Honestly, I can't say I have ever been impressed with the germination rates of leaf mold. Compost- definitely yes, leaf mold no.

I think it is partly due to its usual particle size - too large for effective, easy emergence and rooting; partly due to the surface tension of the leaves. And there is the tannin content too. Reduced, fine milled leaf mold perhaps, but the the usual stuff, no.

This is not to say leaf mold isn't great stuff. It is and I use as much of it as I can make. Especially as a mulch and, as it decomposes, as a source of nutrients and soil structure improvement.

JMO

Dave

As mulch I can see how it's great, but I've seen several sites state the it's a great germination medium BECAUSE of the fact that it's low in nutrients. That really got me confused.

Germination has little to do with the medium you put the seeds in. What is needed is moisture and some warmth, some seeds need more warmth than others, but very often leaf mold does provide just that environment, moist and warm, and seeds germinate. How long these seedlings might last in leaf mold depends on many things, but generally seeds have everything they need to maintain growth through the development of the first true leaves which then need sunlight to start to manufacture the nutrients the roots need to grow some more, in combination with the nutrients the roots uptake from the soil. Contrary to what many people think leaf mold is very rich in nutrients, thye are just not very soluble and so cannot be easily measured.
If someone did say leaf mold is a very good germination medium because it is low in nutrients they might not know anything about how plants grow.

takadi - please link us to some of these sources you are referring to so we can evaluate them. As kimmsr says, some sources aren't real reliable. And, sometimes when they say "low in nutrients" what they really mean is "low" when compared to the high levels in commercial fertilizers. Even high quality compost is sometimes labeled as "low nutrient" (it isn't) because they are comparing it to Miracle Grow!! ;)

Low nutrient levels (IF leaf mold was truly LOW which it isn't) "could" be helpful to germination in one way because very young seedlings can actually be harmed by high nutrient levels. EX: most quality seed-starting mixes contain little or no added nutrients. The seedlings don't need them and are stressed by their presence. Growing on, once germinated, is a whole different issue.

Dave

http://www.ipcc.ie/leafmould.html

"Leaf mould is quite low in nutrients, which makes it excellent for seed germination as the seedlings develop a strong root system, which will help them remain healthy when threatened with pests and diseases. "

http://www.the-organic-gardener.com/leaf-mold.html

"It has the ability to hold losts of moisture and this provides an ideal environment for seed germination.

Moreover, its low nutrient content benefits the early development of healthy seedling roots. "

Since the "authors" of these blogs do not identify them selves the sites are suspect. While having the authors ID on the web site is no guarantee that the information is good and no identification does not mean it is not good, it is suspect. Why else would the author be afraid to identify themselves?

Agree. And I suspect that the references to 'low nutrients' is, as I already mentioned, only when compared to commercial fertilizers.

But the best way to sort these things out sometimes is to give it a try. Do a test germination of a few seeds in a small container of some leaf mold and a comparison container of seed starting mix or 1/2 mix and 1/2 compost. See how it works for you. ;)

Dave

I know it's an old thread, but I've learned that leaf mold is rich in gibberellins manufactured by the decomposing fungi. Gibberellins are plant hormones that stimulate germination and growth. I have some compost which is about half leaf mold and half grass clippings. I was astonished at the sheer quantity of weeds germinating in this stuff when I dumped it outside in a mound; it was quite evidently abnormal. Lambsquarters, which usually grow a couple feet tall max here were 6'+. Upon researching leaf mold and germination, I uncovered the connection. This stuff has proven to be unsurpassed as a seed starting medium, and I intend to try and duplicate it.

Better late than never.

Yes this thread is quite old, but it came up as one of the top search results, so I'll add.

I've been studying & extensively experimenting with leaf mulch for over a decade.

And this herein has become a highly-reductionist topic, with quite overly-simplistic & assumptive answers.

1. Not all leaves are the same.

Nutrient content varies widely from one plant/tree species to another.

Some species are far richer in Nitrogen than others (1x, 2x, 3x times or more). Ditto for all other nutrients.

The leaves of some species of trees are known to contain phytochemicals that, before decomp, are known to inhibit germination of competing species (Black Walnut for example, is known to contain the phytochemical Juglone, which inhibits germination in many seeds, until being decomposed by specific bacteria, like seudomonas putida J1, after which the inhibitory effect subsides or disappears completely).

To the contrary, trees from the Salix Genus are often rich in the hormone Salicylic Acid which often promotes rooting/germination, again depending on the specific seeds (refer to previous Commentors answer about Gibberellins, another hormone in certain species, ditto for Auxins, and other hormones).

2. The age & state (fresh, aged, green, brown, slightly chopped, finely powdered, etc?) of those leaves results in great variations of nutrients (including secondary metabolites, plant growth hormones, Humic substances, etc.).

Even green fresh vs brown dried leaves of the same species vary considerably.

3. Not all seeds are the same, and/or have the same requirements.

The ideal germination requirements of one type seed can differ greatly from another.

