7 steps to making your own terrarium

Terrariums never spill, and they grow beautifully beneath fluorescent light, so they're a great way to grow plants in an office or home. You can make one from anything from a large wine jug to an old aquarium tank.

The air in many homes is so dry that houseplants that need high humidity levels suffer or refuse to grow at all.

• An enclosed glass container filled with plants solves this problem because it works like a miniature greenhouse.
• Plants will grow indefinitely in sealed glass containers because of the greenhouse effect.
• Water evaporates from the soil and provides humidity; droplets then condense on the sides of the glass and roll down the sides into the potting mix, bringing moisture to the roots.

True terrariums are available as plastic or alloy-framed models or as more expensive brass-framed or leaded glass models, often with automatic ventilation controls.

• But you can grow a bottle garden in any glass or plastic vessel.

Naturally, the best plants for terrariums are small ones that that like low light and high humidity.

• Start with a clean container and layer in one centimetre each of sphagnum moss and fine gravel (such as aquarium gravel), a thin topping of aquarium charcoal and five to eight centimetres of sterile, peat-based potting mix that is moist to the touch.

• A paper funnel makes it easy to fill a jug or bottle without getting the sides dirty. Simply roll butcher paper or sheets of newspaper into a funnel and pour the potting mix and drainage materials through it.
• Use a fork taped to a chopstick or an artist's paintbrush to make planting holes for terrarium plants.
• Set plants in place with another chopstick fitted with a small wire hook or loop. In containers with wide openings, you can use tweezers or tongs.
• Tamp down the soil around plant roots with a cork or spool attached to a stick. When you're done, lightly spray the plants and soil surface with water.

Cover your container with its lid, a cork, plastic wrap or a piece of glass to trap moisture and create condensation.

When given proper water and light, terrarium plants often grow happily for more than a year between feedings, and they may need replanting only every three to four years.

• When a plant's leaves begin to stick to the sides of a terrarium, remove it and give it its own little pot.

Don't fertilize bottle garden plants the first year.

• Thereafter, feed very lightly, diluting an all-purpose houseplant fertilizer to about 1⁄8 strength.
• If plants grow too large, prune them, transfer them to a larger vessel or replace them.

• Terrariums kept at normal room temperatures are great places to grow tiny ferns, palms, fittonias and other plants that need high humidity.
• Or you can take a different approach and use a terrarium to grow tiny plants that prefer dry conditions, such as little cacti or succulents.

Put the container in indirect sunlight or place it under a fluorescent light for 12 hours daily. Turn it regularly to keep plants growing evenly.

It's normal to see a little condensation inside a terrarium, but if the glass is so foggy that you can hardly see the plants, it's too wet.

• Leave the top open to help excess moisture evaporate, and wait until no new droplets appear to add more water, five millilitres (one teaspoon) at a time.