How to use this tool
- Set the place. The spot is at the centre of the 3D view.
- Add obstacles. For each fence, wall, hedge, tree or building, choose the type, the direction from your spot, the distance, the height and the width. Three example obstacles are already there; change or remove them.
- Read the verdict. The top card tells you whether the spot counts as full sun, part sun / part shade or shade, based on the average hours of direct sun in the growing season.
- Look closer. The bar chart shows the hours for each month (the grey bars show what the spot would get without obstacles), the heatmap shows the sunny hours of the day, and the 3D view shows the shadows moving.
How obstacles are calculated
Each obstacle raises the horizon in its direction. From your spot, an obstacle blocks the sun when the sun is lower than the angle to its top edge: arctan(height ÷ distance). A 2 m fence 3 m away blocks the sun up to about 34° in its direction; the same fence 8 m away only up to about 14°.
This is why the direction of obstacles matters so much. At mid-northern latitudes the sun is in the south at midday, so obstacles to the south cast the longest shade. Obstacles to the north hardly matter. East and west obstacles cut off morning or evening sun, especially in summer.
What grows where
- Full sun (6+ hours): vegetables such as tomatoes, peppers and squash, most herbs, roses, lavender, fruit trees.
- Part sun / part shade (3 to 6 hours): salad greens, spinach, peas, many perennials, hydrangeas.
- Shade (under 3 hours): ferns, hostas, astilbes and woodland plants.
For more on the classifications and how to measure a garden, see full sun, part shade, shade. For the length of a single shadow, use the shadow length calculator.
Last updated September 23, 2026