Biostimulants and peonies

In 2022 I received my first tissue-cultured plantlets of peony Mieke Bral and I did a small experiment. I dipped most of the plantlets for a quarter of an hour into a solution of some biological fungicides/insecticides and biostimulants. Strains of bacillus amyloliquefaciens, beauveria bassiana and trichoderma were all in the mix. A few did not receive this treatment as a comparison. They were all planted in the same spot and grown under identical conditions. In 2023 I dug them and took some pictures of plants of somewhat the same size (above ground that is) both treated and untreated. On the left side of the images you have the treated ones (5 plants) whilst the untreated ones (3) are on the right.

After one year of growth what could be seen is that the treated ones had much more numerous small feeder roots they and were in the process of making many more, whilst the treated ones also had those same ‘larger’ rootlets, but were missing many of these fine feeder roots. The number of buds was also slightly different, at least when grading the buds into larger ‘primary’ buds and smaller ‘secondary buds’. I couldn’t see much difference in number of primary buds, usually two in these smaller plants. But there was a large difference in small additional secondary buds with the untreated ones having only a very few at most whereas the treated ones did have a lot of them. This would indicate that the difference will only increase in the coming years.

The encouraging results from that small experiment made me more interested in biostimulants. Biostimulants being products that improve nutrient uptake and enhance tolerance to abiotic stress (drought, salinity, moisture…), thereby improving crop quality. Remark that there is a fine line between biostimulants and biopesticides. Biostimulants don’t claim to have a direct effect against a disease or pest and therefore the legal registration process is far easier because companies merely have to say what the product does and don’t have to explain how it does this. In the real world however it is an open secret that some biostimulants can also be used as a biopesticide, but the label on the products cannot mention this. Some growers of course only buy those biostimulants because they know it can also protect their crops from some diseases or pests.

An enormous amount of claims and publications can be found when it comes to biostimulants. We’ve trialled a few and to be honest, most of them didn’t make much difference. Of course it is said that the benign effects of biostimulants show themselves mostly in malign circumstances and those are the ones that you try to avoid anyway. In trials at research stations the same problems arise: very often no difference at all, only sometimes under very specific conditions. A few years ago I took part in a discussion of research into biostimulants with several European institutes presenting their trials (stations in the UK, France, Netherlands and Belgium). Experiment after experiment the same: no noticeable difference between treated and untreated plants, only in a very rare case under very rare circumstances. In my opinion more a coincidence than hard evidence. As it happens nearly all research was about seaweed extracts. There’s much more than only those biostimulants however and upon inquiring about this it turned out that seaweed extracts producing companies were the main sponsors of all the research. I lost all faith in seaweed extracts that day… A good thing that the researchers at least were honest enough to say the results were rather disappointing. Every reader is free to try and decide for himself of course, but this grower will steer clear from this category of biostimulants.

A month ago there was another discussion about biostimulants. This time it was more general with, amongst other themes, an overview of what kinds of biostimulants exist and worldwide research into it, the program of it can be found at the end of this article. For growers that are somewhat overwhelmed with all the products that are advised to improve your plants’ health, it’s very clarifying and can help you in deciding whether or not to invest in them. I found it very interesting and I’ll gladly give a short summary of the most interesting part with some comments from personal experience and some remarks by the researchers. For more details you can listen to the presentatior or have a look at the slides themselves with lots of active ingredients and commercial products.

The full presentation of the biostimulants overview can be downloaded here.

There are six major groups of biostimulants which are commercially available and which you could thus apply to your peonies.

1. Humic and fulvic acids
2. Seaweed and plant extracts
3. Protein hydrolysates
4. Chitosan
5. Inorganic compounds
6. Microbials

Humic and fulvic acids are the results of degrading composts. Humic acids are more difficult to dissolve because they consist of larger molecules and they only work in an alkaline environment. Fulvic acids on the other hand are smaller, dissolve easier and are thus more readily available for your plants. Besides that those fulvic acids work both in acid and alkaline soils. Thus the conclusion is clear when reading the label on those products: look for the contents of the fulvic acids in it… I personally have never seen any positive result from this when tried and the local research station came to the same conclusion. However they tried humic acids with rhododendrons, which tend to grow in acid soils, thus there’s room for a better experiment. If you want to try it: it should improve both drought stress and salt tolerance.

Seaweed and plant extracts I’ve already mentioned… A staggering number of commercial products are available in this category, mostly from seaweeds, but also some from plant extracts like willow bark. Field trials tend to come up with mostly disappointing results however. Same here from personal experience.

Protein hydrolysates, these are mostly amino acids and peptides. Again a very large choice of products is available, some from animals, others from plants, some extracted chemically, others enzymatically. Companies produce them from (byproducts of) blood, fish, chicken, vegetables and so on. Each product is different, so if one works it doesn’t mean another with ‘more or less’ the same ingredients will work just as well. But it doesn’t really matter much in fact: most trial results come up with the same conclusion and that is “no difference with the untreated control plants”.

