How about ipomea either the black or chartruese variety to trail over the side, and plumbago (the tropical variety) to give some sprawl and a nice skyblue color. Should hold up pretty well in your situation as long as you keep an eye on the moisture. I had this set up years ago in an eastern exposure.
Chaz

Hi Natureperson,

You have quite the menu of options! What do you want to see? Flashy flowers, reliable flowers, or just something that generally looks really nice, flowers or not? You can have a mix, and I'm sure you'll get lots of good suggestions from others, but for my money, you can't go wrong starting with some nice coleus (probably not from Lowe's... go a little more high-end for something really nice), and a couple of sweet potato vines (ipomea). For flowers, I personally like fuchsia (do be careful how you pronounce that!), although begonias might do well in the situation you're talking about, and then you can get something really flashy going if you want to. There's always impatiens: personally I'm a fan of the "new guinea" strains... their foliage tends to be more interesting that the more regular types, which helps to carry you through when the bloom is less prominent. Personally, I'd also try to weave some silver foliage into the mix - dusty miller or artemisia - but that's just one of my personal likes.

When I put together a planter such as that you're talking about, the bottom line is I'm effectively trying to create a living bouquet, and contrasting foliage is a big part of that for me. I like the look that you end up with (it's typically busy, but using foliage means that you're not so reliant on getting flowers). Different strokes for different folks, though... there are so many options that it really comes down to a matter of personal taste, and what "look" you're going for.

Regardless, remember that it's just for this year... try some things, see what works and what doesn't, and keep note. Next year, you can keep the favorites and try different things to replace what you didn't like, or you can start over again completely.

One other thing... depending on how big the urns are, and how they're placed, you might also want to think about tucking a small trellis into the back (or the center) and getting some climbers involved. The extra height never seems to disappoint!

Have fun, and I hope they turn out to your satisfaction!

Yes, Chaz... plumbago. Nice choice!!!

Oh... and one other thing, natureperson... When you think you have the pots filled, tuck a few nasturtium seeds into the corners. As long as they're well-watered, they should add nicely to the overall look... and they're tasty!

I like to come up with a color scheme that relates to the front door. Mine is dusty coral. I have pink&Green phormium for my center verticle thing. blackie potato vine (2 each urn), white bocopa for a trailing thing, salmon-coral-ish petunias for a mounding (when they don't droop&trail!) affect, Diamond Frost euphorbia for a light and airy affect, and coral nemesia (or diascia??? I forget) for more coral-pink color.

If you go with tall, mounding and trailing forms with plants that appeal to you, you can't go wrong. Pack em in.

Any verbena will do good in such situation. You may combine different colors of trailing and upright verbena in a same pot.

Wow! You guys are great! I knew I came to the right place! I'm keeping all your ideas, so I won't have to wonder each year what to put in my urns. ;)

Thanks so much! :)

I agree with all above that you must have a potato vine. Not only do they add interest - they are sooooo easy to grow! A wild bunny ate most of mine twice last year and it grew back so fast!
Okay....here is my formula that my mom gave me several years ago and I still hold true to when I shop for my containers (it is basically what WendyB gave you with flower choices): for each, you want something "roundy" something "spiky or tall" and something "droopy/viney"
I also like to mix herbs into my container plants. They add interest, fragerance and different shades of green to the color tones of the other leaves. (plus, they are usually on the patio so you can grab a bit when you are cooking :)
It's too late this year, but I also start some containers inside with some summer bulbs like canna, elephant ear, caladioums, etc. - whatever summer bulbs I find interesting from year to year. It gets the gardening season to start a bit earlier :) and you have estabished plants before anyone else.
Like Moleman54 - I don't know what your style/color scheme/or interest is, but if you follow the roundy/spiky/droopy formula, I think you will be happy. Also, I really crowd my plants in for a full effect. If the plants get too big for the space, you can always pop them into the ground somwhere, right? The fuller container I think always looks more finished and better. I also throw perinniels in too if I like the look of them and then in the fall, I put them somwhere that I want to see them again. And don't feel married to what you choose. I often change my mind and freshen my containers up mid-season with new plants just to change it all up.
Have fun...send us some pics! I bet whatever you choose is going to be fantastic!
Kathy

HI--I have a very similar situation and here's what I've done for 3 years ina row,I like it so much. Purple fountain grass,coleus,licorice plant,chartreuse sweet potato vine and some calibrachoa(?sp). The cali comes in colors--I love the bright pink the best. This combo is really great. I read somwhere that for containers, you want 1)a thriller 2)a filler and 3) a spiller. The above combo has it all. Have fun! Jardinista