Why is my garden so much shadier in winter?

This catches out everyone who plans a garden in summer, which is nearly everyone. The winter shade map of a garden is a different map, not a slightly reduced version of the summer one, and it is the one that governs where evergreens, winter-flowering plants and any seating you want to use in spring can go.

Step by step

1. Understand the geometry.Shadow length is the object's height divided by the tangent of the sun's elevation. When the sun is high, that division produces a short shadow. As the elevation falls towards the horizon the tangent shrinks fast and the shadow lengthens dramatically — which is why the effect is abrupt rather than gradual.
2. Note the second effect: the arc shortens.In winter the sun rises and sets much further round towards the south, so it travels a short low arc. A strip of ground can therefore be in shadow for the entire day rather than being crossed by the sun as it moves.
3. Note the third: the light itself is weaker.A shallow beam spreads the same energy over a much larger patch of ground, and it also travels through more atmosphere. So even ground technically in winter sun receives far less than the same ground in summer sun.
4. Identify what casts your winter shade.It is nearly always something to the south of the area — a fence, a wall, a building, a hedge, an evergreen tree. Anything to the north of a border is irrelevant in winter, because that is not where the sun is.
5. Survey your garden in midwinter.Photograph it from a fixed spot at three points in a clear midwinter day. That is your winter shade map and it is the one that matters for siting evergreens, winter interest and anywhere you want early spring warmth.
6. Plan to the winter map for the things that need it.Winter-flowering shrubs, evergreens, a spot to sit in March, an early bed, a cold frame. All of these belong where the winter sun reaches, not where the summer sun does.

Tips

• A deciduous tree is a completely different obstacle in winter, when it lets most light through, from summer when it does not. An evergreen is the same obstacle all year and casts the long winter shadow at full strength.
• The strip immediately in front of a south-facing wall gets both the winter sun and the wall's stored heat, and is the single best microclimate in most gardens for anything borderline.
• Raising the canopy of a tree — removing lower branches — lets low winter sun under it while keeping the summer canopy. It is often more useful than reducing the height.
• Fence height is worth thinking about before it goes up. A fence on the sunny boundary casts a very long shadow in winter and the difference between two heights is substantial.
• Reflected light helps more than people expect in winter. A light-coloured wall or fence behind a border noticeably brightens the ground in front of it when the sun is low.

Common mistakes

• Planning planting from a summer survey — Summer is the season in which almost everywhere gets some sun. The winter picture is completely different and it is the constraint on everything that has to perform in the cold months.
• Blaming a plant for failing when it is simply in winter shade — Evergreens and winter-interest plants sited on a summer survey are frequently in full shade for months, which is why they sulk. The plant is fine; the position is not.

Questions people ask