Why the shrub that thrived at your old house is dying at this one
Counting hours of direct sun and filling a hole with water tells you more about what will grow than any catalog description. Here is the survey and what to do with it.
Every garden center is arranged to make you buy the plant in flower on the bench in front of you. The label says full sun, moist well-drained soil, and you nod, because everyone's soil is moist and well-drained until they try to dig it in August.
An afternoon spent finding out what you actually have will spare you several seasons of slow, expensive failure. None of it requires equipment beyond a spade, a jar and a cheap test kit, and the answers stay true for as long as you live there.
Count the hours of sun
Light is the constraint you can do least about, so measure it first. Pick a clear day in early summer and photograph each part of the yard at nine, noon, three and six. Six hours or more of direct sun is full sun. Three to six is part sun or part shade. Under three is genuine shade, and no amount of feeding will make a sun-lover flower there.
Two details change the answer. Morning sun and afternoon sun are not equivalent, and most plants labeled for part shade mean sun before noon and shelter after it, when the heat and the light are both harshest. And the picture moves through the year: a bed in full sun in June can be in shadow from March to May, when the sun is low and the house throws a long shadow, which is exactly when spring bulbs and early perennials are trying to work.
Dig a hole and fill it with water
Drainage kills more plants than cold does, and it is the one thing nobody checks. The test is crude and takes a day.
- Dig a hole about a foot deep and a foot across in the bed you care about, ideally when the soil is neither baked nor waterlogged.
- Fill it with water and let it drain away completely. This wets the surrounding soil so the second reading measures the soil rather than the dry hole.
- Fill it again, then measure how far the water level drops each hour with a ruler laid across the top.
- Repeat somewhere else in the yard. Drainage varies enormously over twenty feet, particularly near buildings, where the soil is often builder's rubble under six inches of topsoil.
One to three inches an hour is a comfortable garden soil and you can plant more or less anything suited to your climate. Under an inch an hour means water sits in the root zone after rain, which suffocates roots and rots the crowns of Mediterranean plants like lavender and rosemary over winter. More than four inches an hour means the water is gone before the roots can use it, and your problem in July is drought, not drainage.
Texture, and the number on the pH strip
For texture, half-fill a straight-sided jar with soil, top it up with water, shake it hard and leave it on a windowsill. Sand drops out in a minute or so, silt over a couple of hours, and clay can take a day or more to clear. The bands give you rough proportions. Faster still: wet a pinch of soil and rub it between thumb and finger. Gritty is sand, silky and soapy is silt, and if it smears and holds a shine you have clay.
pH is worth a five-dollar kit because it quietly rules certain plants in or out. Most vegetables and most ornamentals want something between 6.0 and 7.0. Blueberries, rhododendrons, azaleas, camellias, pieris and heathers need genuinely acid soil, around 4.5 to 5.5, and on chalky or limestone ground they yellow between the leaf veins and decline over a few years because iron and manganese are chemically locked away from them at high pH. Sulfur will lower pH and lime will raise it, but both work over months and the parent rock underneath keeps pushing the reading back. On alkaline soil, grow acid-lovers in a pot of ericaceous mix and plant the ground with things that like it.
The corners that are not the same as the rest
Cold air behaves like water: it flows downhill and pools at the bottom. A hollow, or a dip behind a solid fence at the low end of a slope, is a frost pocket that will be several degrees colder than the rest of the yard on a still clear night and will hold frost until midmorning. Blossom on a fruit tree planted there gets caught in years when the same tree twenty feet uphill fruits fine. The reverse also exists: a masonry wall facing the midday sun soaks up heat all day and releases it overnight, and the strip of ground in front of it is the most sheltered spot you own.
Wind gets underestimated because it leaves no obvious damage, just plants that never quite thicken up and leaves scorched brown at the edges. The gap between two buildings is the worst offender, since it accelerates whatever is blowing. If you need shelter, a hedge or a slatted fence works better than a solid panel. Solid barriers do not stop wind so much as throw it over the top, where it drops back down in turbulent gusts a short distance behind, sometimes harder than the open wind it replaced.
What a hardiness zone leaves out
A hardiness zone is built from the average lowest winter temperature at your location, and that is all it is. It says nothing about summer heat, humidity, length of season, or how long the ground stays saturated in February, and that last one matters enormously. A great many plants sold as hardy to your zone die not from cold but from cold combined with wet feet, which is why the survival of lavender, salvia and most silver-leaved plants depends more on your drainage test than on your zone number.
Turning the survey into a shopping list
| Under three hours of sun | Ferns, hostas, hellebores, epimedium. Not tomatoes, not roses |
|---|---|
| Drainage under an inch an hour | Raised beds, or plants that tolerate wet: willow, dogwood, iris, astilbe |
| Sandy and fast-draining | Mediterranean herbs, sedum, bearded iris. Mulch heavily to hold what rain you get |
| pH above 7.5 | Skip the blueberries. Clematis, lilac and dianthus are genuinely happy here |
| Windy and exposed | Small tough leaves rather than large soft ones. Plant smaller and stake low |
Write the numbers on your phone and take them to the nursery. The single most useful thing you can do with a difficult site is stop arguing with it. Heavy wet clay in a shaded corner is not a problem to be solved with three trailer-loads of sand, which mostly makes something closer to concrete. It is a place where astilbes, hostas and a dogwood grown for its winter stems will do better than they would anywhere else in the yard.