What Type of Soil Is in Seattle, WA (98101)?
Maps show what is typical for Seattle, WA. A home test kit tells you the pH and nutrient levels of your yard.As an Amazon Associate, we earn from qualifying purchases.
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| Soil Type | Silty Loam |
|---|---|
| Soil Series | Alderwood |
| pH Range | 5.2 - 6.0 (Moderately Acidic) |
| Drainage | Moderately Well Drained |
| Organic Matter | 5.8% (High) |
| Water Holding Capacity | 0.18 in/in (High) |
| USDA Zone | Zone 8b (min 15°F) |
| Hydrologic Group | C |
What This Means for Your Garden
The dominant soil in Seattle, WA is Silty Loam soil. Loam is considered the gold standard for gardening. It holds moisture without getting soggy, provides good nutrient retention, and has a loose enough structure for roots to spread easily. Most vegetables, flowers, and fruit trees perform well in loamy conditions.
The pH in your area ranges from 5.2 - 6.0, which is classified as Moderately Acidic. Acidic soil works well for blueberries, potatoes, and azaleas. If you need to raise the pH for other crops, agricultural lime is the standard amendment.
Your USDA hardiness zone is 8b, meaning winter lows can reach around 15 degrees Fahrenheit. This determines which perennials, trees, and shrubs will survive winter in your area. Check the plant recommendations below for varieties suited to both your soil and climate.
Best Plants for Your Soil & Zone
These plants thrive in Silty Loam soil and USDA zone 8b.
Vegetables
Fruits
Flowers
Herbs
Trees
Shrubs
How to Improve Your Soil
Here are the top amendments recommended for Silty Loam soil:
- Compost — Improves structure and reduces erosion susceptibility
- Coarse Organic Mulch — Prevents crusting and erosion from rain impact
- Perlite — Improves drainage and reduces compaction
- Cover Crops (Annual Rye) — Root systems hold soil against erosion and improve structure
Test before you amend
Our data is drawn from USDA soil surveys, so it describes the dominant soil across an area — useful for planning, not precise enough for dosing lime or fertiliser. Before you buy amendments for Seattle, WA, run a test on the bed you actually garden: pH and N-P-K vary from one end of a yard to the other.
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Frequently Asked Questions
What type of soil is in Seattle, WA (98101)?
98101 has Silty Loam soil based on USDA soil survey data. It is moderately well drained with a pH range of 5.2 - 6.0.
What USDA hardiness zone is 98101?
Seattle, WA (98101) is in USDA hardiness zone 8b, with minimum winter temperatures around 15 degrees Fahrenheit.
What grows well in Silty Loam soil?
Silty Loam soil works well for many common garden plants. Check the plant recommendations section above for vegetables, flowers, herbs, and trees that thrive in this soil type and zone 8b.
How do I improve Silty Loam soil for gardening?
The best approach is to add organic matter such as compost, aged manure, or leaf mold. See our full amendment guide for Silty Loam soil for step-by-step instructions.
Where does this soil data come from?
All soil data on MySoilType comes from the USDA Natural Resources Conservation Service (NRCS) Web Soil Survey, the most comprehensive source of soil information in the United States.