Balcony Sunlight: How to Assess Light Before You Buy Plants
Find out whether your balcony is full sun, part shade or shade with a simple one-day check, and learn what direction, nearby buildings and the season do to the light.
At a glance
What you need
- Paper and pencil
- Clock or phone reminder
- Phone camera for record photos
- Compass app
Plant labels ask for full sun, part shade or shade, and most people guess which one they have. Guessing is the reason so many first plants disappoint. Balcony sunlight is easy to measure, though, and it takes one clear day and a sheet of paper.
Once you know how many hours of direct sun each part of the balcony receives, choosing plants stops being a gamble. Here is how to do the check and how to read the result.
Why a balcony is harder to judge than a yard
A garden bed sees most of the sky. A balcony sees a slice of it. The building is behind you, there may be a balcony above, walls on one or both sides, and other buildings or trees in front. Each of these blocks the sun for part of the day.
That is why “it feels bright out here” is not a reliable measure. A balcony can be bright all day from open sky and still receive very little direct sun. Plants that need full sun want the sun itself on their leaves, not just a bright view.
What full sun, part sun and shade mean
Garden terms describe hours of direct sun during the growing season. Treat them as rough guides, not exact limits.
| Term on the label | Direct sun per day | Typical balcony spot |
|---|---|---|
| Full sun | About six hours or more | Open, unshaded railing edge |
| Part sun or part shade | Roughly three to six hours | Sun for the morning or the afternoon only |
| Shade | Less than about three hours | Under a balcony above or facing a close building |
Direct sun means you can see a sharp shadow. Bright light without a clear shadow counts as shade for this purpose, even though many shade plants enjoy it.
How to measure your balcony sunlight in one day
Pick a clear day when you will be home from morning to evening. Cloudy days hide the pattern you are trying to see.
- Sketch the balcony. Draw a simple rectangle and mark the door, the wall and the railing. Divide it into three zones: by the wall, the middle of the floor and the railing edge.
- Start early. Soon after sunrise, step out and look. Is direct sun touching the floor, the railing or the wall? Write the time and mark each zone as sun or shade.
- Repeat every hour or two. Set a reminder so you do not miss the middle of the day. A phone photo from the same spot each time makes a useful record.
- Keep going until sunset. Late afternoon sun is easy to forget and is often the hottest of the day.
- Add up the hours for each zone. Count only the time when direct sun reached that zone. Compare each total with the table above.
You will usually end up with two or three different answers for one balcony. That is normal and useful.
Tip
Note the height of the sun as well as the place. Sun that reaches the floor will light a low pot. Sun that only reaches the top of the railing will light a tall plant but miss a small one beside it.
What changes the light
The direction the balcony faces
These descriptions assume the Northern Hemisphere. A compass app will tell you which way you face.
- South-facing: usually the sunniest, with sun for much of the day.
- West-facing: sun from about midday onward, often strong and hot in the afternoon.
- East-facing: gentle morning sun, then shade for the rest of the day.
- North-facing: mostly shade, with perhaps a little early or late sun in summer.
Direction is a starting point only. A south-facing balcony behind a tall building can be shadier than an open east-facing one, which is why the one-day check matters more than the compass.
Things that cast shade
The balcony above works like a roof: it often shades the wall side while the railing edge stays sunny. Side walls cut off morning or evening sun. Neighboring buildings and trees can block low sun entirely, and deciduous trees give more shade in summer than in early spring.
The season
The sun is lower in the sky in winter and higher in summer. Low winter sun can reach deep under a balcony above, while high summer sun may only reach the railing edge. Buildings that block the low sun in spring may not block it in midsummer. A check done in April will not describe July exactly.
Different spots on the same balcony
The railing edge is often the brightest strip, and the area by the wall the shadiest. A difference of a few steps can move a pot from full sun to shade. Use that: sun lovers go where your notes show the most hours, and leafy shade plants take the wall side.
When you lay out the space, shade the sunny and shady zones onto your sketch before deciding where anything goes. The guide to planning a balcony garden on paper shows how to combine the light map with paths and seating.
Reflected light and heat
Glass doors, windows and pale walls bounce light back onto plants. In a shady spot that extra brightness helps. On a sunny south or west balcony it adds heat, and plants close to glass or a pale wall can dry out and scorch faster than the hours alone would suggest.
If leaves near the wall look crisp at the edges in hot weather, reflected heat is one possibility, along with dry potting mix and wind.
Matching plants to what you found
Take your totals with you when you shop, and read each plant label against them.
- About six hours or more: most flowering annuals, many herbs and fruiting vegetables want this much. See the list of flowers that do well on a sunny balcony.
- Roughly three to six hours: many leafy herbs, salad leaves and part-shade flowers manage well, especially with morning sun.
- Less than about three hours: choose plants sold for shade. There are more than you might expect in the guide to flowers for a shady balcony.
Repeat the check in another season
One day gives you a good first answer. Do the check again in midsummer and once more in fall, and keep the three sketches together. You will see how the sunny strip moves through the year, which tells you where to shift pots as the seasons change and what to expect before you buy next spring.
Frequently asked questions
Does bright light without direct sun count as full sun?
No. Garden light terms count hours of direct sun, when objects cast a sharp shadow. A balcony that is bright from open sky but rarely has the sun on it is treated as shade when reading plant labels, although many shade plants grow well in that kind of light.
Which direction is best for a balcony garden?
In the Northern Hemisphere, south and west balconies usually get the most sun and heat, east gets gentle morning sun and north is mostly shade. None is best in itself. Each suits different plants, and nearby buildings can change the picture, so count the actual hours.
How often should I check the light on a balcony?
Do one full check on a clear day before buying plants, then repeat it in another season. The sun is lower in winter and higher in summer, so the sunny area moves. Two or three checks through the year give a reliable picture.
