How Much Sun Do Vegetables Really Need?
Work out how many hours of direct sun your vegetables really need, how to measure the light you have, and what still crops well in partial shade.
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Seed packets say "full sun" as though that were a single, well-defined condition. It is not, and the gap between what a packet means and what your garden delivers is where most disappointing harvests come from.
What "Full Sun" Actually Means
In horticultural writing, full sun means six or more hours of direct sunlight per day during the growing season. Direct means the sun is unobstructed and casting a defined shadow, not filtered through a tree or bouncing off a wall.
Partial sun and partial shade are used interchangeably and both mean roughly four to six hours. Full shade means under four hours of direct sun, or dappled light all day. Deep shade — under two hours, no direct beam — will not grow vegetables, only foliage plants.
Two things the terms hide. First, intensity varies enormously with latitude and season: six hours of June sun in Seville is a different energy budget from six hours of April sun in Manchester. Second, morning and afternoon sun are not equivalent. Afternoon sun is hotter and more stressful, which is why lettuce in a west-facing bed bolts while the same variety in an east-facing bed does not.
Measure Your Light Before You Plant
Guessing here is expensive. Measure instead, on a clear day, at the time of year you will actually be growing.
- Choose two or three candidate spots and mark them.
- Check each one every hour from sunrise to sunset, noting sun or shade.
- Total the sunny hours per spot.
- Repeat once in late spring and once in mid summer, because shade from trees and neighbouring buildings moves a lot between the two.
If you cannot be home all day, an hourly phone photo from a fixed window works, as does a sun-path app. Write the numbers down per bed or per pot — they change what you should plant far more than soil ever will.
The Fruit, Root, Leaf Hierarchy
There is a simple rule that survives almost every edge case: the more of the plant you intend to eat comes from a flower, the more sun it needs.
| Crop group | Hours of direct sun | Examples |
|---|---|---|
| Fruiting crops | 8+ ideal, 6 minimum | Tomatoes, peppers, chillies, aubergines, melons, courgettes |
| Legumes and sweetcorn | 6-8 | Beans, peas, sweetcorn |
| Root crops | 5-6 | Carrots, beetroot, radish, turnip, onions |
| Brassicas | 4-6 | Kale, cabbage, broccoli, kohlrabi |
| Leafy greens | 3-5 | Lettuce, spinach, chard, rocket, mizuna, pak choi |
| Soft herbs | 3-5 | Parsley, chives, coriander, mint |
| Woody herbs | 6+ | Rosemary, thyme, sage, oregano |
Fruit is expensive for a plant to build. A tomato needs enough photosynthesis to fill dozens of fruit with sugar, and below six hours it will grow a perfectly healthy vine that sets three sad tomatoes in September. Leaves are cheap by comparison, which is why salad genuinely thrives in conditions that starve a pepper.
Working With Four to Six Hours
This is the most common real-world situation, and it is more productive than people assume.
Grow the middle of the table. Bush beans, chard, kale, beetroot, spring onions, radish and all the soft herbs will crop well. Carrots will size up, a little slower.
If you want fruit anyway, stack the odds. Choose early, small-fruited varieties — cherry tomatoes over beefsteaks, compact chillies over bell peppers — because a plant ripening 20 g fruit needs far less accumulated energy than one ripening 300 g fruit. Start them indoors so they hit your sunny window already flowering.
Working With Less Than Four Hours
Stop trying to grow tomatoes. That is the whole advice, and accepting it early is the difference between a productive shady garden and three frustrating seasons.
Under four hours, focus on leaves and stems: lettuce, rocket, mizuna, spinach, chard, pak choi, sorrel, mint, parsley, chives, and mushrooms if you fancy a project. Many of these actively prefer it — spinach and rocket bolt in strong sun and stay tender for weeks longer in shade.
Shady beds also grow slower, so sow more thickly and harvest as cut-and-come-again rather than waiting for full-size heads. Expect roughly 60-75% of the yield you would get in full sun, arriving one to three weeks later.
Watering changes too: less evaporation means less frequent watering, and overwatering is the usual killer in shade. Slugs are the other, since damp shade is their preferred habitat. Check pots after dark.
Reflected Light and Season Drift
Two things quietly wreck a well-made plan.
Season drift is the first. The sun sits much higher in midsummer than in spring or autumn, so a bed that gets seven hours in July may get three in September. If you are planning autumn crops, measure in autumn, not in the enthusiasm of May.
Reflected and radiated heat is the second. A balcony with a south-facing masonry wall receives direct sun plus re-radiated heat all evening, effectively pushing it a climate zone warmer. That is superb for chillies and aubergines and brutal for lettuce. If you are planning pot placement, this interacts strongly with container material and volume, and with your companion planting layout.
If you would rather not manage the arithmetic each season, Vegarden takes your measured sun hours per bed and suggests the crops and sowing dates that actually fit the light you have.