A good potting mix is not garden soil. It is a soilless blend chosen to hold moisture, drain freely and let roots breathe. Getting the blend right is the easiest way to prevent the most common houseplant problem: overwatering. 100% Local
Garden soil is full of clay, silt and living organisms that behave very differently once confined to a pot. In a container there is nowhere for water to go, so heavy soil compacts, starves roots of oxygen and stays wet for weeks. Container mixes replace that soil with light, structured ingredients that keep air moving around the roots.
Peat moss and coconut coir form the base. They soak up water and hold onto dissolved nutrients so the plant can take them up between waterings.
Perlite, pumice or bark chips open the mix up. These chunky particles let excess water run straight through and keep oxygen around the roots.
Compost or worm castings add a gentle, slow-release supply of nutrients. They are not a replacement for fertiliser, but they make the mix behave like living soil rather than sterile filler.
By volume, a reliable starting point is roughly 60% base, 30% aeration and 10% compost. Measure with any cup or scoop as long as the proportions stay the same, then adjust for the plant in front of you.
Once the mix drains well, everything else gets easier. Water when the top few centimetres are dry and let the roots do the rest.
Not usually. Compost from a healthy heap is fine. If you have had fungus gnat problems, or you use garden soil, you can pasteurise it in a low oven, but a clean bagged mix is simpler.
Yes, with care. Remove old roots and debris, then refresh it with about a third new aeration and compost. Throw away mix from a plant that had root rot or pests.
Whenever you repot, usually every one to three years. Topping up the surface each spring also helps.
General horticultural guidance for planning only. Verify locally.