The Importance of pH in Plant Life
🔹 What is pH?
pH stands for “potential of hydrogen” and measures how acidic or alkaline a substance is.
🌡️ pH Scale Basics (Ranges from 0 to 14):
- 0–6.9 → Below 7 is acidic
The lower the number, the more acidic.
Example: Vinegar has a pH around 2–3. - 7 → pH 7 is neutral
Pure water is neutral. - 7.1–14 → Above 7 is alkaline (basic)
The higher the number, the more alkaline.
Example: Baking soda has a pH around 9.
🔹 pH Scale Is Logarithmic
Each whole number change on the pH scale represents a 10-fold change in acidity or alkalinity.
Example: A substance with pH 5 is 10 times more acidic than one with pH 6.
🔹 Common pH Examples
| Substance | pH Value |
|---|---|
| Battery acid | 0–1 |
| Lemon juice | 2 |
| Vinegar | 3 |
| Tomato juice | 4 |
| Black coffee | 5 |
| Pure water | 7 |
| Baking soda | 9 |
| Ammonia | 11 |
| Bleach | 13 |
🌱 Why pH Matters for Plants:
1. Nutrient Availability
Plants can only absorb nutrients effectively when the soil or growing medium is within the correct pH range.
If pH is too high or too low, nutrients (like iron, phosphorus, or magnesium) may become locked in the soil — even if they’re present, plants can’t use them.
2. Root Health
Extreme pH levels can damage roots or interfere with beneficial microbes and fungi in the soil.
Healthy roots = healthy plant growth.
3. Disease Resistance
Proper pH helps maintain a balanced environment, reducing the chance of certain soil-borne diseases.
🌿 Examples of Ideal pH Ranges
- Bromeliads: 5.0 – 6.5
- Most Houseplants: 6.0 – 7.0
- Azaleas, Blueberries: 4.5 – 5.5
- Vegetables (general): 6.0 – 7.0
🔧 How to Adjust pH
🔻 To Lower pH (Make More Acidic):
1. Peat Moss
- 🌱 Naturally acidic (pH ~3.5–4.5)
- Mix into potting media to gradually lower and stabilize pH
- Common in bromeliad and aroid mixes
2. Pine Bark
- Adds structure and acidity to the mix
- Slowly lowers pH over time as it decomposes
- A great organic component for long-term use
3. Diluted Vinegar (for water pH adjustment)
- Mix 1 teaspoon of white vinegar into 1 gallon of water
- Only use occasionally — monitor pH to avoid over-acidifying
- Best for temporary adjustments in irrigation water
4. Citric Acid Solution
- Dissolve a small pinch (⅛ tsp) in 1 gallon of water
- More stable and gentle than vinegar
- Works well for rainwater or distilled water lacking minerals
5. Sulfur (Elemental Sulfur)
- Used more for garden soil than container media
- Takes weeks to months to work as soil microbes convert sulfur to sulfuric acid
- Use with caution and test pH regularly
6. Acidic Fertilizers
- Look for fertilizers labeled “for acid-loving plants” (like azaleas or hydrangeas)
- Contain ammonium sulfate, urea, or ammonium nitrate — which lower pH over time
- Use as part of regular feeding, but follow label instructions
🔺 To Raise pH (Make More Alkaline)
🌱 For Soil:
1. Garden Lime (Calcium Carbonate)
- The most common and gentle method
- Available as dolomitic lime (adds magnesium) or calcitic lime (adds calcium)
- Mix it into the soil and water well — results take a few weeks to show
2. Wood Ashes (in small amounts)
- Contains potassium, calcium, and magnesium
- Use sparingly — raises pH quickly
3. Baking Soda (Sodium Bicarbonate)
- Dissolve 1 tsp in 1 gallon of water
- Apply sparingly — not ideal for long-term use
- Good for minor or temporary pH boosts
💧 For Water / Irrigation:
1. Add a Small Amount of Baking Soda
- Use 1/4 to 1/2 teaspoon per gallon
- Raises pH slightly — always test before and after application
2. Potassium Bicarbonate
- Safer alternative to baking soda
- Common in hydroponics and for sensitive plants
3. Aerate the Water
- Let water sit uncovered for 24–48 hours
- Releases dissolved CO₂, which can slightly raise pH
✅ Tips:
- Always test pH before and after amending
- Gradual changes are best — sudden shifts can harm roots and microbes
- Adjust based on plant preferences — for example, bromeliads like slightly acidic conditions