Potting soil is commonly believed to contain soil. However, it may come as a surprise that it doesn’t contain any actual soil. Read on as we dive into the ingredients of potting soil and the reasons behind their uses.
Potting Soil Ingredients
When thinking about potting soil ingredients, you can envision it as a structured, man-made soil material. It’s formulated to fit the basic needs of any plant, providing optimal drainage and space for roots to grow well.
So, what’s in potting soil, exactly? And why doesn’t it contain any, well, soil?
There’s an important distinction to make about any type of soil that we use for planting annuals, perennials, houseplants, trees and shrubs (indoors or outdoors): it is not the same as the dirt that you find in the ground in your yard. Much of the “earth” or “dirt” that you find in your yard does not have the nutrients necessary to help plants survive. In fact, just planting anything directly into your yard with no additional amendments to the soil will almost certainly result in failure. The same goes for when we’re planting in containers - if you were to just use dirt from your yard, your plants will not survive. Instead, it’s vital that we provide an environment where your plants can receive the nutrients necessary to thrive and that’s most often through the use of an intentional mix of ingredients that provide the best opportunity for their survival. This is why soil amendments are used when planting trees and shrubs in the ground and it’s why we use Potting Soil when planting in containers.
This structured soil may contain the following ingredients.
Compost
When looking at commercially prepared potting soils, compost is often created from forestry waste products. High in nutrients, it doesn’t retain moisture as well as some of the other typical potting soil ingredients. So, although this can be a good ingredient in potting soil, it isn’t something that should be used without the addition of other materials—such as with quality, commercially prepared potting soil products.
Peat Moss
This has been a traditional ingredient in potting soil and is still used today. This natural substance accrues in bogs over long periods of time and has been harvested for horticultural use. Theoretically, this could be used as a solo ingredient for plants, but it’s not recommended because, after watering, it stays wet for long periods of time. In more recent years, for environmental reasons, peat moss is incrementally being replaced as one of the potting soil ingredients with something called coco coir.
Coco Coir
Because this is a waste product, its usage is environmentally friendly. This material is simply coconut husk waste that’s shredded. The benefits of this material include how it creates an ideal environment for healthy root systems; as an airy material, it provides plenty of space for roots to grow. It also retains moisture well. Coco coir can absorb nutrients added to the soil, though, ones that could be better used by the plants you’re growing.
Worm Castings
After worms digest their food, they break the nutrients down into forms that are available for other uses. In other words, complex nutrients become bioavailable. So, worm castings make an excellent ingredient in potting soil, enriching the soil quality and providing valuable plant nutrition in ways that have a very little environmental impact. Worm droppings can be gathered in commercial ways through worm composting.
Perlite
Perlite is an interesting ingredient, it’s naturally occurring and fairly shapeless that’s actually volcanic glass formed from lava or magma. When using potting soil with this ingredient, you might see white flecks that look like Styrofoam. That’s perlite, extracted from mines and added to many commercial potting soil products. This material serves as a filtration system, allowing excess water to drain while holding onto the moisture and nutrients that plants need. This material also allows for good airflow, meaning that your plant roots can breathe, and its natural hardness slows down any soil compaction. Another mined ingredient, vermiculite, is sometimes added to enhance drainage.
Rice Hulls
When rice is processed for consumption, about one-fifth of the material is then considered to be waste; this mostly consists of the hard covering of the grain: its hulls. This substance improves drainage in potting soil and can be a wonderful substitute for peat moss. It can also serve as a protective top layer to prevent the growth of weeds and/or moisture loss and, when broken down by microbes and bacteria, adds valuable nutrients to the potting soil.
Kenaf
This is another one of the sustainable potting soil ingredients, a waste product of a certain type of hibiscus plant. As microbes and fungi act upon this ingredient, it releases nutrients that can be beneficially used by plants.
Shredded Bark
When used in commercial potting soil, its role is largely that of a filler. That doesn’t mean it’s without a worthwhile purpose, though. Larger pieces help to form air pockets in the soil for better aeration while the bark itself absorbs and therefore retains moisture for the plant roots to use.
Alfalfa Meal
This adds nitrogen to the potting soil along with other trace minerals. Plus, it naturally contains an ingredient called triacontanol which is a fatty acid growth stimulant. There are other types of meals added to potting soils as well.
Best Potting Soil For Indoor Plants
Gardening experts at Decker’s Nursery will be more than happy to discuss what’s best for your specific plants. If you’re looking for an all-purpose product, then consider the Espoma Organic Potting Mix—which can be used in container gardening both indoors and out. Potting soil ingredients in this product include sphagnum peat moss, humus, and perlite that’s been fortified with earthworm castings and meal (alfalfa, kelp, and feather meal) while also being enhanced with Myco-tone®.
Growing roses? Orchids? Succulents? Ask us about the best potting soil for indoor plants that are specifically targeted for them. Interested in organic? This kind of potting soil doesn’t contain pesticides or any other chemicals, using all-natural ingredients, including manures and composts. Regular products without the organic label may contain minerals to improve drainage and aeration.
Depending upon your specific wants and needs, we can answer the question of “What’s in potting soil?” for the particular product of interest.
Contact Decker’s Nursery for Your Potting Soil and More
Our family-owned and operated retail garden center offers what you need to grow healthy, beautiful houseplants as well as outdoor container gardens, and more. We have a wide inventory of products, all at reasonable prices, and our experts have a passion for growing plants and helping you to do exactly that.
We’d love for you to stop by during our business houses, contact us online, or call us at (631) 261-1148. Let’s talk about plants!