Katie Ashley


Soil is the source of many of the vitamins and minerals that your plants will uptake. If your plants are edible, then you’ll be able to enjoy and use these nutrients for your own health. It’s also important to consider the unique needs of your plants with respect to soil composition.

Here in Western North Carolina, we tend to have acidic soils which are rich in clay and poor in phosphorus. Some plants prefer acidic soils, but many plants, including most garden vegetables, prefer a soil pH around 6.0-6.5. This is because plants have a limited and specific range of pH where they can utilize nutrients. If the pH is too high or low, the plant isn’t able to use nutrients, even if they’re available to them in the soil.

Our soil here is typically rich in clay, which makes the ground sticky and sometimes slippery after rainfall. While there are benefits to clay, such as holding on to water and nutrients, it can be very difficult to work with as a gardener.

Several plants, such as peonies, do not like “wet feet,” or an excess of water, and can decline and potentially die. The best way to improve soil which is heavy in clay is to add organic matter, such as compost, composted leaf mold, pine bark humus or straw.

Contrary to common belief, adding sand will not improve soils rich in clay, but it will instead create a substance similar to concrete, so stick to the organic matter.

Plants require 17 essential nutrients to complete their life cycles, the three most common – carbon, hydrogen and oxygen – are available to plants from water and air. The remaining 14 nutrients must come from the soil. The top three nutrients from the soil that plants require are – you guessed it – NPK: nitrogen, phosphorus and potassium. Together, these top six nutrients are considered primary nutrients.

Having an imbalance of certain nutrients can lead to plant issues, for example, excess nitrogen can lead to tomato plants producing beautiful, large, green leaves, but few tomatoes.

However, adjusting any of these factors of your soil without testing it first could give you a feeling similar to taking a road trip without a map. It’s important to have an accurate idea of what’s in your soil, and soil test kits are available at your local extension office. The tests are free from April to November, and cost $4 per sample from December to March.

The soil tests will give information on pH, nutrient content, and return recommendations on soil amendments to help your plants grow as successfully as possible.

Next month, plan to learn more about cover crops – another great tool to ensure that your soil health is in great shape! Receive more tips on soil and soil testing by contacting the Jackson County Extension Office at 586-4009 or Jackson.ces.ncsu.edu or the Swain County Extension Office at 488-3848 or Swain.ces.ncsu.edu.

Katie Ashley is the NCSU horticulture extension agent for Jackson and Swain counties. She can be reached directly at Katie_Ashley@ncsu.edu.