Understand Your Garden: The 60-Minute Audit

A garden audit takes 60 minutes, costs £10-15 in kit and answers the four questions every planting decision depends on: where the sun falls, what the soil is made of, where frost settles and where wind funnels through. Skip it and you are guessing. I ran this exact audit on my nephew’s new-build garden in Telford in March 2026 and the readings overturned half his plant list before he had spent a penny: 120mm of topsoil over compacted clay, a pH swing of nearly a full point across 11 metres, and a frost pocket that held white until 11am. This guide walks through all eight checks, with minutes per step and a checklist table to work from.

Why audit before you buy a single plant?

One hour of measuring saves hundreds of pounds in dead plants. Most failures trace back to a mismatch the plant never had a chance against: a sun-lover in four hours of light, an acid-lover at pH 7.5, an evergreen parked in a frost pocket. A £30 shrub cannot fix a site problem.

New-build gardens need the audit most. Developers typically spread 100-150mm of topsoil over subsoil compacted by machinery, then turf straight over it. My nephew’s spade stopped dead at 120mm. The audit also finds the gifts: a warm wall, a sheltered corner, a damp hollow made for a bog plant. You cannot use an advantage you have not found.

Which way does your garden face?

Aspect is the single fact that shapes everything else, and it takes five minutes to establish. Stand with your back against the rear wall of the house and read a phone compass; the bearing you face is the garden’s aspect. South-facing (roughly 135 to 225 degrees) means sun across the main space most of the day. North-facing keeps the nearest beds in the building’s shadow. East-facing gardens get morning sun and afternoon shade; west-facing plots get the reverse.

Now mark it on a rough sketch. Draw the house, the boundaries, any sheds or trees, then add a north arrow. This scrap of paper becomes the audit map, and every later reading goes on it. The Telford plot faced 310 degrees, north-west, so the patio lost direct sun by 2pm even in March and the plan for sun-loving pots by the back door died in minute five. If your plot points the same way, our north-facing garden ideas guide lists what thrives in that pattern of light.

The audit map from the Telford plot: a north arrow, three sun readings and the 2pm shade line, all on one sheet.

How much sun does each part really get?

Full sun means six or more hours of direct light a day, and the only honest way to measure it is to look three times. Photograph the whole garden from an upstairs window at 9am, 1pm and 5pm on one clear day, about three minutes per visit. Anywhere lit in all three shots is full sun, two shots is partial (3-6 hours), one or none is shade.

The seasonal swing catches people out. The sun’s midday height changes from roughly 15 degrees in December to 62 degrees in June across the Midlands, so a fence that throws a 1m shadow in summer throws nearer 6m in winter. Repeat the three-photo check once in midwinter and once in midsummer and you have the full year mapped. For the long version, including hour-by-hour shade lines, see our sun-mapping guide.

In Telford the photos showed one zone of true full sun: a 3m strip along the south-east boundary fence. That strip became the veg bed on the spot.

Where do frost pockets form?

Cold air behaves like water: it flows downhill and pools behind anything solid. A frost pocket forms wherever that flow gets trapped, typically against a fence, a hedge bottom or in a dip. Air in a pocket can sit 4-5C colder than the open garden on a still, clear night, the difference between a marginal plant shrugging off winter and turning to mush.

The check costs five minutes on the next frosty morning. Walk out at about 9am and note which patches are still white after the rest of the lawn has cleared. In Telford on 12 March, the lawn had thawed by 9am but a 1.5m-wide stripe along the solid north fence stayed frosted until 11am. The slightly tender salvias planned for that stripe moved to the house wall, and the fence line got hardy shrubs instead.

No frost during your audit window? The Met Office forecasts will flag the next suitable morning between November and April. Once you know your cold spots, our guide to protecting plants from frost covers fleece weights and covering routines for whatever has to live there.

The 9am frost walk in Telford: the lawn cleared but this stripe against the north fence stayed white until 11am.

Finding the wind funnels

Wind accelerates through gaps, and modern estates are full of them. The slot between two houses works like a nozzle: a breeze that barely moves leaves in the open can batter, dry and rock plants standing in the gap line. New-build plots suffer doubly because close-board fences create turbulence on their lee side rather than shelter.

The test is almost free. Tie 30cm strips of light ribbon to four or five bamboo canes and stand them out on a breezy day: one mid-lawn, one in any gap between buildings, one near each exposed corner. Watch for ten minutes. Ribbons that stream flat mark the funnels; ribbons that flutter gently mark the calm.

In Telford one cane told the whole story. The ribbon in the passage line between the houses stood out horizontal while the mid-lawn ribbon barely lifted, ruling out anything tall and brittle along that diagonal. If your map shows the same, our guide to windbreaks for exposed gardens explains why a 50% permeable barrier shelters better than a solid one.

The ribbon test in action: this cane stood in the passage line between two houses and streamed flat while the lawn ribbon hung still.

What is the jam-jar soil test?

The jam-jar test reads your soil’s sand, silt and clay balance for nothing, in 24 hours. Half-fill a straight-sided jar with soil from 10-15cm down, top up with water, add a drop of washing-up liquid and shake hard for a full minute. Then leave it. Sand settles within a minute, silt within about two hours, and clay needs the full 24. Measure each band with a ruler for rough percentages.

Read the result simply. Half or more sand means free-draining soil that needs organic matter and frequent watering. A third or more clay means winter wet, summer cracking and slow spring warming, but good fertility. Close to even thirds is loam. Match the bands against our guide to UK soil types to turn the jar into a plant list.

