Every plant has specific soil needs, depending on its original environment. The soil provides moisture, nutrients, and micronutrients, and it supports the roots and stem as the plant grows. With a few exceptions, potting soil should drain freely when watered. When seeking potting mix for plants, it is necessary to determine if the plant needs a dry, moist, consistently moist, or boggy environment. In addition, some plants, such as orchids, need special potting mixes to thrive.
Basic potting mixes
Potting mixes contain a mixture of organic and inorganic ingredients. They do not include standard garden soil. Organic matter includes peat moss, composted pine bark, or coconut coir, while inorganic matter includes perlite, vermiculite, or sand. Some potting mixes may include a slow releasing fertiliser and a wetting agent.
Flowers and vegetables
Most flowers and vegetables prefer neutral to slightly acidic soil with a pH of 6.0 to 7.0. Peat moss is acidic and lowers the pH in the potting mix, while pine bark and coir are neutral. The inorganic ingredients in the mix are also neutral. Most plants thrive in a general use potting mix that incorporates approximately two parts peat moss, one part pine bark or pine bark mixed with coir, one part perlite or sand, and one part vermiculite.
Acid loving plants
Some plants thrive in acidic potting mixes with a pH less than 6.0. Blueberries, gardenias, rhododendrons, azaleas, and camellias thrive in acidic soils. Potting mixes intended for acid loving plants generally have a larger amount of peat moss and labelling that indicates it is an acidic potting mix. The mix may incorporate a slow releasing fertiliser that includes sulphur to lower the pH of the mix.
Special potting mixes
Special potting mixes include the appropriate proportions of organic and inorganic ingredients for specific types of plants. Some mixes may include bark chunks, gravel, or lava rocks that create larger air spaces within the mix.
Cacti and succulents need well-draining potting mixes, as the tender roots rot if exposed to excessive moisture for long periods. A commercially prepared cactus potting mix may contain equal parts compost, sandy loam, and coarse sand. Cacti and succulents also require a slow releasing fertiliser to thrive in a container garden because the plants are heavy feeders.
Orchids vary in their soil needs. The native dendrobiums from the eastern mountain slopes of the continent grow on rocky outcroppings and require fast-draining, rocky potting mixes that include bark chunks or coir to imitate their natural habitats. Meanwhile, many orchid species native to rain forests need a fast-draining chunky potting mix, such as bark chunks. An orchid potting mix generally does not contain additional fertiliser, and a gardener needs to add a liquid fertiliser weekly, biweekly, or monthly after watering, depending on the species and specific nutritional needs.
Custom potting mixes
Gardeners who prefer to make potting mixes can mix equal parts compost, peat moss, and perlite, vermiculite or coir. When making a custom mix, a gardener should soak the dry peat moss overnight before mixing the ingredients. Before opening the bag of perlite and combining the potting mix components, it is important to put on gloves, a dust mask, and safety goggles, as perlite dust is bad for the lungs and eyes. After mixing the ingredients thoroughly, the potting mix is ready for general use. Additional peat moss is appropriate for acid loving plants, while less peat moss creates a sweeter soil.
Bog and water garden mixes
Aquatic planting mixes are available for purchase, but many water gardeners make their own mixes. A general purpose potting mix is too light, has too much organic matter, and clouds the pond water. A heavy, silty loam is ideal for water gardens because it holds plant roots in place. Some gardeners also add unscented, non-clumping, clay cat litter to water garden planting mixes. The clay secures the roots and holds nutrients within the pot. Some gardeners also add time-release stakes or aquatic plant food tablets to the potting mixes before sinking the pots into the water.
How to buy potting mixes on eBay
Before you plant your flowers or vegetables, take time to peruse the vast array of listings on eBay. You can type keywords into the search bar found on any page to find "general potting mixes", "orchid potting mixes", and more. A simple click of the search button reveals a plethora of potting mixes for different uses. After selecting the appropriate mix, prepare for a busy planting season filled with plenty of flourishing plants.