I am going to say it right away so that you can’t miss it. Fertilize now. Like, right now. Stop reading and go do it! Seriously, early fall is the best and most important time to fertilize all of your bonsai. The only trees that you would not fertilize right now are those that are sick. Your best bet there is spot on watering. Health aside, our trees are now entering a phase of vascular growth in which they bulk up the trunk and branch tissue by adding that thicker, light colored ring that you see in a cross section. Spring growth is elongating and making solar collectors (leaves) and fall is about bulking up and storing sugars for winter hardiness and next spring’s growth.

That also means that this is the time of year that wire can really start to bite in. My fall initiative is to be disciplined and not design any new trees until I have checked, removed, and/or replaced the wire on all trees that I have styled. Ooh that’s tough to swallow, but I gotta do it. No sense in ruining my hard work.

But I digress. I have often said that the bonsai cycle starts in the fall, and fertilizing is a firm foundation. We covered fertilizing quite a bit back in April of this year with a handy reference sheet. This time I want to talk more about how we apply fertilizer.

I have been working on some casual experiments for a couple of years, trying many different methods for fertilizer application. Though these are not as scientific as I would like, they may give you some ideas on how to treat your own trees. My purpose here is not really to talk about the fertilizer itself, or schedule, amounts, etc… We did that in April. I will say that I have been using some Bio-Gold, mostly Portland Rose Society Fertilizer (RSF), and some of my own - homemade poo balls. I am tending to migrate to the two premade types, just so I don’t have to keep all the separate ingredients around. I had 50-pound bags of fish meal still around after 10 years and that is enough. So, my last custom batch I just threw everything in, emptying out 4-5 bags and mixing it up. Fish meal, bat guano, bone meal, blood meal, cottonseed meal, etc. It is all low level organic, so precision is not really a factor.

First off, I am going to look at are tea bags and the like. The reason we use tea bags is that most of the organic fertilizer that we can get our hands on is dry and granular. If we just put it on top of the soil, even in a pelletized form, it disintegrates, spreads out, and clogs up our nice bonsai soil. Now this is going to happen to some degree no matter what you do with an organic. By the winter it turns into a slimy black goo. Not the best scenario, but we can control it to some degree.

One option is to use something to contain the particles from slipping too quickly into the soil. And wouldn’t you know it, tea bags are designed just for that task. There is only one catch. The fertilizer has to be broken down by microorganisms before the tree can utilize the nutrients. It’s possible that the tea bags can block the microbes from gaining access to the fertilizer. So, we may be stuck in between. This is where I had wished I could be more scientific in my experiments.

I have tried several different types of tea bags and it is really hard to tell how much each has affected the success of fertilizing. In photo 1 you can see several types. The common drawstring type, a fold over, and a sachet bag. Some tea bag materials are made of paper, but some seem to be of a spun polyester or something, with holes stamped in. What you want is something that either has existing holes small enough to hold the fertilizer in, yet larger enough to let the minerals leach through, or let the microbes through. Or something flimsy enough like paper that it breaks down very quickly to let things pass through. This is one case where you might actually want the cheapest, low quality solution.

Synthetic Drawstring Tea Bag, Folding Tea Bag, Sachet Bag

Tablespoon for filling and bin of bags ready for placement.

The good news is that you don’t really need a microscope to see what is going on. If the system is working and the microbes are breaking down the fertilizer, then it simply disappears. Your evidence is the fact that it is gone. This works really well and is very obvious with a large pellet like Bio Gold, which does not just disintegrate with water but dissolves over time. To tell the truth, I don’t get to see the fertilizer simply disappearing enough with my trees. Still working on that balance of water and oxygen.

Another option that Boon put me onto a few years ago are sachet bags, or wedding gift bags, whatever you might call them. They are incredibly cheap and I get them on the internet, though my first attempt fizzled out and I lost my $25. I got black because I thought they would look a lot better. Though I have to say, all fertilizer methods bring curious looks and questions from visitors to the garden. I thought that I might reuse the sachet bags but gave up on that gooey mess. My initial thoughts are that they work just as well or better than the tea bags with their larger openings. I use them exactly as tea bags. What is so great about a bag is that you can nail it to the side of rock plantings, at funny angles, etc…, so they will always have a use.

The poo ball method works very much like Bio Gold. After I mix up a batch nice and wet, I let is sit for a day so that it starts to bind together and then I just use a scoop to place a fresh, wet ball in several locations on the soil. I do this right after watering so that it has a few hours or day to set up and it is just fine after that. They hold their shape. No need to pre-dry in the sun. In fact, you don’t really want them dry. As Andrew Robson mentioned in his recent talk, we really want that fertilizer to stay wet and active.

Bucket of homemade Poo ready for placement.

That brings me to my next method, with plastic cups. There are a lot of different forms here and I think I can be a bit more definitive on what works. I had already started to use some cups with my small quantity of Bio Gold to help keep it in place and away from the birds. But Greg Brenden really gave the idea that supercharged the use of RSF. He talked about it, so I am just picturing it here and giving my own twist. I use the cups that are designed to be inverted.

The problem with the Bio Gold is that I had to invert them really quickly or spill the pellets. The problem solved is to set out a whole tray of cups and then fill them ¾ full of RSF, or any other organics. Only partially full because as you water them, they swell. So now that you have them filled, water them several times and let them soak for a few days. I slid mine inside a plastic garbage bag to hold the smell and heat.

The watering does two things. It activates the fertilizer – you can see in the photo that they were already producing mold before I applied them, and the swelling pellets and granules coagulate together to hold firmly in the cup and make application much easier. No mess or waste, and it is preactivated.

There are two sizes and I use the smaller ones for shohin. My little twist is hold them down with nails. The tabs provided are not enough to deter birds and squirrels I use a 6 D, 2inch plain box nail. 6 D or 6 penny is the diameter, which barely fits through the holes, but is the smallest size to get that 2 inches I need to hold it down. I’ve found the nail 100 percent effective with established soils.

In newly planted trees, the little buggers simply dig around the fertilizer cups, so I am still working on a solution for those. I also use nails to hold down tea bags. For those, I use the 4D, 1.5-inch size, since I can push those right to the soil level. This makes the bags very easy to remove.

Large and small cups filled and starting to mold

Critters dug soil around cup but it stays in place

There are other plastic holders which I have pictured. The one is very similar to the inverted cups. It has a spike on the bottom and lid on top. I found that I had to cut half the spike off because I could not penetrate the soil with lava and pumice very far with it. They maybe work OK, because I can drive them right to soil level where there is better contact, but nothing like the inverted cups. The third one looks really cool, but it keeps the fertilizer suspended in the air. I sort of feel like this putting the fertilizer in a pinata and the microbes are swinging at it, just hoping that they get lucky. To be sure, some of the fertilizer washes down. I tried it with Bio Gold, but can’t recommend them over the other methods.

Cup (round 1) Poo Ball (Round 3) Tea Bag (Round 2)

In the last few pictures you can see that I have used all different methods. The inverted cups went on about May. I didn’t have enough to go around, but I did not want to fertilize some trees anyway. The next round was some of the tea bags in July. And lastly the poo balls that went on just a week or two ago. There is no problem mixing methods and it conveniently tells me when I applied it. You can see this in the last photo how fertilizer is spaced out and the last application placed between the first two. Now, go forth and fertilize. See you at the Jamboree.

Scott