Experiment No. 3: Repotting and Preparing Potting Mixture

Introduction to Potting Mixtures

• Potting media, also known as potting mixture, is utilized in container gardening and differs from garden soil.

• Potting mixtures can be broadly categorized into:

  • Soil-based media

  • Peat-based media

• These potting mixtures can be customized at home by blending specific ingredients.

Components of Potting Media

• Sphagnum Moss

  • Peat moss, a coarser texture, serves the purpose of good aeration and water retention, preventing soil from drying too quickly.

  • It should be moistened prior to mixing with other ingredients.

  • Excessive peat moss can hinder soil drainage.

• River Sand

  • Coarse, sharp, or construction sand is a primary ingredient in potting media.

  • Sand enhances drainage and aeration but does not improve water retention.

  • Excess sand may cause containers to be too heavy to handle.

  • Sand must not be mixed with clay.

• Perlite

  • A manufactured, expanded volcanic rock, heated to approximately 1,800°F.

  • Perlite provides excellent drainage.

  • It is lighter than sand and holds more air, making it applicable in both peat-based and soil-based potting media.

  • Its water holding capacity is poor; it requires moistening before mixing with other ingredients.

• Vermiculite

  • A clay mineral that expands in flakes when heated.

  • Unlike perlite, vermiculite retains water and nutrients, in addition to air.

  • Susceptible to compaction, which diminishes its ability to hold water.

Making Soil-Based Potting Media

• A basic recipe for soil-based media consists of:

  • 1 kg of sterilized garden soil

  • 1 kg of coarse sphagnum peat moss

  • Coarse construction sand

• Preparation Steps:

  1. Combine equal parts of garden soil, coarse sphagnum peat moss, and coarse sand/perlite or vermiculite.

  2. Adjust the texture of the mixture to ensure it is loose and well-drained.

  3. If sand feels gritty or clay feels sticky, add more sand or peat moss in small increments until the desired texture is achieved.

Making Peat-Based Potting Media

• Soilless mixes or peat-based potting media do not contain soil and typically consist of:

  • Peat moss

  • Vermiculite or perlite

  • Fertilizer

• Standard Recipe:

  1. Pour 1 kg of peat moss into a basket.

  2. Add 1 kg of either perlite or vermiculite.

  3. Moisten the mixture before using it in pots.

Adding Ground Limestone and Fertilizer

• Small amounts of ground limestone and fertilizer should be incorporated into both soil-based and soilless potting media.

• These ingredients can be blended in a separate container before adding to the mixture.

• Soil-based media may or may not need extra fertilizers depending on their nutrient and mineral content.

  • Ground limestone enhances cation exchange capacity (CEC) for nutrient retention and water holding capabilities.

  • A complete fertilizer can ensure that nutrients are available to plants, provided the pH level is maintained between 6.0 (slightly acidic) and 7.0.

  • If the media's pH is below 6.0, adding ground limestone may elevate the pH due to its calcium content, which strengthens plant cell walls.

Specific Potting Media Recommendations

• Foliage Plants:

  • Potting medium should be moderately rich, have a loamy base, and adequately hold moisture and fertility.

  • Recommended: Mix 1 teaspoon of superphosphate fertilizer to promote good root growth.

• Indoor Flowering Plants:

  • Potting medium should contain about 50% humus from compost or garden soil.

• Cacti & Succulents:

  • These plants need less humus material; a higher proportion of sand should be present in the potting mix.

• Orchids & Epiphytes:

  • Should be grown in a mix consisting of very porous materials that do not retain water for long.

  • A common mix might include 1 part peat moss to 6 parts coconut husk.

Depotting

• Process of Depotting a Plant:

  1. To remove the plant from its old pot, gently knock the pot against a hard surface.

  2. Turn the pot upside down while supporting the soil with your hand.

  3. Gently pull the plant away from the pot, ensuring the root ball remains intact.

Repotting a Plant

• Steps for Repotting:

  1. Place a mesh over the drainage hole of the new pot to prevent soil from leaking out.

  2. Add a layer of pebbles to the bottom of the pot, followed by new potting mix to raise the root ball of the plant to an inch below the rim of the pot, allowing for watering space.

  3. After depotting, if necessary, trim the root ball by a half inch from the bottom using clean, sharp scissors, removing dead roots.

  4. Place the plant into the new pot, filling in around the root ball with fresh potting mix and gently pressing to eliminate air pockets.

  5. Water thoroughly but refrain from further watering until the top of the soil dries out.