Willem van Riemsdijk (Stinze Stiens)

In the Stinzenplant season of 2019 the theme of the Stinzenflora-monitor is: ‘OndersteBoven van Stinzenflora’. The Dutch expression means something like ‘being flabbergasted’ by stinzenplants.  Literally OndersteBoven means ‘downside up’. So this year the focus will be: what is happening under the soil surface? The idea behind this theme is, among other things, to pay more attention to the soil in which the Stinzenplants grow and the management of that soil in such a way that the soil quality is improved, promoting the growth of the Stinzenplants. The soil in our garden at Stinze Stiens is not too heavy clay soil. This soil is per se not very suitable for a Stinzenplant garden, but it has a lot of potential. By increasing the organic matter content of the soil and stimulating the soil life, a very good soil quality can develop within a few years, which is very suitable for many Stinzenplants.

The role of the soil

There is currently more attention for the role of the soil in agriculture and for the ecosystem. Minister of agriculture Carola Schouten, for example, propagates ‘circular’ agriculture. Another interesting and relatively recent phenomenon is what is called ‘Regenerative Agriculture’. This  form of agriculture can supposedly improve degraded soil by using creative farming methods. Investing in the quality of the soil is one of the pillars of this movement. A particularly inspiring book in this area is ‘Dirt to Soil‘ by Gabe Brown (London [Chelsea Green Publishing], 2018). In English the first meaning of ‘dirt’ is soil, the second is dirt. The verb ‘to soil’ means to make dirty. The title of the book indicates that it is about restoring degraded soil (dirt) to good healthy soil. Gabe Brown describes in the book his experiences and various experiments that he has carried out on his own farm with an area of 3000 hectares.

Another interesting movement is the Permaculture movement. The soil also plays a very important role in this philosophy. It is assumed that the soil should remain covered throughout the year. When we talk about soil, it is about the physical, chemical and biological properties of the soil. It is important to realise that the soil is alive and that there is a whole range of organisms in the soil that interact with that soil, with each other, and with the plants that grow on it. This interplay between soil organisms, such as earthworms, woodlice, bacteria and fungi, like mycorrhizal fungi, is called the soil food web. The food for the organisms living in the soil consists of suitable types of organic matter. Recent dead organic material originating from plants and trees is an important nutrient for the soil organisms and is degraded by the food web while releasing nutrients that the plant needs. The net effect of the input of organic matter into the soil and the degradation of organic matter is the organic matter content of the soil. The food web and the soil organic matter are crucial for a healthy soil of good quality with a good structure. Plant roots not only absorb substances from the soil, but also release organic compounds produced by them to the soil (root exudates). This process stimulates soil life close to the root (the rhizosphere), of which the plant itself also benefits.

What do we learn from this for the Stinzenplantgarden?

As an owner of a Stinzenplantgarden, the question is what we can learn from nature and the above-mentioned developments in agriculture and horticulture for the optimization of our ‘pleasure garden’. Studying the places in nature where different Stinzenplants occur can give some indication to the conditions that certain plants prefer. In Herbal books of the 16th century we can read that Snowflakes grow in dark moist forests and many other species of Stinzenplants grow under hedges and on the edges of agricultural fields. While Crocuses are present in alpine meadows, Snake’s Head Fritillaries occur in floodplains.

In forests and under hedges the soil is little disturbed and the leaf litter remains in the autumn on the soil surface, which is good for a healthy soil life. The soil structure is in such circumstances in general very good. The Bulbous Corydalis thrives, for example, between the roots of bushes and trees. From research we know that in this type of soil environment fungi play a relatively more important role than bacteria.

