If you're fertilizing & feeding right but still seeing yellowing leaves, stalled flowers or slow growth? You might be bumping into pH lockout — when nutrients are present but stuck in the soil, out of reach of roots. The fix isn’t guesswork or heavy-handed dosing. It’s a gentle tune-up: test → tweak → repeat.
In this guide we’ll show you how to spot pH issues fast, set a simple testing routine, and choose the right adjuster for indoor/semi-hydro and outdoor/organic setups.
What pH Lockout Looks Like (In Plain English)
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You feed, but plants still fade. Leaves yellow, tips burn, growth stalls, blossoms drop.
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Runoff EC looks fine, but symptoms linger. Nutrients are present; availability isn’t.
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Small changes fix big problems. A tiny nudge up or down can open the door to N, P, K, Ca, Mg and trace uptake.
The Sweet-Spot (Typical Targets)
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Soilless/indoor (coco, semi-hydro): ~5.8–6.3
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Potting mixes/organic soils: ~6.2–6.8
Different crops have quirks, but these bands keep most nutrients happily available. Always check your plant’s preferences and media.
Step-by-Step: Test → Tweak → Repeat
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Test regularly
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Indoors/semi-hydro: check input and runoff/reservoir weekly.
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Outdoor/organic: test monthly and at key milestones (pre-plant, mid-season).
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Diagnose direction
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Too high (alkaline): Fe/Mn lockout, pale new leaves, stubborn micronutrient issues.
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Too low (acidic): Ca/Mg/K issues, weak stems, tip burn.
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Adjust gently
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Make small changes, then re-test at the next watering or after a light drench.
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Indoor & Semi-Hydro Growers: Precision Wins
For houseplants, hydro and coco, stability is everything — small drops go a long way.
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Flairform pH Up (potassium carbonate) — nudges pH up safely in reservoirs or watering cans.
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Flairform pH Down (citric acid) — brings pH down smoothly for semi-hydro and indoor feeds.
How to use (quick guide):
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Start with your mixed nutrient solution.
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Add a few drops, stir well, and re-check pH.
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Repeat tiny adjustments until you hit the sweet-spot.
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Log your dose so next time is even easier.
Pro tip: Aim for consistency over perfection — keep readings within your target band rather than chasing a single number.
Outdoor & Organic Soils: Balance from the Base Up
In beds and large containers, you can build a naturally stable pH with slow-release minerals.
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Dolomite Lime (Ca+Mg) — helps prevent calcium and magnesium deficiencies before they show as curled, brittle leaves.
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Black Basalt Rock Dust — supports strong stems and resilient growth with silica plus broad minerals; great for fruit & veggie beds.
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Elemental Sulphur — gently lowers alkaline pH over time so roots adjust without stress. Expect gradual movement (think around a point per month with light, regular applications and favourable conditions).
How to use (quick guide):
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Topdress or blend into the top few centimetres; water in.
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Re-test in 2–4 weeks; repeat light applications rather than one big hit.
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Keep organic matter up — compost and mulches improve buffering.
Shop Dolomite | Shop Basalt | Shop Sulphur
Troubleshooting: pH Too High vs Too Low
| Symptom snapshot | Likely pH issue | What to do now | Re-test when |
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| New leaves yellow, veins green | Too high (alkaline) | Add pH Down indoors; consider elemental sulphur outdoors | Next feed / 2–4 weeks |
| Weak stems, Ca/Mg issues, tip burn | Too low (acidic) | Add pH Up indoors; consider dolomite outdoors | Next feed / 2–4 weeks |
| Nutrients piling up in runoff | Swinging pH / salt build-up | Reset with mild flush, then re-establish sweet-spot | After reset + next feeding |
Safe-Use Checklist (Works for Both)
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Measure first; adjust in small increments.
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Never mix adjusters together in concentrate.
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Foliar feeds? Only in cool hours and never with strong acid/alkali.
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Store bottles sealed; keep powders dry.
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Keep records — the right dose becomes repeatable.
Recommended Products
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Flairform pH Up (potassium carbonate) — precision pH rises for indoor/semi-hydro.
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Flairform pH Down (citric acid) — smooth pH drops for indoor/semi-hydro.
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Dolomite Lime — buffers Ca/Mg and supports steady pH outdoors.
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Black Basalt Rock Dust — mineral-rich top-up for robust, balanced soils.
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Elemental Sulphur — gradual pH reduction for alkaline beds/containers.
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pH Meter / Test Kit — simple, reliable checks at home.
FAQs
Do I need a lab test to manage pH?
No — a simple meter or test kit is plenty for home growers.
How often should I test?
Indoors/semi-hydro: weekly. Outdoor/organic: monthly or when plants change phase (flower/fruit), plus after big rains or top-ups.
Can I “set and forget” with one big dose?
Better to go little-and-often. Gentle adjustments keep roots happy and uptake steady. Swinging your pH too far at once can also be detrimental to your living soils beneficial microbes and biology. Click here to read about the The Impact of pH Adjusters on Soil Biology
Will elemental sulphur fix high pH overnight?
No — it’s designed to be gradual.
Why do my readings drift?
Water source, fertilizer type, media age and microbial activity all shift pH. Track your inputs and you’ll see predictable patterns. Temperature will also impact your readings, aim to take your pH reading when soil temperatures are between 23-26C.
Ready to unlock the sweet-spot? Shop pH Up | Shop pH Down | Shop Dolomite | Shop Basalt | Shop Sulphur
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