What does it mean when a plant requires "partial" sun?

It simply means that the plant doesn't need a full day of sunlight to thrive. It will do fine with between 4 to 6 hours of sunlight a day. Some plants do better with a break from the hot sun. Plants that require partial sun are great for gardens like mine as it doesn't get a full day's sunshine in all areas.

Partial sun refers to the plants need for indirect sunlight. Which can also mean that the plant can TOLERATE some direct sun, but not much, and especially not mid-day sun. Finding areas for the plants can be fun, and what you would want to do is walk around your planting areas in the mid-day, taking note of areas that are in the shade at this time. This gives this plant the best chance for survival and happiness.

The sun in morning shade in afternoon idea is ok, but it is flawed especially if the plant is exposed to ALOT of mid-day sun. The most important factor for you to realize.

Essentially, "partial sun" is a meaningless phrase because it's so vague. I have been gardening for decades and I can assure you that there is no definitive meaning to it.

For example, depending on who is using the phrase it can mean that a plant needsa minimum of "partial" sun (whatever that is) in order to bloom, or it might mean that it should have afternoon shade or it will get burned up.

One of my greatest frustrations as a gardener as been the cavalier way in which these sun requirement terms are used by plant suppliers and other "experts".

It means that it is sensitive to hot areas of your yard. You want to plant it somewhere that gets good morning sunlight and afternoon shade. NEVER afternoon sun because the petals or leaves will burn. Useually plants that need "partial sun" are plants that store a lot of water in their leaves. The HOT afternoon sun starts to heat up the water in their leaves to high temperatures thus melting the plant with it's own insides.

Plant it somewhere that half of the day - or so - it'll be in the shade, but before or after the sun has moved past a particular point, it'll have sun. On one side of a bush is ususally good; then, when the sun is on the one side, it'll have sun, and on the other, it'll have shade.

sun in the morning for at least four hours, and then shade for the rest of the day if possible. Or shade for at least six hours.

Like the side of a house.

It means sun in the morning,shade in the afternoon, or vise versa. Bye