Chitosan, which is found in the outer skeleton of shellfish. Now this is a more interesting group because it is known to be anti-pathogenic, thus a biopesticide as well, although officially not claimed this way usually. It is however also rather difficult to prove any beneficial effects and is rather expensive. We have no personal experience here, so it may be worth a trial perhaps. But there are others that are probably more worthwhile testing…

Inorganic compounds. Those have some ‘beneficial’ chemical element, like Cobalt, Selenium, Aluminium and so on… Here are some that are supposedly quite good. Two stand out amongst the flock, and both come with a warning if you don’t want to be fooled. The first being silicon which results in a better uptake of calcium and potassium (=kalium). Now that warning which was mentioned: it is mostly sold as SiO2, yet this one has poor solubility and therefore is mostly wasted. What is needed is orthosilic acid of which the formula is H4SiO4, so it’s important to have a close look at the label accompanying the product. The second compound which is known to have beneficial effects are phosphonates. Yet another warning here: phosphonates are not the same as phosphates. The former are biostimulants whilst the latter are mere fertilizers. It also to be noted that phosphonates are also sold as biopesticides (Potassium phosphonate for example is being used against botrytis).

Bacteria and beneficial fungi. This is the group of biostimulants where growers have most faith in (there was a live survey amongst the growers during the presentation). It is also the group where I personally have seen good results as mentioned already. From personal communication it also the group where some of the researchers have seen the best results in field trials. So if you’re thinking about splashing some money on biostimulants and you’d also like to see some return from your investments, this is probably the best place to start. There are some bacteria that are able to increase nitrogen uptake for example. A better known one here is methylobacterium (sold als BlueN or Utrisha for example) which is sprayed on the foliage of the plants after which this bacterium takes up nitrogen from the air, making it available for your plants. A big advantage of this is that you only have to spray it once in the beginning of the growing season after which it works for the remainder of the season. It has been remarked that a big obstacle to using many of the biostimulants is the fact to you have to apply them at regular short intervals, which takes a lot of work and discipline, so a product not needing this clearly has the edge over many others.

Nitrogen-fixing bacteria

Then there are also Arbuscular Mycorrhizal Fungi (AMF). Funneliformis mosseae (formerly glomus mosseae) is for example one that tends to give good results as you can see from the next image showing intersectional hybrids from tissue culture after the same growing period. Trichoderma strains are some others giving good results. Together with some bacteria that also suppress diseases (thus in fact again a biopesticide/fungicide), bacillus amyloliquefaciens for example, you can get good results. These three fungi/bacteria are in my opinion currently the best way to apply biostimulants to your peonies. They can be applied as a dip before planting them and from my observations they are worth their money. Both other growers and researchers tend to agree here. My own results shown above where from trichoderma and bacillus amyloliquefaciens (beauveria bassiana is a fungus that merely kills pests, so not really a biostimulant). The images from Don Smith below made want to try AMF as well. We have no results with peonies from this so far but if we do we’ll add them here as an update somewhere in the future. We did note however that they are not always easy to obtain, AMF themselves are not difficult, but if you really want the funneliformis mosseae in them, the range of products decreases somewhat. Then there were some which simply didn’t dissolve in water and were unusable in a dip before planting so we had to disperse them into the soil directly. Others that you could dissolve took months and months before they could be delivered. Some have only a short shelf life after which they are useless and still others need to be kept in cold storage to remain viable. So it’s fair to say that it’s not as easy as regular chemicals. But given the decreasing availability of regular chemicals and the trend towards more sustainable farming, it’s a road which cannot be ignored.

From: Smith, Don. “A Basic Review of the Propagation of Semi-woody and Woody Peonies in the Modern Era”, 2021.

To conclude a referral to a website, bio4safe, listing all scientific and (decent) commercial research on biostimulants (no biopesticides!). You can search for the main groups or active ingredients or crops (alas, no peonies) and see what results have been obtained with them. Only for crops begin grown in Europe (thus the temperate zone, no tropicals). There are some 290 scientific publication and trial reports in the database with some 907 unique entries, 250 biostimulant products and 130 different crops. It is very, very important to note that products are usually available in only one country and do change a lot in composition so nobody really has a good overview off all that are on the market. Thus it is best to only take into account the active ingredients and look for that one in a product that is available in your region.
The database is at https://bio4safe.eu/

Unrelated to this webinar at the University of Wageningen in The Netherlands some researchers have also compiled an overview of biostimulants and their workings. It includes at the end an overview of scientific papers with short results as well. It is a good and readable introduction (a summary in dutch is present in it, but the main part is english, just scroll further through it). It may be downloaded here.

All comments from your own trials and experiences (with peonies?) are more than welcome as it is still largely uncharted territory.

The webinar can be viewed online as it was recorded. It’s in english, which makes it accessible to a lot of people.
This was the program, you can thus easily skip towards the part you’re most interested in:
1. Insights in the new legislation EU2019/1009 – Patrick Dujardin (Gembloux Université)
2. Who is EBIC (European Biostimulants Industry Council), what they do and their key issues & biostimulant market situation – David Barton (Prospero & Partners – member of NIAB)
3. Unraveling the biostimulant mode of action – Ali Siah (Junia)
4. Biostimulants unveiled: a diversity of types – Els Pauwels (Viaverda)
5. ebicBio4safe: free on-line database on biostimulant research for growers, agronomists and researchers alike – Matevz Papp-Rupar (NIAB)