If you've heard your friends, family or other gardeners talk about amending the soil of their gardens, then you probably know this is something that's important. You've probably asked the question: “What are soil amendments?” but gotten mixed, confusing answers.
More importantly, you probably want to know how to use them in your gardens, when to add them, how much is needed, and if, in fact, you need them at all. Well, we have the answers right here.
As we get into the nitty-gritty, our focus is to make things simple and easy for you to understand. Therefore, we don't want to confuse you with the the science behind gardening because it can make your head swim if you’re not careful. However, we know some of you might want to know more about plant growth and soil health, so we want to give an overview here.
For those of you that just want to know the answer to the question "what exactly are soil amendments and how to use them in your gardens?" you can skip over the science and follow our advice at the end of this article.
An Introduction To Soil Health
The simple fact is plants need certain things to survive and thrive. They need light, water, nutrients, and air, or more specifically, Carbon Dioxide (C02) from the air. No surprise here.
They get light from the sun, water from the rain or your garden hose and CO2 from the air. They take in CO2 and release oxygen in a process known as photosynthesis. This is a lesson you probably remember from school. It's the very basic explanation of how plants grow.
This leaves the fourth thing they need - nutrients. Where does a plant get nutrients? From the soil of course.
When you evaluate the quality of your soil, you'll probably find out it's bad. Most of the soil in any home yard is lacking in some or all nutrients.
Think of this. When your home was built, the builders certainly did not add soil that would be ideal for growing plants. The soil you have under the ground where you live is probably native to your area. It could be composed of mostly clay, sand or anything between these two extremes which aren't ideal for plants.
This is why you need to amend the soil in order to get plants to grow better. This is also why you need to add fertilizer periodically to your garden. Plants use up the nutrients in the ground over time so without adding more, they will not grow as well.
Don't confuse fertilizer with soil amendments. Amendments can be anything added to the soil, of which fertilizer is just one type. There are however, more.
Soil PH And Why That Matters
The PH levels of the soil affect the ability of the plants to absorb nutrients. Some plants require more acidic soil while others prefer a soil that’s more alkaline.
The important number to remember is 7.0 which is neutral. The lower the number, the more acidic the soil and the higher the number, the more alkaline.
While you COULD know the exact PH needs of each plant in your garden and adjust the soil accordingly, we find it’s not essential. Just knowing which plants favor slightly acidic soils and which ones like soil a little more alkaline is sufficient.
For instance, rhododendrons and azaleas like more acidic soil, whereas lilacs and clematis prefer the opposite.
The question then becomes: “How to do you know your soil’s PH level?” Testing of course. You can send it off to your local extension office or do it yourself by buying a soil PH meter at your local garden center.
You would generally want to start with a more neutral soil and then adjust the PH a little at a time if needed for certain plants. This is what we do with the soil amendments we use.
Types Of Soil Amendments
In addition to nutrients, soil texture is also important. Soil should be loose and supple to the touch to make it a good medium for growing plants. Different amendments will accomplish this but different amendments are used for different purposes, so understanding which to use when will help you get the right balance.
There are 2 types of soil amendments.
- The first type improves the soil texture and it's ability to hold water and nutrients in.
- The second type is something that adds nutrients, such as fertilizer.
The line can be blurred at times because sometimes one amendment will do both things. Here are a few more details.
The texture of your soil is probably something you've never thought of before but you should. Soil texture is important.
Is your soil sandy? If you live in coastal communities this might be the case. Is your soil clay like? In many areas, clay soil is prevalent.
You can understand the difference if you grab a handful of soil from your garden. Does it crumble and fall to the ground? It's probably sandy. Does it stick together and compact when you press it together in your hand? It's probably composed of more clay.
Some plants might prefer more sandy soil than others. However, no plants that we know of do well in clay soil.
Sandy soil will often make roots and the plants less stable and not hold in water and nutrients well. Clay soil on the other hand will drain poorly and the roots might end up sitting in water. Clay soil is like planting plants in a bathtub that holds water. Not good.
Plants need water, yes, but they also need well drained soil. The ideal way to think of it is that the soil needs to stay moist, but not drenched.
The bottom line is you need a soil that's in between the two extremes of sandy and clay like.
As you probably know, nutrients are very important to plant health and different plants require different nutrients. I'm sure this comes as no surprise. However, this is where things could get a little dicey! Let us make it simple.
The 3 main nutrients are Nitrate, Phosphate and Potassium and different plants require different amounts of each.
For more explanation of these elements and how they affect plants, read our article about the different types of fertilizer.
The purpose of soil amendments is to add texture to the soil plus a wide variety of nutrients that are not specific to any one plant. Therefore, a general purpose soil amendment will work.
The specific nutrients each plant needs will come from the fertilizer you add at when you initially put the plants in the ground, plus what you add over time.
List Of Soil Amendments And Their Uses:
What types of soil amendments you should use depends on what you need to accomplish. Here are some of your choices:
If you need to adjust soil texture you could use:
- Peat Moss: Provides no nutrients but improves the soil with aeration. Especially good for clay-like soils.
