Care

Soil pH Guide

Match plants to their ideal soil pH

Look up optimal soil pH ranges for hundreds of plants. Learn how pH affects nutrient availability and get recommendations for amending acidic or alkaline soils.

Soil pH Guide

Look up optimal soil pH ranges for common plants. Drag the slider to filter by your soil's pH.

Acidic (4.0) Neutral (7.0) Alkaline (9.0)

Showing plantas · in your pH range

Soil Amendment Tips

  • To raise pH: Add garden lime (calcium carbonate) at 5 lbs per 100 sq ft. Retest in 3 months.
  • To lower pH: Add elemental sulfur at 1 lb per 100 sq ft, or use acidifying fertilizer. Retest in 3 months.
  • Your soil is in the ideal range for most plants. Maintain with regular organic matter additions.

How to Use

  1. 1
    Test your soil pH

    Use a home test kit, pH meter, or send a sample to your local extension service for accurate results.

  2. 2
    Look up your plants

    Search for each plant in your garden to see its ideal pH range and whether your soil is a match.

  3. 3
    Review amendment recommendations

    If your pH is outside the ideal range, see suggested amendments like lime (to raise) or sulfur (to lower).

About

Soil pH is one of the most important and most overlooked factors in plant health. Even in soil rich with nutrients, plants can starve if the pH is wrong because acidity and alkalinity control which minerals are chemically available to roots. A tomato plant in strongly alkaline soil may show iron chlorosis (yellowing between leaf veins) despite abundant iron in the ground, simply because the high pH has locked the iron into insoluble compounds the roots cannot absorb.

The Soil pH Guide pairs each plant with its optimal pH range and explains what happens at either extreme. For gardeners whose soil falls outside the ideal range, the guide recommends specific amendments -- lime to raise pH or elemental sulfur to lower it -- with application rates that account for soil texture, since clay soils buffer pH changes and require larger doses than sandy soils. The guide also covers organic strategies for gradual pH adjustment, such as acidic mulches for blueberries or gypsum for sodic (high-sodium) alkaline soils. Testing your soil pH is inexpensive and simple with a home kit or through your county extension office, and the results are often the single most actionable piece of information you can learn about your garden soil.

FAQ

What is soil pH and why does it matter?
Soil pH measures the acidity or alkalinity of your soil on a scale from 0 (extremely acidic) to 14 (extremely alkaline), with 7.0 being neutral. pH matters because it controls the chemical availability of essential nutrients in the soil. In strongly acidic soil (below 5.5), aluminum and manganese become toxic to roots, while in alkaline soil (above 7.5), iron, zinc, and phosphorus become chemically locked and unavailable to plants even when physically present in the soil.
What pH do most garden plants prefer?
Most common garden vegetables, flowers, and lawn grasses grow best in slightly acidic to neutral soil, between pH 6.0 and 7.0. This range maximizes the availability of the most essential nutrients simultaneously. Notable exceptions include blueberries (4.5 to 5.5), azaleas and rhododendrons (4.5 to 6.0), and lavender (6.5 to 8.0). Always check the specific requirements of your plants rather than assuming the average range is correct.
How do I raise soil pH (make it less acidic)?
The most common amendment for raising pH is agricultural lime (calcium carbonate). Dolomitic lime adds both calcium and magnesium. Apply rates depend on your current pH, target pH, and soil texture: clay soils require more lime per pH unit than sandy soils because of their higher buffering capacity. Lime takes two to three months to fully react with the soil, so apply in fall for spring planting. Wood ash also raises pH but is less predictable in its calcium content.
How do I lower soil pH (make it more acidic)?
Elemental sulfur is the standard amendment for lowering pH. Soil bacteria convert sulfur to sulfuric acid over several months, so apply in fall. Iron sulfate acts faster but requires larger quantities. For long-term acidification around blueberries and azaleas, mulching with pine needles or acidic peat moss and using ammonium-based fertilizers helps maintain lower pH. Avoid using vinegar or coffee grounds as pH amendments -- their effects are negligible and temporary.
How often should I test my soil pH?
Test soil pH once a year, ideally in early spring or fall when you plan to amend. Soils in regions with heavy rainfall tend to acidify over time as calcium and magnesium leach out, while soils in arid regions tend to become alkaline as salts accumulate. Regular testing catches gradual drift before it affects plant performance. If you have amended your soil, retest after two to three months to confirm the amendment reached the target pH.