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Soil pH determines whether your plants can absorb nutrients. Get it right and everything thrives. Get it wrong and plants struggle even with perfect fertilizer.
The pH Scale for Gardeners
pH runs 1-14. Seven is neutral, below 7 is acidic, above 7 is alkaline. Most vegetables and flowers thrive between 6.0 and 7.0. At the wrong pH, nutrients lock up in soil and become unavailable to roots.
Ideal pH by Plant
- Most vegetables: 6.0-7.0
- Blueberries: 4.5-5.5 (very acidic)
- Roses: 6.0-6.5
- Azaleas: 4.5-6.0
- Lavender: 6.5-7.5
How to Test pH
- pH meter — Insert probe into moist soil. $10-30. Reusable and reasonably accurate.
- Test strips — Dip in water and soil mix. Compare to chart. Fast and cheap.
- Lab test — Send soil sample to extension service. $15-25. Most accurate.
- DIY test — Vinegar fizzes on alkaline soil. Baking soda fizzes on acidic soil.
Lower pH (More Acidic)
Add elemental sulfur for long-term results (takes 2-3 months). Peat moss, pine needles, and coffee grounds also acidify slowly. Retest after 3 months.
Raise pH (More Alkaline)
Apply ground limestone in fall before spring planting. Wood ash raises pH quickly and adds potassium. Test soil every 2-3 years to maintain ideal range.