4. Soil/biota conditions of the producing trees result in widely varying fluctuations of nutrient content of resultant leaves.

Numerous studies show how similar species of plants/trees grown in different conditions/soils/locations produce leaves of widely varying nutrient content (I suggest a bit of time searching & reading various studies provided by the likes of Google Scholar or other such tools).

So, there is no easy or universally applicable answer.

That said, I germinate thousands of seeds yearly and always incorporate leaf mulch/mold.

And am used to near 100% germination rates.

But I often combine those with worm castings.

Leaves are often composed of much cellulose, lignans & other such.

That cellulose is one of the toughest natural compounds to break-down.

But inside that cellulose is often quite abundant levels of nutrients.

The enzymes (like cellulase) & microbes often contained in worm castings help break down that cellulose quickly (sometimes in mere days).

Thus it's far more complicated than has been suggested/presented.

Experiment, observe, learn.

Even if you fail, learn from that "failure".

Make small changes/variations & then experiment again.

As per my previous post, there is far more to germination & plant growth & health than mere N-P-K.

N-P-K is a highly-reductionist approach.

There are hundreds, if not thousands of nutrients, minerals, secondary metabolites, enzymes, plant growth hormones, and other compounds necessary for proper growth & development.

The mere reliance on just N-P-K has been a huge mistake.

Too many people seemingly fail to understand that plants are incredibly similar to humans, in that they have largely diverse & complex nutritional needs.

Mere focus/reliance on N-P-K is like making sure humans ONLY get like vitamins A, B & C.

Or relying only on steroids (you may induce rapid growth, but many other biological functions are jeopardized and/or inhibited).

Iron is important, as are Calcium, Magnesium, Boron, Selenium, even Sodium, etc.

Ever fed a Tomato or Pepper plant too much Nitrogen?

Excess Nitrogen interferes with Calcium uptake, often leading to blossom end rot in fruits.

There's a good deal of research & data showing how the plant growth hormone ethylene positively effects seed germination rates.

That ethylene has also been identified as a key hormone responsible for signaling leaves to fall, and is present in many fallen leaves.

Carbon, which is used as energy, has also shown positive effects on seed germination.

Know what leaves have in abundance? Carbon.

A former CIA polygraph expert/analyst/researcher named Cleve Backster experimented with polygraph machines on plants and determined based on his experiments & observations that plants possessed what he called Primary Perception, i.e. mental cognition, even memory & such.

More modern research has shown how plants & insects (i.e. pollinators) interact via chemical, energy, and other signals.

Same is true between microbes & plants.

The point being all those complex functions rely on holistic & complex nutritional needs.

I suggest research on the natural formation/development/creation of things like natural vitamins, natural antibiotics, polyphenols, flavonoids, etc. for greater & more comprehensive knowledge.

Those microbes (bacteria & fungi) you mention, themselves are highly-dependent on various other nutrients & compounds, for health, growth & proper biological functioning.

Do you know that leaves are like entire worlds, in their own right, with massive & diverse populations of billions of microbes?

Which is far too complex to get into here.

Seeds themselves are often full of enzyme inhibitors (which work to prevent premature seed degradation) which must be overcome in order to sprout (hence the reason many health foods are made with sprouted seeds, to avoid the nutritional inhibitory effects of those enzyme inhibitors).

There is perhaps a lot more readily-available nutrients in leaf mulch (I would suggest you define "leaf mold" to proceed with a more comprehensive discussion, as to many, myself included, leaf mold implies that the breakdown process has already begun, hence the term "mold", and thus nutrients are already being released and/or created).

There are a vast number of stages between leaf "mulch" and "mold", as it is a continuing process (i.e. you can have a product that is 1% "mold" or 99% "mold").

But even leaf mulch (freshly chopped leaves) start degrading & releasing & creating nutrients, immediately.

It's an ongoing process that continues.

I have a large pile of freshly ground leaves that is already full of sprouting seeds.

Decomposition begins immediately.

Thus the release/development of nutrients and numerous other compounds begins immediately.

Just the process of chopping (aka "mulching") leaves breaks cell walls, which release enzymes (which are catalysts for both new cell composition & existing cell decomposition), which breakdown cells more, which releases the contents that microorganisms start feeding on.

Degradation/decomposition in a very basic overview:

1. Enzymes break open cell walls.

2. Microbes (bacteria, fungi, etc.) feed on the stuff inside those cells.

3. Other organisms (worms, arthropods, Carrion insects, and other decomposers) either feed on the remnants of that other stuff, and/or on those microbes themselves.

"Soil" is the poop of all those things eating (yes, everything poops).

"Soil" can also be a mix of that poop & still yet to be decomposed organic matter.

Decomposition is the digestion of matter, by various organisms.

Again, there is no one-size-fits-all answer.

People need to not rely on what others say, and just try stuff.

And continue trying, observing & learning along the way.