Everything You Need to Know About Soil
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Different types of plants need different types of soil. While many common houseplants are fine in a regular potting mix, some plants are native to different terrains and cannot survive in the wrong soil. You can buy pre-mixed soils or you can buy the individual ingredients and mix your own for these plants. Soil mixes for different plants are widely available at gardening shops.
STORE-BOUGHT PRE-MIXED SOILS
Most store-bought soil mixes only contain a few ingredients. The main ingredients work together to create a balance of water retention, nutrients, and airflow. It’s safer to buy pre-mixed soils as a beginner, however learning to mix your own soil, or amend your soil, will give you greater control and success in the future.
Pre-mixed regular potting mixes work for a wide variety of plants, but not all of them. Some plants will need a special potting soil mixture which are widely available. Orchids, cacti, succulents, african violets and carnivorous plants all have their own special mixes.
The average regular potting mix will contain at least the following:
Perlite: White volcanic rocks in soil that keep it loose and airy.
Compost: Decayed organic matter that delivers nutrients over time.
Peat moss: Contributes to water retention and acts as fluff to fill the pot.
Amending soil can be a good idea if you think the mix you have has too much or too little of something, depending on the needs of your specific plants. For example, I bought a cacti/succulent mix and added perlite to help drain water faster for my cacti. I often find standard cacti/succulent mixes hold too much water so I often add perlite and/or sand to them.
Other scenario’s for amending your soil may be:
- Your plant likes a more acidic or alkaline soil.
- The mix you bought dries out too quickly, because you have low humidity in your home. You may then add Coco Coir, or vermiculite to your mix.
- Your soil may be devoid of micronutrients found in high quality organic fertilizers. Mixing in some good fertilizer can boost a low quality soil.
MAKING YOUR OWN SOIL MIX FROM SCRATCH
Making your own mix is easy, cheap, and an overall better practice. I highly recommend it for a variety of reasons:
◈ More economical
◈ Better control over soil contents making it custom to the particular plant, your gardening habits or home environment.
◈ You’ll be able to buy more ecological ingredients like Coco Coir instead of Peat Moss.
Simple recipe for regular potting mix:
2 parts compost or earthworm castings
2 parts Coco Coir
1 part perlite
Mix your own cacti or succulent mix:
1 part horticulture sand
1 part perlite
2-3 parts organic potting mix depending on your home’s humidity levels. 3 Parts for a very dry home (35% and lower humidity level), 2 parts for a more humid home (35% or more humidity).
RE-USING OLD SOIL
If you want to mix old soil with new soil, don’t add more than 30-40% of old soil. If you are looking to only use old soil, you should add one part compost to 3 parts old soil. Do not re-use soil from tomato plants, diseased plants, or bug infested plants. If you used chemical fertilizers in the old soil, be generous with the amount of compost that you add.
AIRFLOW BELOW THE SOIL LINE
Roots need oxygen to absorb water and nutrients. Unglazed pots, drainage holes, and potting mix contribute to the amount of air that can flow through the soil. The larger the particles in the soil, the more air that can flow through the pot. Perlite and sand are the common ingredients that promote airflow. A pot raised off of a surface so that the drainage hole is not covered can increase airflow to the bottom of the pot as well. Fancier pots sometimes have this kind of lifted design.
COMMON MISCONCEPTION: PLACE A LAYER OF ROCKS AT THE BOTTOM OF A POT TO HELP WITH DRAINAGE
This is a widely spread incorrect tip. It has been debunked by experts that rocks at the bottom of a pot will help with water drainage. For pots without a drainage hole, excess water gets trapped at the rock layer making it hard to wick back up through the soil and evaporate. The water accumulates and stagnates and often rots the bottom roots and plant. It also takes away growing space for the plant. Rocks look great in terrariums but do not help with water drainage!