How Much Sun Does Your Yard Really Get?
A simple way to map light across your yard before choosing plants — and why “full sun” on a plant tag means something different in Houston.
Chris GosselinFounder
Most planting failures trace back to a light guess rather than a light measurement. Someone decided a bed was "pretty sunny", bought accordingly, and watched half of it decline over two seasons. The fix costs a day of attention and no equipment.
Why plant tags mislead here
Plant tags are written for a national market. "Full sun" generally means six or more hours of direct light, "part shade" three to six, and "shade" less than three. Those bands are useful, but they count hours without weighing them.
Six hours of July afternoon sun on a west-facing Houston bed, with heat radiating off a brick wall, is a far harsher exposure than six hours of morning sun in a milder climate. This is why a good number of plants labelled full sun perform better here with afternoon shade — and why local experience beats the tag whenever the two disagree.
The four-photo method
Pick a clear day. Stand in the same spot — an upstairs window is ideal — and photograph the yard four times: around 9am, noon, 3pm, and 6pm. Then mark on a rough sketch where the shade line fell in each photo.
Four photographs will tell you more than a season of guessing, and the sketch becomes the most useful document in the whole project. Do it before you buy a single plant.
If you want to be thorough, repeat it once in winter. The difference is larger than people expect.
Morning sun and afternoon sun are not the same thing
Separate them on your sketch, because the distinction matters more here than the total.
East-facing beds get gentle light and then cool off through the hottest part of the day. West-facing beds get the hardest hours, often with reflected heat added. A bed with four hours of morning sun and a bed with four hours of afternoon sun have the same tag rating and want substantially different plants.
The zone nobody maps: reflected heat
Mark this too. South and west walls, light-coloured masonry, driveways, pool decking, and metal fences all bounce heat into whatever is next to them. A narrow bed between a light brick wall and a concrete drive is a genuinely extreme environment, hotter and drier than open lawn a few feet away.
The same effect works in your favour on a pool deck, where a lighter surface bounces heat rather than storing it — the reasoning is set out in pool deck materials that stay cool underfoot.
Remember that the map moves
A light map is a snapshot, not a permanent record. Winter sun sits lower and reaches further under a canopy. Deciduous trees drop their leaves and let light through for months. A young tree shades a little more each year, and eventually the sunny border you planted becomes a shade border that has not been told.
Neighbours build. Fences get replaced with taller ones. This is not a reason to avoid planning; it is a reason to expect the shady side of a yard to need revisiting every several years, and to treat that as maintenance rather than failure.
Turning the map into decisions
| What the map shows | What it means here | What to do with it |
|---|---|---|
| 6+ hours, mostly morning | The best growing conditions in the yard | Lawn, roses, vegetables, sun perennials |
| 6+ hours, mostly afternoon | Harsher than the tag suggests, especially near paving | Heat-proven natives; avoid anything marginal |
| 3–6 hours | The most forgiving band; many plants suit it | Most shrubs and perennials, and grass if drainage is good |
| Under 3 hours | No turfgrass will hold here, whatever the care | Shade planting, ground covers, turf, or paving |
| Reflected heat, any hours | Effectively a hotter, drier microclimate | Tough low-water planting, or hardscape |
The under-three-hours row is the one that saves the most money, because it ends the annual cycle of reseeding a lawn that cannot work. The alternatives are covered in best ground covers for Houston yards and artificial turf vs. real grass in Houston.
Map the shade that does not exist yet
A sun map records this year. Plants and buildings are not finished moving, and the two commonest disappointments in a yard both come from ignoring that.
The first is planting a sun-loving bed beneath a young tree. In five years the tree is doing its job and the bed beneath it is failing, having been correctly planted for conditions that no longer exist. The second is the reverse: a shade bed that loses its shade because a tree comes down in a storm and is not replaced.
- Note the eventual canopy spread of every young tree, not its current one, and plan the bed beneath it for the shade it will cast.
- Treat any single tree providing all the shade for a planting area as a risk, and choose plants with some tolerance either side.
- Look over the fence: a neighbour’s new addition, fence, or fast-growing hedge can change your afternoon light entirely.
- Remember that your own new structure changes the map — a patio cover or pergola creates a shade zone the yard did not have.
Test it in a pot first
For a large or expensive planting, there is a cheap way to check the map before committing: buy one plant, keep it in its pot, stand it exactly where the bed will be, and look after it there for a season.
A potted plant is harsher than the ground — less root volume, more heat, and faster drying — so a plant that comes through a summer in a pot in that spot will almost certainly come through it in the soil. It is a slow test, but a season of waiting costs far less than replacing a bed of thirty plants that were never going to be happy there.
The map is not only for plants
Once you have it, the same map answers questions that have nothing to do with planting — and these are the ones that are expensive to get wrong, because they involve building something.
- Where the dining table goes, which wants shade between roughly four and seven in the evening rather than at noon.
- Which end of the patio needs a roof, and how far out it has to project to shade anything at all.
- Where a dark paving material will be uncomfortable barefoot, and where it will be fine.
- Which side of the pool people will actually sit on in August.
- Where a lawn will struggle regardless of species, and should be something else.
- Where solar-powered anything is worth installing, and where it will disappoint.
A patio built on the sunny side of a yard because that was where the space happened to be is one of the commonest and most permanent mistakes in a garden. The map is four photographs; the patio is there for twenty years.
One more use for the map
It tells you where to sit. The spot that is shaded at 6pm in July is where an outdoor room belongs, and it is often not where the builder put the patio. Knowing that before you pour anything is worth more than any plant list, and it is the reason we map light at the design stage rather than at planting.
Our process page covers what else gets recorded before a design starts, and landscape installation covers how the planting itself is done.