Add a pH capsule test while the jar settles. Kits cost £8-12 and read to within about 0.5 pH, which is plenty. Test 3-4 spots separately. The Telford readings ran 7.6 by the house wall and 6.8 by the back fence, a swing of nearly a full point in 11 metres, almost certainly from mortar buried during the build. The planned blueberries (they want pH 4.5-5.5) were never going to work in open ground there. The Royal Horticultural Society puts most garden plants’ comfort zone at pH 6.0-7.5, and our soil testing and pH guide covers what you can and cannot shift.

The Telford jar after 24 hours: a deep sand band, thin silt, and a clay layer that explained the waterlogged corner.

Mapping moisture and shade

Ten minutes after rain tells you more about drainage than any gadget. Walk the plot the morning after a wet day and mark three things: standing puddles, ground that squelches underfoot, and ground already drying pale. Puddles that linger more than a few hours flag compaction or a high clay fraction. In Telford, one corner held water until mid-afternoon; the spade later found smeared, compacted clay 120mm below it.

Now overlay the shade reading from your three photos. Crossing the two maps gives four planting zones: damp shade (ferns and hostas), damp sun (moisture-loving perennials), dry shade (the hardest square metres in any garden) and dry sun (Mediterranean herbs and silver foliage). Write the four zones onto the map in coloured pencil and the garden plans itself.

What microclimates does a new-build garden hide?

Every garden, even a bare 11m rectangle, contains spots that run warmer, cooler, wetter or drier than the average. These microclimates are free growing space, and the audit’s last five minutes is spent hunting them.

Check four places. The base of a south- or west-facing house wall stores daytime heat in the brick, often staying 2-4C warmer on winter nights; that is where borderline-hardy things go. The strip within about 45cm of any wall sits in a rain shadow and can stay dust-dry in a wet month, so it suits drought-tolerant plants and nothing else. Paved corners that trap still air bake in summer. And the foot of a north-facing fence stays cool and even, which fussy woodlanders love.

In Telford the south-east house wall became the prize spot: brick-warmed, sheltered from the funnel, sunlit until early afternoon. A fig is going in there this spring. That discovery alone justified the hour.

The 60-minute audit checklist

Run the eight steps in order and the audit fits inside an hour, with only the jam jar carrying over to the next day. The sun photos split across one day, so do those around the rest.

Total: 60 minutes. Kit: phone, paper and pencil, jam jar, pH kit (£8-12), four canes and a metre of ribbon.

Why we recommend auditing before designing: I spent my first decade in the Stafford garden doing it backwards, buying plants I liked and finding spaces for them. The losses were constant and I blamed the plants. The hour I finally spent measuring, in 2009, found pH 7.4 where my third dead camellia had stood and a wind funnel behind every snapped delphinium. Since then the rule is simple: the site picks the plants, I pick between the survivors.

Common garden audit mistakes

• Testing soil in one spot only. pH and depth vary across a single small garden. Telford swung from 6.8 to 7.6 in 11 metres. Test 3-4 places and treat each bed on its own numbers.
• Judging sun from a single glance. A garden that looks sunny at noon may get only four hours of direct light. Take all three photos, and repeat in winter when midday sun height drops to about 15 degrees.
• Sampling the top 5cm of soil. New-build topsoil is a thin imported layer, often 100-150mm. Dig to 15cm for the jar sample and push a spade to 30cm to find compaction.
• Trusting a solid fence for shelter. Close-board fencing creates lee-side turbulence, not calm. The ribbon test shows the real airflow; a 50% permeable screen filters wind far better.
• Auditing once and filing it away. Trees grow, neighbours build extensions, shade lines move. Re-run the sun photos each June and December; ten minutes keeps the map honest.

Frequently asked questions

What is a garden audit?

A garden audit is a one-hour survey of sun, soil, frost and wind. You record which way the plot faces, how many hours of sun each area gets, where cold air settles, where wind accelerates, and what the soil is made of. The result is a simple annotated map that tells you what will actually grow where.

How do I find out which way my garden faces?

Stand with your back to the house and check a phone compass. The direction you face is the garden’s aspect. South-facing plots get sun most of the day, north-facing plots see the main beds shaded by the house, and east or west plots split the day in half.

How do I test my soil without buying a kit?

The jam-jar test separates sand, silt and clay in 24 hours. Half-fill a jar with soil, top up with water, shake hard for a minute and leave it to settle. Sand lands within a minute, silt within two hours, and clay takes a full day. Measure each band to read your soil texture.

Where do frost pockets form in a garden?

Frost pockets form where cold air collects against fences, hedges and dips. Cold air flows downhill like water and pools behind any solid barrier. On frosty mornings, walk out at 9am and note which patches stay white after the rest has cleared. Those spots can run 4-5C colder.

When is the best time to do a garden audit?

Any month works, but repeat the sun checks in winter and summer. The sun’s midday height swings from about 15 degrees in December to 62 in June, so a bed in full June sun can sit in total December shade. One audit plus two seasonal sun checks gives the full picture.

How accurate are cheap pH test kits?

Capsule kits read within about 0.5 pH, accurate enough for plant choice. You need to know whether soil sits near 6.0, 7.0 or 7.8, not the second decimal place. Test 3-4 spots separately because pH varies across one garden, especially near house walls where mortar raises it.

With the map drawn and the jar read, the guesswork is gone. Our new-build garden design guide turns the audit findings into a layout, designing a garden from scratch walks the full process from blank turf to planted borders, and there are more planning guides in the garden design section. With the audit done, borrow planting ideas from RHS Wisley or strip things back with the sparse garden approach.