Plant care calculator
Soil pH Amendment Calculator
Calculate amendments to reach the ideal 5.5 - 6.5 pH for Bougainvillea nutrient uptake.
Quick Answer
Bougainvilleas require a slightly acidic soil pH between 5.5 and 6.5. If your soil is too alkaline (above 7.0), the plant cannot absorb iron or phosphorus, leading to yellow leaves with green veins (chlorosis) and zero blooms. To lower pH: use iron sulfate for fast results that also correct iron deficiency, or elemental sulfur for a slower, longer-lasting effect.
Enter your details
Enter the labeled values below. Results appear without leaving this page.
Recommended Output
Method
Calculates the difference between current and target pH, multiplied by a base requirement of material (lime vs sulphur), and adjusted by a soil texture factor (clay requires more, sand requires less).
Reference Table
Static Bougainvillea Soil pH Calculator Reference
Visible baseline values
These baseline ratios and decision rules are included directly in the page so visitors can review core guidance before using the interactive calculator.
| Scenario | Baseline Rule | Safety Note |
|---|---|---|
| Inputs used by this tool | Unit System, Garden Area, Current pH, Target pH | The interactive calculator refines the result from these inputs. |
| Outputs generated | Total Material Required, Application Rate, Application Method, Safety & Timing Advice | The static table gives baseline logic; final value depends on entered values. |
Formula summary: Material = |Target - Current| x Base Rate x Soil Texture Factor.
The Problem
Adding too much lime or sulphur can severely damage soil chemistry and take years to correct. Most gardeners guess the amount, leading to nutrient lockout.
When to Use This Tool
Use immediately after receiving a soil test report, before planting season begins.
Who is this for?
- Gardeners preparing beds for acid-loving plants like blueberries
- Lawn care enthusiasts fixing acidic turf
A wrong pH locks out the nutrients your Bougainvillea needs to bloom.
Why 5.5 to 6.5?
In this slightly acidic range, iron, phosphorus, and potassium are highly soluble and easily absorbed by the roots. If you are feeding your plant bloom-booster but still getting no flowers, your pH is likely too high (alkaline).
Elemental Sulfur vs. Iron Sulfate
Both lower pH, but they work differently. Iron sulfate acts faster (weeks) and simultaneously corrects iron deficiency — ideal when you see yellowing between leaf veins (chlorosis). Elemental sulfur acts slowly over months but is longer-lasting and better suited for preventive management.
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Next Best Actions
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'Barbara Karst'
Bougainvillea 'Barbara Karst' is a vigorous, popular cultivar prized for its brilliant magenta-red bracts and prolific, nearly year-round blooming habit. One of the hardiest bougainvilleas, it thrives in hot, full-sun gardens, on fences and trellises, and in large containers across tropical and subtropical climates.
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Duck Feet
Bougainvillea 'Duck Feet' is a rare compact cultivar prized for its distinctive lobed leaves resembling duck feet and bright pink-magenta bracts. Ideal for containers, balconies, and small gardens where foliage interest matters as much as flower colour.
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Vietnam Mix
This Vietnam Mix bougainvillea is valued for its bright pink to magenta bracts and its vigorous climber with strong repeat bloom. In warm tropical and subtropical gardens, it performs as a resilient ornamental climber that rewards full sun, sharp drainage, and a restrained feeding regime with long flushes of colour.
Base Rate Adjustments (lbs per 100 sq ft per 1.0 pH change)
| Soil Type | To Raise 1.0 pH (Add Lime) | To Lower 1.0 pH (Add Sulfur) |
|---|---|---|
| Sand | 2.5 lbs | 0.8 lbs |
| Loam | 5.0 lbs | 1.5 lbs |
| Clay | 7.5 lbs | 2.0 lbs |
Troubleshooting Guide
1 I applied lime 2 weeks ago and the pH hasn't changed
Cause: Agricultural limestone is practically insoluble in water. It requires time and soil microbial activity to break down.
Wait at least 3 to 4 months before re-testing the soil. Keep the soil moderately moist to help the reaction.
2 Leaves are turning yellow between the veins after adding sulphur
Cause: Rapid pH drop can induce magnesium or iron deficiency, or the sulphur application rate was too high (above 5 lb/100 sq ft).
Test soil pH immediately. If pH has dropped below 5.0 for most vegetables, stop further applications and add finely ground lime cautiously. For mild yellowing, apply a foliar spray of Epsom salts (magnesium) or chelated iron.
3 Plants look stunted, and the soil surface has a white crust after repeated lime applications
Cause: Over-liming has raised pH above 7.5, causing calcium to precipitate and lock up phosphorus, iron, and manganese.
Stop adding lime. Incorporate organic matter (compost, leaf mould) to help buffer the excess alkalinity. For severe cases, add elemental sulphur very slowly (1 lb per 100 sq ft per season) while monitoring pH monthly.
4 I applied sulphur six months ago, and pH hasn't changed at all
Cause: Sulphur oxidation requires warm, moist, well-aerated soil. Cold, dry, or compacted soil slows bacteria to a crawl.
Ensure the soil is not waterlogged. Aerate compacted areas. In cold climates, apply sulphur in early spring so it has the full growing season to react. Consider using a finer grind (pelletised sulphur can be slower).