One of the most confusing subjects for new gardeners is soil, especially the "added value" kind of soil that you buy at the garden center.
Isn't soil just dirt, cleaned up and packaged?
As a new gardener, I didn't know the difference between "planting mix" and "potting soil," and bought whatever was on sale.
Dead plants were the result of my ignorance.
Dozens of garden soil options were available at the garden center but I didn't understand what they were for.
Apparently, many of the garden center sales people didn't know either.
So, I'm going to be the help that I wish someone had been for me!
I recently presented on "Soil 101: What Soil Should I Buy" on the Home & Family Show on the Hallmark Channel.
My goal was to introduce the viewer to the role soil plays in plant viability as well as explain the key ingredients added to commercial soil mixes.
Let's dig in!
Watch my garden segment in the video above from Home & Family show!
WHAT IS THE ROLE OF SOIL IN A PLANTS LIFE?
Since this isn't Biology 101, I'm going to stick to basic concepts about soil and its relationship to plants.
Your plants live in the soil; this is where they source all that they need to grow and thrive.
The fundamental roles of soil in plant life include:
- Soil provides physical support and anchors plant roots so they can stand upright.
- Soil retains moisture for plants to tap into.
- Soil provides nutrients for plants and beneficial bacteria that help break down nutrients for easy absorption.
- Soil provides air pockets so oxygen can get to the plant's roots.
The bottom line is that ALL the bagged soils provide these services to plants, albeit in different quantities and with different ingredients.
One of the most pro-active, educational habits a new gardener can adopt is to read the labels on bags of soil.
Ditto for fertilizer labels and ingredient lists for any garden amendment.
These labels contain the "nutrition facts" and a list of ingredients in the bagged soil beginning with the most plentiful to the least plentiful in the product.
When you understand the functions of soil – plant support, moisture, nutrition, aeration and drainage – you will begin to identify ingredients in soils that speak to these roles.
You will become a "well read" gardener!
COMMON INGREDIENTS IN BAGGED SOIL
Compost is simply decomposed organic materials. In other words, it's stuff that used to be alive.
Formerly living things include leaves, grass clippings, stems, and branches.
Compost enriches both native soil (in the ground) as well as potting soil that you use in containers with nutrients.
If you don't keep a compost pile, I recommend buying some and making it a staple in your garden.
Benefits of compost include improved tilth (soil texture), bringing a degree of expansion within the soil so that air can circulate.
Compost can help break down clay soil with time and may affect the soil's PH level.
Most of all, compost makes nutrients from formerly living matter available to your plants.
It's the circle of life!
Add compost to your native soil and in containers when planting bare root roses and trees.
Vermiculite is a sterile mineral that acts like a sponge and traps water in the soil for plants to tap into.
Since vermiculite is lightweight, it is used in seed starting mixes where seed rot from excess water is a potential problem.
Improved oxygen flow is also a benefit.
As a mineral, vermiculite reacts with other soil compounds, making other nutrients available such as calcium, magnesium and potassium.
Perlite is hard, porous volcanic glass with tiny surface crevices that hold water and air.
Added to soil mixes, perlite improves drainage and releases water to the soil as needed.
Many gardeners have discovered that fine and medium grade perlite by itself is an ideal seed starting medium.
You can also grow plants in perlite, provided you supplement it with fertilizer, as perlite does not provide the essential macro and micro nutrients plants need.
Horticultural sand is washed to remove salts and is added to clay soils to improve drainage and aeration.
When adding sand to clay soils it must be added in 50/50 ratios or poor drainage can become even worse.
You'll find horticultural sand as an ingredient in succulent/cactus and tropical plant soil mixes.
COCO COIR OR PEAT MOSS
Coco coir and peat moss function in the same way; both hold moisture in soil, contribute organic matter, improve soil texture and are lightweight additives.
Of the two, coco coir is considered to be the more sustainable and renewable one.
Coco coir has the amazing ability to hold up to 10 times its weight in water and is made from coconut husks.
This is an ingredient that you want to see in soil mixes.
