How to Make a Lovely Closed Terrarium In a Jar

A successful terrarium lasts years

By
Kerry Michaels
Kerry Michaels

Kerry Michaels is a container gardening expert with over 20 years of experience maintaining container gardens in Maine. She specializes in writing and capturing photography for gardening and landscape design for print and broadcast media, including the Discovery Channel, Small Gardens, and Disney, among others.

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Updated on 04/26/24
Reviewed by
Julie Thompson-Adolf
Julie Thompson-Adolf
Reviewed by Julie Thompson-Adolf

Julie Thompson-Adolf is a Master Gardener and author with over 30 years of experience in year-round organic gardening; seed starting, growing heirlooms, and sustainable farming.

Learn more about The Spruce's Review Board
Mason jar terrarium with small plant and rock inside closeup

The Spruce / Adelyn Duchala

Project Overview
  • Working Time: 15 - 30 mins
  • Total Time: 30 mins
  • Yield: One terrarium
  • Skill Level: Beginner
  • Estimated Cost: $20 to $40

A terrarium is a miniature, self-contained indoor garden. Once established, they can last for years and need very little care. They're easy to make with found materials, and, depending on the plants, terrariums are generally inexpensive projects. They thrive on neglect, so even a determined serial plant killer can keep one of these alive.

There are closed jar terrariums and open jar terrariums. Closed jar terrariums maintain moisture very effectively, while open jar terrariums need occasional misting or other methods to provide moisture. There are also differences in the kinds of plants you'd choose for each (drought-tolerant succulents do better in open jar terrariums, for example).

Making a terrarium in a mason jar is easy but requires a little finesse because you are working with a very small planting area. While you can make a standard terrarium by planting them right side up, the look of the upside-down jars is also very appealing. To do this, you use the lid for your planter. 

Read on to find out how to make a terrarium in a jar, so you can proudly display it around your home.

Do Jar Terrariums Need Charcoal?

Activated charcoal isn't necessary in terrariums, though it can be helpful. It absorbs impurities from the air and water when used as the drainage layer of the substrate materials. It can also prevent mold and mildew growth and reduce humidity. However, over time, it may become less effective.

There are some alternatives to charcoal. One option is using moss to absorb odors and excess water. Moss also helps stabilize humidity levels for plants that need it. Another alternative is to use filtered or distilled water instead of tap water to avoid chemicals or impurities that need to be removed.

Another charcoal alternative is using springtails (small wingless insects) or isopods (miniature crustaceans) as terrarium cleaners. Springtails feed on fungus, mold, and decaying matter in your terrarium. Isopods keep a terrarium clean by eating away unwanted materials, fertilizing the soil, and making it soft by tunneling.

What You'll Need

Equipment / Tools

  • Spray bottle or plant mister

Materials

  • Mason jar (or any other jar with a screw-on lid)
  • Small plants
  • Springtails or isopods (optional)
  • Moss (optional)
  • Activated charcoal (optional)
  • Stones, shells, ornamental objects (optional)
  • Raffia ribbon (optional)

Instructions

Materials and tools to create a mason jar terrarium

The Spruce / Adelyn Duchala

Instructions for Making a Simple Jar Terrarium

  1. Clean the Jar

    Wash the jar completely with mild, non-toxic soap and water, especially if it's ever been cleaned with glass cleaner or harsh soap. Then let it air out completely. When making a closed terrarium, it's important to wash the lid thoroughly.

    Mason jar washed on outside of glass with white towel

    The Spruce / Adelyn Duchala

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  2. Create the Substrate Layer

    The substrate layer is a layer of soil, sand, and/or moss that provides an absorbent base for your terrarium plants. These materials create good drainage and also support the roots of your plants. Placing a layer of sand on the bottom works well for drainage, while moss on top helps retain moisture and also keeps the inside of the terrarium cleaner.

  3. Moisten the Soil 

    Dampen the potting medium of your plant and then remove its pot or cell, making sure not to pull it out by the top. If it is in a pot, tap the pot and slide the plant out by gently squeezing the sides and tipping it into your hand.

    If your plant is in a cell pack, squeeze the bottom and push the plant out. If the plant is rootbound, rough up the roots either by rubbing them or tearing them at the bottom

    Small plant slid out of pot and soil dampened with mist container

    The Spruce / Adelyn Duchala

  4. Place the Plants

    Squeeze the root ball and then place the plant over the substrate layer of the jar. You want the root ball to be compact and if possible, have all the roots covered with soil. Press the root ball into the soil layer so that it is mounded, but doesn't overflow.

  5. Arrange the Plants

    Make sure your plant placement allows for good visibility and also an attractive arrangement. Slightly taller plants in the center of a round jar make the best design.

    Tip

    Cleaning the inside of the jar as you go makes it easier to do a final cleaning when you're done. Use a soft cotton cloth; paper towels might leave fibers that cling to the glass.

    Mason jar placed over plant to test the fit

    The Spruce / Adelyn Duchala

  6. Add Moss (Optional)

    To give the terrarium a finished look, take small pieces of moss and press them onto the soil around the plant, creating a nice green mound. Keep the moss away from the crown of the plant.

  7. Dress Up Your Terrarium

    You can use any terrarium plants that will fit. To add a whimsical or decorative touch to your terrarium, place stones, shells, miniature figurines, or anything else that will survive the humid atmosphere of a terrarium. Make "memory" terrariums by collecting and adding keepsakes from vacation, and create a terrarium with those as the theme.

    To give as a gift, simply tie a ribbon or piece of raffia around the lid of the mason jar.

  8. Care for Your Terrarium

    Keep it out of direct sunlight, but try to give it bright indirect light. You may not have to water it for months, though you should check every few weeks to make sure the soil is moist, not wet. If you see lots of condensation on the jar, leave it open for a few hours to dry the soil out a bit.

    Open jar terrariums need more moisture and regular misting, so check them at least once a week.

    Terrarium plant being misted with water to keep soil moist

    The Spruce / Adelyn Duchala

Choosing Plants for a Closed Terrarium

The type of plants you choose for a closed terrarium should be plants that thrive on moisture. Also, choose plants that are not susceptible to mildew or fungus, both of which may be a problem in a closed, moist environment. Try the following plants for a closed terrarium.

FAQ
  • Can you use a Mason jar for a terrarium?

    Yes, a Mason jar is excellent for a terrarium, especially wide-mouthed Mason jars which make access very easy.

  • How do you care for moss in a terrarium?

    Mosses do best in a closed terrarium, where they have more consistent moisture. In an open terrarium, you will need to mist with water to keep the moss consistently moist.

  • Do jar terrariums need sunlight?

    While shade-loving plants can do well in terrariums, most terrariums need at least some sunlight. Bright but indirect sunlight is best.

Terrarium Care and Tips: 10 Mistakes to Avoid