How much sun does my garden get? Work it out by season

How much sun does my garden get?

How much sun your garden gets depends on three things: the latitude of your location, the direction your garden faces, and what stands directly around it. A 50 m² south-facing garden in Maastricht with low buildings around it can receive 2,000 direct sun hours a year. The same garden facing north with the neighbours’ detached house alongside it stays below 400 sun hours a year. The national average in the Netherlands, according to KNMI data, is around 1,800 sun hours.

Those numbers say something different from what the sun does at a specific spot in your garden. You are asking not only “how much sun does my plot get”, but “does that corner at the back of the garden where I want to plant a grape vine get enough sun to produce fruit?”. That is a point question, not a plot question. For that point question general climate data does not work; you need a 3D model of your house and surroundings plus an hour-by-hour sun-path calculation for every day.

The four seasons: why your garden is lit differently through the year

In the Netherlands the sun does not sit at the same height all year round. On 21 June (the summer solstice) the sun in Amsterdam reaches its highest point at around 61 degrees above the horizon. On 22 December (the winter solstice) only 14 degrees. That difference in height determines the length of shadows: a house nine metres tall casts a 36-metre shadow at 12:00 on 22 December, but only 5 metres at the same time on 21 June.

The sun’s arc also changes in width. In June the sun rises in the north-east (azimuth 48°) and sets in the north-west (azimuth 312°), an arc of 264 degrees. In December it rises in the south-east (128°) and sets in the south-west (232°), an arc of just 104 degrees. For a north-facing garden that means, concretely: in June a north-facing garden gets direct sun in the morning and evening (the sun is then in the northern half of the sky), in December never.

For plant choice it is therefore useful to measure your garden on four test dates: 21 March, 21 June, 22 September and 22 December. Those days define the four quarters of the growing season and roughly match what the TNO sunlight standard does for permit assessment (albeit that it picks slightly different test dates: 19 February, 21 June and 21 October). Plant and seed catalogues usually take the average from May to September as the “summer season”.

Full sun, partial shade, shade: what those categories really mean

Every plant label from Intratuin to Praxis uses the same three or four categories. They are not arbitrary; they correspond to the number of hours of direct sun a plant needs to function healthily during the summer half of the year. The table below is the usual Dutch classification as Tuinieren.nl and Moestuinland apply it.

Important: the number of hours is specific to the summer months. A tomato that has seven hours of sun in July may, in the same spot in May, still be three hours short of adequate light. Plants often do not mind this (they only start to fruit once it is warm enough), but for the flowering times of ornamental plants you do notice it. A classic mistake is to measure on a sunny September day and then say “anything grows here”, while in April the same spot is still in shade two thirds of the time.

How to choose spots for your terrace, vegetable garden and seating area

A garden design stands or falls on the right spot for three functions: the terrace for the evening sun, the vegetable garden for full-sun plants, and the seating area for the morning sun. The ideal spots usually do not clash, but you do want to think it through carefully before you lay paving or dig out an earth bed.

• Terrace. Choose the evening sun. On 21 June, measure between 17:00 and 21:00 how much of the terrace gets direct sun. The ideal terrace orientation in the Netherlands is south-west to west, where the evening sun shines on the terrace for hours. A terrace directly against the rear façade of an east-west-oriented house risks lying entirely in its own shadow from 18:00.
• Vegetable garden. Choose the midday sun. On 21 June, measure between 10:00 and 15:00. Full-sun plants such as tomatoes want continuous sun during those hours. A location that lies in the shadow of the neighbouring house at 10:00 and only gets sun from 11:30 is marginal for fruiting vegetables, excellent for leafy greens.
• Seating area or morning breakfast. Choose the morning sun. On 21 June, measure between 07:00 and 10:00. A spot in the east of your garden that gets sun early is perfect for a small table where you drink your coffee; that same spot is often in shade from 14:00, which gives a cool resting place for the rest of the afternoon.
• Shade border. The north or east side of a tall wall or fence provides constant coolness. Ideal for hostas, ferns, astilbes and other foliage plants that cannot tolerate fierce midday sun.

The north-garden myth: is a north-facing garden a lost cause?

“Nothing grows in a north-facing garden” is one of the most stubborn garden clichés in the Netherlands. Not true. A north-facing garden is lit differently, not without light. The summer half of the year often yields between 400 and 800 direct sun hours, which is ample for a flowering border and a productive leafy-greens vegetable garden. The winter half of the year is shady, but that is less relevant for plant growth because most species are dormant then.

What does work differently in a north-facing garden:

• Direct sun comes mainly early in the morning (from the east) and late in the evening (from the west), not between 10:00 and 16:00. That means cool-loving plants get their sun in the morning and evening and are less prone to stress on hot days.
• Hostas, ferns and shade-lovers thrive exuberantly. A north-facing garden can be a treasure trove for anyone who loves foliage textures.
• Fruiting vegetables (tomato, pepper, aubergine) are possible in pots on the sunniest part, usually near the east or west boundary. Or move them to a windowsill with southern light.
• Vegetable-garden plants that bolt (run to seed, throw up flower stalks) with too much heat actually do well here. A lettuce bed in a sunny south-facing garden bolts within two weeks in July; in a north-facing garden it does not.

The only scenario in which a north-facing garden becomes really difficult: when tall buildings on the south side of your house cast additional shadow over the summer half of the year on top of that. Then you get a garden that receives fewer than 200 sun hours even in June. For situations like that, a concrete 3D calculation per quadrant is the only way to decide whether to replant or simply enjoy the coolness.

How Schaduwplan supports this process

Schaduwplan carries out automatically the three steps a garden designer would spend hours on by hand. You enter your address and the tool retrieves the 3D model of your home and the surrounding buildings via 3DBAG. AHN4 supplies the heights of your surroundings to the centimetre. The sun path is modelled at hourly intervals using the SunCalc algorithms; the same formulas that professional planetarium software uses.

You place measurement points exactly where you have a question: the south-west corner where you are considering a terrace, the middle of the bed where the tomatoes should go, the spot by the back door where the morning table will stand. For each measurement point you get the sunlight duration in minutes per test date (21 March, 21 June, 22 September, 22 December) plus an annual heatmap. The free preview shows everything you need for garden-design questions. The PDF report is only necessary when you also want to formally record the outcomes, for example with a garden architect or a large-scale vegetable-garden project.