How to Implement Light Analysis in Your Garden Planning Process

Why light analysis is the first step in garden planning

Most gardening mistakes aren't caused by bad technique — they're caused by planting the wrong crop in the wrong place. A tomato planted in four hours of daily sun will never perform like one in eight hours, no matter how well you feed and water it. Light determines what you can grow, when, and how productively.

Before you choose varieties, lay out beds, or order seeds, you need to know how much direct sunlight each part of your garden receives, and how that changes across the growing season.

The three light categories every gardener needs to know

Vegetables fall into three broad categories based on their light requirements:

• Full sun (6+ hours of direct sun per day) – tomatoes, peppers, cucumbers, courgettes, squash, beans, sweetcorn, aubergines. These crops need maximum light to produce well.
• Partial shade (3–6 hours per day) – lettuce, spinach, rocket, parsley, dill, radishes, peas. These tolerate — and sometimes prefer — some shelter from the hottest afternoon sun.
• Deep shade (under 3 hours) – very few vegetables thrive here. Some herbs (chives, sorrel, mint) manage, but yield will always be limited.

The goal of light analysis is to map your garden into these zones and allocate crops accordingly.

How to manually track sunlight hours

The simplest approach costs nothing and is surprisingly accurate. Over one or two clear days in late spring or early summer:

1. Draw a rough sketch of your garden with major features marked: buildings, fences, trees, tall hedges.
2. Check each area of the garden every 1–2 hours from sunrise to sunset.
3. Note which areas are in direct sun vs shade at each check.
4. Count the total hours of direct sun for each zone.

Mark the results on your sketch: green for full sun, yellow for partial shade, grey for deep shade. This becomes your light map.

One important caveat: repeat this in early spring and again in midsummer. The sun's angle changes dramatically between seasons. A bed that's sunny in May may be heavily shaded by a neighbouring tree by July once the leaves are fully out.

Using your phone to measure light

Several free apps (lux meter apps) turn your phone camera into a basic light meter. They measure illuminance in lux, which gives you a more precise reading than "sunny" or "shady". As a rough guide:

• Over 30,000 lux – full sun, suitable for all sun-loving crops
• 10,000–30,000 lux – bright partial shade, good for leafy crops
• Under 10,000 lux – too dark for most vegetables

Take readings at solar noon for the highest daily value, and at morning/afternoon for a picture of the full day's pattern.

The shadow problem: buildings and trees

Static obstacles like buildings cast predictable shadows, but trees are trickier. A fruit tree that has no leaves in April casts almost no shade — the same tree in August may shade a 4-metre radius. If you plant shade-sensitive crops near trees in spring, they may be struggling by midsummer.

Always account for the mature canopy of any trees or large shrubs when planning bed placement. A new tree planted this year will shade increasingly more of your garden over the next decade.

The sun's lower angle in spring and autumn also means longer shadows from fences and buildings. A south-facing fence that seems irrelevant in June may cast a 2-metre shadow in September.

Integrating light analysis into your garden layout

Once you have your light map, layout decisions become straightforward:

• Full-sun beds: Reserve for tomatoes, peppers, cucumbers, squash. Place these furthest from shade sources, ideally facing south or south-west.
• Partial-shade beds: Use for salad crops, herbs, and early-season brassicas. East-facing beds often work well here.
• Tall crops on the north side: Always place tall crops (sweetcorn, staked tomatoes, climbing beans) on the north side of your plot, so they don't cast shade on shorter neighbours.
• Succession planting by season: Use the knowledge that shade patterns change — plant cool, shade-tolerant crops in spots that will get more sun later in the season.

Digital shade analysis: automating the process

Manual observation is valuable, but it has limits — it takes time, depends on clear weather, and needs to be repeated for different seasons. Digital tools can model shadow patterns computationally based on your location, the time of year, and the position of obstacles in your garden.

Gardener Planner includes a built-in shade analysis feature. You mark trees, buildings and fences on your garden plan, and the app simulates the sun's arc for your location at any date. The result is a visual shadow map overlaid on your plan — showing exactly which beds are sunny or shaded at different times of year. This means you can plan with the full-season picture before you've even started digging.

Common light analysis mistakes

• Measuring only in midsummer – shade from deciduous trees is minimal in spring; measure across the season.
• Ignoring reflected light – white walls and fences can significantly boost light levels on adjacent beds.
• Assuming south-facing always means sunny – a south-facing bed next to a two-storey building may still be in deep shade for much of the day.
• Forgetting about the future – a small ornamental tree planted in a neighbouring garden will eventually shade your plot. Account for its mature size.

Light analysis as an ongoing practice

Your garden's light environment changes every year as trees grow, structures are built or removed, and your own plantings mature. A light analysis done once and never revisited will gradually become inaccurate.

Make it a habit at the start of each season: walk the garden, check which spots seem darker than you remember, and update your plan. The crops you grow and where you grow them should evolve with your garden's changing light conditions.