In bonsai, we spend so much time in the design. We sculpture our branches and the pads to look beautiful. The tree is our art piece, we make it look the best we can and top dressing helps us achieve that along with aiding in fine root growth at the soil surface.
Without top dressing, when you water your bonsai, the top layer of soil has the potential to shift. This movement will disturb, disrupt, or inhibit root growth in the upper 1/3 of the bonsai pot. We need to utilize the whole container in bonsai.
Topdressing helps slow the evaporation of water from the top of our soil from the sun and wind. The soil stays more moist but more importantly, it stays evenly moist throughout the container. This allows for more even root growth throughout the pot as there is a balance of water and oxygen.
Creating Bonsai Top Dressing
When creating top dressing for your bonsai, you will want to gather all of your supplies before you get started.
You will want to wear a face mask of some sort. When you shred and sift the sphagnum and green moss there is a lot of dust created and you do not want to breathe that in.
The sphagnum moss I like to use is the Spagmoss by Besgrow. It is from New Zealand, it’s inexpensive, and it’s high quality.
Using your soil sifter and the largest screen, you want to take a nice handful of sphagnum moss and grate it over your screen. I do this over a 5-gallon bucket.
Now that you have some shredded sphagnum moss, it is time to sift it. I use my smallest screen for this. You could also use the middle screen if you want. I sift over another 5-gallon bucket. You will take some shredded moss out of your bucket and place it on your screen. Then shake your sifter to remove all of the fines.
Now that you have sifted out the fines from your shredded sphagnum moss, you will now want to dye it a darker color. This is more for aesthetics. Please wear gloves while doing this part. If not you will dye your hands black for a few days.
Take a 5-gallon bucket and put 1 or 2 gallons of water in it. Take your black Sumi Ink and add a bunch to your water. If you are using a squirting style like I am, add in a full squirt or two to start.
Add in some of your sifted sphagnum moss to saturate it. Take it out and squeeze out the water. If you like the color then add more moss and saturate it. I ended up using 4 squirts of ink.
Once you have dyed all of your sphagnum moss you will want to place it on some flat surface to dry. I used a plastic repotting tray. Some use plastic tub covers. Anyway you do it, it needs to dry.
While the Sphagnum moss is drying go ahead and shred and sift your green moss. I do this the same way as I do the sphagnum moss.
After the sphagnum moss is dried you can mix the shredded green moss in with the dryer sphagnum moss. Some people keep these separate and mix only when using. This allows you to custom mix the amount of green moss.
When mixing the two mosses you want a 50-50 ratio.
With the sphagnum and green moss mixed you can go ahead and sprinkle a thin layer over the top of your soil surface. Sprits the top dressing with water and take your tree outside and water thoroughly. You now have a great place for that green moss to grow and expand. As the green moss continues to grow your soil will soon enough be covered in green moss.