We also know that many Stinzenplants prefer a calcareous soil. They do not grow well in an acidic soil, that is a soil without lime with a relatively low pH. The pH can be measured quite easily in different ways. We recently purchased a pH meter that can measure the pH directly in the soil and we measured the pH at various locations at Stinze Stiens, Philippusfenne, and Martenastate. This has provided the necessary insight. Usually the measured pH was high enough, above 6.5, but sometimes the soil was more acidic. The soil can be made less acid by adding grit of sea shells as is sold as a source of calcium for chicken. Agricultural lime is not recommended because it works too fast, causing fast breakdown of organic matter releasing nitrogen. Apart from the undesirable lowering of the organic matter content of the soil it may also create problems due to  excessive growth of Nettles and Ground Elder. Later on we will discuss making and applying Bokashi. To a Bokashi heap grit of sea shells are added and Bokashi will thus be beneficial for achieving a soil pH that is suitable for most Stinzenplants.

Soil structure

At Stinze Stiens we have recently observed increased local growth of moss locally. It is striking that this does not occur under bushes and trees, but on the somewhat more open areas of the garden. Moss is often an indication for a low pH, but that is here not the case. Moss can also be found at places where there is a lot of shade, but that is not the case here either. The cause here is almost certain that the soil contains too little air, that is to say it is too dense, in other words the soil structure is not optimal.

A technical solution is to make the soil artificially more open and to remove the moss by means of what is called scarifying. With this operations small holes are made in the soil, so that the air can penetrate better into the soil. At Hackfort this is applied together with the addition of fairly large quantities of leaf compost, which is imported. This works fine.

Until recently, the management at Stinze Stiens consisted of mowing with the removal of the clippings twice a year. We do not remove leaf litter in the fall. The rate of decomposition of the leaf  litter depends on the type of tree where the leaves originate from. Leaves of the Lime tree, Caucasian Wingnut, Hawthorn and Field Maple decompose rather quickly and does not easily form placards. Leaf litter of Sycamore trees degrades a bit slower and can form placards. This may be detrimental to some Stinzenplants such as Winter Aconites that can not sow well in such an environment and also have difficulty getting through these placards. If this seems to be problematic, one can consider collecting these leaves in early January or to spread them over a wider area. If the leaves are removed it is wise to add organic material as food for the soil life. We do remove the leaves from the paths of our garden. This leaf litter is used in other places to cover the soil or we use it to make Bokashi or compost.

Bokashi or Compost?

On the more exposed parts of our garden there is minimal leaf cover in winter. This is partly because fallen leaves are blown away by the wind and partly because there are fewer trees in the direct neighbourhood. So it may well be that the soil life does not function optimally in these exposed areas. This may explain moss formation in these places, because there is not enough input of suitable organic material. In the early years we occasionally imported chopped rapeseed straw and spread it in some places on the soil surface. This supports soil life without adding much inorganic nutrients (it is low in N and P). It seems that at present there is no moss growing in places where there has been a relatively high dosis of this straw in the recent past.

The question is what strategy we may choose to improve the situation. In the summer of last year we decided that we no longer will export excess organic matter that is produced in the garden. We also decided to make Bokashi from this excess organic matter and not compost. At Philippusfenne Bokashi has been produced for the first time at the end of last year and has been applied in their garden at the beginning of this year. We will keep you informed of the effect of the Bokashi on the Stinzenplants if any. 

Last year, the Martenastate Foundation became the owner of a 30-year-old small grove, planted due to land consolidation. It is adjacent to the old park. The grove is transformed into a Stinzenflora-forest. A lot of work has already been done. In areas where the first bulbs have been planted, the soil has been improved by mixing  partly decomposed chopped branches and chopped rapeseed straw through the topsoil. A thin layer of Bokashi has been applied to the soil surface. This Bokashi was produced from grass cuttings from a natural grassland by It Fryske Gea.

The big difference between compost and Bokashi is that oxygen is needed for composting, so the heap should not be dense but have an open structure. When making Bokashi oxygen should be excluded, because it is an anoxic fermentation process. The Bokashi heap is therefore made compact and wrapped into a plastic cover to exclude penetration of air.

Another important difference between the two processes is that there is virtually no decrease in weight or volume as a result of the fermentation process, whereas in composting the volume can decrease by more than half by conversion of part of the organic matter to CO2 and water. With a limited amount of organic material available, you will produce more food for the soil life using Bokashi than using composting. At least that’s the idea.

