The particles are small, and likely to break down.

Often, there are salts in the coffee grounds that can accumulate in the soil.
If one rinses or composts the coffee grounds, then the small nutrient value would
be rendered null - and the particles would be too small to be of any structural value.

That said, I get big bags of free coffee grounds from Starbuck's and I dump them in my garden
and around my yarden beds.

Since bonsai pots are generally small, I choose only the best materials to make my mix.


Josh

Josh
I saw your answer on another post but it tells me why not to use it. It doesn't tell me why 2 well known bonsai artist are using them to improve feeder roots.

Paul

Josh
I found the articles:
Salvatore Liporace "old coffee grounds stimulate root growth naturally" Issue 116, July Aug./2008
Lorenzo Agnoletti "The (coffee) pads contain minerals which help achieve dark green foliage for pines and junipers." issue 121, May June 2009.

Chopped celery can stimulate root growth naturally too, but that doesn't mean I'd consider it as a soil amendment in any of my soils. It's your call, and who am I to disagree with a master, but it doesn't make sense to me either - at all.

Bonsai soils are all about structure. We take great pains to build porosity sufficient to ensure that we don't rot roots into our soils, so why would we add coffee grounds, a soil amendment we KNOW breaks down quickly, decreasing porosity and increasing water retention in the process? What could possibly be in coffee grounds that should tempt us to take the risk of having a sludgy layer of broken down coffee grounds at the bottom of our pots? Nothing I can think of that couldn't be supplied in a good fertilizer or by using a nutrient supplement to change (lower) the pH of the soil solution, which is where many issues re chlorosis lie; but there's more.

Discussions across multiple forums frequently center on the question of adding dilute coffee/tea or used grounds to plants as a 'tonic', but Arabica (coffee) and Camellia (tea) are known for their toxic alkaloid (caffeine) content and their allelopathic affect on plants as well as autotoxic (poison to their own seedlings) effects on future generations. Caffeine interferes with root development by impairing protein metabolism. This affects activity of an important bio-compound (PPO) and lignification (the process of becoming woody), crucial steps for root formation.

We also know that the tannins in both coffee and tea are known allelopaths (growth inhibitors). There are ongoing experiments to develop herbicides using extracts from both coffee and tea that cause me to want to say they might serve better as a nonselective herbicide than as a tonic. I would not use either on my plants; nor would I add tea bags/coffee grounds to my container soils - especially to my bonsai soils.

{{gwi:5648}}

Al

Al
I still use that picture when I mix my soil.
Some of the pcs look like they are 1/4"???
Is my perception accurate.
Paul

Hey, Paul, I'm sure Al will respond when he has time...
but let me just say that Yes, some of those particles - the Bark, primarily - are up to 1/4 inch.

Although the bark might start out on the large side, it is the least durable of the ingredients
and will gradually break down into the optimum size-range (and beyond).

I've even been guilty of including particles as large as 3/8 of an inch in my mixes.


Josh

We all have our favorite mixes.
Many in the western world (including me) think it's not necessary but But I still use a drainage layer of turkey grit.

Indeed, and some mixes are superior to others.

Drainage layers don't create drainage, though, to be perfectly clear.
It's not that it's unnecessary, it's actually counter-productive.

Josh

Josh is right, Paul.

While there is plenty of leeway for personal preference in how we apply the growing sciences, much of the science itself is quite rigid. IOW, we can reliably predict a great deal of what happens, both physically and chemically where soil science is concerned based on input. For example, we can predict that heavy soils, like Miracle-Gro (et al) based on peat or other fine particles will support a perched water table (PWT) of a given height in any container, regardless of its size or shape; and that a PWT of similar ht will occur in the same soil when it is situated above a coarse strata of grit. Coarse drainage layers serve only to raise the position of the PWT in a soil.

To illustrate: Let's say you're using a soil that supports a 3" PWT. In a 3" deep bonsai pot, the entire volume of soil will be saturated at container capacity. If you situate 3" of the same soil in a 6" pot above a 3" drainage layer, you will have 3" of well-aerated drainage material at the bottom of the pot with 3" of saturated soil above it.

I have chosen to build/design my soils so they are adjustable for water retention, yet they hold no (or very little) perched water. Returning to the perspective that structure is the most important aspect of container media, it's difficult to argue FOR the possibility that a soil that retains perched water for any significant interval could possibly be superior to a soil that doesn't.

Al

I guess I am just hard headed.
W. P. recommends about the same as you, a consistent soil size and the same type of ingredients.
My problem is that the Japanese still use a drainage soil at least according to articles recently published and they are usually a progressive people. Some of them must have tried a mix such as you and W. P. suggest but I have read none as of now.
Paul

For what it's worth, the fellow at the Turf supply where I purchase Turface is also Japanese,
and he mentioned that he's sent soil-less mix samples down to a San Fran bonsai group.

Josh

Except for the turkey grit I try to follow Al soil mix as much as possible.
I did buy a small bale of Sphagnum moss and some times use it instead of pine bark.
Paul