Light is the one input you cannot buy. You can improve soil, add water and feed a hungry crop, but you cannot give a north-facing bed another three hours of afternoon sun. Working out how much light each part of your plot actually gets, and then planting accordingly, is the cheapest improvement available to any gardener.
What aspect means
Aspect is the direction a garden or a border faces, and it is measured by standing with your back to the house wall and noting which way you are looking.
- South facing gets sun for most of the day. The warmest and driest option, ideal for fruiting crops, Mediterranean herbs and anything that needs heat to ripen.
- West facing gets afternoon and evening sun. Warm by the end of the day, which suits both plants and people who are out at work.
- East facing gets morning sun and is in shade by lunchtime. Cooler, and the one aspect where early sun after a frost can scorch tender growth, so it is not the place for early camellias or magnolias.
- North facing gets little or no direct sun, particularly close to a wall. Cool and often damp, which is a genuine constraint but not a dead loss.
Aspect is a starting point rather than the answer, because a south-facing garden with a large sycamore in it is not a sunny garden. What decides your planting is the light that actually reaches the ground.
The shade categories the RHS uses
The RHS classifies shade by hours of direct sun at midsummer, which is far more useful than adjectives.
| Category | Direct sun at midsummer | What grows |
|---|---|---|
| Full sun | Over 6 hours a day | Everything, including fruiting vegetables |
| Partial or semi-shade | 3 to 6 hours a day | Sun lovers survive with noticeably fewer flowers; shade tolerant plants do well |
| Light shade | Open to the sky but screened from direct sun | Many plants that tolerate partial shade, though flowering is reduced |
| Dappled shade | Diffused light through an open canopy | Shade lovers flourish, but may need extra water under trees |
| Moderate shade | 2 to 3 hours a day | Usually grown for foliage rather than flowers |
| Deep or heavy shade | Under 2 hours a day | A very limited selection of extremely shade tolerant plants |
The RHS also makes a point that explains a lot of failed planting: shade tolerant plants have broader, thinner leaves with more chlorophyll, which is how they cope. Sun lovers put in shade respond by elongating their stems trying to escape, which is why a sun-loving plant in a dark corner goes leggy rather than simply growing more slowly.
Mapping your own Garden
This takes one day and is worth more than any amount of reading.
Pick a clear day near midsummer. Go out at 9am, midday, 3pm and 6pm, and each time sketch or photograph where the shadows fall. Four snapshots are enough to see which beds get morning sun, which get afternoon sun and which get neither.
Then adjust for the time of year, because the sun is much lower in spring and autumn. A bed that gets five hours in June may get almost nothing in March, when you are trying to start seedlings. Shadows from a two metre fence stretch a long way in early spring and barely at all at midsummer. If you can, repeat the exercise once in spring, and you will have a light map that lasts as long as the fences do.
Record it somewhere you will find again. Our garden planner is a reasonable place to keep the bed layout alongside what you have decided each area can support.
Matching crops to light
Vegetables sort themselves into a clear order of demand.
Six hours or more. Tomatoes, peppers, chillies, aubergines, courgettes, squash, sweetcorn and outdoor cucumbers. These convert sunlight into fruit and there is no substitute. The RHS advises planting tomatoes out only once temperatures are reliably above 16°C, which tells you how much warmth they are asking for.
Four to six hours. Beans, peas, potatoes, carrots, beetroot, onions and garlic will all crop, though a little less generously than in full sun.
Three to four hours. Leafy crops. Lettuce, spinach, chard, rocket, kale and most salad leaves. Lettuce in particular actively benefits from shade in high summer: the RHS notes that some light shade during the hottest part of the day is preferable, because too much heat makes lettuce bolt. A bed that is useless for tomatoes may be the best summer salad bed you have.
Under three hours. Not really vegetable ground. Mint, chives, parsley, lemon balm and wild garlic will cope, and beyond that you are into ornamentals.
Walls, slopes and frost pockets
Two other features of a site interact with aspect and are worth mapping at the same time.
A wall stores heat. A south or west facing wall absorbs sun through the day and releases it overnight, which creates a warmer microclimate against it than anywhere else in the garden. That is why traditional kitchen gardens trained fruit against south walls, and it is why a fig or a grapevine that struggles in an open border can do well tight against brickwork. A north facing wall does the opposite, staying cool and often damp, and the ground within half a metre of any wall is in the rain shadow of it, so it is drier than the rest of the bed whichever way it faces.
Slope changes both light and temperature. Ground sloping towards the south catches sun at a better angle and warms earlier in spring, which can be worth a fortnight on sowing dates. Cold air, meanwhile, behaves like water: it flows downhill and pools at the lowest point, or against a solid fence or hedge that blocks its escape. A dip at the bottom of a garden, or a bed against a close-boarded fence at the foot of a slope, will therefore frost harder and later than anywhere else on the plot. If you have lost tender plants in one specific spot year after year, that is usually why, and the fix is either to plant something hardier there or to let the cold air drain away by opening up the base of the barrier.
Making a shady corner work
- Grow foliage, not flowers. Ferns, hostas, heucheras, epimediums and hardy geraniums earn their place on leaf shape and texture. A shade border designed around foliage looks deliberate; one designed around flowers looks like a failure.
- Use light colours. Pale flowers, variegated leaves and a light-coloured fence or wall bounce a surprising amount of light into a dark corner.
- Deal with dry shade separately. Shade under a mature tree or against a house wall is dry as well as dark, and the dryness is usually the bigger problem. Improve the soil, mulch generously and water new plants properly for their first two seasons.
- Prune before you replant. Crown lifting or thinning a tree can convert deep shade into dappled shade, which changes what will grow. Check first whether the tree is protected by a Tree Preservation Order or sits in a conservation area, because in either case you need the council's consent before doing the work.
- Put the seating there. A corner that is hopeless for growing is often the most comfortable place to sit on a hot afternoon.
This is general growing information rather than advice on a particular garden, and anything involving tree work or boundaries is worth checking with your local authority first, since rules on protected trees and conservation areas vary by council. For the timing side, our month by month calendar covers when each crop goes in, and our small garden article deals with making a limited space work harder.