Does anyone know if using leaf compost for potting soil without adding any other kind of soil is more or less beneficial for the plants?
Less.....and by a wide margin! Potting soils have a rather unique combination of materials that make them suitable for container use. Growing plants in containers is vastly different from growing plants in the ground, as particle size, aeration, drainage and moisture retention are far more critical in the confined space and reduced drainage a container provides. Excessive amounts of any organic matter that is not fully decomposed or fast to decompose - compost, leaf mold or compost, grass clippings, etc. - as a base or even a sizeable component for a potting mix will continue to breakdown and as it does, reduces aeration and porosity and creates compaction and compromises drainage.
Visit the Container Gardening forum for details.
Since most all commercial potting mixes are soilless, meaning they have no soil in them, and soils are known to create drainage problems in containers there is no real reason to add soil to a potting mix. The leaf mold, just like compost, will make a good potting soil.
Unfortunately, the above is just not true. Leaf mold, leaf compost, ANY kind of compost is NOT a potting soil nor will it provide a good base for one. To state otherwise is to not understand the unique dynamics of container culture and water movement and retention in the medium.
Any highly organic, easy to decompose material - such as those listed above - do not provide the necessary porosity, texture and drainage ability that are essential in successful container growing. This is why container soils generally contain a high percentage of very slow to decompose organics (bark fines, coir, peat moss) as well as mineral-based materials that provide porosity and increase drainage ability - pumice, perlite, high-fired clay particles (Turface), etc.
You can add a small amount of leaf compost, but you really need to focus on other materials to provide a good base.
I really do suggest you visit the Container Gardening forum to get some advice from some experts in this field :-)
Here is a link that might be useful: here's one place to start
Ditto what gardengal says.
Unfortunately, so many of those good organic materials, such as compost, offer few helpful qualities when forced to live within the confines of a container. They are best left to the outdoor garden areas.
I agree with Pam and Dori - leaf compost as the primary % of a container soil is unlikely to work well. The physical behavior of water in soils for container culture is different enough from its behavior in the garden that it requires a different set of strategies to insure adequate aeration for the intended life of the planting.
I wouldn't argue the point that you MAY be able to get it to work satisfactorily, depending on what standards you may have set for yourself, but there are other ingredients that would allow a much wider margin for error and that could make your endeavor less challenging/more fruitful.
Several articles over the last several years about using leaf mold as potting soil have appeared in Organic Gardening magazine, and leaf mold is a good, acceptable substitute for peat moss. I have used either leaf mold or compost for potting soil for several years now and do not find any problem with drainage, and find either one is a better potting soil than peat moss ever was.
Of course if you use partially digested leaves you will have problems, but there will be no problems if the leaf mold is digested.
Thanks everyone. Very helpful imformation.
Kimmsr, could you provide a link to one of those articles in Organic Gardening magazine? I looked and the only ones I could find mentioning leaf mold and potting soil were this page of potting soil recipes listing leaf mold only as a part of the potting soils:
Classic soil-based mix
1/3 mature compost or leaf mold, screened
1/3 garden topsoil
1/3 sharp sand
Note: This mix results in a potting soil that is heavier than modern peat mixes, but still has good drainage. Compost has been shown to promote a healthy soil mix that can reduce root diseases. Perlite can be used instead of sand. Organic fertilizer can be added to this base.
Prick-out mix for growing seedlings to transplant size
6 parts compost
3 parts soil
1-2 parts sand
1-2 parts aged manure
1 part peat moss, pre-wet and sifted
1-2 parts leaf mold, if available
1 6" pot bone meal
and this page that says "leaf mold is great in potting mix" ~ in potting mix, not as potting mix.
Unfortunately that would involve searching through a lot of magazines I no longer have since I passed them on to others. However, along with compost I have used leaf mold as a potting "soil" with no problems, except a tendency at first to make that mix too wet. Most all commercial potting mixes are peat moss or fine bark, almost the same texture as leaf mold and they do not pack tightly when wet so common sense should tell one that leaf mold could be used as a potting soil.
It is frequently possible to grow things in mediums that aren't ideal.
That doesn't mean it is the ideal ;)
I think the easiest way for folks to decide for themselves what they prefer to work with is a simple backyard experiment. Fill one container with whatever organic recipe one likes the looks of and then fill another with whatever mix one likes the looks of from the container gardening forum.
Grow similar plants in each and see what happens ;)
I'm not sure how big a factor 'common sense' should play in the equation. There is a science behind container soils and their requirements that supercedes what common sense may or may not dictate. While leaf mold may appear similar to peat or bark fines in texture, it has a much greater and faster tendency towards further decomposition than either of these do and so the texture will NOT remain constant over the life of the container planting. If you are not able to maintain adequate pore space and aeration - which will be lost as the leaf mold or compost continues to breakdown - you lose drainage ability and risk rotting out your plants.
This is a fact that has been established beyond argument with regards to container culture. Personally, I wouldn't approach either of the two previously posted 'recipes' for any long term container growing - they could possibly work for seedlings (although the soil would hold far too much moisture) or a single season crop, but neither reflects a correct understanding of how container soils work and how water moves through them and their ability to hold up long term is minimal.
But gardeners overlook or ignore the science all the time, with varying results. The only way one can determine this on their own is to trial various methods/recipes and see how the growth of the plants is reflected. If the plants produce for you satisfactorily, then use whatever method or ingredients you prefer. 25 years of container gardening both personally and professionally has convinced me of the best approach.
I agree with GG 100%.
Short term plantings may well work out 'just fine' in a mix that is far less than ideal. The reason is that the mix may be OK until such time as the vigorous annual or veggie sends roots throughout the container. In this case the roots have created their own passageways through the soil and when that soil structure collapses the roots can keep it open enough.
Reusing that mix the next season would be a mistake which is why the general recommendation is to replace highly organic mixes each season.
If one has longer term plantings, grows plants that won't root colonize the container before structural collapse occurs or simply wants a more durable mix that can be reused multiple seasons with no loss in plant performance then the potting mix has to be made of ingredients that are more durable and won't break down into muck quickly.
It is possible to build a potting mix that can go 5 or more years (indefinitely actually), but these mixes are entirely or almost entirely inorganic (not to be confused with 'synthetic' or 'chemical'). Organic is great in the ground precisely because it get's decomposed. Decomp of potting mix ingredients is not conducive to the health of plants in a container though. Decomp of potting mix ingredients leads to loss of aeration.