GrowingHQ

Your soil

Soil is the constraint every other piece of growing advice sits on top of, and the one most people never establish. Half an hour with a spade tells you more about what will succeed in your garden than a season of trial and error.

Start here if you do not know what you have

Four hand tests will place almost any garden in one of the eight soils below. None of them needs a laboratory, and each one states plainly what it does not tell you — which is the half that gets left out everywhere else.

Work out what you haveThe squeeze test, the vinegar test, the drainage hole, and finding a compaction layerWhat can and cannot be changedTen interventions, each with its ceiling stated — including the one GrowingHQ recommends against

The property that decides the most

Drainage is what separates a soil that grows perennials from one that kills them, and it is invisible until a week after heavy rain.

How three soils behave a week after heavy rainThree side-by-side soil cross-sections a week after heavy rain. The free-draining profile, typical of sand or chalk, holds no standing water and roots reach the full depth, with drought the main risk. The moisture-retentive profile, typical of loam or silt, holds water in the pores in the lower third while still admitting air, and roots reach full depth. The impeded profile, typical of compacted clay or a pan, has standing water filling two thirds of the depth, and roots stop short at the top of the wet zone and rot over winter.Free-drainingSand, chalkno standing water

Water gone within hours. Roots have air; the risk is drought.

Moisture-retentiveLoam, siltwater table

Holds water in the pores and still admits air. What every soil is measured against.

ImpededCompacted clay, panwater tableroots stop

Water stands. Roots stop at the wet zone and rot over winter.

All three look identical from above. The difference only appears a week after rain, and it is what decides whether a perennial survives its first winter.

Where your soil sits on the pH scale

The bands below are the resolution a home test kit can actually distinguish. Most crops want a narrower range than people expect, and the acid-lovers sit well outside it.

The soil pH scale and where common crops sitA horizontal pH scale from 3.5 to 8.5 divided into six bands: very acid, acid, slightly acid, neutral, slightly alkaline and alkaline. Markers below the scale show blueberries sitting in the acid band around pH 4.5 to 5.5, most vegetables spanning slightly acid to neutral around pH 6 to 7, brassicas favouring neutral to slightly alkaline where clubroot is reduced, and chalk gardens sitting in the alkaline band around pH 7.8 to 8.5. The useful range for most crops is narrow, and blueberries sit well outside it.Very acidAcidSlightly acidNeutralSlightly alkalineAlkalinepH 4pH 5pH 6pH 7pH 8Most cropsBlueberry— will not grow above about 5.5Most vegetablesBrassicas— clubroot is reduced above 7Chalk gardens
The bands are what a home test kit can actually distinguish. A kit reading 'acid' spans pH 5.0 to 6.0 — the difference between a blueberry bed and a brassica bed.

The eight soils

Enough resolution to be useful and few enough that you can place yourself. A soil map distinguishes hundreds of associations; a gardener with a spade can reliably distinguish these.

SoilFeels likepHPrefers itStruggles
Heavy claySticky when wet, sets hard when dry, and takes a polish when rubbedNeutral32 crops3 crops
SandyGritty between the fingers and will not hold a shapeSlightly acid102 crops3 crops
Chalky and alkalinePale, often stony, frequently shallow over solid rock, and always alkalineAlkaline49 crops50 crops
LoamThe balanced mixture every soil description uses as its reference point: holds moisture without waterlogging, and works over a long seasonNeutral205 crops—
SiltySilky rather than grittyNeutral162 crops—
Peaty and acidDark, spongy and acid, formed under waterlogged conditionsAcid8 crops—
Shallow over rockThe balanced mixture every soil description uses as its reference point: holds moisture without waterlogging, and works over a long seasonNot established110 crops8 crops
Made ground and urban soilThe balanced mixture every soil description uses as its reference point: holds moisture without waterlogging, and works over a long seasonSlightly alkaline1 crops30 crops

Those counts are computed by comparing each plant’s recorded requirements against each soil’s recorded characteristics, over 223 plants. They are not a ranking of soils: a soil that suits fewer crops in the catalogue may suit yours exactly, and every soil here grows something better than loam does.

Three things worth knowing before you start

You cannot change what your soil is made of

Organic matter, drainage and — within limits — pH can be moved. The mineral fraction cannot. Clay with twenty years of compost in it is well-structured clay, not loam, and it will still be sticky in a wet February. That is not a counsel of despair: well-structured clay is excellent ground. It is a reason to stop at the right point.

Not preferred is not impossible

The pH ranges published for a plant are the band it does best in, not the band outside which it dies. GrowingHQ treats a near miss as workable and says so, and reserves “struggles here” for a substantial mismatch — because the alternative is a machine for telling people not to bother.

A container beats a decade of soil correction

Where a plant needs conditions your garden fundamentally does not have — a blueberry on chalk is the standard case — a pot of the right compost is immediate, permanent and cheap, and attempting to change the ground is none of those things. This site will tell you that rather than describe a method that does not work.