Quick Summary
- Ideal Range for 90% of gardens: 6.2 – 6.8
- To Raise pH: Add Garden Lime (Calcium Carbonate).
- To Lower pH: Add Elemental Sulfur.
The Master Vegetable pH Chart (A-Z)
| Plant Name | Optimal pH Range | Notes |
|---|---|---|
| Apple | 5.0–6.5 | Prefers slightly acidic |
| Artichoke | 6.5–7.5 | Tolerates alkaline |
| Arugula | 6.0–7.0 | Wide tolerance |
| Asparagus | 6.5–7.5 | Alkaline lover |
| Basil | 5.5–6.5 | Herb, moderate feeder |
| Beans (Bush) | 6.0–7.0 | Nitrogen fixer |
| Beans (Pole) | 6.0–7.0 | Nitrogen fixer |
| Beets | 6.0–7.5 | Alkaline tolerant |
| Blackberry | 5.5–7.0 | Berry, wide range |
| Blueberry | 4.5–5.5 | Strict acid lover |
| Broccoli | 6.0–7.0 | Heavy feeder |
| Brussels Sprouts | 6.0–7.5 | Brassica, heavy feeder |
| Cabbage | 6.0–7.5 | Heavy feeder |
| Cantaloupe | 6.0–7.0 | Melon, moderate feeder |
| Carrots | 5.5–7.0 | Root crop |
| Cauliflower | 6.0–7.0 | Heavy feeder |
| Celery | 6.0–7.0 | Heavy feeder, moisture lover |
| Chard (Swiss) | 6.0–7.5 | Leafy green |
| Chives | 6.0–7.0 | Herb, perennial |
| Cilantro | 6.0–7.0 | Herb, cool season |
| Collard Greens | 6.5–7.5 | Alkaline tolerant |
| Corn (Sweet) | 5.8–7.0 | Heavy feeder |
| Cranberry | 4.2–5.0 | Extreme acid lover |
| Cucumber | 5.5–7.0 | Heavy feeder |
| Dill | 5.5–6.5 | Herb |
| Eggplant | 5.5–6.5 | Nightshade, warm season |
| Endive | 5.8–7.0 | Leafy green |
| Garlic | 6.0–7.0 | Allium, moderate feeder |
| Ginger | 5.5–6.5 | Rhizome crop |
| Grape | 5.5–7.0 | Perennial fruit |
| Kale | 6.0–7.5 | Alkaline tolerant, heavy feeder |
| Leek | 6.0–7.0 | Allium |
| Lettuce | 6.0–7.0 | Leafy green, light feeder |
| Melon (Honeydew) | 6.0–7.0 | Heavy feeder |
| Mint | 6.0–7.0 | Herb, invasive spreader |
| Mustard Greens | 6.0–7.5 | Brassica |
| Okra | 6.0–7.5 | Alkaline tolerant, warm season |
| Onion | 6.0–7.0 | Allium, moderate feeder |
| Oregano | 6.0–7.0 | Herb, drought tolerant |
| Parsley | 5.5–6.7 | Herb, biennial |
| Parsnip | 5.5–7.0 | Root crop |
| Peas | 6.0–7.5 | Nitrogen fixer, cool season |
| Peppers (Bell) | 6.0–7.0 | Nightshade, warm season |
| Peppers (Hot) | 6.0–7.0 | Nightshade, warm season |
| Potato | 4.8–6.5 | Acid lover, prevents scab |
| Pumpkin | 5.5–7.0 | Heavy feeder |
| Radish | 6.0–7.0 | Fast-growing root |
| Raspberry | 5.5–6.5 | Berry, slightly acidic |
| Rhubarb | 5.5–7.0 | Perennial vegetable |
| Rosemary | 6.0–7.0 | Herb, drought tolerant |
| Rutabaga | 5.5–7.0 | Root crop |
| Sage | 5.5–6.5 | Herb, perennial |
| Spinach | 6.5–7.5 | Alkaline lover, leafy green |
| Squash (Summer) | 6.0–7.0 | Heavy feeder |
| Squash (Winter) | 5.5–7.0 | Heavy feeder |
| Strawberry | 5.5–6.5 | Berry, perennial |
| Sweet Potato | 5.0–6.0 | Acid preferring, warm season |
| Thyme | 5.5–7.0 | Herb, drought tolerant |
| Tomato | 6.0–6.8 | Nightshade, heavy feeder |
| Turnip | 5.5–7.0 | Root crop |
| Watermelon | 6.0–7.0 | Heavy feeder, warm season |
| Zucchini | 6.0–7.0 | Heavy feeder |
Data verified against the [University of Connecticut Soil Analysis Lab] standards.
The “Troubleshooting” Guide (Visual Diagnosis)
Plant health problems often stem from pH imbalances that control [nutrient solubility], effectively locking out food even if it is present in the soil.
