When it comes to plants, each species has certain sunlight requirements it needs to survive. Whether you are researching trees to plant, vegetables to grow, or any of the thousands of flowers – they all have unique growing requirements.
And when researching plants to grow or reading the plant labels at a gardening center, you will often encounter various terms such as Full Sun, Partial Sun, Part Shade, or Full Shade. These are referring to the growing conditions that the plant will prefer. And although these terms seem descriptive, there are actually some time ranges for each one. I’ve listed them in the table below for your convenience:
| Growing Conditions | Hours of Direct Sunlight per day | Typical yard location |
| Full Sun | Minimum of 6 hours | In the open, or south facing side |
| Part Sun | 4-6 Hours | East or West side of structure or tree. No sun can reach it from the South. |
| Part Shade | 2-4 Hours | Under a tree canopy, but receives dappled sunlight |
| Full Shade | 0-2 Hours | Under full canopy, or shielded from the sun by structures, homes, sheds, etc. |
Click on the buttons below to jump to different sections for a deeper explanation:
What is direct sunlight?
Direct sunlight occurs when there are no obstacles between your plant and the sun. So, the sun can shine directly on it. Now, if a plant is receiving sun that is filtered through a tree, that would be known as dappled sunlight.
Full sun
Full sun is defined as anything greater than six hours of direct sunlight per day. If you have a flower bed that faces south, or is completely exposed from all sides then it would be considered full sun. Thus, full sun flowers should get at least 6 hours or more of direct sunlight per day.
To determine if your location is full sun, just make observations to an area to see if it is in sun or shade throughout the day. And if it is in direct, unfiltered sunlight for six or more hours, the location is considered full sun.
What happens if you plant flowers that want full sun in the shade?
If you plant flowers, vegetables, or trees in a location that does not receive full sun, several things typically happen. First, the plant will not grow as large. Second, it will not produce as many blooms or fruits. And third, if certain species only get sun from one side, they will often grow in that direction. This can result in leaning plants and bent trees. In fact next time you walk in the woods, you may see some trees growing in funny curves. This is the result of a tree growing in strange directions
Partial sun
The terms partial sun, or partial shade is a bit tricky. But, it is typically accepted that a plant that likes partial sun needs 4-6 hours of direct sunlight per day. If it receives more sun than this, it may wilt or become sunburned. Plants that get more sun than they prefer are also prone to drying out or drought stress.
Where to locate plants that need part sun
Plants and flowers that require partial sun (4-6 hours per day) can be planted on the east or west side of structures, behind trees or shrubs, or where taller trees may shade them in the afternoon. The key feature is to protect them from receiving more than 4-6 hours of direct sunlight. Plants that prefer part sun tend to like more moisture.
If a plant receives 6 hours of direct sunlight, and then an additional 3 hours of dappled sunlight (sunlight that is filtered through a tree canopy, for example), then that is perfectly fine.
Part shade
Plants that require part shade will prefer just 2-4 hours of direct sunlight per day. You may see examples of these plants in open woods, or along the extreme east or west side of a building or forest. I even encounter them along roadsides in the mountains where the tall tree canopy only allows for a couple of hours of direct sunlight per day.
Shade
Full shade plants are defined as any plant that needs 0-2 hours of direct sunlight per day. You may find these deep in the forest under thick a thick canopy of trees.
To see examples of these plants, just take a hike in a mature forest or park with a tall thick forest canopy. Some common North American examples would include ferns, Red Elderberry, sedges, and Baneberry.
Where you can plant full shade plants
Full shade plants can generally be located in wooded lots. They can also be planted along the north side of a building provided it still receives some shade from the east and west.
Frequently Asked Questions
Can you grow flowers in different sunlight conditions?
There is no hard answer to this question, as each species is different. But, as a general rule, full sun plants can grow in part sun conditions, but they won’t be as large or showy. Likewise, many part-sun plants can grow in full sun conditions provided they receive enough moisture so they don’t dry out.
A great example of this would be Columbine, which although it is always listed as shade to part-sun, I’ve grown it in full sun for many years without any problems. For an alternative example, Purple Coneflower can grow in part sun conditions, but it will not produce as many blooms and is generally shorter.
Is west facing considered full sun?
If a plant is located so that it only receives sunlight from the west, it would be considered full sun provided that direct sunlight shines on it for at least six hours during the active growing season. In fact gardens or flowerbeds that face west will have the second most sun (behind south facing). However if there are trees or other structures that shade it from the SSW, or WNW, then it may not receive as much sunlight.
What happens if flowers get too much sun?
Most flowers that are listed as shade, part-shade, or part-sun have foliage that is prone to drought stress or sensitive to sunburn. If they get too much sun, they may wilt or become stressed that can cause the onset of disease.
What happens if a plant doesn’t get enough sunlight?
If plants that prefer full-sun do not receive enough sunlight, it will generally be smaller, produce less flowers, or for vegetables, have less yield. This is because the main mechanism plants use to grow is photosynthesis, which converts sunlight to energy. Not getting as much sunlight as a plant would like results in smaller, less healthy plants.
Plants that produce nectar, fruit, and sweet vegetables (raspberries, strawberries, watermelons, etc) need sunlight to make sugar. If they do not get enough sunlight, their fruit will not taste as sweet. This is in contrast to non-sweet veggies like lettuce, herbs, or beans, which can do quite well in part sun, provided the soil is fertile enough.
Find more gardening tips here
References:
[1] – Better Homes and Gardens new complete guide to landscaping, Iowa : Better Homes and Gardens, 2002, pp411
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