Updated: Jan 7
When starting out in Bonsai at least for me Moss was an important part to the aesthetic of my trees, it made me feel like i had real bonsai, But the more i researched bonsai the more divide i seen between those who use moss and those who don't, so what have i learnt all these years later? lets take a look.
Before i begin i just want to apologise for the few days of delay of this article, i recently tested positive for C-19 and although it didn't really affect me much besides 1 day of hot and cold sweats i still though it was a good idea to just take it easy.
Now lets have a chat about Moss for Bonsai
There is no doubt that adding moss to the surface of your pots can add an extra level of pleasing aesthetic design but there is a few horticultural points that come along with adding a layer of moss to your pots as well. Like anything in Bonsai there is both good situations to add moss and bad situations to add moss but hopefully if we can talk about these points in detail a little bit today you will be able to make that decision for yourself depending on your trees and your environment and also you'll be able to see through the blankets answers you see to this question on the internet, You might even be able to teach somebody something.
So first of all with aesthetics out of the way lets talk about why its beneficial to add a layer of moss to your bonsai pots as a horticultural practise. Think of moss like a protective blanket for your soil surface, Moss can act as an insulator and a filter at the same time. So in the hotter months having that layering of moss can help keep the moisture inside the pot longer by preventing the soils surface from evaporating rapidly. The moss will provide protection from the wind and also the direct sun which are the 2 biggest factors from drying out your soil surface. Moss can also act as a filter for your water which is useful for town water that is fairly hard, Now this isn't a solution to hard water but it will certainly lessen the affect the hard water will have on your root ball then say if you didn't have the moss. One of the biggest bonuses you will get from that protective layer of moss though is the fact that roots will be encouraged to grow closer to the surface. Without some kind of beneficial top dressing ( not pebbles and stones ) the soils surface gets too much light exposure and air exposure for roots to grow, By covering that surface layer with moss you have now completely taken away the light and drastically reduced the amount of oxygen in the surface layer which will encourage the roots no now grow in that area. The reason this is important is because in a small growing environment like a bonsai pot we need to make use of every last mm we can squeeze our root ball into, We want that small pot but we still also understand that the more root ball the tree has the stronger it is at fighting pests and disease naturally and it will also have more hydrating abilities. So being able to make use of an extra inch of soil is a big win.
Now I'm calling this section the bad but the moss itself is not bad, but improper use of it can be. Maybe you've already figured out what I'm going to say just by the information above. If we take the idea that Moss creates a protective layer of the soil surface how can this become bad for someone who is in experienced? Well there is a few ways, Lets just way you are putting moss on the soil surface of a Bonsai that's potted in Organic soil, You have big amounts of water holding capabilities that are already a problem and now you are covering the surface slowing down that drying time, With in organic soils this is a good thing through the hotter months and not really here nor there in cooler weather, But with organics this can just fuel the root rot fire.
Also there is an issue during windy days or warmer weather where people tend to water for the moss and not for the tree, meaning that they see the moss drying out and take that as a sign that the tree is drying out and needs to be watered again. This can cause a person to over water their trees constantly. If your moss is drying out you need to mist it with a spray bottle rather then actually watering the tree. Once you have moss on your tree you need a pretty good idea on how to water your trees properly especially if you have your entire surface covered in moss and cant see if it is wet or dry.
You also need to watch out for moss starting to cover your nebari or work its way up your trunk, Moss tends to keep wood wet and causes rot, so make sure that you only have it on the soil surface and not on any woody part of the tree. If you need to get it off the trunk or nebari you can put some vinegar on it and leave it for a day, it will dry up and drop off.
What Moss Should I Use For Bonsai?
Most people will go out and collect their own moss which is great and is a fantastic way to get it, but there are some things you should do which will make your moss practise a lot more successful.
Always collect moss from a similar environment to where your tree lives. If you are away on holidays and come across a gold mine of moss it might not be worth collecting if that holiday location is a long distance away from where your trees live and the environments are completely different, say you live in an arid area and your collecting moss from a wetland where the moss is constantly shaded and damp. If you take that moss home and put it out in the hot arid weather chances are it will die pretty quickly. So check your local areas and try to collect moss that gets a good amount of sun exposure.
Once your moss is collected try to avoid just bringing it home and dumping it on your soil surface as it is. The moss will likely have dirt or sand stuck to the bottom of it which will work its way into your soil system and potentially cause issues. You will want to re cultivate the moss you have collected before use. You are probably thinking back to the time when you seen a professional moss a tree using big slabs of moss and seemingly doing what i just told you not to do, But you will find that is actually moss they have re cultivated in a tray ready for future use. They would have grown it on a thin layer of either organic matter or fine bonsai medium particles.
So How Do You Re Cultivate Your Moss?
You will first want to let your collected moss completely dry out so leave it out on your benches or somewhere that it can dry out completely. Once it has dried you will want to use a medium to large screen in your sieve and slowly work off the layer of dirt or sand that will be stuck to the bottom of the moss, stop when you are almost to the actual moss it self leaving a thin layer. Once that it all done you can now use a medium size screen to grate your dried moss up into a bucket dirt and all. Once you have it all ground up no you will have to get your smallest screen on your sieve and sift out the dirt from the moss, obviously this will require a screen that is large enough to let dirt particles through but small enough to stop your moss from falling through. After you have done that you should now be left with your moss all dry and ground up into smaller particles. Store it somewhere safe out of any gentle breeze, trust me it only takes the slightest breeze for it too all blow away.
Next you will want to get some sphagnum moss and grab some big hand fulls of it and grate it through your medium screen as well. you will want to grate up an equal amount to the moss you have. Once you have done that you can mix the 2 together at a 1:1 ratio. At this point you have 2 options, you can apply this mix directly to the soil surface of your trees which will grow a very natural looking layer of moss on your soil surface, but be aware as you are applying it spray with a misting bottle at the same time because even if there is no breeze present there will be as soon as you pull that mix out of the bag and if it is dry it will end up in the neighbours yard. You will also need to keep it moist for the next few weeks until it begins to natural adhere to the surface. Your second option is you can spread a fine layer of soil in a seed raising tray and spread your mix evenly. This will grow a tray of moss which you can use to cover your trees for shows or have some already cultivated for when ever you need to cover a trees soil surface.
Like Most things in Bonsai there is a way that will be correct for most people and a way that will be incorrect for others, everything is circumstantial but hopefully now you can at least make your own decisions on what is the wrong and right situations for putting moss on Bonsai Trees.
Until Next Time, Enjoy Your Bonsai Journey