Diagnosing pH Problems by Leaf Color
| Symptom | Likely pH Issue | Locked-Out Nutrient |
|---|---|---|
| Yellow leaves with green veins (new growth) | Too Alkaline (>7.5) | Iron |
| Yellow leaves (old growth, progressing upward) | Too Acidic (<5.5) | Magnesium |
| Purple or reddish undersides of leaves | Too Acidic (<5.0) | Phosphorus |
| Stunted growth, dark green leaves | Too Acidic (<5.5) | Nitrogen availability reduced |
| Pale leaves, slow growth, tip burn | Too Alkaline (>7.5) | Manganese, Zinc |
| Blossom-end rot (tomatoes, peppers) | Any pH with calcium deficiency | Calcium (mobility issue) |
Why This Happens: At pH below 5.5, aluminum and manganese become toxic while calcium and magnesium precipitate. At pH above 7.5, iron, manganese, and phosphorus bind into insoluble compounds that roots cannot absorb. The “sweet spot” of 6.0–6.8 maximizes nutrient solubility.
Note: If you cannot fix your pH immediately, [Arbuscular Mycorrhizal Fungi] can act as a bridge, helping plants access locked-out Phosphorus even in acidic conditions.
How to Correct Your Soil (The Math)
Do not guess amendments. Soil type dramatically affects how much material you need. These rates apply to the top 6 inches of soil depth.
Correction Rates per 100 Sq. Ft.
| Visual Symptom | Likely pH Issue | Locked-Out Nutrient |
|---|---|---|
| Yellow leaves, green veins (New growth) | Too Alkaline (>7.5) | Iron (Fe) |
| Yellow leaves (Old growth) | Too Acidic (<5.5) | Magnesium (Mg) |
| Purple/Reddish leaf undersides | Too Acidic (<5.0) | Phosphorus (P) |
| Stunted growth, dark green leaves | Too Acidic (<5.5) | Nitrogen (N) availability |
| Pale leaves, tip burn | Too Alkaline (>7.5) | Manganese/Zinc |
| Blossom-end rot | Any (Irregular watering) | Calcium (Ca) mobility |
Application Guidelines:
- Lime: Use dolomitic lime (contains magnesium) or calcitic lime (calcium only). Apply in fall; takes 3–6 months to react. Water thoroughly after application.
- Sulfur: Use elemental sulfur (slow-release) or aluminum sulfate (fast-acting but risks toxicity). Work into soil 2–3 months before planting.
- Safety Rule: Never change pH by more than 1.0 point per growing season. Dramatic shifts shock plant roots and kill beneficial microbes.
Calculation Example:
- Your loam soil tests at pH 5.0. You want pH 6.5.
- Change needed: +1.5 points
- Amendment: 5.0 lbs × 1.5 = 7.5 lbs of lime per 100 sq. ft.
FAQ (Featured Snippet Targeting)
Q: What is the fastest way to lower soil pH?
Answer: Aluminum sulfate works instantly (lowers pH within weeks) because it releases hydrogen ions immediately upon contact with water. However, it risks aluminum toxicity if over-applied. Elemental sulfur is safer but requires soil bacteria to convert it to sulfuric acid, taking 2–4 months. For long-term pH management, use sulfur. For emergency correction of containerized plants, use aluminum sulfate at half the recommended rate.
Q: Does baking soda lower soil pH?
Answer: No, baking soda (sodium bicarbonate) raises pH slightly and adds sodium to soil. Sodium disperses clay particles, destroys soil structure, and inhibits water infiltration. Sodium buildup creates a toxic environment for most plants. Never use baking soda as a soil amendment.
Q: Can I test pH without a kit?
Answer: The “Vinegar and Baking Soda Test” provides rough estimates but cannot replace calibrated pH meters or lab tests.
Method:
- Collect 2 soil samples (1 cup each).
- Add white vinegar to Sample 1. If it fizzes, soil is alkaline (pH > 7.0).
- Add baking soda + water to Sample 2. If it fizzes, soil is acidic (pH < 7.0).
- No fizzing = near-neutral pH (6.5–7.5).
Accuracy: This test only indicates whether soil is above or below pH 7.0. It cannot distinguish between pH 5.0 and pH 6.0, both of which produce no reaction. For vegetable gardens, invest in a digital pH meter ($15–30) for precision.
Q: How often should I test soil pH?
Answer: Test annually in spring before planting. Sandy soils require more frequent testing (twice per year) because they lose amendments quickly through leaching. Clay soils hold pH stable longer. After making corrections, retest after 3–6 months to verify results before planting.
Q: Can I use wood ash to raise pH?
Answer: Yes, wood ash contains 25–45% calcium carbonate and raises pH rapidly—sometimes too rapidly. It acts 3–5 times faster than lime. Risk: Over-application causes potassium toxicity and locks out magnesium. Use sparingly: maximum 2 lbs per 100 sq. ft. per year. Never apply wood ash from treated lumber (contains toxic chemicals).