How to Know How Much Sun Your Flowers Need to Thrive

Sunflower under a sunny blue sky

You know that different plants have different needs for sun. Plants and seeds usually come with a description of how much sun they need. It’s essential to pay attention because the right amount of sun is what plants need to grow, thrive, and flower. Without enough sun, or too much, plants may be unhealthy, inviting diseases, won’t flower well, and may not develop nice strong stems.

Amount of sun is mostly about the duration of sun. That is, the number of hours of direct, unobstructed sun.

But the number of hours does accumulate in a day. So if you have the shade of a few trees pass over your garden, you can add the number of hours before and after that shade passes through to determine your total.

Plant labels differ somewhat, but here are the numbers of hours that fit most of them:

Full sun: 6 or more hours of direct sun per day

Sun to part sun: 6 or more hours of sun but handles less, to 4 hours, mostly afternoon sun, but usually better blooming in more sun.

Part sun: 4 to 6 hours of direct sun per day, including some afternoon sun

Part shade: 4 to 6 hours direct of sun with most of that from morning sun

Full shade: less than 4 hours of direct sun per day with mostly morning or late afternoon sun, or dappled shade all day

Dense shade: This is no sun, deep, dark shade, suitable for mushrooms

Sun or shade: There are some plants that are flexible, like some coleus and Vinca minor, but not for any cutting flower I know of (unless you want to cut coleus as foliage for bouquets…which would be pretty!)

There are in-betweens

Many plant labels say they take full sun to partial shade. They’ll do well in either situation. But you may need to estimate how they will work in your particular area. Because, depending on where you live, your sun hours will be more or less intense than in other areas.

In many northern regions and with more humidity or cloudy summer weather your sun may be less intense. This means full sun to part sun may do better in full sun.

Likewise, if you live in hotter, southern regions (in the northern hemisphere, that is) your sun may be more intense. Especially in dry climates and at higher elevations. Full sun to part sun plants may do better with a respite from the sun, like a little shade of a tree passing over, or with 6 hours only of sun per day, or with some shade from the hot afternoon sun, or shade for much of the morning.

The Blue Sage label below says it takes takes full sun to partial shade. That represents a wide range. In my 2,500 ft. elevation, and warm dry climate, which is getting much hotter each year, plus we are experiencing prolonged drought. But since it grows well in full sun, and I know that it’s a drought tolerant plant…I’ll plant this where it gets part sun.


Three plant labels with three sun needs
Plant labels with different sun needs

So try to estimate how these differences apply to your area. Make your best guess and the next step is to try it out. Perennials can always be transplanted, preferably in the fall. And annuals can be placed in a new spot next season.

Signs that plants are not in the best amount of sun are problems mentioned above: lanky growth, not much flowering, vulnerability to diseases like powdery mildew, and long weak stems, and looking like plants are reaching for the sun. Or watch for plants that wilt and don’t recover, stunted growth, or have a yellow-white burn or scorch on the foliage.

Plant labels help you choose whether you have the right space for a plant. But sometimes you’ll need a little trial and error is needed to hone in on the right sun for your area.