Potting soil is a necessary part of growing houseplants that drastically impacts how the plant grows. It seems like you should be able to toss a plant in dirt, and it will grow, but that’s not the case. The composition and makeup of the mix provide different values. If you use the wrong potting mix, a plant can die, but a custom mix specifically intended for a particular type of plant will help that plant thrive. Learn how to select the right potting soil for your houseplant.
What is Potting Soil
Rocks, minerals, and organic content comprise soil. The immediate environment impacts the makeup of nearby soil. The plants grown in the area, the rocks in the vicinity, the amount of rainfall, and sunlight all contribute to the soil quality.
The soil in your backyard or outdoor garden bed differs from the potting mix for houseplants. Potting soil formulated for houseplants is often lightweight and airy, making it easy for roots to grow and push through.
Why the Right Potting Soil Matters
Soil makeup matters for houseplants because the plants hail from different regions. Plants evolve to thrive in their natural habitats. When those plants become houseplants, they adapt to living indoors but still have certain preferences.
For instance, the Alocasia amazonica is a tropical South Asian plant that prefers rich, slightly acidic soil. Echeveria are found throughout Central and South America and prefer low-quality soil with excellent drainage. Each plant thrives in the proper soil but would struggle and possibly even die in the wrong soil.
Drainage
Soil is often classified by how quickly it dries out or how much water it retains. The makeup of the mix determines the drainage rate.
Sandy
Tiny particles of rock and sand are the dominant ingredient in sandy potting soil. The rock and sand do not impede drainage, making sandy soil excellent for succulents and cacti.
Clay
Clay is excellent at retaining moisture. Houseplant potting mix will not have much, if any, clay. Clay can naturally occur outdoors, making it more of an issue for outdoor gardeners.
Loamy
Loamy potting mix is well-rounded and features equal amounts of sand and clay. Sand allows water to drain, while clay retains moisture. When both sand and clay are present, the soil holds some, but not all, moisture. A loamy potting mix often has a dark brown color. Loamy soil is suitable for most houseplants.
Organic Content
Organic content is decayed plant matter that has biodegraded. In nature, dead leaves and branches accumulate on the ground and eventually break down. Organic content is essentially naturally occurring compost. Coco coir or peat moss are common ingredients in many DIY potting mixes that provide organic matter.
Broken-down organic content gives potting mix nutrients that support plant growth. A rich potting mix has high organic content, while a blend with low or no organic content is often described as low- or poor-quality. Using the term low-quality is deceiving because low organic content benefits certain plants, like succulents.
Many ready-made potting mixes will include slow-release fertilizer amended into the blend to provide additional support.
Soil pH
Typically, only advanced plant owners concern themselves with the soil pH. pH stands for ‘potential of hydrogen’ (abbreviated as H on the periodic table), and it measures how much hydrogen is in a substance. The pH reading establishes how acidic or alkaline a substance is or if it is neutral. The pH level is helpful knowledge when caring for houseplants.
Most African Violet and Monstera deliciosa prefer a slightly acidic potting mix. Test kits are available to measure the pH, allowing you to fine-tune your plant care. You can also use an acid fertilizer to make a neutral or alkaline soil more aligned with the needs of specific plants.
DIY Potting Soil
Many outdoor and indoor gardeners choose to make their potting mix. Making your DIY potting soil can be cost-effective, especially if you have a lot of plants or a large garden or landscape space. A do-it-yourself approach enables you to customize the mix to give each plant precisely what it needs.
DIY potting soil has advantages, but you can always buy premixed soil. Purchasing ready-to-go mixes is often a time saver and easier if you don’t want to bother buying the separate ingredients and creating a blend unique to each plant. There is no right or wrong method, and it’s a matter of personal preference.
Potting Soil Alternative
Most houseplants need potting mix to grow, but some can live without soil. A planting medium is still required, and that is typically sphagnum moss. Sphagnum moss is often used in potting mixes but can also get the job done solo. Orchids are the classic example of a plant that grows without soil. Staghorn ferns are another example of an epiphytic plant that can live soil-free. Anything loose and airy is a good choice for orchids and staghorn ferns, and sphagnum moss checks both boxes. For what it’s worth, Tillandsia, or air plants, can live without any growing medium.
Help Your Houseplants Thrive
Potting soil matters and can significantly impact how a houseplant lives and grows. A general potting mix is often a good choice, but a specialized blend is sometimes the best option. Understanding what your houseplants need to thrive enables you to select the right mix.