Shop Products
Houzz Logo Print
carolinocala

Soil Receipes

carolinocala
13 years ago

I am about to transplant my first to "yearling" bonsai seedlings and I would like any advice about the best soil mixtures that anyone uses for fastest/strongest growth of their bonsai. I know each species has it's different mixtures, but a general all round mix so that I can get the most growth in the shortest period of time. I have a sweetgum and a golden rain tree that are in need of repotting and was wondering what is BEST. Any advice and experiences would be most helpful.

Comment (1)

  • tapla (mid-Michigan, USDA z5b-6a)
    13 years ago
    last modified: 9 years ago

    We can probably avoid a lot of conflict if we avoid the superlative (words like best/worst) and stick to the comparative (better/not as good).

    Soils are going to be a balancing act. Generally speaking, the more air you can build into them the better; but there is a point, where the 'balance' comes in where we need to look at our convenience. That is to say we don't want to build so much air into the soils that they hold too little water. So how much is enough water, is a pivotal issue.

    If FL, you may WANT lots of water retention, but here we have 'balance' to consider again. By that, I mean if you build too much water retention into the soil to satisfy YOUR needs or convenience, it's possible you sacrifice some of the potential vitality of your plant.

    What we strive for then, is how to create a soil that holds lots of air AND lots of water. This seems impossible at first, because water retention is usually directly correlated with particle size. I.e., the smaller the particles the greater the water retention. The fly in the ointment is that as particles become smaller, air retention decreases and the level of perched water increases. Perched water is water that is held so tightly in soils, due to capillary attraction, that the force of gravity is not enough to cause it to drain from the soil. Air must return to bonsai soils quickly. Fine (hair) roots exposed to anaerobic conditions succumb quickly, so even if you don't actually SEE the stress soils with perched water cause your plants, it is there. As young roots die from lack of air, the plant has to devote either stored energy or current photosynthate to replacing lost roots. This is the price we pay for using heavy soils - especially in shallow pots. A soil that supports only a 2" perched water table (PWT) will remain 2/3 airless and saturated in any 3" deep pot ...... which is why you're asking questions about appropriate soils.

    Going back now to how to create a soil that holds lots of air AND lots of water. What if we try a different strategy - different than using soil particulates so small they hold too much water between particles and support a PWT? Let's try to build a soil with LARGE particles, so it holds lots of air, but let's use porous materials, so they hold water INSIDE of the particles. If we could do THAT, we could build a soil that holds lots of water, but has no saturated layer of soil at the bottom of the pot. That would solve the issue of water retention and aeration, while at the same time avoiding a PWT.

    I won't go into a lot more detail about particle size, but you can read more about it here. I'll just say that at at a little under a particle size of about 1/8", the PWT disappears entirely.

    I combine 3 ingredients, in equal parts (by volume), to make my basic soils. You might be able to find ingredients that do the same thing, but these are worth looking for, and I might be able to help guide you to a source, depending on where you live. I use screened pine or fir bark, screened Turface, and crushed granite. The Turface is the workhorse. It's clay, baked at high temps until it's ceramic-like. It has excellent internal porosity, and with 14 acres of surface area per pound, an excellent CEC (holds nutrients well). The crushed granite holds water only on its surface, and the bark acts as a filler material, having approximately the same water retention as the average between the Turface and granite, so it compliments the other ingredients well.

    One of the key issues here, is that this soil is adjustable for water retention. You can increase the amount of Turface and decrease the amount of granite, while still limiting the bark's presence to under 1/3 of the o/a volume, which will increase water retention, or decrease the Turface and increase the granite to decrease water retention. It's very difficult to find fault with a soil that resolves the water retention/aeration issue; or to point out that different growing areas require different soils. It simply needs a variation in how you combine the ingredients to cover an extremely wide range of applications, from very cool/wet to hot/dry.

    {{gwi:1295}}

    Al

Sponsored
Hoppy Design & Build
Average rating: 5 out of 5 stars9 Reviews
Northern VA Award-Winning Deck ,Patio, & Landscape Design Build Firm