Sunlight secrets: 10 neat things about sunlight in the garden
We all know plants need sunlight, but how they use it is a brilliant story of chemistry, strategy, and even movement. From sunburnt hostas to sun-tracking sunflowers, the dance between light and leaves is more complex than you think. Click through to learn how the sun shapes colour, flavour, and resilience in your garden.
1. Sunlight powers the plant’s entire system.
Photosynthesis isn’t just about “making food”, it’s the biochemical engine that drives a plant’s entire metabolism. Inside each chloroplast, sunlight energizes electrons in chlorophyll molecules, sparking a chain of reactions that split water molecules and fix carbon from the air. The sugars produced don’t just feed growth, they’re also used to fuel respiration, produce fragrances and pigments, secondary metabolites, and even defend against pests.
2. Some plants like it hot.
Tomatoes, peppers, eggplants, and squash are sun worshippers. They thrive in full sun (at least six hours a day) and perform poorly without it. Sunlight helps them develop flavourful fruit and reduces fungal diseases by drying moisture off leaves. Without enough sunlight, they get leggy and weak.
3. Not all do.
Many plants are naturally adapted to grow in the filtered light of forests, where direct sun is scarce. Their broad, thin leaves are designed to capture as much diffuse light as possible, which makes them vulnerable to damage in intense sun. Too much light can overwhelm their machinery and lead to the plant equivalent of sunburn. Add heat and dryness, and these shade-adapted plants wilt or scorch.
4. Sunlight is always changing.
Through the seasons and through a single day, the angle and intensity of sunlight is different, especially in northern latitudes. In summer, it rises higher and stays up longer, giving more direct light to your garden. But in spring and autumn, it sits lower in the sky and casts longer shadows—even a nearby tree or fence can turn a full-sun bed into part shade. Structures like sheds, garages, or even a hedge that seem harmless in July might completely block winter sun.
5. Clouds of smoke.
In recent years, wildfire smoke has become a serious factor, especially in midsummer. Smoke filters sunlight, reducing its intensity and altering the spectrum that reaches plants. While some species may stretch or slow their growth, others are surprisingly resilient. However, prolonged smoke can reduce photosynthesis and delay flowering or ripening.
6. Plants can get sunburnt.
Even the most ardent sunworshippers get sunscald. Sudden exposure to full sun—especially after being grown indoors or in a greenhouse—can damage leaves and stems. Harden plants off gradually before transplanting to prevent this.
7. Sunlight can change colour.
For many plants, sun brings out the best in colour. Deep purples, reds, and burgundies in foliage often intensify in bright light, as do vibrant flower hues. But for others, especially shade-loving varieties, too much sun washes colour out or even damages delicate pigments. Blue hostas, for example, owe their colour to a waxy coating on the leaves. In strong sun, that bloom literally melts away, leaving a duller green behind and sometimes even scorched patches.
8. Shade can be strategic.
Creating partial shade can help cool-loving crops like lettuce or spinach survive summer heat. Use taller plants like corn or sunflowers, shade cloth, or structures to filter midday sun and extend harvests.
9. Too much sun can dry things out.
Full-sun areas dry faster, increasing irrigation needs and stressing plants. Mulching and grouping plants with similar sun and water needs help to manage this. Succulents and prairie natives evolved to handle intense sunlight with special adaptations like waxy leaves and hairy surfaces.
10. Some plants seem to move like they have muscles.
Heliotropism is the fancy name for the way some plants track the sun across the sky. Young sunflowers are the most famous example: they pivot their faces from east to west during the day, then reset overnight. It’s not magic or muscles, but flexible cells in the stem that expand and contract in response to light. This movement helps the plant absorb more energy during critical growth stages. While most plants don’t visibly swivel, many subtly angle their leaves or stems toward the light. It’s one of the many ways plants quietly respond to the world around them.
