Why do plants grow badly in one part of my garden?

Gardens are not uniform. A twenty-metre plot can hold a frost pocket, a rain shadow, a wind funnel, a bone-dry root zone and a permanently wet corner, and the difference in growing conditions between two ends of one border can be larger than the difference between two counties.

Step by step

1. Count the hours of direct sun the area actually gets.Look at it at mid-morning, midday and mid-afternoon on a clear day and note whether the sun is on it. Most people badly overestimate. Under four hours is shade for practical purposes, and a great many plants sold as full sun will simply sulk there.
2. Check the aspect and what casts the shade.Shade from a wall is dry and dense but constant. Shade from a deciduous tree is seasonal, and lets in a spring window that bulbs and woodlanders exploit. Shade from an evergreen is year-round and usually combined with dry, root-filled soil.
3. Look for a rain shadow.The ground within about a metre of a wall or fence, particularly on the sheltered side, receives a fraction of the rainfall the open garden does. Under an overhang or a dense evergreen, effectively none. Plants there need watering all summer regardless of the weather.
4. Go out the day after heavy rain.Standing water, a squelching surface, moss on the soil and a sour smell all mean the roots there spend days without air after every downpour. This is the single most common cause of a corner where nothing thrives.
5. Find the tree and hedge roots.A mature tree or a hedge takes enormous quantities of water and nutrients from a radius well beyond its canopy, and the top spit of soil there can be a solid mat of fine roots. Push a fork in — if it will not go in easily, that is the answer.
6. Watch what the wind does.Wind funnels between buildings, over a low fence and along a side passage, and constant wind dries leaves faster than roots can supply, shreds soft growth and stunts everything. A corner that is always brown on one side is a wind problem, not a feeding problem.
7. Dig, and find out what is under it.Around new-build houses in particular, topsoil is often thin over compacted subsoil and buried rubble. Dig a hole 45cm deep and look at what comes out. If the second spit is grey, hard and structureless, no amount of feeding will help until it is broken up.
8. Consider what used to be there.A shed base, a path, a bonfire, a mixing spot for concrete, a place where weedkiller was stored. Cement leaves the soil alkaline, a bonfire site leaves it sterile and salty, and both persist for years.
9. Decide honestly between fixing and adapting.Drainage, compaction and thin soil can be fixed with real work. Shade from a neighbour's tree, a rain shadow, a wind funnel and a frost pocket usually cannot, and the sane response is to plant things that suit those conditions rather than fight them annually.

Tips

• Look at what grows there by itself. Moss and buttercup mean wet; nettles mean fertile and disturbed; a bare patch under a conifer means dry and dark. The weeds are a free soil survey.
• Raised beds solve compaction, thin soil and drainage in one move and are often less work than trying to correct the ground.
• A frost pocket at the bottom of a slope can be several degrees colder than the top on a still night. Move tender plants uphill rather than protecting them where they are.
• In a rain shadow, mulch is doing very little because there is no rain to conserve. Watering and a drip line are what work there.

Common mistakes

• Feeding a difficult area repeatedly — Almost none of these causes are nutritional. Feed added to a waterlogged, compacted or root-filled spot does nothing and can scorch.
• Assuming a north-facing area is hopeless — North-facing beds are cool, even and often moist, which suits an enormous number of good plants. The genuinely hard shade is dry shade under a conifer, and that is a different problem.
• Digging one improved hole in bad ground — It becomes a sump in clay and a dry pocket in sand. Improve an area or accept the ground and choose plants for it.

Questions people ask