- Compost: Provides some nutrients and also helps with soil aeration. Great if your composting your garden debris and food scraps. However, it can be purchased as well.
- Manure: Don’t use manure directly from a farm. Purchase it already composted.
- Plant Debris And Leaves: Providing it’s free of seeds, which could sprout in your garden, plant and leaf debris will help your soil texture. This is why soil in the forest is so fertile. Lots of leaves and plants decompose in the woods.
If you need to adjust the nutrients in your soil you could use:
Amending your soil with nutrients means adding fertilizer and as we've said, depending on the plant’s needs, you’ll choose the fertilizer that's right for the job.
For our purposes here, we are not discussing different types of fertilizer but you can read our in depth article about it HERE. Combining that article with this one, you'll have a well rounded undestanding of both and should get good results.
The Best Soil Amendments That We Recommend
Here’s what we do for all of our clients, whether we're planting new gardens or adding to existing ones.
Soil Amendment #1: The best soil amendment we use and love is "Miracle Gro Garden Soil For In Ground Use." This is our go-to soil amendment most of the time. Don't get confused. There are many Miracle Gro products and soils available on your local garden center’s shelves. Click here to see the one we recommend.
Soil Amendment #1 Alternative: We sometimes use our own compost in our garden or clients compost in their gardens. However we have not seen a difference between using actual compost and Miracle Gro.
You'll want to use the ratio of approximately 50% native soil to 50% compost or 30-70 or somewhere in between. No need to measure it though. Just eyeball it as you add it to your gardens.
Soil Amendment #2: Peat Moss. We always mix Miracle Grow Garden Soil with Peat Moss in a ratio of about 50-50.
We have an excellent guide on amending your soil when preparing your garden for planting. Click here to read that article.
Soil Amendment #3: For a slow-release fertilizer we use a product called Osmocote. This is especially good for new plantings of annuals and perennials. We always use it when we're planting new plants as it will provide nutrients over time to the the plant’s roots.
Read more about Osmocote here.
These 3 amendments are all we use in 99% of our clients gardens and we’ve had great results. Whether we're doing a garden installation, or adding plants to an existing gardens, we use this same process and nothing more. It works.
You will notice that this process is not specific to the actual plants at all. We have never done a soil test for our clients unless there are problems with our planting.
Most professionals, especially larger companies doing large commercial spaces, don't have the resources or time to get more specific with soil amendments or fertilizers.
However, when clients have issues with their gardens or specific plants after the initial planting, this is when a more detailed analysis is necessary. If we find the soil lacking something, specific amendments will be added on a case by case basis.
Here are some of the other soil amendments we use from time to time on a case by case basis:
Soil Amendment #4: If plants need a boost we will sometimes use a generic 10-10-10 fertilizer. It comes in granular form and is sprinkled over the garden area. This fertilizer has equal amounts nitrate phosphate and potassium, hence the 10-10-10.
Many fertilizers on store shelves will say, “good for this” or “good for that” and what not.
All of these statements are just marketing language to get you to purchase those products for that specific use. This language does make it easier for average homeowners to know which products are good for which purpose.
Looking behind the language used, certain fertilizers are good for those plants because they have ingredients that are good for those plants. If you know the ingredients you want because a plant you're using requires them, you can look at a bag to look for those specific ingredients.
For example, when a bag that says 10-10-10 on the front, you know what you're getting. When a bag says "good for cactus" you know it has ingredients that are good for cactus.
Soil Amendment #5:
One fertilizer we like is Hollytone. This is a product that adds acidity to the soil for acid loving plants such as hollys and azaleas. It comes in granular from and is sprinkled over the specific plants that need it. Read more about Hollytone here.
Soil Amendment #6:
To adjust the PH of soil, you can use lime to raise the PH, which lowers the acidity, or sulphur to lower the PH, which will lower the alkalinity.
If you get your soil tested by a professional, you will get a recommendation of how much of which product you’ll need to add. Never adjust the PH too rapidly which could hurt the plants. Gradual is the name of the game.
Can You Get Soil Amendments At Home Depot?
Where can you purchase soil amendments?
Of course Home Depot carries many you will want to use. All of the brands mentioned above are stocked at Home Depot as well as Lowes and the garden centers of many other stores, both big and small.
If you live in an area without big box stores, not to worry. Gardening is a worldwide hobby. You should be able to find the ones we recommend or at least similar substitutes.
The Simple Final Answer To The Question Of What Are Soil Amendments
We hope you now have a good understanding of what soil amendments are and how they can improve your gardens.
Are they a choice? Well, no. They are necessary each and every time!
As professionals, we find it utterly amazing at the number of people we know that do not amend their soil with anything, especially when planting new plants yearly in already existing gardens.
Perhaps they think gardening is magic. Just stick a plant in the ground and it will grow.
Well to us, gardening and landscaping is magic. Nature is amazing. The plant world is amazing. The natural process of plant growth is amazing. However, helping them along with the right soil amendments makes the magic even better.