We all know that getting the right soil mix for our bonsai is important, and the idea of encouraging mycorrhiza is our pots has been around for a while. I found an old Bonsai Mart Catalogue the other day from over 20 years ago with many products relating to soil health. Have a look below.

However in recent years a more targeted approach has been sought as our knowledge of soil science has increased. The relationship between roots, soil, mycorrhiza and bacteria has been studied and now is being applied into agriculture and horticulture with exciting results and gives us the ability to reduce the use of chemicals for fertilisation and pest and disease control.

However, transferring this knowledge over to bonsai isn’t as easy as you’d think with our soil mixes being very different from that of open ground and also the containerisation of out trees adding an extra element to deal with. Research has been carried out on many fronts with the most notable being Bonsai Mirai with Ryan striving to push the limits of what we can do with bonsai soil to make our trees healthier. The ‘Compost Tea Experiment ‘ would appear to have its issues with a shotgun approach of giving the trees a myriad of bacteria to chose from but some proving to be detrimental to certain species. In the last Mirai podcast on the subject here was talk of a more targeted approach.

So this leads me to my latest adventure which started in 2019. It’s no surprise to anyone who knows me that I have a close friendship with Peter Warren of Saruyama Bonsai. I have also been working with Michael Guerin and Ray Egan from Counties Limerick and Clare in Ireland and we all have a similar approach to bonsai. Like attracts like in bonsai and we have a good friendship built on trust and trees. Michael has the highest quality bonsai collection in Ireland, and that’s no coincidence. He strives to gain every percentage point he can in making his trees better and I’m delighted to have played a small part in that. Bearing that in mind, he met Dr Karen O’Hanlon a few years ago at a horticultural event in Ireland and after discussing Bonsai and soil health with her, he applied one of her Probio Carbon soil health products to his trees with very positive results. Jump forward to this year and after further discussion between the 5 of us, Dr Karen produced a three strain live bacteria inoculation specifically aimed at improving the soil health of bonsai and increasing resistance to pests and diseases. All this without producing unwanted strong growth. In fact shorter inter-nodal length and production of back buds seem to be one of the outcomes of this three strain product.

If you have read this far, well done. I now want to add a reality check. This is not a miracle product claiming to be the answer to our bonsai dreams. (yes I dream about bonsai 😂 ) We’ve all seen Superthrive type products come and go. Most have been shotgun approaches with a little of everything thrown in hoping something sticks. This product however in intended to be used as a sniper rifle specifically targeting the desired outcomes.

So what’s the product? It’s been named Danú after the Irish Goddess of nature. In Dr Karen’s own words,

“probio Danu Bonsai is a new product developed in 2020 specifically for the Bonsai community. This is a 3 strain mix containing live bacteria chosen for their anti-fungal, induced systemic resistance, siderophore production and plant signalling characteristics. This mix will encourage the trees to build natural plant immunity and will not induce a massive increase in yield.”

If you want to know more details about the product and Karen’s approach to soil health then please watch the two Youtube videos below. Peter Warren interviews Karen live on a stream about the product and indeed speaks to anther bonsai enthusiast who has been working towards improving soil health in bonsai. In the second video, Peter goes a little deeper into how to apply Danù to the trees and discusses its impact on trees live on stream with Michael Guerin.

Still reading? Ok, I’ll outline my personal experiences so far. I treated most of my trees with Danú back in February/March. I applied it via sprayer initially, especially the bigger trees, but followed up by dunking some trees in a strong solution to speed up the population of the rhizosphere with the bacteria. This I feel allows the bacteria to establish a foothold in the pot faster and is a far more economical way to apply.

My trees are in the whole already healthy so when looking for change following application, I wasn’t expecting to see any major swing. Between March and June I saw some positives in the collection and, more importantly, zero negative impact. My Escallonia, normally a slow grow being a very old tree, was looking lush in colour, extending well and even flowered for the first time in 4 years. My 3 Taxus produced tighter foliage than in any previous year under my care with no other variable. A Japanese White Pine on it’s own root stock produced its best flush of growth yet under my care. There was flowering but I think everyone experienced that this year. Satsuki, Hawthorn and Japanese Maples all looked more vibrant.

A larch that was repotted this Spring into Akadama/pumice/lava and was treated with Danú has shown evidence of a massive increase in Mycorrhizal activity with the fungal bloom at the soil surface as seen below and excellent growth. There is extension growth but as the tree is in development this was encouraged with fertiliser and was desirable.

Another positive for me was one of my problematic trees, a Japanese Flowering Apricot. I have street trees outside my home that are Prunus and I always seem to have trouble with fungal issues with all my prunus in the garden as a result. Dr Karen heard about this and suggested a fungal treatment with a spray and dunk of a three strain product she is trialing. This is not identical to Danù but does contain Basillus subtilis a crossover over between the products with anti fungal properties. So much so that Bayer have a product listed as a fungicide containing this bacteria. There were other variables in the treatment with the application of a lime sulphur wash after removal of infected leaves and application of sulphate of iron. Both these had been used previously on this tree.

The tree back in May

After removal of infected leaves

Video showing dunking of tree into Probio Carbon Fungal treatment solution.

Spraying of fungal treatment onto foliage were its left to dry.

Tree now six weeks on from defoliation.

Leaves looking in great condition.

Even back budding onto old wood on trunk!

It’s also worth pointing out that Dr Karen’s strains are all Irish in origin and have been carefully selected from the environment for their strength and robustness. From what I understand this makes them rather unique. More on this product to come in the future I would think.

Lastly, you’ll be glad to hear, is another product from Probio Carbon that I will be using mostly at repotting season. Her Olive Stone bioichar that has been enriched with Bacillus subtillus is a perfect size for added into your potting mixes allowing the bacteria to populate quickly and giving other desirable bacteria a perfect place to attach when introduced via Danú.

To finish I just want to add that I have ‘no dog in the hunt’ regarding this product other than to try and advance the benefits of soil science for bonsai. I do not profit from any sales. My hope is to be able to offer this to those working with me at retail price as per Probio Carbon website without them having to pay postage. All orders outside of that should be done via Dr Karen’s website. Ordering biochar and Danú together also makes financial sense with regards to delivery. Those who give it ago are encouraged to document their finding and share it with us. We are looking at doing a scientific trial to nail down the specifics of what the product is doing in Bonsai soil media but this will take time.

Any queries can be directed to Dr Karen O’Hanlon directly or via Saruyama Bonsai who will shortly have a FAQ page on his website regarding Danú. Please watch the videos first though as this will answer a lot of your questions.

Over to you, time to ‘Book your Danú. 😁