Understanding Montgomery County Soil

March 22, 2020

Guest Blog by Cynthia Stern:

Earth lovers know how pleasing it is to go green and natural by digging to prep for planting grass, trees, and gardens. Healthy soil in Maryland should have a pH balance between 6.0 and 7.0 — but how you get there is important. Maryland and Montgomery County both prize natural methods of attaining good soil. Understanding the process is a start to having a thriving lawn and garden.

Basics of Soil


What is soil pH? The letters pH stand for “potential of hydrogen” and it is a measure of the hydrogen ions in a solution. Hydrogen is not itself a nutrient, but its presence greatly affects whether plants can absorb them. The pH scale runs from 0 to 14, with 7 as the neutral midpoint. Anything below 7 and the soil is acidic. Numbers above 7 mean the soil is alkaline.

Soil with overly high or low pH won’t allow vegetation to absorb nutrients.


Plants absorb nutrients from the soil through roots and leaves. The science behind it is somewhat involved, but vegetation feeds through air and water. Carbon, hydrogen, and oxygen make up about 95% of vegetation’s dry matter. The other 5% comes from mineral elements such as nitrogen, calcium, boron, manganese, and phosphorus.

Maryland Soil

Montgomery County soil is chiefly classified as part of the Piedmont Plains soil group. Its base is mineral material made of igneous and metamorphic rocks, including schist, metabasalt, phyllite, marble and gneiss.

It tends to be clayey and on the acidic side. Clay is a heavy, sticky, nutrient-rich soil when it’s wet, but gets hard when dry. Clay soil works well for fruit trees, vegetables, and ornamental plants that can handle its texture.

6 Types of Soil in the Area

Clay is one of the six types of soil found around Washington, D.C., and Maryland. The area boasts a diverse ecosystem of valleys, mountains, marshes, beaches, dunes, deltas, river lands, and bays.

Centuries of time and tilling have changed many areas of Montgomery County. You might have one of the other five soil types. They are:

  • Peat soil. It is dark and very moist and tends to be rather acidic. That makes it work well for peas, beans, and other legumes. Root vegetables thrive in well-draining peat soil.
  • Loam soil, which is a combination of sand, silt, and clay. It drains well to support most gardens but needs occasional fertilizing to regulate acidity.
  • Silt soil. It absorbs moisture and is ideal for fruits and vegetables. The silky, soapy texture helps ornamental grasses thrive.
  • Chalky soil is rather alkaline and needs some added fertilizer. It covers limestone and chalk, containing more rocks than the other kinds of soil. With great drainage, shrubs tend to do well in chalk
  • Sandy soil usually needs to be amended for added nutrients, but it’s good for root crops, greens, and strawberries.

Soil and Plants

The ideal soil is a blend of 45% mineral material, 25% air, 25% water and 5% organic material.

The mineral material provides a base for the roots to grab. Air space provides room for roots to grow and soil-improving insects to move about. Water moves is absorbed by the foliage, spurring photosynthesis that breathes in carbon dioxide and exhales oxygen. Organic material provides micronutrients that are key to plant health.

The soil also insulates roots from extreme temperatures.

Soil Testing


Testing the soil in your yard and garden is the best thing to do before planting native trees, shrubs, flowers, and grasses.

In general, soil testing should be done every three years or so. In Maryland, soil testing is even more important to help you avoid chemical fertilizers in favor of an organic lawn and garden.

To protect water quality in the Chesapeake Bay and its tributaries, a Maryland law went into effect in 2013 that restricts the use of excess nitrogen and phosphorus on lawns. Runoff of these nutrients in watersheds leads to algae blooms and kills aquatic life. Montgomery County also has a new law restricting pesticides on lawns. It went into effect in 2019.

Soil testing kits are available at your local garden store, but you’re better off taking a sample to a certified laboratory. When obtaining a dirt sample, use a clean trowel, remove roots, leaves, and other vegetation and blend it together. Take separate samples from different areas where soils could be different.

With varying soils in Montgomery County and surrounding areas, the grass and greenery in your yard, flowerbeds, and garden may have different growing needs. Start with an expert analysis of what you have to work with, and then go from there.

Cynthia Stern is a landscaping and gardening writer who has a passion for decorating outdoor living spaces. She plants only native flowers and trees in her yard.

4 comments on "Understanding Montgomery County Soil"

  1. Sally says:

    I need soil testing for PH. At least. Live in Olney, MD 20832. Lots of clay down low but other above. Yard sits below the neighboring artifially built roadways. Mold is slowly taking over the yard in shady or wet areas. If I can get a sample the right way where would I take it?

    1. Sally Jones says:

      Buy an electric Ph/thermometer spike from Amazon. They are not expensive and very easy to use. Just pop a battery in and out the spike into the ground.

  2. Andrew Johnson says:

    Can you update your page for certified labs? The link to UofMD is dead. Thanks

    1. Mary Travaglini says:

      Andrew, we fixed the link–thanks for the update!

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