All plants require sunlight to photosynthesize, but the type and amount of light changes throughout the day. Morning sun and afternoon shade are perfect for crops like lettuce or cilantro that wilt in the summer afternoon heat. On the other hand, direct afternoon sun is ideal for warm-weather crops like succulents, cacti, and Mediterranean herbs growing in the northern zones of their range.
The best timing of sunlight varies widely depending on the plant species’ native growing environment and your garden’s unique microclimate. Let’s dig into the key differences between morning sun and afternoon sun, including the effects of intensity, temperature, UV spectrum, and climate on plant growth.
The Short Answer: Morning Sun is Better for Tender Plants
Generally, both morning and afternoon sunlight are beneficial for plant growth. For most vegetables and herbs, the morning sun is superior because it is gentler and cooler. The morning sun is lower in the sky and less direct. It also quickly dries the nighttime dew from the plants to prevent disease.
The less intense UV light can be beneficial because it helps the plant meet its photosynthetic needs without scorching the leaves or causing wilting. Some plants prefer full sun (6+ hours of direct light), but sometimes droop in extreme heat. These appreciate rays of morning sun with some afternoon shade.
The Long Answer
Many different factors can affect a plant’s light exposure, including shade from trees and nearby structures.
Wild plants are exposed to a wide range of different lighting conditions depending on their location on Earth and the plants growing around them. For example, an understory fern only receives dappled sunlight through the canopy whenever the sun trickles through the trees above. On the other hand, a prairie grass or tall wildflower in a wide open grassland likely receives direct sunlight throughout the entire day.
In our gardens, things are a bit more complicated because homes, structures, and trees cast shadows at different times of day. A vegetable garden full of tomatoes and peppers may struggle on the north end of a two-story house because it won’t receive enough direct sunlight at any part of the day. The sun will rise in the east and move across the sky throughout the day, but the house will likely cast a big shadow over the garden.
However, an ornamental bed of blooming rhododendrons may struggle on the south side of a house in a warm climate. If there aren’t any trees or other structures, the afternoon sun may be too intense and dry out the soil too quickly, stressing the plant and leading to a host of other issues. Rhododendrons are generally forest-edge plants that enjoy partial shade from trees, but their cousins, azaleas, are more adapted to direct sun.
Finding a balance of proper lighting often requires some trial and error and a lot of observation. Understanding the nuances of morning versus afternoon sunlight can help you optimize plant health in different areas of your garden.
Clues to Plant Light Preferences
The plant’s native environment offers the best indication of its light requirements.
The best clue to a plant’s light needs is its native environment. Lavender naturally thrives in rocky, exposed Mediterranean slopes, so it’s no surprise that it needs 6+ hours of direct morning and afternoon sunlight to thrive and produce lots of flowers.
On the other hand, the wild ancestor of cucumbers (Cucumis hystrix) tends to climb through bushes and trees in Southeast Asian jungles where sun exposure is fairly low. It makes sense then that garden cucumbers often wilt under the intense afternoon sun and much prefer the dappled shade of morning UV exposure.
No matter what you are trying to grow, I recommend researching where the plant evolved. Our Epic grow guides include the light requirements of hundreds of different plants, including descriptions of their origins.
Differences Between Morning and Afternoon Sun
The intensity of UV radiation differs between morning, midday, and evening sun.
Morning and evening sun rays have less intense UV radiation than midday afternoon sun. For the purpose of this article, we’ll consider the morning sun as the light between sunrise and 11 AM, and afternoon sun between 11 AM and 4 PM. Evening sun tends to affect plants similarly to morning sun because the sun is lower in the sky.
As you can imagine, the angle and exposure to light throughout the day can dramatically affect how different plants photosynthesize and perform in different areas. Let’s explore the key differences between morning and afternoon sun, including light intensity, temperature, seasonality, and variations in latitude and climate.
Light Intensity
Morning exposure is less likely to cause sunburn, benefiting both you and your plants.
It is no surprise that the morning sun is less intense than the afternoon sun. The gentle rise of the sun happens in the east, and its rays travel a much greater distance through Earth’s atmosphere. This means the intensity of UV rays is much lower because they are farther away and hitting the Earth at a different angle. You don’t usually get sunburnt in the morning, and your plants won’t either.
Afternoon (midday) sun is more intense because of the Earth’s angle in relation to the sun. Visibly, the sun is the highest in the sky and typically the most direct into your garden because it rises above any trees or structures.
The hours between 11 AM and 4 PM usually have the hottest, most intense sunlight because the UV rays travel a shorter distance through the atmosphere and have a straight path to Earth, so they hit our skin and our plant leaves directly. This is when tender plants are most susceptible to wilting and water stress if they don’t have any protection from taller plants or shady structures.
However, afternoon sun is excellent for plants that evolved closer to the equator. Tomatoes, potatoes, peppers, sunflowers, agave, cacti, bamboo, and many tropical fruits are examples of plants that bask in afternoon sunlight.
Key Takeaway: Cooler weather temperate plants prefer less intense morning sun, while equatorial hot-climate plants appreciate intense afternoon sun.
Temperature
Plants that prefer cooler temperatures tend to thrive with morning sunlight.
Generally, plants that like cooler temperatures will prefer the morning sun. Plants that like hotter temperatures appreciate afternoon sun or full-day sun. This is important when growing species on the edges of their range.
