Hermetospheres

Experiences with plant life in closed glass containers

About

The purpose

The goal of this weblog is to encourage people to enjoy the miracles of tropical plant life without travelling. If no garden is available and daily duties like watering seem tedious, the hermetosphere (closed terrarium, eternal terrarium) is the perfect choice. It is a miniature, self-sustaining, tropical ecosystem, cheap and easy to realize: start a container and observe what is going on inside. Follow a few simple rules and learn with every attempt. My weblog can help you avoid mistakes and find explanations for your own observations.

The medium

Why a weblog in times of YouTube, Instagram and Tiktok? It doesn’t take much to enjoy a hermetosphere, but it does take time. Hermetospheres are therefore an opportunity to slow down, some call it meditative. Things develop slowly in the container. The slower the better, as we will see. While you wait, you have time to read and get to the bottom of things. Hermetospheres are not science, and science is not required. However, my aim is to use sources of information that are as reliable as possible and to disclose them. The weblog allows me to tell stories that seem remarkable to me about the plants I use.

The history

Wardian cases are said to be the first forms of hermetospheres. They were made from wood and glass and completely transformed botanical science, as they made it possible for the first time to transport live plants across continents by ships around 1830. This led to an immense increase of knowledge about the flora of the tropical regions among European scientists. This context is nicely described and illustrated in an article on Kew. But the consequences were not limited to the world of academia. The Wardian case was also a major economic game changer. It did not only help bringing the Brazilian rubber boom to an end but also the British Empire becoming independent of tea deliveries from China. The Australian curator and historian Luke Keogh published an excellent book about all this in 2020.

The traditions

Self-sufficient ecosystem, bottle garden, nano terrarium, wabi kusa and biOrb represent different forms and traditions of small glass containers where a selection of plants is grown. The special thing about hermetospheres (also called closed terrariums or eternal terrariums) is that they are closed systems* and need hardly any maintenance.

The reasons

What makes hermetospheres so fascinating? Among other things …

A hermetosphere is much more than a terrarium with a lid. I would describe it as the essence of terraristics. To maintain a small piece of tropical plant life in your home for years, all you need is a glass container with a seal, some moist substrate, a few plants and perhaps a few isopods. No expensive and fancy stuff like water pumping, filtering or misting. To quote the marketing slogan of a Swiss brand: Reduce to the max.

Outside of sealed glass containers, even the simplest houseplants have died under my care. Most have withered away; some have probably drowned, starved or been infested by pests. In most cases, I didn’t even understand why the plants died. With the hermetosphere, once it’s set up, there is nothing more to do, so you can’t go wrong. This works for me – not always, but more and more often.

The plants used have their natural habitat in one of the tropical regions around the equator. For someone living in the temperate zones of the northern hemisphere, tropical habitats can be very fascinating. Finding information about my plants means virtually travelling to their countries of origin. These journeys cost little, have no impact on the climate and do not bring any of the disadvantages of mass tourism to the destinations.

Many aspects of our lives are characterised by a fast pace, high frequency and short timeframes. Some people find this unsettling and try to rediscover a sense of slowness. Hermetospheres are ideal for this purpose. It takes weeks or months, or in the best-case scenario even years, for results to become apparent. During this time, there are many small changes to observe, but no action needs to be taken. The less you have to do, the better.

A hermetosphere is the result of careful planning at the outset, followed by a period of waiting and a constant willingness to learn. You have an idea of which plants might work well together. Sometimes it works, and the terrarium remains stable for years. Sometimes it doesn’t, and one plant runs rampant and crowds out all the others. Sometimes a fungus creeps in unnoticed, suddenly spreads and kills the plants. Sometimes a plant appears out of nowhere after a seed has found its way into the jar unnoticed. In this respect, the hermetosphere can be a lesson for life: Good planning is helpful, but it allows only limited control over what happens. What remains are observation, patience, perseverance and learning.

My way

How I got the bug, I described in one of my first entries.

As with most occupations, there is no right and wrong with hermetospheres. Over time, I established my own way of exploring this wonderful world. Here, you find the basic principles that worked best for me so far.

Every new container is an experiment. My ambition is to find set-ups where the initial selection of plants stays in balance for as long as possible, and every plant is able to develop second and third generations with as few interventions as possible.

  • My standard glass container is a 5-liter household preserving jar with swing stopper and rubber gasket seal.
  • The basis of my substrate is lava. It is close to chemically inert, i.e. it releases neither salts nor acidic or alkaline eluents. Every grit size between sand (>0.63 mm) and pebbles (as long as they fit into the opening of the jar) applies.
  • Because lava releases virtually no nutrients, and because I plant my jars sparingly, I add a limited amount of nutrients to my substrate: 1 part of earthworm humus (N:K2O:P2O5 = 1.2:1.2:0.9) is mixed with 5 parts moistened (drained) coco peat, and this mixture is then mixed with 20 parts moistened (drained) lava. The coco peat helps retain moisture and nutrients in the substrate.
  • Following Ulf Soltau’s advice, I start the jars with the amout of moisture that just not produces stagnant water at the bottom of the container. In the event of the occurrence of mold, I slightly reduce the water content by opening the jar for a while and letting the condensed water at the inside of the glass pane evaporate. The water I use is demineralised or distilled (as my tap water contains a lot of calcium carbonate).
  • Where the containers are placed, they do not receive direct sunlight and most likely too little natural light. Therefore, they are additionally illuminated by two LED lights in a 12h rhythm; light intensity varies between 10 and 100 µmol m-2 s-1 depending on the time of day and the position on the shelf. Direct sunlight is avoided at all time; it rapidly heats up the inside and thus damages life.
  • I only combine plants of the same geographic region. For information on the native distribution of a plant species, I rely on the database of the Royal Botanical Gardens Kew. Information provided by dalers is often incomplete or incorrect. This is not only the case for geographical data but also for genus and/or species indications. Before buying a plant, I try to collect as much evidence as possible to be sure it really is the plant I need.
  • Containers are opened for minor adaptions and window-cleaning only. On this occasion, I usually take pictures to document the development.
  • I strive for slow growth of my plants. By using mainly small and slowly growing species, I reduce the risk of one species overgrowing the entire container while others get eliminated.
  • I only use plants that can deal with the specific conditions in my indoor containers: Permanently high relative humidity of up to 95%; small differences between day and night temperatures, around 20°C year-round. So, almost all my plants are native to the humid, tropical low-land regions of Central and South America, Africa or South-East Asia.
  • As far as I know, all plant species I use are cultivated natural forms. Because of a high demand from collectors, a lot of tropical plants are endangered in their natural habitats. Under all circumstances, I try to avoid buying or trading plants that were harvested in nature.

Me

Drawing by beaW

Almost thirty years after my degree in plant physiology and microbiology, the newly discovered passion for hermetospheres led me back to my personal roots.

Herbert Winistoerfer

* Strictly speaking, the hermetosphere is not a closed system either. Besides occasional opening, where gas exchange happens, the system is only closed in terms of materials. In terms of energy, light (radiation energy) enters the system and warmth (thermal energy) leaves the system.