Another big difference between Bokashi and compost is that with compost you get a nice homogeneous soil like product, while with Bokashi the appearance of the material changes little during the process. Sauerkraut is produced by fermenting finely cut white cabbage and the result is that it still looks like cabbage strings, but it has become much more digestible. The same applies to the fermentation of garden waste. Depending on what is used as source material, for example leaf litter or clippings, a somewhat different type of Bokashi will result. When the Bokashi is applied to the soil surface it will be converted and broken down by the soil life fairly quickly.

Bokashi at Stinze Stiens

Recently two bins of 3 cubic meters each have been constructed to facilitate in making Bokashi. The idea is that in one bin Bokashi is made, which takes around two months and that the other bin serves as a stock for later use. Because the bins were only very recently finished we had a lot of material lying in a heap. In addition, we had a pile of chopped branches  from the autumn prunings. We have put this material in alternating layers in the Bokashi bin, enclosed by thick plastic to keep oxygen out.

For each cubic meter of Bokashi it is advised to use 10 kg of sea shell grit and a liter of a culture of microorganisms that promotes the fermentation. It is also recommended to mix clay minerals through the heap. We have not done this because there is already a sufficient amount of clay in the heap from collected weeds from the flower beds that grow in our clay soil.

What is striking is that the heap of organic material that came from material collected during the summer, had already been composted to a large extent. If the bins had been ready earlier, this might have happened less. Now the material has already decreased in volume. In practice this will always be a problem, unless you can set up the Bokashi in a short period with fresh organic material.

The municipality of Leeuwarden recently made Bokashi from collected leaf litter. This material is collected during  a limited period of time in autumn, and is therefore ideal for making Bokashi. Bokashi of leaf litter is excellent for a Stinzenplanten garden. The question is whether making Bokashi in our situation is a clever idea. Time will tell.

Mowing and clippings

We mow large parts of the garden a few times a year. The intention is to use the clippings to make Bokashi. We started sinus mowing last year, which means that you do not mow everything at once but each time a certain fraction. This is supposedly optimal for the butterflies, because there will always be patches where the vegetation is short, long and in between. However this approach is less ideal for making Bokashi. Because the material is produced during a longer period, a large part will have to remain in the storage for a shorter or longer period, so that it will already be partly composted before it can go into the Bokashi bin. We have set ourselves the goal to recycle all garden waste and to import as little material as possible from outside. The amount of compost or Bokashi that you can make from material produced on site is limited.

In order to stimulate soil life on a larger scale, there are still a number of other possibilities. For example, the height at which one mows is a factor. Recent insight indicates that if the vegetation is mown close to the ground, root growth will be inhibited for a considerable period of time. The plant will produce almost no root exudates during that period, which is a source of nutrients for soil life. When the terrain is being mown higher, this inhibition is less and the soil life can stay more active, which is important for a good soil structure.

Mowing in the autumn close to the soil surface, when the temperature has already dropped below 9 degrees celsius, does no harm. This is because root growth at these low temperatures is already minimal. A short vegetation in the winter is beneficial for possibilities for herbs to germinate. It is also beneficial for the stinzen flora.

Compost tea

A very different method is the use of compost tea. We recently have applied this method at Stinze Stiens and in part two of this blog I will discuss how this can be done and our first experiences with this process. We will also explain the idea behind this method. It is nice to gain experience with these methods and to observe what gives the best result, ideally with a limited input of labor.

We strive to create optimal opportunities for the development of the Stinzenplants and we also strive to obtain a high biodiversity. We hope to learn from these experiments and of course we will learn also from experiences of others. We also hope that these blogs are an inspiration for other gardeners who love Stinzenplants.

• Trefwoorden: Stinzenflora, Tún
• Volgende: Compost tea, ‘high tea’ for soil life in the Stinzenflora garden
• Vorige: The Snowdrops of the Weem in Warffum felt a draught