve when we try to bring the garden to our containers.

Al

Al, has anyone ever told you you should write a book? LOL!! You have such a knack for stating the science of container growing so clearly and so succinctly that even the most novice of growers can understand and gain help from. And you refute the inaccuracies in such a tactful and informative way. Thank you again for sharing your enormous amount of experience and knowledge with all the forums - you are such an asset to this community!

YPP

ps. how IS that book coming along, btw?