Also in Z5? Which way does the porch face?

If the porch gets a small amount of morning or evening sun, you might look into hostas instead, which can be planted in pots. North facing porches can be a challenge, especially with trees in the way, so I don't have an answer there. Hostas are not flowering plants, but they come in some very beautiful colors and tend to prefer gentle light or shade. By mixing and matching color varieties, you can get something even more striking than a pot of flowers.

Hostas how-to (planting, wintering, soil, light, etc.):

http://www.lotsahostas.com/faq.html

To show the extensive varieties of color, check out this website, and there are many more than this site has to offer.

http://www.plantdelights.com/Hosta-for-sale/Plantain-Lily/Buy-Hostas/Hosta-Plants/Hosta-Nursery/?view_all#/?Activeproduct=y&Breadcrumbparent=Hosta&search_return=all&Activeproduct=y

I cannot WAIT to have a yard of my on filled with these guys!

Why low water requirements?

One more thing: not to mislead, but crown rot can be a problem in container-grown hostas, and this website explains what you can do to mitigate that in winter. It all depends on your zone.

https://www.bridgewoodgardens.com/cart/pages.php?pageid=44

Excerpt:

"The most common causes
for failure of container grown hostas are poor drainage and late freezes, both
of which can lead to crown rot. Just remember that when the plant goes dormant
in the winter it does not need care, it needs protection. There is virtually
nothing going on inside the plant during dormancy, so all you need to do is stop
bad things from happening.

It really isn't as hard
as we might make it sound. If you're trying it for the first time, we recommend
you use the less expensive varieties, and you should probably stay away from
blue varieties, which seem to be the hardest to grow in containers. Just be
realistic and remember that Mother Nature didn't design the plants to grow in
pots, so you have to provide for them and accept the risk.

Most of the information
below applies to cold winter areas. I have no experience in areas where it does
not freeze, so you are on your own there"