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Bonsai Soil Tests: Part 1: Water Retention

Welcome to Appalachian Bonsai. This video is one of a series to discuss soil components and some of their properties as they pertain to bonsai. These components are what we’re available to me at this particular time. What’s available to you may vary by region or by country. When it comes to bonsai soil no two person’s soil mixtures are alike. Each soil mixture depends upon the species, the climate, and the person who’s using them. I hope that just seeing these components in testing will allow you to make choices for your own.

Thanks for watching. Today, we’re going to look at water retention and a little bit on drainage. All plants need water so let’s see how much water these components hold. Both organic and inorganic materials were considered. Just because something holds moisture doesn’t make it good. Conversely, just because it might not absorb moisture doesn’t make it bad. I began by measuring equal volumes of each component and measured their dry weight for reference. Next, I added distilled water to each type and let it soak for one hour. This should allow plenty of time for each type of soil to fully saturate.

After an hour, the components are removed from the water and allowed to drain. Each is weighed out over time to calculate retention. Let’s see the differences. We’ll begin with organic materials. Coconut coir is commonly used in flower baskets and hydroponics. It is sold in brick form and soaks up water like a sponge. It fills the entire cup. That’s a lot of water! But, all available space is filled, which isn’t necessarily good for bonsai. We’ll will look more on that type of drainage in another video. After draining for an hour and 45 minutes, we weighed each sample. We weighed the samples again 3.5 hours later.

By comparing the different weights, we are able to determine the amount of water retained, and a basic percentage of loss. At 129 grams of water retained, plus minimal loss, Coconut Coir ranks number one in organic material water retention. This is mushroom compost I bought in bags at my local nursery. It is damp at purchase time, so I oven-dried it before I used it. Small twigs and sand may be present, and the content will vary depending on where you purchase.

It drains well and has a slight alkalinity. I’ll do a video on pH at a later date. At 26 grams of water retained and 31.5% lost, Compost comes in at number three with water retention for organic material. Sphagnum moss is found in cooler damper regions of the world and is known to hold moisture very well. However, in the United States commercially available peat moss comes in a fine kiln dry powder.

Unlike fresh sphagnum. In this processed form it does not whet easily, much like baking flour. More information will be available in a future video. You can see it has absorbed very little water, and is actually floating on top. If powdered peat moss in a soil mix is allowed to dry out potential dead zones may occur. If it is saturated, powdered peat moss will hold plenty of moisture, but for this test, it did not perform well. After draining for five and a quarter hour, peat moss only held six grams of water with 40% loss. It ranks number four on the organic list. Pine bark and fir bark are fan favorites in the bonsai world. I have pine bark available in my region.

Here, pine bark chips can be sold as soil conditioner. I sift it to a proper size and put the rest in the garden. Sifted bark drains well and holds good moisture. Beneficial microorganisms like bacteria can thrive in these porous structures. As a quick note, pine bark is on the acidic side. At retaining 22 grams of water at a 14.8% loss, pine bark comes in at number two in organic water retention. Let’s look at the Inorganic materials and aggregates. Akadama is the classic gold standard of Japanese bonsai mixtures. Here in most of the U.S., it is expensive and not readily available. It is often purchased online or at dedicated bonsai nurseries. Its large particle size drains well and its porosity absorbs and retains moisture. Because of the expense and its scarcity outside of Japan, people around the world look for alternatives to akadama. With water retention of 22 grams at a 26.6% loss, Akadama ranks number two overall in inorganic material.

Diatomaceous Earth, or diatomite, is a lightweight fossilized clay that is used as an absorbent in kitty litter and oil dry. This product needs to be sifted well before use. It also compacts and breaks down over time. We will look at that in another video. Like Akadama, it absorbs and retains moisture very well, and in fact, retains more water than akadama. At 37 grams of water retained with 30% loss, Diatomaceous Earth comes in at number one overall ranking, Chicken grit or granite chips is a popular aggregate in soil mixtures. Its popularity stems from its excellent drainage, its inert structure, and it’s pretty cheap. It’s also one of the heaviest components used. The color depends on the quarry, and for the most part is non-porous and absorbs little water. Most of the water retained is merely from surface tension. With only one gram of water retained and a 94.4% loss, Granite chips ranked last in our list of inorganic materials. Expanded shale is becoming more available as a soil component because of its ability to prevent compaction. It has a semi porous structure and can absorb some moisture.

The large particle size I had available to me drains very well. It has a good color, too. Unlike some other expanded materials this one does not break down easily over time. With only two grams of water and 84.6% loss Expanded shale ranks number nine on the inorganic list. Lava-Rock, which is sometimes known as scoria, is a hard yet porous material with excellent drainage. Its large pores absorb some moisture and can house beneficial bacteria. It also has a pretty color which makes it a good choice for top dressing. Similar to expanded shale and granite, it can last a long time without breaking down.

But 4 grams of water at 76% loss, Lava Rock or Scoria ranks number eight overall in inorganic material. Perlite is a type of volcanic glass that is expanded with high heat. It is common in growing mediums here in the U.S. Its porous structure allows it to float. Much like lava rock and granite, most of the water retained is through surface tension. Also like these other components, It does not break down easily over time One of the problems for bonsai is its stark white color. This usually means it’s only used for training trees and not for formal presentations. At 14 grams of water and 36% loss this product ranks number six on our list. Pumice is a less dense, but more porous variety of Lava Rock.

It, like processed perlite, will float. Like nearly all materials that you use in bonsai, you need to make sure that you sift it and wash it well before you use it. It drains well, and it’s similar to Akadama and its ability to hold and retain good moisture. With 22 grams of water retained and only 29% loss, Pumice holds the number three rank for inorganic material. Sand is one of the most available components around the world. It’s also the heaviest of the components that we tested. Small grains of sand can easily block drainage, so it must be sifted well before use. Sand also drains very well, but the majority of the moisture held within it is from surface tension and not from absorption.

With 12 grams of moisture retained in 67.5% loss, Sand ranks number seven on our list. Turface is a type of Lightweight Expanded Clay Aggregate or L.E.C.A. It is one of the most common Bonsai soil mediums used outside of Japan. It readily absorbs moisture, but like all of these components, it does have some drawbacks that will be discussed later in another video. Turface drains well and has a very good color. Though it’s relatively stable, it can break down over time. Turface held 30 grams of water with 36% loss.

This ranks at number 4 on our Inorganic list. Vermiculite is sold in various forms, including this expanded type. It’s most common use in the gardening world is to break up clay soils. Its use in bonsai depends upon the person. Even though it floats along the surface it does absorb moisture without becoming soggy. There is potential for vermiculite’s small size to clog drainage. Because of its 28 grams of retention with 41.6% loss, Vermiculite comes in at number five. Bees. Again, this is not a full list of components used for bonsai soil mixtures, but what we’re available to me at this time.

I have more tests to show you so stick around. Leave a comment in the section below about what types of tests you’d like to see me perform in the future. If you haven’t already, Follow us on Facebook or Instagram Stay tuned… There’s always more to come! Thanks for watching!! .