Terrariums

Terrariums are miniature worlds combining the beauty of light through glass, living plants, and objects which are pleasing to the eye. For those of us who remember the terrariums of the 1960s and 1970s which were meant to be closed and self-sustaining (and therefore often damp and mildewy, with condensation blocking one's view of their interiors), the 'new terrarium' trend comes as a welcome innovation. My initial inspiration for the simple terrariums shown here was the excellent book Terrarium Craft: Create 50 Magical, Miniature Worlds, but many other examples of new terrarium ideas can be seen by googling photos on the Internet. The book Terrarium Craft gives more attention to the creative and decorative possibilities of terrariums than it does to their sustainability, but if one is willing to create simpler terrariums, longevity should not necessarily be a problem if one selects the right plants and gives them the right amount of water and light. Glass vases should be of clear (not colored) and not-too-thick glass to let in sufficient light and avoid excessive glare. Decorative objects can include rocks and seashells picked up from the beach, small ceramic or stone figures, or anything else that will not disintegrate after long exposure to water.

For the terrariums below, I used succulents (Finnish: mehikasvi) and glass vases purchased from Finland's largest nursery center, Viherlandia. Brief experience has already shown that roundish succulents with a rosette-like structure such as Aeonium, Sempervivum, Echeveria and even Aloe are harder to keep beautiful in terrariums than succulents with stem-like or rock-like structures such as Crassula, Pleiospilos, and Sedum because when they get too dry, the rosette-shaped succulents can start to lose their bottom leaves even before one notices it, and this detracts from their appearance. Succulents with stems tend to not lose any leaves right away, they just start to look droopy or their leaves look 'thinner', which gives you time to react and give them more water.

Succulents (and almost all other plants) don't like for their roots to sit in water, and so drainage is important. Put at least 3–4 cm (1–1.5 inches) of rocks, gravel, shells, or small broken pieces of ceramic pots at the bottom of the terrarium before adding the soil. Soil for succulents should have a some sand in it. I've mixed potting mix specifically for cacti with ordinary potting mix (which has less sand and more organic matter) because I've noticed that the soil in small terrarium containers can dry out fairly quickly, and the higher the sand content, the more quickly it will dry out.  If you want to have layers of substrate (i.e. stones, shells, sand, gravel, pebbles, etc.) which are visibly separate from the soil above them, make sure you put a layer of small bits of drainage medium like perlite (Finnish: kevytsora) as a filter in between your soil and the substrate (stones, sand or shells) below it, because otherwise the soil will just wash into your stones, shells or sand and they will turn a dark brown when you water your plant. Or at least the filter idea should work in theory. My filter of perlite seems to work so far, but over the long run the soil above may end up trickling down through the perlite into my substrate.

Update (October 2013): For many succulents, glass containers just won't work and they need unglazed clay pots (which 'breathe' so that moisture can leave them more quickly). Please see 'Succulents' post. 

In this photo, you can see the perlite (dark brown pebbles) layered between the soil and the white decorative stones.

This terrarium combines a small Crassula ovata (Finnish: rahapuu) with natural black and white stones from Shelter Cove, California.

Update (October 2013): This Crassula is still growing happily in this container.

A terrarium containing Sedum spathulifolium, Crassula perforata (the long one trailing out the mouth of the terrarium), and two unidentified Sempervivum-like succulents (the grey one possibly Echeveria?), plus two halves of a geode and a mussel shell.

Update (October 2013): This terrarium didn't make it. There was not enough air circulation for the amount of moisture needed for the plants, and fungus set in, rotting all the plants. I was able to save leaves from the grey Echeveria, and have successfully started ten new plants from them (see post Succulents, caudiciforms and air plants part 2).

Split-rock succulents (Pleiospilus nellii) scattered among real stones.

Update (October 2013): Nothing much has happened with these. I water them about once every 3 weeks .  

A close-up of Pleiospilus nellii showing the 'baby' leaves growing inside the 'parent' leaves. The baby leaves slowly drain water from the outside parent leaves, which then wither away into brown crusts. During this phase of their growth, the plants do not need water. So far, I have not watered these for three months and they seem perfectly happy. I have read that watering will only cause them to rot. They do need water in spring when flowering, apparently. 

A Sedum growing in soil above a substrate of perlite (kevytsora, the brown pebbles at the bottom) and round pumice stones found on a beach in the Azores.

A small Crassula 'Gollum' with split-rock succulents (Pleiospilus nellii). This terrarium posed a practical challenge: how to plant the Crassula and the Pleiospilus together, when the first needs water but the second should remain dry? After first putting in the perlite, I planted the Pleiospilus in a very small plastic pot, placed the pot carefully inside the terrarium, and then filled the rest of the glass vase around the pot with soil, into which I planted the Crassula. I carefully added a bit of soil to just barely cover the rim of the small plastic pot, which needs to be almost level with the soil so that water given to the Crassula cannot find its way to the Pleiospilus roots. Water is given to the Crassula through a syringe (like the kind used to give medicine to small children) so that it stays on the Crassula's side of the terrarium.

Update (October 2013): I had to replant these, since the Crassula 'Gollum' grew so fast that it outgrew the terrarium in no time. Crassulas like this are supposed to be prone to root rot, but I kept mine for nearly 3 months in glass containers with no drainage with no problem. It did get infested with mealy bugs, and is now in a clay pot.

This terrarium with a small Aloe and Sedum was planted by my 8-year-old daughter. The green color in the middle of the container is moss which started to grow after the terrarium was planted, but it just adds a nice splash of color, in my opinion.

Update (October 2013): This one is still growing happily.