Photos used by Rutgers show the Kousa hybrids made there growing in the open.

Here is a link that might be useful: Dogwoods

My Cornus kousa chinensis has been in full sun since it was planted some 10 years ago.

Err whats a popple tree??

Bottom line you want to avoid that late afternoon sun.

I had 'Wolf Eyes' in full sun (6+ hours) with limited late afternoon sun. It did fine but the leaves did curl as they typically do with too much sun.

I believe the OP meant Poplar tree (Populus).

We call it a popple aka Poplar

Popple is rarely used as a common name so most folks won't know it. Poplar is a more common name.

Populus is what should be used, helps avoid confusion of popple, poplar, aspens, cottonwoods, carp tree, crap tree, etc.

Yes, Popple is midwest slang for Poplar...or 'Populus' if we all have to be PC on this forum, but since the post is technically about Cornus Kousa dogwood...

I think we all know what a Poplar is.

You'd be surprised! Not PC, using Populus would help clarify what your talking about, after all this is a worldwide forum.

To your point its about a C. kousa, hopefully you got the info you needed.

Assuming your kousa is not one of the variegated one, it should be fine in full sun. I have a Heartthrob Cornus kousa in 95% sun with 0 (ZERO) mid day or afternoon protection that is absolutely fine as long as it's watered enough during the dry days of summer. Eventually I probable won't have to to that. I'm in north Arkansas, and our June to August sun intensity is far greater than you will ever see in WI, as well at the heat being greater and longer.

Arktrees

I wouldn't be counting on C.kousa to be a significant provider of 'shade' for 20 years or more.

To arktrees point the moisture is critical...the foilage would be completely fine. This applies to many Cornus species. Like C. alternifolia, which enjoys life in the shade, can be taken out of the shadows given adequate moisture and cooler soil temps.

And I'm sure the popple will be sucking up most of the moisture in my yard, and moreso with each passing year...I think we're going on the 6th growing season...

I know the C.Kousa won't provide shade for awhile...which is the primary reason the popple is still there...

I also have Rhody's that won't be very happy when that tree is gone...which means rearranging landscaping...

dogs enjoy the summer shade too...

still trying to talk myself into removing it NOW.

Is Magnolia 'Merrill' a considerably faster grower than the Cornus Kousa?

I'd say much faster...grows about 12-18" a year around here. Cornus kousa can actually be a weak grower in our area if it doesn't have good soil and moisture.

So the only cons, really, about the Magnolia near my patio is the drop of the flower petals (slimey), and the buds can get blasted with a late frost/freeze.

But I'm thinking if it blooms early in the season, and only for one week, if I remember correctly, I'm not going to be spending weeks on end cleaning up flower petals, so that I could handle.

From what I gather, these are the only downsides.

What about the shade quality and average height for the Magnolia? Will it provide dappled or total shade (say, five years after planting)?

I may change my mind and go with the Magnolia 'Merrill' instead.

Are any diseases or insect problems prevalent in Magnolias that I need to be aware of? My Grandma had a Magnolia - it always had earwigs on it - I had always equated Magnolias with earwig problems because of that - but that's not the case? Is it the dogwood that's known for fungal problems?

Odds are she had a Saucer Magnolia which are a little more troublesome. I think all trees have their issues though. If you can meet their cutural requirements you don't have to worry as much about the diseases and pests.

Magnolias will provide a deeper shade...it would still take some time. Merrill bloomed earlier than Leonard and Royal Star, but the two latter selections don't get very big (well over 20 years maybe).

I never had "slimey" flowers on any of magnolias...they did get damaged (browned up) one year from an early frost.

Honestly I'm a sucker for Magnolias as I think they have some of the most attractive foilage and branching (winter silouette as well).

I'd still try to get a Cornus kousa if you can work it in a spot with good soil/moisture. Interesting branching, nice wine red fall color and don't forgot the flowers! Minors has 'Wolf Eyes'...pink fall color was quite stunning.

In my experience here in the northeast, my Kousas (I have two in quite different sites) have grown faster than my magnolias (about 10 in varied sites.) Interesting how the differences in climate and soils make such a difference growth rates. My generic Kousas went in about 5 years ago as approximately 5 foot trees (balled and burlaped) and are both now over 12 feet. One is in full day sun with a western exposure, but plenty of soil moisture in an old pasture area. One is on a dappled shade slope that tends to be a bit dry. Soil is acid, fine silty loam.

I believe Merrill is one of the most vigorous Magnolias out there. Otherwise Magnolias are pretty slow from what I've seen.