For example, most rosemary shrubs are hardy to about 10°F, or zone 8. If you want to grow rosemary as an outdoor perennial in zone 7, you could get away with planting it in the most south-facing open part of your garden, where it gets direct afternoon light for most of the day and throughout the year.
On the other hand, take a temperate cold-climate shrub, like lilac. Lilacs are considered hardy in zones 3-7 because they need cold exposure and winter dormancy in order to trigger flowering. You could get away with growing some varieties of lilac in zone 8 or 9 if you choose the right species and plant it in an area with protection from the afternoon sun, like an east-facing part of the garden.
For vegetables and herbs, take note of which plants wilt the quickest under the afternoon sun. Some of this can be remedied with more water and compost amending, but many of these crops are communicating that they need respite from the afternoon heat. Interplanting basil and lettuce under tomatoes or growing squash vines under a corn patch can help ensure proper light exposure to all the plants involved.
Key Takeaway: Afternoon sun is hotter, and morning sun is cooler. Cold-climate plants appreciate protection from the afternoon sun if they are grown in southern zones.
Seasonality
North-facing gardens may not receive any morning sun in the winter.
The winter sun sits lower in the sky, which means less sun hitting your garden overall. Morning winter sun is particularly reduced and may not touch a north-facing garden at all. The summer sun is more intense and bright because it rises higher in the center of the sky.
If you live in a far northern area where winter sunlight is quite low (or there is a lot of cloud cover), a west-facing or south-facing garden bed is important to maximize both morning and afternoon light. The morning sun will be especially diminished during the northern winter months.
Perennial plants are typically adapted to changes in seasonal sunlight, while annual plants can be strategically grown in garden beds with sun exposure that changes through the year. Before you start transplanting plants to new areas, I recommend simply observing a plant at different hours of the day and year.
- If it looks stunted, pale yellow, flowerless, or it has “leggy” growth, it may not be getting enough sun.
- If it looks burnt, whitish, or wilted on hot days, it is probably getting too much sun.
To see how light moves over your garden in different seasons, use a tool like SunCalc to visualize the sun’s position. Alternatively, just watch your yard throughout the season. You will intuitively know what areas are the most shady at different times of the year. Prioritize your brightest exposed areas for full sun flowering plants and fruiting vegetables.
Key Takeaway: The winter morning sun is low in the sky and has far less UV rays. Summer afternoon sun is the most intense of all and may require protecting some plants by transplanting, interplanting, increasing water, or using shade cloth.
Latitude and Climate Variations
To grow subtropical or desert plants in the north, maximizing afternoon sun is crucial.
Northern gardeners have less sunlight exposure overall than southern growers due to the tilt of the Earth and the angle of the sun at different latitudes. Recall that latitudes are imaginary lines looping around the Earth, dividing it into horizontal sections. The equator (0° latitude) is the hottest and most direct sunlight area on Earth. The farther north your garden is from the equator, the less direct sun your climate receives. The same is true for far southern areas toward Antarctica and the South Pole, but we aren’t growing food there (thank goodness!)
Key Takeaways: Southern latitudes are closer to the equator and receive brighter sun across all hours of the day. The afternoon sun is especially intense, and many temperate vegetable and fruit crops need partial shade to protect them from the afternoon sun. Northern latitudes are farther from the equator and, therefore, experienced less overall sunlight. If growing desert or subtropical plants in northern zones, you’ll want to maximize afternoon sun as much as possible.
Disease Prevention
Plants vulnerable to fungi could fare better if relocated to a south-facing or east-exposed spot.
One final consideration is disease prevention. Morning sun is ideal for drying plant leaves after a nighttime of dew accumulation. In dry climates, this isn’t a problem. But in humid climates, morning sun is important for reducing overall moisture on the leaves.
A west-facing garden may be shaded from morning sun, which means the leaves stay wetter farther into the day. If these plants are prone to fungal pathogens like powdery mildew, they may benefit from being moved to a more south-facing or east-exposed location because the morning sun helps dry them out.
Key Takeaways: Morning sun dries nighttime dew. Afternoon sun takes longer to reach wet leaves.
Final Thoughts:
Sunlight requirements vary widely across plant species, climates, and latitudes. It’s hard to make specific recommendations for your garden until you have done your own observations. Consider:
- Plant Needs: Full sun plants need 6+ hours of sunlight per day, including morning and afternoon. Partial sun and partial shade plants typically prefer morning sun because it’s less intense.
- Climate Variations: Northern climate gardeners benefit from south-facing or west-facing gardens because they maximize the amount of overall sunlight throughout the day. Hot southern gardeners can grow temperate plants in north-facing or east-facing beds because the morning sun is less intense. Humid climate gardeners can prioritize morning sun to help dry out leaf dew.
- Real-Time Observations: The way the sun hits your yard depends on many factors unique to you. Take some time to sit with your garden at different times of day in different seasons and notice how the light comes in. This meditative practice benefits both you and your garden plants!
If a plant looks yellow, or pale, or lacks flowers, it may not be getting enough light overall. If it is wilted in the afternoon sun or has scorched leaves, it may be getting too much intense light and should be moved to an area with more morning sun and less afternoon sun. Don’t be afraid to transplant when needed!
