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As an organic grower I make up a dukes mixture...about one half 10% organic content garden soil, about 20 percent pro-grow, about 20 percent coir, about 5 percent expanded water crystals and about 5 percent fine ground wood chips.
The high organic content of the garden soil is partly due to the fact I dump all my pots in a spot with some good compost mixed in with the garden soil the fall before I use it.
I have done something more or less like this for more than fifty years of making my own potting soil. When using this potting soil the next spring I allways see the worms going into my pots. We also see an occasional worm going back to the dumpping spot in the late fall.
This practice produces results as shown in the stacked pot flowers grown on my patio.
We still water daily and feed teas very weak weekly. We have a few weeds to pull but I still like this better than any commercial potting soil.
I don't like commercially prepared soils either, but I take a different approach to container culture. The most important consideration for container media is long term aeration. Your soil needs to support an adequate volume of air for the intended life of the planting or you deny your planting the ability to grow to its genetic potential, within the limits of other cultural influences.
To ensure long term aeration, and avoid the compaction associated with fine particulates like topsoil, sand, peat, coir, compost, I avoid including a significant fraction of these ingredients in any of my container soils.
I use pine bark as the basis of one of the soils I use for display plantings and veggies.
5 parts pine bark fines
1 part sphagnum peat or finished compost
1 part perlite
dolomitic (garden lime) @ 1 tbsp/gallon or 1/2 cup/cu ft
For long term plantings - plantings that will be in the same soil for more than a single growth cycle, I use
1 part pine or fir bark, screened 1/8 - 1/4"
1 part screened Turface (baked clay granules screened through insect screening)
1 part crushed granite (chicken grit in grower size or #2 cherrystone)
This is a VERY durable soil that provides excellent aeration for an extended period.
Yes my mix in part is there all winter. Pro-mix is available in many hardware stores in this part of the country. A lot of greenhouse folks use it here as their only potting soil. Their purposes are to get plants up and do it fast not grow stuff on without chemicals. I usually just have my left overs and pot dumppings working over the winter. I finish the pile so to speak in the early spring. This year I have three pots that are three years held over without changing or adding soil and two that are in their fourth year.
Where I live these must go into the in house winter care groupings.
I use biologically alive potting mixes and use no man made harsh chemicals to kill that biology. For some reason or no reason at all there are advisements out suggesting that this can not be done. That of course is pure and simple baloney. About seventy five percent of our market growers including our greenhouses are owned and operated by the Dutch. The Dutch use sustainable biologically sound principles. Their famous excellent products are mostly grown on manure and the elements of compost. They like I just add to that excellent soil for our potting mixes. I really do not need to do anything more than refresh the old, build the ballance back up and repot the simplest and best way I know how. Some folks think it can not be that simple but it really is.
Now you will have to forgive me for spelling. My computer has been down. The spell check went away when it was in the shop. I need help to bring it back into my tool bar.
There is a marked difference between growing in manure and compost in the garden and beds vs in containers. Water behaves much differently in these two distinctly different types of culture. Soil recipes containing a high % of fine particulates are often fraught with difficulty (as is evidenced by the large number of people who DO try unsuccessfully to grow in heavy, water-retentive soils), and the list of potential problems is long.
I've been actively helping people improve their growing skills for a long time, both in forum settings and in the community. By far, the highest % of growers having difficulty growing in containers are those with an 'all organic' mindset. They are determined to bring their gardens to container culture and to make soils with high % of compost/peat,coir, and other fine ingredients work. Very often they don't, because water management is very difficult. I find, over and over, that once these growers understand how important aeration is to a plant's ability to grow to it's genetic potential, and to its o/a vitality; - they never look back at where they came from.
I'm not saying - have never said - you can't make an all organic approach work. You can if you work at it, but unless you're bound so tightly by an ideology (and I understand that many are), or have something to prove, it makes no sense to me to go through all the extra effort and uncertainty when highly aerated and durable soils are a snap to grow in, and offer a MUCH wider margin for grower error.
I have been gardening for 20 years and am absolutely amazed at what I am learning in this thread and in the one that tapla links to here. I read gardening magazines, books, websites, etc. How this valuable information has escaped me up to now is a mystery. Is soil composition not a "glamorous" topic so it is widely ignored? Is it me not paying attention?
Already looking forward to next spring so I can try out these revelations in my containers.
Thanks especially to tapla, and to docgipe, and to MGCrystal for starting this thread!
I think, in large part, it's an awareness issue - you being evidential. People don't realize there are options available to them, other than commercially prepared, peat-based soils or other heavy soils; or they adhere to an ideology that is limiting by default.
Basically, most of what you read is tailored toward trying to help you work within the limiting factors of heavy soils. I spend a lot of time helping in that regard by offering suggestions on how to cope, but I'm much more about throwing off the limits entirely.
There is no denying that fine roots begin to die very soon after being subject to anaerobic conditions. How long they are subjected to anoxia is a key determining factor in how many roots die and how large they are. Noxious gasses (sulfurous compounds, excess CO2, methane) which inhibit a plants ability to grow to its potential are also produced under anaerobic conditions. This occurs to varying degrees in all soils that support appreciable amounts of perched water. I've simply found ways that totally eliminate these issues, and I needn't worry about an accumulation of excess soluble because I have to water in sips to prevent root rot. I can water & fertilize freely w/o worry - what's not to like?
I guess I might as well answer that question, for the sake of full disclosure. You have to find the ingredients and combine them, and you also need to water highly aerated soils more frequently, so you sacrifice some convenience. Balancing this is the fact that growing in general is much easier. There are far fewer problems with disease (root rot being a primary, here) and insects, and your plants have a much greater potential to grow to their genetic level of vigor within the limits of other cultural factors.
Golden - Yes - either soil works great for forcing bulbs or for bulbs in general. The key to beautiful bulbs in the spring is:
* A good start in the fall
* Arrange your bulbs so they're not touching
* For mixed plantings, layer with bulb varieties that prefer to be planted deeper are closest to the bottom
* Use a fast soil that's barely damp - never wet. Keep container in your unheated garage - toss a little snow on them from time to time so they don't completely dry out.
Crystal - many people would say you need to adjust your watering habits to suit the soil, but the problem with THAT idea is it requires you to water in small sips, which ensures soluble salt build-up from the dissolved solids in your tap water and fertilizer solution. If your soil is free-draining and well aerated (these physical properties are what makes a soil 'fast', as in 'fast draining'), you can be much less concerned about root rot ... unless you're willing to work really hard at it. ;o)
You're right in thinking you need to adjust your soil to your watering habits, BUT, your watering habits become much less important as the soil's particle size increases. Think about a soil made with BB size particles - you could run a hose on it continually with no worry about root rot ...