Free Growli tool

Soil pH guide
— ideal pH for any plant.

Pick a plant and the guide returns its ideal soil pH range, a plain explanation of what that pH means, four ways to test your soil, and the exact amendments to raise or lower pH if you need to. 30 popular vegetables, fruits, herbs, and acid-loving shrubs covered, ranges cross-checked against cooperative extension and RHS guidance.

Pick a plant or crop

30 popular species. Ranges cross-checked against US cooperative extension publications and the Royal Horticultural Society.

Ideal pH for blueberries

4.5 to 5.5

strongly acidic

One of the most pH-fussy crops. Above 5.5 the leaves yellow and growth stalls because iron and other micronutrients become unavailable.

4.0 acidic5.57.0 neutral8.0 alkaline

What pH actually means

Soil pH measures how acidic or alkaline the soil water is, on a scale from 0 (very acidic) to 14 (very alkaline), with 7 being neutral. pH controls which nutrients dissolve into the soil water for roots to take up — so the wrong pH means a plant can be sitting in fertile soil and still starve.

How to test your soil pH

Soil testing lab (most accurate). Send a sample to a cooperative-extension lab (US) or RHS Garden Advice (UK). $15-25, with full nutrient profile alongside the pH reading.
Paper test strip. A cheap pack of strips dipped into a soil-water slurry. Reads to roughly 0.5 pH unit — fine for spotting if you are far off target.
Home pH probe. Cheap analogue probes ($10-20) drift with use; digital probes ($40-80) hold calibration if you re-zero them each season.
Plant indicators. Acid soil grows moss in lawns, vivid blue hydrangea blooms, and free-flowering rhododendrons. Alkaline soil grows chickweed, clover that pinks rather than blues, and yellowing on acid-lovers.

How to adjust your soil pH

To lower pH (more acidic)

Elemental sulphur — most reliable. Apply 1-2 lb per 100 sq ft to drop one pH unit on loam. Soil microbes convert it over 3-6 months.
Peat moss — mix into the planting hole for blueberries and azaleas. Acts as both acidifier and moisture retainer.
Pine needles or pine bark — mulch annually to maintain acid pH around acid-loving shrubs.
Ammonium-based fertilisers (ammonium sulphate, urea) — slowly acidify the bed when used over multiple seasons.

To raise pH (more alkaline)

Garden lime (calcium carbonate) — standard fix. Apply 5-10 lb per 100 sq ft to raise one pH unit on loam. Incorporate in autumn for spring sowing.
Dolomite lime — magnesium-rich. Best for sandy soils that are short on magnesium as well as calcium.
Wood ash — strong and fast. Use sparingly (a light dusting) because it also adds potassium and over-application can scorch roots.
Mushroom compost — gentle lift, plus organic matter. Great for raised beds that have drifted slightly acidic.

Patience required. Soil pH changes slowly — expect 3 to 12 months for sulphur or lime to fully take effect, longer in heavy clay. Re-test 6 months after amending, and never try to swing the pH more than one full unit per growing season.

Save your soil profile to Growli

The Growli app remembers your soil pH alongside every crop you plant — so if your bed is at 5.8, it stops recommending spinach and cabbage before you sow them, and offers the right amendment if you want to grow them anyway.

Save to Growli →

Why pH matters more than fertiliser

pH controls nutrient availability. At pH 7 most nutrients are equally accessible. Drop below 5.5 and iron and aluminium dominate, locking out phosphorus and calcium. Climb above 7.5 and iron, manganese, zinc, and boron become unavailable even when present in the soil — the classic chlorotic yellowing on rhododendrons or blueberries growing in neutral soil.

That is why heavy fertilising will not save a plant in the wrong pH bed. You can pour nitrogen and phosphate on a blueberry at pH 6.5 and the leaves will still yellow because iron is locked up in insoluble forms. Fix the pH first; the fertility will follow.

What this tool does not capture. Soil texture (sand vs clay changes how much amendment you need), drainage, organic matter, or your local groundwater chemistry. For a full soil profile, send a sample to a cooperative extension lab once every 3 to 5 years.

Frequently asked questions

What does soil pH mean?

Soil pH measures how acidic or alkaline the soil water is on a 0 to 14 scale, with 7 being neutral. Anything below 7 is acidic and anything above 7 is alkaline. pH controls which mineral nutrients dissolve into solution and reach roots — at the wrong pH, fertile soil still leaves plants short on iron, phosphorus, or calcium.

What is the most common pH range for vegetables?

Most common vegetables thrive between pH 6.0 and 6.8 — slightly acidic. Tomatoes, peppers, lettuce, carrots, cucumbers, peas, beans, onions, and garlic all sit inside this band. Brassicas (cabbage, broccoli, kale) prefer the upper end at 6.5 to 7.5 partly because clubroot disease is suppressed near neutral pH. Potatoes prefer the lower end (5.0 to 6.0) to suppress common scab.

How long does it take to change soil pH?

Slowly — that is the most important practical fact. Sulphur (to lower pH) and garden lime (to raise pH) typically take 3 to 6 months to register their full effect, and 12 months on heavy clay soils. Never try to swing pH more than one full unit per growing season; broadcast the amendment in autumn for spring planting, retest after 6 months, and re-amend if needed.

How do I lower my soil pH for blueberries?

Apply elemental sulphur in autumn at 1 to 2 lb per 100 sq ft to drop one pH unit on loam soil, mixed into the top 6 inches. For acid-loving blueberries (target pH 4.5 to 5.5), mulch annually with pine bark or pine needles to maintain the acidity once you have got it down. Avoid using aluminium sulphate as a long-term acidifier — it can cause aluminium toxicity over time.

How do I raise my soil pH if it is too acidic?

Apply garden lime (calcium carbonate) at 5 to 10 lb per 100 sq ft to raise one pH unit on loam. Use dolomite lime if your soil is also short on magnesium (most sandy soils). Wood ash is faster but stronger — use sparingly. The lift is fully effective 3 to 6 months after application, so amend in autumn for spring crops.

How is this different from the Growli app?

The guide gives you a static look-up for one species at a time. The Growli app stores your soil pH per bed, flags crop incompatibilities before you plant (no spinach in a pH 5.5 bed), and tracks amendment timing — it tells you when to retest after liming and when the bed is ready for the brassica block.

Soil pH guide — ideal pH for any plant.