How to Choose the Best Bonsai Potting Compost Mix
Some people shy away from growing bonsai because they’ve heard it’s difficult to grow them.
It’s not that hard, but one of the major aspects you need to get about right is the compost. Bad compost conditions equals a sick tree, so here’s how to choose the best bonsai potting compost mix
The right mix is essential
The best bonsai potting compost mix will contain a mix of growing mediums such as pine bark or peat and plenty of materials that create free-draining conditions such as perlite, quartz, sand, or grit.
You might think bonsai compost just looks like a load of dry stones that couldn’t sustain anything but these are the condition they like best! Experts often suggest a 40/60 or even a 50/50 split of growing medium and drainage materials.
Good water retention for healthy growth
Bonsais are mini trees and they need plenty of water or they drop foliage to conserve their supply. Some bonsai mixes include pine bark which is an excellent natural moisture retainer.
Others use peat, coconut fibres, or water-retaining crystals in their specialist mixes. It’s important your compost mix has at least one of these to retain enough moisture.
Good drainage is really important
Bonsai need a steady supply of moisture, but soggy, wet roots will kill it.
Excess moisture must be able to run away, so bonsai compost must contain vermiculite, grit, sand, perlite quartz crystals, or other hard, fine materials to create free-draining conditions.
Good aeration prevents root rot
Hard materials in bonsai compost should vary in size enough to create pockets of air in the soil. Good aeration prevents root rot by allowing oxygen into the mix to dry out too much water and promote microbial growth in the soil.
If your bonsai mix arrives looking too dense it’s a good idea to add horticultural grit, vermiculite or perlite before using it. You can find them in garden centres or online easily enough.
Aim for the right pH balance
It’s best to look for a bonsai potting compost that has neutral to slightly acidic pH.
Pine bark is naturally slightly acidic, but mixes without pine bark are offered with less lime content too. It might not seem worth the bother, but your bonsai will be able to tell the difference.
Check out our FAQs below if you need more information on how to choose the best bonsai compost.
Bonsai Potting Compost Mix FAQs
Do you need special compost for bonsai trees?
Bonsai won’t survive long in plain old garden dirt. It’s too hard and dry and won’t provide the right conditions for your bonsai to thrive.
It’s best to buy or make a bonsai potting compost mix that has plenty of drainage from sand, grit, perlite, vermiculite, volcanic rocks or similar with a bark or peat base. Bark is better for the environment!
A well-drained mix encourages healthy roots that can suck up nutrients and water effectively.
Should I feed my bonsai tree?
Yes, bonsai trees need regular feeding because they’ll use up all the nutrients in their pot and start to suffer the ill effects of poor nutrition.
Choose a specialist bonsai fertiliser because they need weak feeding that promotes slow strong growth rather than a flurry of greenery.
Can I use cacti soil for bonsai?
You can and it works well because both species need aeration and well-drained soils.
Many manufacturers offer joint bonsai and cacti compost in one which is worth considering if you have both types of plant.
When should I report my bonsai tree?
This will vary between species and pot size, but in general young trees need repotting every two years and established trees every 3-5.
Check beneath the pot and if there are roots breaking through the drainage hole it gives a good indication that repotting is required.
Choose a pot only a little bigger than its current one or your bonsai will try to fill the soil with roots rather than producing greenery that we love to admire.