What this mapper works out
This tool estimates daily direct sunlight from a garden's orientation, the severity of surrounding obstacles and the season, and reports which planting category the result falls into.
It is a rough guide rather than a survey. The most reliable way to know how much sun a spot gets is to look at it through a day, but the guide is useful for planning before that.
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Before you use the result
- Orientation is the direction the garden faces from the house — a south-facing garden lies to the south of the building.
- Obstacle severity covers fences, walls, trees and neighbouring buildings on a 0 to 10 scale. A garden enclosed by tall trees rates high.
- Choose the season you are planning for. A spot in full sun in June may be in shade from November to February.
- Different parts of a garden differ enormously. Assess areas rather than the whole plot.
The sun is far lower in winter, so shadows are several times longer than in summer. A fence that casts a two metre shadow in June casts six metres or more in December. That is why an area that seems bright in summer can be in permanent shade for a third of the year — and why evergreen planting decisions should be made on the winter picture.
How this calculator works
A base figure adjusted for season and obstacles:
Base hours by orientation: south 8 · west 6 · east 6 · north 3
Less 3 hours in winter, less 1 in spring or autumn
Less 0.45 hours per point of obstacle severity
6 hours or more — full sun · 3 to 6 — partial shade · under 3 — mostly shadeThe categories match the terms used on plant labels. Full sun generally means six hours or more of direct sun; partial shade three to six; and shade less than three. Those figures refer to the growing season rather than a winter day.
Worked example: a south-facing garden
Using the default figures — south-facing, obstacle severity 3, summer:
- Base: 8 hours · No seasonal reduction · Less 1.35 for obstacles
- Estimated direct sun: 6.65 hours
- Category: full sun
Change the season to winter and the same garden drops to 3.65 hours — partial shade. That shift is the point: a garden described as full sun is full sun in June, and a plant needing six hours year-round will not get it. Choosing evergreens, winter structure and early bulbs on the summer figure is a common and expensive mistake.
Common mistakes
- Assessing the whole garden as one. Aspect and shade vary across a plot.
- Judging only in summer. Winter shadows are several times longer.
- Ignoring deciduous trees. They cast heavy shade in summer and little in winter, which suits some planting well.
- Forgetting the neighbour's growth. A hedge or tree next door changes the garden over time.
- Treating plant labels as precise. Many plants tolerate a wider range than the label suggests.
Frequently asked questions
How do I check sunlight properly?
Observe and record. Photograph or note the shade pattern at two-hourly intervals across a clear day, and repeat in a different season. It takes two days spread across the year and gives a far better picture than any estimate. Some smartphone apps overlay the sun's path on a camera view, which helps for planning.
What do plant labels mean by full sun?
Generally six or more hours of direct sun during the growing season. Partial shade usually means three to six hours, or dappled light through a canopy. Full shade means under three hours of direct sun. Labels are guidance rather than requirements, and many plants perform acceptably a category away from their ideal.
Does a north-facing garden limit what I can grow?
It changes what thrives rather than preventing gardening. North-facing gardens suit ferns, hostas, hydrangeas, camellias and a great many woodland plants, and they are more forgiving in drought. The part nearest the house is the shadiest; the far end may get considerably more sun than expected.
Can I improve light levels?
Sometimes substantially. Thinning or raising the crown of a tree, replacing a solid fence with a lighter one, painting a wall a pale colour and removing overgrown shrubs can all make a real difference. Work on a neighbour's tree requires their agreement, and protected trees require consent.
Is what I enter stored?
No. Your selections are processed in your browser and never transmitted or retained.
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References
- Royal Horticultural Society — plant selection for sun, partial shade and full shade
- Met Office — UK sunshine hours and seasonal daylight data
Sources are checked at publication and can change — how I choose and check references.