BAGGED GARDEN SOIL VARIETIES
SEED STARTING MIX
Seed starting mix is a soil less mixture which helps control against bacteria, weed seeds and insects found in regular soil.
Use it for starting seeds.
GARDEN SOIL FOR FLOWER AND VEGETABLES
Garden soil blends for flowers and vegetables is meant to be added to outdoor garden soil to improve tilthe (texture), add nutrients and help retain moisture.
Never use a garden soil mix for container plants!
Garden soil is too heavy and will not allow sufficient air flow in a container environment.
Compost is a gardener's best friend and can be added to outdoor planting beds as well as container plants.
Full of nutrients and beneficial bacteria, compost can be used in the garden as a mulch or top dressing, mixed with lawn seed when preparing new lawns, and used for planting bare root roses and trees.
Add compost to your soil when creating new garden beds.
Dig in 3 to 4 inches of compost to your soil to a depth of 6 inches every season to replenish the nutrients and organic matter that has been absorbed and broken down.
SPECIALTY SOIL MIXES FOR DIFFERENT PLANTS
There are a number of specialty soil mixes available for specific plants.
You will find soil for succulents, tropical plants, African violets, orchids, and more.
These soils are worth looking into, as they are blended to incorporate ideal ratios of organic materials, wetting agents, drainage, and nutrients for specific plants.
CACTUS AND SUCCULENT SOIL
Succulents, cacti, and many tropical plants require excellent drainage.
Sometimes soils that drain too fast aren't able to retain nutrients that plants need.
A commercial succulent mix offers the ideal ratios of sand, compost, humus, and nutrients to keep your plants fed and their "heads above water!"
ORCHID SOIL MIX
Although many people plant orchids in simple orchid bark, you can also use an orchid soil mix enriched with nutrients as an alternative.
The added benefit of an orchid mix are nutrients such as worm castings and oyster shells for time released sustenance.
CERTIFIED ORGANIC SOIL LABEL
If growing plants organically is a priority for you, choose soils that have the OMRI seal (Organic Material Review Institute).
There are companies that produce organic products but have not paid fees to be certified as "organic," as it is an expensive process.
Read more about OMRI certification here.
Now that you have some basic information about common ingredients in bagged soil, you should be able to navigate your way through the soil aisle.
Soil is a very deep subject and we've just scratched the surface.
Please leave me your questions in the comment section below!
Shirley Bovshow, professional garden and landscape designer and Garden Lifestyle Expert on Home & Family Show on Hallmark Channel.
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I use Gardner & Bloome Organic Compost. EB Stone also carried excellent soils.
You can’t go wrong by adding some commercial compost mix to grass area if you are concerned with free toxic compost.
Compost will help “loosen” you clay soil a little for better water penetration. Good luck.
Thanks for your question.
Unless your soil is contaminated, you can just mix in the compost as well as garden soil as a supplement to your native soil.
For growing vegetables and flowering plants, ammend your soil with at least 3 to 6 inches of compost or garden soil and mix in with spade to depth of 8 inches!
what would i buy to improve my yard…….knowing that I am limited in money and that my soil is pretty dusty so cannot buy much but think I might need some….am about to scalp and reseed yard with a grass mix that is drought and heat tolerant…well to a degree of course, but best I have found……also going to plant 1/3 of yard with native OK plants which probably won't need the soil enhanced as much….we have compost from the city but it is derived from yards and most use pesticides and herbicides and quite sure some use stuff that is illegal for lawns. Yard is now all stickers because of drought, heat, mistakes I made and not maintaining….would say it is mostly red clay……metro Oklahoma City area. Thanks for a reply here or at my emaol.
Great article. There is so much to learn about soils. When we plant in the ground, are the soils you mentioned meant to be supplements for the natural ground soil – or to replace it entirely? Are we supposed to mix them together?
Do you have a preference in compost……mushroom, chicken, steer, etc. Thinking of the bagged varieties, which work best for vegtable gardens? Thank you for the info, getting ready to start my indoor seeds now and can hardly wait to be outside.