HOW-TO · NO-DRILL BALCONY
Map Your Balcony’s Sun Before You Buy a Single Plant
Map usable sun in each balcony container position before buying plants; direction alone does not describe the actual light.
Do not choose balcony plants from the compass direction alone.
A south-facing balcony can be shaded by the balcony above. A west-facing corner may receive intense afternoon sun while the wall beside it stays shaded. Railings, neighboring buildings, trees, and seasonal sun angle can turn one balcony into several different light zones.
Spend a day observing the exact places where containers could actually sit. That gives you more useful information than a label such as “bright balcony.”
Mark the usable container positions first
Before tracking sunlight, remove the parts of the balcony that should not become planting space.
Keep the door swing and walking path clear. Note any building restrictions, railings you cannot attach to, drainage areas, utility equipment, and places where a container would interfere with normal use.
You only need to map the sun on spaces that are genuinely available.
Sketch the remaining floor or take a photo and mark three or four candidate container zones: for example, outer corner, wall side, beside the door, and under an overhang.
Observe the same spots through the day
UC Master Gardeners recommend observing how sun hits a site at several points throughout the day and accounting for obstructions and time of year.
On a reasonably representative day, check the candidate zones in the morning, around midday, during the afternoon, and later in the day. You do not need minute-by-minute logging.
Record whether each zone is in direct sun or shade.
At the end, turn the notes into a useful estimate such as:
Outer corner: about 5 hours of direct sun in the current season Wall side: direct sun only in late afternoon Door side: bright but no direct sun observed
That is enough to make the next plant decision much better.
Do not create false precision
A one-day sun map is not a permanent solar survey.
Clouds can distort the observation, and the sun's path changes over the year. UC guidance specifically recommends factoring in the time of year because tree cover and shadows from structures change with season.
If the day was unusually cloudy, repeat it. If a crop is right on the edge of the light you observed, check again in another season before building a permanent setup around that number.
The goal is an honest range, not “4 hours 37 minutes.”
Use the plant requirement after the observation
Once you have a current-season light estimate, compare it with guidance for the crop or plant you are considering.
Do not work backward by buying a plant first and then renaming the balcony conditions to match its tag.
If you want vegetables, many common fruiting crops need substantial sun, while some leafy crops tolerate less. The exact requirement depends on the crop, variety, climate, and season.
The sun map is therefore a filter, not a planting calendar.
Remember that heat can make a sunny zone harder to maintain
The brightest position can also become the hottest and fastest-drying position, especially on hard balcony surfaces.
Oregon State notes that containers can dry quickly in full sun, while NC State notes that dark-colored containers absorb more heat and that larger containers generally dry more slowly.
So the best growing zone is not automatically the one with the highest sun count. It is the zone whose light matches the crop and whose watering demands you can realistically maintain.
A small hot outer corner may need a different container strategy from a brighter but less exposed area near the wall.
Keep the map with the balcony plan
Write the month on the map.
That one detail prevents a useful summer observation from turning into a misleading winter assumption.
When the season changes noticeably, update the zones that matter. You do not need to remap the entire balcony every week.
A current light map gives the rest of the garden plan something concrete to work from: planter depth, crop choice, watering expectations, and where a shade-tolerant or sun-loving plant should actually go.
Sources
UC Master Gardener Program of Alameda County — “Planning your garden in 5 easy steps” https://ucanr.edu/site/uc-master-gardener-program-alameda-county/planning-your-garden-5-easy-steps Reviewed: 2026-08-11
Oregon State University Extension Service — “Container gardening: Grow vegetables even without yard space” https://extension.oregonstate.edu/news/container-gardening-grow-vegetables-even-without-yard-space Reviewed: 2026-08-11
NC State Extension — “18. Plants Grown in Containers” https://content.ces.ncsu.edu/extension-gardener-handbook/18-plants-grown-in-containers Reviewed: 2026-08-11