When you enter a garden center and behold all of the lush foliage and gorgeous flowers before you, what is it you immediately do? You are drawn to the look of certain flowers, be it a shape, size, or color. Immediately you walk in that direction and look briefly, if at all, at the tiny informational tag associated with that plant.
Stop! Do look for a moment at this plant tag and read it. The first important care instructions are the light preferred for that plant. Full sun, part sun, part shade, full shade, or dappled shade.
A plant’s light needs are determined by the LEAST AMOUNT of sun the plant requires to thrive.
The definitions of full sun, part sun, part shade, and shade are:
- Full Sun is direct, unfiltered sunlight for AT LEAST 6 hours each day.
- Part Sun is direct, unfiltered sunlight for 4-6 hours each day.
- Part Shade is sunlight for 4-6 hours each day, direct sunlight in the morning only.
- Full Shade is where sunlight is filtered, yet is available throughout the whole day.
This seems simple enough, on the surface, but there is a catch. Notice the range of how many hours of sunlight? That is determined by your climate as well as the time of day the plant is getting sun. Let me explain.
Morning light is the preference for most plants that are not adapted to intense sun radiation all day. Even plants labeled as ‘Full Shade’ plants do best with 2 hours of the morning sun, then shaded the remainder of the day, NOT areas that do not get any sun. Dappled Shade is sunlight is filtered, yet available throughout the day, but is unfiltered during the winter, such as under a mature deciduous tree that drops its leaves in the winter.
Due to the angle of the sunlight, which determines how much atmosphere it is filtering through, morning sunlight is gentler than mid-day sunlight. Ask any photographer or atmospheric scientist. I am guessing you are more likely to know a photographer :).
| Morning Sun | Sunrise | 10 AM |
| Mid-day Sun | 10 Am | 3 PM |
| Afternoon Sun | 3 PM | 6 PM |
| Evening Sun | 6 PM | Sunset |
This is why gentle morning sun is preferred by plants adapted to part sun or part shade conditions. How about the afternoon sun you ask? Isn’t it also coming in at an angle? Yes, however, there is often less water, fog, being held in the air in the afternoon, filtering and you will also need to factor in the added heat stress that has accumulated during the day. For plants, life is a balancing act between sunlight availability, heat tolerances, water management, and other resource management.
Afternoon sun exposure is more difficult on most plants because the heat from the day combined with the added heat from the sun adds up to too much water loss. Resulting in wilting to conserve water (yes, even with water available at the roots), or even sunburn on the leaves, both of which reduce the amount of photosynthesis (conversion of sunlight into energy the plant can use to grow) the whole reason behind it all.
Different plants are adapted to take advantage of, and do best in, different light (energy) conditions. Just like how wind can either power a windmill, or at different wind strengths, either not be strong enough to turn the windmill, or too strong and breaks it. Like Goldilocks and which bed she liked. Juuusssttt right.
The sunlight is the same. If a plant is adapted to grow in the full-on, blazing sun all day, it is not going to thrive in only 4 hours of the morning sun. This is because it has adopted mechanisms to reduce the intensity of the sunlight and its damaging effects. This puts it at a disadvantage in less sunny areas. Just like how a giraffe has adapted a long neck to see far distances and eat high leaves from scare trees on the wide-open savannas. The long neck would be a disadvantage in the jungle where it would have difficulty navigating the jungle without getting hung up on branches!
Full Sun tolerant plants that need at least 6 hours of direct sunlight a day, some are adapted to the intense sun from the time the sun rises to the time that it goes down.
If you are growing plants in full or intense sun, here are a few signs to pick out the plants adapted to the full intense sun:
- Silver/grey leaves, usually this silver/grey cast is due to small hairs, like fuzz or fur, that reflect some of the light/heat or that shade the leaves from the most intense sunlight.
- Dark coloration to the leaves, deep reds or darker maroon shades, sometimes even a golden yellow. I am not talking about fall foliage color, this is mid-summer colors. These are pigments the plant produces that act almost like a sunscreen for the plant cells. The color gets deeper the more intense the sunlight and will grow just a green shade in lower light situations.
- Smaller leaves. Large, wide umbrella-like leaves are not needed to maximize sunlight collection in full sun situations, however, smaller leaves conserve moisture in which full sun can dry out of larger leaves.
Shade tolerant plants prefer 2 hours of morning sunlight, but can be grown in light shade throughout the day. You will notice the leaves will get larger, plants taller, and one-sided as they stretch to gather the available sunlight. Here are a few signs that a plant is shade tolerant.
- Large leaves
- Darker green coloration, chlorophyll packed leaves
- Fast growth to rapidly take advantage of any sun opportunities that emerge.
There are plants in either category that do not show these characteristics, however, these are a few clues to get you headed in the right direction.
Now that you know this, it is much simpler to judge the amount of sun/shade you have in the areas you want to grow in. A local garden center will have local knowledge of sun intensity or heat stresses. With those, you can interpret the plant care tags with ease and shop with confidence!
Remember, right plant, right place! Do not get your heart set on a plant you saw on Pinterest, and try to force it to grow where you want it, despite if it is adapted to there. Know your space, your soil, your moisture, your heat, and your light situations first, THEN go find a plant that is adapted for those conditions. It will be more beautiful, and so much easier to care for than one that is not. Don’t ride a water buffalo in the dessert, or a camel in the marsh!
Related Questions:
How to measure full sun or shade?
- Sketch your yard
- In the spring:
- Make 8 copies
- Label the copies for sunrise and every 2 hours until sunset
- Note the sun pattern at sunrise
- Note the sun pattern every 2 hours, each on its time labeled copy
- Write down on a master copy the quality of sun definitions:
- Full Sun is direct, unfiltered sunlight for AT LEAST 6 hours each day.
- Part Sun is direct, unfiltered sunlight for 4-6 hours each day.
- Part Shade is sunlight for 4-6 hours each day, direct sunlight in the morning only.
- Full Shade is where sunlight is filtered, yet is available throughout the whole day.
- Dappled Shade is sunlight is filtered, yet available throughout the day, but is unfiltered during the winter
- Notate on the master copy sketch the different areas of your yard which get which of these 5 categories od sun
- Repeat at the height of summer.
- Repeat in the winter for perennial and woody plantings.
- Bring with you to the garden center!
How do you know what type of sun you have in the area you want to grow in? You really do have to observe for a full day. I know you think you can guess from when you leave in the morning, and looking at when you come back. Don’t do it. You will waste money buying plants, and wondering why they didn’t thrive as expected. The best way is to really take note on a day you are home all day. Check it at 6 am, check it every 2 hours until the sun goes down for a typical yard. This has to be done AT LEAST once in the summer and once in the winter for perennials and woody plants expected to grow year after year. I am telling you, yes you, who is sure that this is unnecessary and those who are sure they know already. You will be surprised. If you write this down along with a sketch of your bird’s eye view of your space, you won’t have to do it again in a few months. Just do it, you will thank me.
https://www.annualreviews.org/doi/full/10.1146/annurev.ecolsys.39.110707.173506
