The ground cover of your bonsai is one of the important elements that will add greatly to the overall visual composition aspect of your bonsai tree, as well as assist in providing soil chemical stability and retaining temperature and moisture for the bonsai tree’s surface roots. A good choice of ground cover vegetation coupled with other landscaping accessories will complement your bonsai tree greatly and is one of the assessment factors in bonsai competitions.
Before you begin adding ground cover plants, a few things to remember are the feeding and watering aspects. Feeding your bonsai tree with pellets should only be conducted at the roots, and try not to wet the ground cover plants if they originate from dry, rocky, or alpine conditions (these make the best choices actually). If the ground cover plants receive too much nutrients, they will grow too luxurient; and if they receive too much water, they might perish. But that should not be too much of a problem, as a properly maintained bonsai tree will also result in happy “underling” plants.
Lawn Lobelia (Pratia angulata) is a perennial alpine plant from New Zealand which forms suitable mat cover over the ground. It produces small stemless white flowers and needs rather stable moist soil to flourish.
Sea Heath (Frankenia laevis) is a plant of the upper level saltmarsh areas of Europe near seashores. It produces pale lavender flowers in summer and has leaves that resemble heather.
Baby Tears (Soleirolia solerirolii) is a popular choice of many bonsai growers worldwide. Evergreen, with small, round, green leaves and a penchant for spreading rapidly, it is easy to grow and thus as a ground ground cover, it is suitable for many styles of bonsai. However, Baby Tears can also overwhelm your bonsai tree and design due to it’s vigorous growth habit, and should always be kept in check. It tends to spill over the pot, and needs constant pinching.
Raoulia (Raoulia australis) is a tiny mat forming alpine plant with stemless pale yellow flowers. It has tiny greyish leaves and when it blossoms in summer, produces a carpet of yellowish hue on the ground. It cannot stand prolonged drought, but sensible watering is all that is needed to keep it healthy. Able to tolerate light shade.
Corkscrew Rush (Juncus effusus spiralis) is a type of evergreen dwarf rush that looks like long green colored noodles from a distance. It needs constant high moisture, and so is best for trees that also grow in wet conditions, like Swamp Cypress or Willow.
Dwarf Mondo (Ophiopogon japonicus) is a native Japanese evergreen perennial grass, that can stand partial drought, though it doesn’t like full sunlight, and can do well in partial shade. Since Dwarf Mondo grass spreads by underground tubers, you will need to examine under the surface every few years (during re-potting of the bonsai is a perfect time) to ensure that it isn’t taking over space needed for the bonsai tree roots.
Dwarf Lady Fern (Athyrium filix-femina crispum) is a great perennial fern for the larger bonsai trees. All the Lady Ferns make good gardening subjects in general, as they do not get in the way of the main subjects and are shade tolerant. The dwarf variety are thus suitable for bonsai growing.
Despite the bewildering array of ground cover plants, you might want the easy alternative – mosses/liverworts. Just getting a partial cover of short moss to grow around the roots works fine. Mosses and liverworts can be found growing in damp areas along stream side boulders or old buildings where the walls are shaded. Keep them moist by regular spraying until they get established.
There exists a multitude of suitable ground cover plants for growing bonsai, and those above are but a fraction of the plentiful choices available. It must be remembered that the ground cover should never be totally shaded and covered up with growth, as the soil needs the warmth from the sun to provide conducive conditions for root growth.