Uses of pine needle soil and how to grow orchids with it: it must be composted and sterilized before use

Pine needle soil is a leaf-mold soil formed from pine needles that have accumulated and decomposed over a long period. It is commonly found in the surface soil of the forest floor in pine woods, and it can also be made artificially by collecting pine needles, piling them up and composting them until they ferment. It is loose in texture, has good air permeability, is slightly acidic, and contains a certain amount of humus. It is a commonly used material when mixing growing media for acid-loving plants.

The most outstanding advantage of this type of soil is that it is loose and airy and drains smoothly. After watering, it does not easily become compacted, and roots can breathe relatively well in it. Because it tends toward acidity, it suits orchids as well as acid-loving plants such as rhododendrons, gardenias and camellias. It is usually mixed with bark chunks, leaf mold, perlite and the like to balance water retention and air permeability.

When using pine needle soil, pay attention to thorough composting and sterilization. Fresh, uncomposted pine needles will continue to ferment and release heat inside the pot, which can easily burn the roots and also tends to attract insects and carry pathogens. For pine needle soil collected yourself, it is advisable to spread it out in the sun first, or treat it by steaming or with chemicals, remove stones and clumps with excessive mycelium, and sieve it before potting.

When using it to grow orchids, it is generally not used alone; it is mostly mixed with bark or granular potting media so that the pot has both nutrients and no waterlogging. Pine needle soil has moderate fertilizer-holding capacity, and topdressing can be done with slow-release fertilizer or diluted liquid fertilizer. If the potting soil is found to be wet for a long time and to have mold and a bad smell, it is most likely due to poor drainage or too high a proportion of pine needles. In that case, repot and change the soil promptly and prune the damaged roots.