Is Irish Moss Good or Bad in a Terrarium?

Written by irum sarfaraz | 13/05/2017
Is Irish Moss Good or Bad in a Terrarium?
A terrarium is an attractive way to bring the outdoor landscape indoors. (Ryan McVay/Lifesize/Getty Images)

Terrariums are clear plastic or glass containers used for growing small plants to create miniature, indoor landscapes. The containers may be closed or open and have no drain holes. Small plants, like Irish moss, are good for terrariums as they maintain a low height without the need for excessive pruning. Larger plants are often avoided since they need to be pruned to keep to size.

Suitability for Terrarium

The University of Missouri Extension recommends Irish moss (Sagina subulata), with its mature height of 1 to 3 inches, as being suitable for terrarium growth. The perennial plant is a native of northern Europe and is primarily grown for its lush, dark green foliage. Irish moss is also referred to as heath pearlwort or Scotch moss and is frequently also used for filling in the spaces between stepping stones in outdoor landscapes.


Despite the name, Irish moss is not a real moss. The plant has a creeping, dense growth habit that makes it well suited for use as a ground cover in terrariums. Irish moss is grown primarily for its small, slender, cylindrical foliage that tapers to a point. The very small, white flowers bloom singly, appearing between mid-spring and early summer. Irish moss requires minimal pruning to keep to shape in terrariums. Pruning the plant helps to produce a bushier growth.

Growth Requirements

The plant does well in the moist, humid environment characteristic of terrariums. Plant in rich soil amended with organic material for best growth and place in a bright area preferably out of direct sunlight. Irish moss keeps its dark green colour all through the year. Keep the soil moist but not wet and use a slow-release fertiliser once a year in spring. It is not unusual for the plant to lose colour during summer, but colour is regained rapidly in cooler fall temperatures.

Plant Selection Suggestions

When choosing plants for terrariums, makes sure that all plants have similar growth requirements. Since Irish moss prefers bright areas out of direct sun, choose other plants that will also thrive in similar conditions. Creating a variation of sizes, textures and forms of plants helps to increase the aesthetic value and interest of the terrarium. Use insect-free, healthy plants for terrariums as one sick plant will infect all the others and replacing and replanting is not an easy procedure in terrariums.

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