The complete guide to great garden soil

We answer all your questions about do-it-yourself at home soil testing.

A Garden that Needs Soil Testing

Have you ever tried to grow a garden, and shortly after seeing all your favorite plants start to bloom, the problems begin? End bloom rot, yellow leaves or stunted growth are clear signs that the soil in your garden or planters is not up to par.

Having the correct pH level, sunlight intensity and moisture content are vital for any plants to grow to their fullest capacity.

What is Soil Testing?

Soil testing is the process by which you capture the statistics of your soil. Most soil testing devices are "probes" that are pushed into the ground, then display a number of different readings.

Many years ago, soil testing involved taking a sample of your dirt, and sending it off to a far-away labratory or a local university. With the advancement of technology over the last decade, this is no longer needed. There are now cheap tools that will check our soil within a matter of seconds at an accuracy that is perfectly fine for the regular do-it-yourself'er.

Things Soil Testing Tells You

All soil testing tests provide one or more of the following statistics about the dirt being tested:

  • Moisture content is the amount of water absorbed by the soil being tested. This is important because too little water will dry out a plant and too much will cause it to rot.
  • Soil pH is a measure of the concentration of hydrogen ions (acidity) in the soil solution. The pH of soil greatly affects the solubility of minerals or nutrients of the plants.
  • Sunlight intensity, which describes how much direct sunlight a plant gets. This is important because direct sunlight is one of the major plant growth factors as you can imagine.
  • Temperature, which is not as important as the other metrics above unless you are at risk of getting close to the frost mark of 32 degrees Fahrenheit. Frost usually kills garden plants, so it is important to plant most vegetables after the last chance of frost based on your home's hardiness zone.

What is a Hardiness Zone?

2012 USDA Hardiness Zone Map

Enter your zip code below to get your home's hardiness zone with its first and last frost dates.

The US is broken up into 13 major hardiness zones, each with their subzones. This map is the standard by which gardeners and growers across the US can determine which plants are most likely to thrive at a specific location. The USDA Hardiness Zones within the map are based on the average annual minimum winter temperature, divided into 10°F sections.

Why does pH Matter?

pH is possibly the most important metric that needs measured in your houseplants or garden. pH affects everything from absorption of nutrients to the growth of beneficial bacterial and microorganisms.

Low pH is most common problem when it comes to pH levels within a garden. Lime is usually added to acidic soils to increase their pH levels. The addition of lime replaces the missing hydrogen ions and raises soil pH, which will eliminate most major problems associated with highly acidic soils. However, lime also provides two nutrients, calcium and magnesium to the soil - which are critical to healthy plants and fruit.

in the event that your soil's pH levels are too high, add compost to the affected areas. Using compost (or sometimes sulfur-coated fertilizer) will lower your soil's pH to acceptable levels that will promote healthy plants.

Why is Soil Testing Important?

Spending hours and hours cultivating the perfect garden can go downhill in a very quick instant if the soil your vegetable plants is insufficient. Blossom end rot, poor water absorption and misdiagnosed sunlight levels are all issues that can effect a garden that has soil that is deficient in one or more areas that a simple soil tester would catch.

When Does Soil Need Tested?

Ideally, you should test your soil a couple times a year - every year. Waiting for a plant to tell you something is wrong, is almost surely a recipe for disaster. By the time a plant calls out for help (wilting, bad fruit, no fruit, etc), it is almost too late to anything about it. Testing early and often is the way to go with these testers, especially since they are reusable for many years.

Where should you place your Soil Tester?

We have had the best test results by roughly dividing up our garden into the sections that held different plants (onions vs. tomatoes vs peppers vs potatoes, etc). I like to take a soil test from within each section, which will usually give me a good idea of how the plants that lived there the prior year effect the soil. You will find that each plant will change the soil it lived in slightly different from the other plants. Tilling it all over will also help "even" out the soil's mineral and pH contents.

The Best Times to Test Your Soil

There are three perfect times for you to test your outdoor garden's soil:

  1. Springtime - Check the pH. If it is low, add lime. If it is high, add more compost.
  2. At planting - In addition to pH (this should be one of the metrics you always pay attention to), you should check the temperature of the soil first thing in the morning. What you are trying to prevent is planting your seedlings in soil that is too cold to sustain them.
  3. Before fruit grows - In case something has changed with your garden's soil, it makes sense to test your soil one last time before the fruit starts growing. The best time to do this is after the flowers have started blooming, and the fruit are still in their bud or "tiny" forms. What you should be particularly concerned with here are the pH levels.

If you are looking to check your houseplant's soil, we recommend testing it every 2 months.

High-tech Soil Testing Devices

There are a few high-tech soil testing devices coming out of the IoT space, but none of them performed well enough to overtake the much less expensive options we recommend for soil testing.

The problem with these high-tech soil testers such as Edyn, PlantLink and Parrot is that while the results are adequate, they do not justify their extremely high price point, which is almost $100 over the low-tech ones that work just as well.

Low-tech Soil Testing Devices

Believe it or not, our top soil testers are all low-tech. This is one industry that has tried to modernize with WiFi or Bluetooth connected devices and apps, but has yet to come up with something worth all that extra money.

In the case of soil tests, low-tech does not mean inaccurate. Actually quite the opposite. In our tests, the low budget testing devices all out-performed their more expensive cousins, which goes to show you that high-tech is not always necessarily always better.