Soil is the foundation of every thriving garden, but not all soil is created equal. The type of soil in your garden affects how well native plants grow, retain water, and access nutrients. Understanding your soil can help you make better planting decisions and improve soil health over time.
Six Main Soil Types
There are six primary soil types, each with unique characteristics that impact plant growth.
Sand
- Texture: Gritty, loose, and drains quickly.
- Water Retention: Poor—water passes through quickly, often drying out plants.
- Best for: Drought-tolerant plants like Butterfly Weed (Asclepias tuberosa) and Prickly Pear (Opuntia spp.).
Silt
- Texture: Soft, smooth, and flour-like when dry.
- Water Retention: Moderate—better than sand but still prone to erosion.
- Best for: Moisture-loving native plants such as Swamp Milkweed (Asclepias incarnata) and Joe-Pye Weed (Eutrochium purpureum).
Clay
- Texture: Sticky when wet, hard when dry.
- Water Retention: High—holds water well but drains poorly, leading to compaction.
- Best for: Native species adapted to heavy soils, such as New England Aster (Symphyotrichum novae-angliae) and Blue Flag Iris (Iris versicolor).
Loam (The Ideal)
- Texture: A balanced mix of sand, silt, and clay.
- Water Retention: Moderate—drains well but holds enough moisture for plant roots.
- Best for: Most native plants thrive in loamy soil, making it the gardener’s dream.
Peat
- Texture: Spongy and rich in organic matter.
- Water Retention: Excellent—holds moisture well but may need drainage improvement.
- Best for: Bog plants like Cranberry (Vaccinium macrocarpon) and Pitcher Plants (Sarracenia spp.).
Chalk
- Texture: Gritty and alkaline, often containing limestone.
- Water Retention: Poor—drains too quickly and lacks acidity.
- Best for: Plants that tolerate alkaline conditions, such as Wild Columbine (Aquilegia canadensis).
The Soil Texture Triangle
The Soil Texture Triangle is a chart used to classify soil based on its proportions of sand, silt, and clay. These three particle sizes determine how soil behaves—its drainage, nutrient-holding capacity, and how well plants can grow in it.
- The triangle has three sides, each representing one of the three soil components:
- Sand (largest particles) – Provides drainage but doesn’t hold nutrients well.
- Silt (medium-sized particles) – Holds moisture and nutrients better than sand.
- Clay (smallest particles) – Holds water well but can become compacted.
- Each side of the triangle has percentages from 0% to 100%.
- By finding where your soil’s sand, silt, and clay percentages intersect, you can determine its official classification (e.g., loam, sandy clay, silty loam).
How to Read It
Let’s say your soil is:
- 50% sand
- 30% silt
- 20% clay
On the triangle, these percentages lead to sandy loam, a soil type that drains well but still holds some moisture—great for many native plants.
Soil Tests
Want to find out what type of soil you have? Try one of these quick tests at home.
Step 1: The Squeeze Test
Take a handful of moist (but not soaking) soil and squeeze it:
- Falls apart immediately? Likely sandy soil.
- Forms a soft ball but crumbles with touch? Loam or silty soil.
- Holds its shape like putty? High clay content.
Step 2: The Jar Test
- Fill a clear jar halfway with soil, then add water until nearly full.
- Shake vigorously and let it settle overnight.
- Observe the layers:
- Bottom layer (fastest to settle) → Sand
- Middle layer → Silt
- Top layer (slowest to settle) → Clay
Step 3: pH Test (Optional but Helpful)
Soil pH affects nutrient availability for plants. You can buy an inexpensive soil pH test kit or use this DIY method:
- Add ½ cup of soil to a container.
- Pour ½ cup of vinegar over it. Fizzes? Your soil is alkaline.
- If no reaction, add ½ cup of baking soda + water mix. Fizzes now? Your soil is acidic.
- No reaction at all? Your soil is neutral (pH around 7).
Sources
Agriculture and Agri-Food Canada. (2021). Soil types and their characteristics. Government of Canada. Retrieved from https://agriculture.canada.ca
Brady, N. C., & Weil, R. R. (2016). The nature and properties of soils (15th ed.). Pearson.
National Environmental Satellite, Data, and Information Service (NESDIS). (n.d.). Learn about soil types. National Oceanic and Atmospheric Administration (NOAA). Retrieved from https://www.nesdis.noaa.gov/learn-about-soil-types
Soil Science Society of America. (2020). Soil basics. Retrieved from https://www.soils.org
United States Department of Agriculture (USDA). (2023). Soil texture and classification. Natural Resources Conservation Service. Retrieved from https://www.nrcs.usda.gov
University of Minnesota Extension. (2022). Understanding soil texture and structure. Retrieved from https://extension.umn.edu