Right Plant, Right Place: How to Read a Site First

Most planting failures are siting failures

A plant that dies of the wrong light, the wrong drainage or the wrong exposure was not badly cared for. It was badly placed, and no amount of subsequent care fixes it.

Assessing the site takes one day spread over a season. Doing it before you spend money is the single highest-return habit in gardening.

Light: measure, do not estimate

Pick a clear day in late spring or summer when deciduous trees are in leaf, and check the spot every hour from morning to evening. Note when it is in direct sun.

Almost everyone overestimates. A border that feels bright often turns out to receive four hours, not eight.

Two things to record beyond the total:

• Which hours. Six hours of morning sun is a different environment from six hours of afternoon sun. Afternoon light is hotter and harsher.
• What kind of shade. Dappled shade under an open canopy suits many plants. Dense shade at the foot of a north wall suits very few.

Drainage: dig a hole

The test is simple and it is the one most often skipped.

Iowa State Extension gives the method: dig a hole at least 12 inches deep and 4 to 12 inches wide, fill it with water and let it drain. Refill immediately, measure the water depth, wait 15 minutes, and measure the drop in inches. Multiply by four for the hourly rate.

1 to 3 inches per hour is desirable for most plants. Much faster and the site is droughty. Much slower and you have a drainage problem that will kill anything not adapted to wet feet.

Do this in the actual planting position, not nearby. Drainage varies enormously over a few feet, particularly near buildings where subsoil and rubble were disturbed during construction.

Soil

Get a test. It gives you pH and nutrient levels, and pH in particular rules whole plant groups in or out — blueberries and rhododendrons need acid soil no amount of feeding substitutes for.

Also just look and feel. Squeeze a moist handful: gritty and crumbling is sandy, sticky and mouldable is clay. Dig down and see how deep the topsoil goes before it changes colour and texture, because thin topsoil over compacted subsoil is a common and consequential finding.

Exposure and microclimate

Wind. Persistent wind desiccates foliage and breaks growth. Sites at the corner of a building, or funnelled between two, are far windier than they look on a calm day.

Frost pockets. Cold air flows downhill and pools at the bottom of slopes and behind solid barriers. A frost pocket can run a full zone colder than open ground a few yards away.

Reflected heat and shelter. A south or west-facing wall stores and re-radiates heat, running warmer than the open garden — which is why marginally hardy plants survive there.

Then read the label properly

Take your notes to the plant, not the other way round.

The tag gives light requirement, mature height and width, hardiness range and soil preference. If any of those conflict with what you measured, the answer is a different plant — not better care, not a soil amendment, and not hope.