Planning for Tree Planting Success, Part 2: Prepping Your Soil

by Gabrielle LaTora, Agriculture and Natural Resources Agent

Now that you’ve selected the perfect site for your new tree, it’s time to prepare the soil! Preparing your soil includes correcting the pH, adding nutrients and organic matter, adding any other soil amendments, and assessing drainage. Just like selecting a site, preparing the soil gives your tree its best chance for success—that means protecting your investment, which saves you time and money in the long run.

The first step to prepare your soil is to take a soil test. Soil tests from your county Extension office will tell you important information, like the pH and nutrient levels at your site, and provide recommendations tailored to the type of plant you plan to grow. Your county agent can even help you interpret your soil test results.

Taking Your Soil Sample

Note: Soil sampling instructions may be different for Extension offices outside of Georgia.

1. Only sample from the area where your new tree will be installed. Imagine your full-grown tree at that site and where its dripline will be. That will be the rough outline of your sampling area. The area you sample from should have consistent sunlight, soil type, and drainage characteristics.
2. Use a zig-zag pattern to collect several (6-8) “sub-samples” from around your site. For each sub-sample, use a trowel or shovel to take a “slice” of soil 6 inches deep. 
3. Combine all your sub-samples in a plastic bucket and mix together. This composite sample will represent the average nutrient levels of your whole site. 
4. Remove about 1½ cups of soil from the bucket and lay it out to dry on a plastic bag or newspaper in a protected location. This is your soil sample! Your sample should be completely dry when you bring it into the Extension office.
5. Once your sample is bone-dry, transfer it to a plastic zip-top bag or designated soil sample bag and bring it to your local Extension office.

You should receive your soil sample results via email within two weeks. Click here to learn how to read your soil test report. If you can’t find the type of fertilizer recommended in your test results, you can use the UGA Fertilizer Calculator to convert your fertilizer recommendation to another formula. 

Apply fertilizer and lime as recommended on your soil test results. Depending on your fertilizer, you may need to incorporate it into the soil or water it in. Keep in mind: adjusting your soil pH with lime is a gradual process and won’t happen overnight. Check out this article to learn more about liming, and don’t hesitate to contact your Extension agent with any questions. You may also add a layer of compost and work that into the top layer of soil. Organic matter, like compost or mulch, improves drainage and soil texture.

This is also a good time to test your soil drainage. One of the most common reasons ornamental trees and shrubs fail is poor drainage and resulting root rot. You can do a “percolation test” to evaluate the drainage at your site.

From Iowa State University Extension:

Use a shovel or post-hole digger to dig a hole at least 12 inches down and 4 to 12 inches wide. Avoid working in overly wet soils as it may glaze the side of the test hole, which can give false test results. A planting hole can be used for this test to avoid excess digging.Fill the hole with water and let it drain. This could take just a short period or an entire day. This step saturates the soil. Immediately after the water drains for the first time, refill the hole with water. Measure the depth of the water with a ruler and after 15 minutes, measure the drop in water in inches. Multiply this number by 4 to calculate how much water drains in an hour.

from Testing and Improving Soil Drainage

You’ll want your soil to drain 1-3 inches in an hour. Soils that drain more than 4 inches of water per hour are very well-drained, and soils that drain less than one inch per hour have poor drainage.  

What If You Have Poor Soil Drainage?

If you’ve done your percolation test and discovered that your site has poor drainage, don’t panic! You have a few options:

• Select a different tree for your site! Go back to the previous blog post in this series and select a plant that actually likes to have wet feet! There are plenty of trees, from birches to willows to sycamores, that won’t just tolerate poor draining soils but will thrive in them.
• Amend the soil with compost. Spread a 2-4” layer of compost over the soil and work it into the top 6-12 inches with a shovel or pitchfork. You can also use a rototiller or cultivator, but be careful not to over-till. Too much tillage breaks up valuable soil aggregates and can create a hardpan under your soil surface. Till sparingly and with intention!
• Physically break up soil by tilling, spading, or aerating. (But keep the last bullet point in mind!)

Now that you’ve taken your soil test, amended with fertilizer and lime as needed, incorporated organic matter, and assessed drainage, you’re finally ready to plant your tree! Trust us, all this work up front will pay off when you have a successful, long-lived tree in your landscape.

Stay tuned for the next installment of our “Planning for Tree Planting Success” series: Planting Your Tree! This is a step that can make or break your tree’s long-term health, so you’ll definitely want to hear these tips.

Learn More

Soil Testing for Home Lawns, Gardens and Wildlife Food Plots (UGA Extension)