Adding Plants to your Terrarium
You may want to consider putting your plants on "quarantine" for a while before you plant them in a terrarium. This observation period allows you to see if the plant might manifest any pests or mold. For more information on how and why to quarantine plants see the post here.
Try to plant your largest plants first by digging a small hole with the bamboo skewer or spoon if you can reach. Plant the largest plant and add more soil if necessary and then work your way down in size.
Have a plant with a big messy rootball? Try gently "coning" the roots by rolling them in a piece of paper. This should form the roots and soil into a narrower shape.
Remember: you can always add more plants to a healthy terrarium later but it is hard to remove them without making a mess and disrupting other plants.
Once you have added plants into the terrarium you'll want to mist down the soil with water (distilled is best). Soil will need to remain damp throughout the life of your terrarium to support your plant growth.
Also think about creating a terrain for your terrarium. You can build little hills or cliffs by piling up the dirt. At the very end you can add decorative elements and I like to put some rocks and bark to create a natural look. Give it a good spritz of distilled water and if it is an open top I like to put some cloth on top to keep out gnats, dust etc. Place it in filtered light and you are good to go!
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