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Sunlight is a key component of plant growth and health. But you may have a variety of plants and a variety of sun conditions in your growing space. How much sun does your plant need?
In this article, we'll discuss how to tell how much sun a plant needs and how to choose plants that fit best with the sun conditions you have.
In this article, we'll cover...
- How much sun?
- Common sun condition terms
- Can I make it work in a sun condition other than the recommended one?
- What about indoor gardens?
How Much Sun?
The first place to check for sun condition information is your seed packet. It should indicate how much sun your plant prefers using phrases like "full sun" and "part shade." Some varieties have different sun needs than others of the same species, so the seed packet should have the information for that specific variety. Many seed companies also post this information on their website.
If you bought the plant as a start (a young plant) instead of a seed, it should have a tag that identifies the plant along with basic growing information, including sun conditions among other things. If not, consult our gardening facts articles.
Every Plant to Plate gardening facts article includes sun information. These articles are intended as quick-reference guides for when your seeds are separated from their packet or when you are planning for your garden on a larger scale and don't want to look at every single packet.
Common Sun Condition Terms
Whether you look at the seed packet, the tag, or our site, you will see similar terms used to describe the sun requirements of plants.
Full sun means the plant needs direct sunlight for 6 hours or more each day. Full sun is the most common sun condition among common fruits, vegetables, and herbs. Sunlight starts and speeds up the photosynthesis process, which is what gives plants more energy and allows them to absorb nutrients more quickly. Fruits, roots, flowers, and oils take more energy and nutrients for the plant to produce than leaves and stems do. So it makes sense that most of the plants we consume need the faster photosynthesis that happens with more sunlight in order to produce the parts of the plant that we consume, especially in regions with short to medium-length growing seasons. See our article on full sun here for more information.
Dappled shade and dappled sun both refer to sunlight that is filtered through a canopy of tall trees. This sunlight may be less direct or may move around throughout the day more than unobstructed sunlight would. Some plants that do not normally tolerate shade may be fine with dappled shade. For example, cherry and Roma tomatoes fall into this category due to the smaller size of their fruits, even though larger varieties of tomatoes must have full sun in most areas. See our article on dappled shade here for more information.
Part shade means the plant needs 3-6 hours of sunlight per day. As mentioned above, leaves do not take as much energy or as many plant resources to produce. So most of the practical plants that prefer this category are leafy greens such as chard, orach, and hostas. But a number of other plants will tolerate it, especially the higher end of the range. Some plants are particular about whether they receive morning or afternoon sun, while others do not mind as long as the total daily amount of sunlight falls into this range. See our article on part shade here for more information.
Full shade means the plant receives 3 hours or less of sunlight per day. This is the least common sun condition, but it is tolerated among some leafy plants. See our article on full shade here for more information.
Some plants list a range of sun conditions, the most common range being full sun to part shade. We have an article for that too! Check it out here. Basically, most of these plants prefer full sun but will tolerate dappled and part shade.
Can I Make It Work in a Sun Condition Other Than the Recommended One?
The answer to this question largely depends on the plant and the climate.
For example, bell peppers and large tomatoes typically need full sun; most varieties do not tolerate shade under average conditions. But in hot regions (or seasons or weeks), they may actually require part shade conditions to avoid sun scald and stunted growth when the temperature is over 90°F. However, even in hot temperatures, these plants are unlikely to fruit if you place them in a full shade area that only gets 2 hours of sunlight per day.
This is another situation where our gardening facts articles come in handy. If there is a range of sun conditions, we will list it. So you might read on your calendula seed packet that full sun is recommended. But if you have an area that receives 4-5 hours of sun per day (so in the part shade range), you might wonder if you can make that spot work. The sun section of our Growing Calendula article says that calendula tolerates part shade, but it may grow more slowly and have fewer flowers than if it was grown in full sun. From there, you can decide if this is acceptable to you or if you would prefer to substitute it for a shade lover like chard and put the calendula somewhere sunnier.
But be sure to take the climate and other conditions of your area into consideration, including factors like humidity, wind intensity, and percentage of cloudy or stormy days, among others. If you are new to the area or just new to gardening in the area, it can be useful to read up on gardening in your region, both in books and on Master Gardeners websites, in addition to talking with more experienced gardeners nearby.
What About Indoor Gardens?
In other words, how do sun condition terms relate to plants grown indoors?
If grow your indoor plants on the windowsill or otherwise near a window, try to select a south- or west-facing window. Plants that face these directions receive the most direct sunlight throughout the day. If your plant is facing south or west, you can generally follow sun condition recommendations as if it was outside. So full sun is 6 hours or more, part shade is 3-6 hours, and so on.
If your window faces north, your plant receives indirect sunlight. This is equivalent to having a constant cloud cover, even on sunny days. Even in a long string of sunny days, it likely receives the equivalent of part shade at best. Of course, this could still work for some plants. I once lived in a place that had only north-facing windows, and I successfully grew dill, arugula, romaine lettuce, and several types of mint on those windowsills with no additional lights.
More likely, though, if your plant is in a north-facing window or not near a window at all, you will need to supplement it using grow lights. These are the ones I have, use, and am happy with. Grow lights with a timer and adjustable brightness levels, including the lights I just linked, can be set to mimic outdoor sun conditions. When using grow lights, you can generally follow the sun recommendations for the plant you are growing.
And there you have it! Hopefully you have all the information you need to determine how much sun your plant needs and how closely to follow the seed packet or online recommendations for sun conditions.
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