By James Tababa
Growing or potting media is the material where a plant grows. It supports plants by providing anchorage for the roots, as well as water, air, and nutrients.Topsoil or the soil taken from the top layer of the earth is the most common growing medium for plants. However, there are cases where topsoil alone is not an ideal growing medium because it is sometimes too dense for air and roots to move around. Soil can be a potential source of pests and pathogens and may also contain weeds that can compete for nutrients.
For that reason, plant growers use several kinds of growing media. These growing media can be used by themselves or blended with different substrates to conform to the ideal growing conditions of the plants. An ideal growing media is free from pests and pathogens. It should also not be toxic to the plant.
The most common factor in selecting the best growing media is how it affects water and air availability. Water drainage is important because some plants prefer to avoid having their roots soaked in too much water for a very long time. A well-draining media also increases the air circulation in the roots. Availability of air in roots is needed for root growth to absorb water and nutrients efficiently. Poor root aeration slows down plant growth. Here are 10 of the most common growing media gardeners use:
Rockwool is densely packed manufactured mineral fiber. It is created by melting and spinning rocks until they become something like fiberglass. It Is usually sold in cubes, blocks, or slabs.
Rockwool is usually used as propagating media for seedlings because it is easy to manage. It can be easily shaped into the desired shape and size. Also, it can retain moisture very well and has excellent aeration for the roots to grow efficiently. Rockwool is commonly used as a medium for hydroponics in growing tomatoes and other vegetables.
The use of rockwool can be a health hazard when its tiny particles are inhaled. It is also non-biodegradable, so it does not decompose.
Usually, rockwool is used only as germinating or propagating media for tomato, pepper, cucumber, melon, eggplant, lettuce, and strawberries. For ornamentals – rose, gerbera, and cymbidium orchids.
The clay pellets are growing media that come in different sizes but are usually in the form of balls or pebbles. Clay pellets are made by heating clay at 1200 °. Through heating, the gas expansion inside the clay produces small spaces inside clay pellets. It is also called hydroton or LECA (lightweight expanded clay aggregate).
Clay pellets provide larger spaces for water and air to pass through than perlite, vermiculite, and sand. It is used in some potting mixes to increase water drainage and aeration. Though, clay pellets do not provide good water-holding capacity.
Clay pellets are reusable. They are washed if green algae start to grow around them. However, they can also be expensive.
Clay pellets are usually used for growing vegetables in soilless hydroponics systems. They are also used as growing media for ornamentals like orchids, hoyas, pothos, philodendrons, and monsteras.
Pumice is a lightweight inorganic natural material. It is a product of volcanic activity. Pumice is popular as a soil amendment and conditioner to decrease soil compaction and improve water drainage and aeration. It is lightweight and porous because it contains many air pockets inside. The microscopic pores hold and retain water, while the large pores drain quickly to provide air and prevent water logging. Pumice is a commonly used substrate in aquaponic flood and drain systems.
The use of pumice as a sole growing medium is observed in hydroponics to grow vegetables. It is usually added to other growing media to prevent overwatering. Pumice can be added as 15-50% of potting mixes to ferns, monsteras, philodendrons, and peperomias. For cacti and succulents, pumice is often added to sand.
Perlite is another medium with a volcanic origin. The volcanic rocks are heated to 1000 °C and crushed to produce the white pieces of rocks. The rocks are porous, and they fairly hold water. Perlite sometimes tends to float because it is lightweight. Perlite helps in loosening compacted soil, improves soil aeration, and is used to insulate the roots to fluctuating temperatures. It is commonly used for plants that do not need too much water like cacti and succulents.
Perlite is popularly added to soil mixes for propagating seeds and cuttings because of its capability to retain moisture. Plants propagated through cuttings like monstera can grow well in a 50:50 mix of perlite and compost.
Vermiculite is produced by heating the rock minerals in temperatures between 700 to 1000 °C to form plate-like particles. It is used for its high water and nutrient retention properties. Vermiculite can hold water three to four times its weight. It also supplies potassium, magnesium, and calcium. These qualities make it a desirable potting media.
Vermiculite is an excellent addition to potting mixes because of its slow release of stored water and some minerals needed by the plants. Vermiculite is suitable for monstera, photos, philodendrons, spider plants, calathea, and spathiphyllum.
Sand is a common potting medium because it is cheap and naturally available. Sand has a particle size of 0.05mm to 2.0mm. Sand is one of the heaviest planting media making it hard to transport. It has low water retention, so it is a preferred medium for cacti and succulents. Sand is a popular soil amendment to slightly improve water drainage and loosen compacted oil.
Aside from cacti and succulents, ornamentals like sedum, lavender, artemisia, and daylilies grow well in sandy soil. Root crops such as potatoes, carrots, and radishes prefer sandy soil.
Coconut coir or coconut fiber is an organic growing media. It is derived from the husk of the coconut fruit. Coconut coir can provide good water-holding capability and aeration. It contains a significant amount of phosphorus and potassium.
Coconut coir is made of lignin and cellulose, so it is more resistant to microbial breakdown and shrinkage than other organic media.
Coconuts that are near coasts may have high salinity, which is why most gardeners wash the coconut coir first before using it as a growing media
Coconut coir is relatively affordable in areas where there are many coconuts. Ferns, bromeliads, orchids, and anthuriums can be grown in this growing medium.
Bark and wood chip
Bark and wood chips are by-products of the wood and paper industry. These materials can be fresh or composted. Composted bark and wood chips are preferred because they have less toxins that may affect the plants. These materials can be bought at affordable prices.
Barks and wood chips are lightweight materials that can provide good aeration. However, they only provide low to moderate water retention so frequent watering is required.
Bark and wood chips are oftentimes used as ground cover to prevent weeds from growing around the plants. They can be used to grow orchids and mushrooms.
Similar to bark and wood chips, it is a planting medium option if there are near woodworking industries. It is also a low-cost material, and it has high water retention.
Old or slightly decomposed sawdust is preferred because it has a reduced amount of toxins. However, microbial activity in decomposing sawdust may compete for nitrogen, requiring an increased amount of nitrogen fertilizer.
Like bark and wood chips, sawdust is also used as organic mulch for weed control. It is a good component for a potting mix to increase organic matter. Sawdust is an excellent component for growing mushrooms.
Compost is generally any fully decomposed organic material. It can vary greatly depending on the raw material used and how it is composted. Agriculture wastes such as animal manure and plant wastes are the most common raw materials for compost.
Plant pathogens and weeds may contaminate compost, but sterile composts are available in stores. Compost can act as slow-release fertilizer providing nutrients for plants in the long run.
Composts are confused with soil because they look very similar. It is discouraged to plant directly in compost because it dries out fast and can be prone to compaction. Nonetheless, compost is a great addition to potting mixes for most plants.