Soil and Roots FAQs

Q: What does healthy soil look like?

In general, a healthy soil is free of crusts, compaction, pesticides and other toxins, salt buildup and excessive erosion, and contains sufficient organic matter and nutrients, in proper balance, to support a large and active population of native organisms. Your soil may look different depending on the region you live in, so make sure to compare your soil to local samples.

Q: How should I test my soil?

Homeowners may use a pH test kit from a local nursery or hardware store. A professional arborist can follow up by analyzing the soil and submitting it to a laboratory, and provide a plan to correct soil deficiencies. Homeowners can also take a soil sample to send it to their local university cooperative extension for analysis.

Q: What is soil pH, and why does it matter?

The pH scale measures how “acidic” or “basic” a substance is, on a scale of 0 to 14. Trees require specific pH levels (depending on the species) in order to thrive. Testing your soil pH levels prior to planting will tell you what adjustments you will need to make with fertilizers.

Q: What is the best way to apply fertilizer to my soil?

Fertilizers can be applied to the soil or foliage, or they can be injected directly into the tree. Sub-surface soil application is the preferred technique, and it is recommended to adequately fertilize the soil before planting the tree, as surface applications are less efficient. Foliar spray or trunk injections should be reserved for rare cases when soil application is not effective or not practical to apply.

Q: What kind of fertilizer should I use?

This will change depending on the condition of your soil, and your tree’s nutrient needs. When choosing a fertilizer, homeowners should select a fertilizer that is at least 50% slow-release, and has a salt-index of less than 50. Avoid fertilizers with a high ratio of potassium and phosphorous. If you correctly select and apply a slow-release fertilizer formulated for your tree, you should only need to apply 2 to 4 pounds of nitrogen per 1,000 square feet per application. The total application for a growing season should not exceed 6 pounds of nitrogen per 1,000 square feet.

Use TCIA’s search tool to hire a professional arborist or tree care company.