What is a Terrarium?
A terrarium is any glass enclosure for keeping plants. Plants that require little water and soil, such as cacti and succulents, thrive in terrarium environments. Different glass containers are selected according to the various forms and shapes of the plants. In most cases, cacti and succulents are suitable to be kept in open-terrariums, this is to provide a fresh air circulation.
What is a Cactus?
All cacti belong to the plant family Cactaceae. They store large quantities of water in their leaves, stems or roots, giving them a fleshy character. Cacti grow in drought-prone, nearly arid climates or physiologically dry soil.
The spines (thorns) can absorb moisture in the air to some extent. It hardly loses the absorbed water. The spines perform another important function. They trap moisture and create a moisture layer near the surface of the cactus stem. This helps the plant to reduce transpiration and thus conserve some water. Spines can also protect the plant from herbivores.
Most of the time cacti have a waxy layer on the stems, and possess a very thick cuticle, which is impervious to water. When considering the body shape of the cactus plant it is cylindrical.
The main problem that plants growing in dry and hot environments face is the excessive water loss due to transpiration. An important adaptation shown by cacti and other succulents to overcome this problem is their Crassulacean acid metabolism (CAM). CAM plants open their stomata at night capturing carbon dioxide and close them during the day when it is hot and dry. This reduces transpiration in the plant to a greater extent.
This shape reduces the surface area which receives sunlight. Cacti roots are not deeply rooted. They are close to the surface and are wide spread to collect maximum possible amount of water covering a larger area.
The most important aspect of the mixture is good drainage. The pearlite helps create this by keeping the soil loose and "airy". Gravel and pebbles are good medium for establishing good drainage.
It isn't a bad idea to re-pot these plants every 2 or three years with a fresh mix. The best time to do this is shortly after the plant has finished blooming. This is when it will be ready to start growing again. One might also add some fertilizer to the new mix such as bone-meal and/or Osmocote.
A well drained soil is critical for keeping the water from rotting the roots off the plant. With the proper soil, however, watering is really quite simple.
Method: Succulents require nutrients too. Water the plants with organic liquid fertilizer once a month.
Maintenance. Succulents require little maintenance. To discourage rot, it is best to remove fallen leaves with the tweezer. It is also good to allow the terrarium to receive fresh air from an open window when the weather allows.
This is a good rule of thumb, but there are exceptions. During extended hot, dry periods one may water twice in one week.Conversely, when it is cool and rainy switch to once every other week for outdoor cacti. Indoor plants should have less variation in watering needs.
If the plant is over watered, the stems will also look shriveled, but the soil will be damp. If this is the case, do not give it more water. An over-watered plant will start to turn yellowish, then get more and more mushy and dark reddish-brown like a rotten apple. This is because the cells took in so much water they broke and are now dead and rotting. This usually happens from the ends first. This will continue even after you stop watering too much.
Method: Spray the inside of the terrarium with water from the spray bottle/ squirt water near the roots to moisten the succulent plants lightly. Water the terrarium only when the soil dries out completely to the touch. Keep succulents healthy by erring on the side of underwatering the terrarium rather than overwatering it. If the plants begin turning yellow and drying up, water more frequently.
Check the water level by sticking a finger/ dry tool into the soil. If the soil is very dry, add a little water. If the soil feels moist to the touch, leave the plants alone for another day.
Cacti can survive in a wide range of light conditions. The ideal condition for Jungle Cacti is full morning sun and then shade for the afternoon.
There are three other lighting situations that are not as ideal, but often times necessary due to space constraints. These are morning shade/ full afternoon sun, full shade, and full sun.
Plants can get sunburn just like people do. If one have a plant that has been mostly shaded, don't just stick it out in direct sunlight or one will certainly end up with a badly scared cactus.
In the case of limited natural light, full-spectrum fluorescent lights can be used to supplement or replace sunlight. All cacti and succulents that are not getting enough light will exhibit thin, stretched-out growth.
Method: Place the terrarium in a location that receives indirect sunlight. Provide fresh air circulating inside the terrarium to keep the terrarium environment healthy. If plants begin looking washed out or faded, then they're receiving too much light.
Avoid direct sunlight shining on the terrarium for an extended period because this may cause the interior temperature of the terrarium to rise too high.