We have a front porch and used the white plastic lattice around it. We put up black landscape fabric behind the lattice to hide what was behind it (in our case that included the structure of an old porch that was there before the renovation...) The skirting board is low to the ground. The porch deck is a pale gray and the framing around the lattice is painted pale gray too. On one side of the front steps the driveway comes right up to the porch skirt so it is all visible; pots give some additional screening in the summer:
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On the other side of the steps, there is a very narrow bed under the overhang of the porch roof. It is dry and shaded except for a few hours in the morning. It is planted with Emerald Gaiety euonymus, rodgersia and, on the corner that gets sun, a clematis. The green and white euonymus blends well with the white lattice and, of course, is evergreen for a year-round look. The big leaves and white flowers of the rodgersia add additional summer interest. The clematis is a bit over-the-top when it blooms and, would not be an option if your area is entirely shaded but it might be worth trying a more shade tolerant one like Ramona.

Emerald Gaiety and Rodgersia (very dense screening - you can barely see the lattice in some places):
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The flashy mid-summer bit:
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Yours looks great!!

My porch is probably 3 times your size.

Still thinking of a barrier. But I also need plants.

Woody Oak....that is beautiful!

Theedudenator: There are a few options. I do like the lattis, which is what I have on the skirting of my deck.

Here is an interesting play on the lattis:
http://images.google.com/imgres?imgurl=http://www.doschwoodworking.com/images/porch-rail-skirt2.jpg&imgrefurl=http://www.doschwoodworking.com/architectural3.html&usg=__7Kjo930sZrSYkSVTXHfST8vFpl4=&h=400&w=560&sz=35&hl=en&start=4&tbnid=07GzoxlyiYDx4M:&tbnh=95&tbnw=133&prev=/images%3Fq%3Dporch%2Bskirt%26gbv%3D2%26hl%3Den

You could also try beaded wainscoting.

Or, depending on how large of an area as well as the style of your house and/or porch, you could build a planter around the entire porch. Just use plain cement block on the back side and something more attractive on the front. Then, of course, plant something beautiful like roses, hostas, or annuals.

The front of the porch is currently dirt.
We just had a large maple removed.

So a clean slate.

I was thinking some sort of perennial type bush with mulch under it.

That's a beautiful option that Dirty Wench has posted, but to me it misses part of the reason for closing off the under-porch: access for animals. Of course they can always dig in if they really want to nest there, but if it's just a question of the neighbour's cat or a sick dog having crawled in there and having to be gotten out... I'd rather have it either closed off well, or not at all.

If lattice will do the trick, then why not cedar lattice, like that used for fence panels?

KarinL

My guess is that solutions that are permanent and effective and look good and cover a large area are going to cost somethin' not too shabby. And the PVC seems lower maintenance than custom building and keeping painted white. But, if it is possible to do something "custom"--by that I mean, make up your own version of some kind of fencing which MIGHT be cheaper if able to use selected building materials and not manufactured PVC--I don't know--then, for the deck "skirt" this would become, you might be able to paint it dark green (Charleston green or whatever that kind of black-green is) and not have as much upkeep.

Anyway, if you do put up a barrier, take a minute to analyze what are your leaf issues--are they big leaves that blow under? If so, do they come from mainly one direction or specific areas? If so, use that to help determine whether your barrier will not only block leaves from the deck, but also collect big drifts of leaves and whether you want to design plantings that allow for easier leaf-removal vs. types of plantings that are a pain to rake amongst and around.

Take 3/4 or 1-inch wire mesh wide enough to fill the gap, paint it black with rust-proofer (use a roller), and staple it to the porch. Embed the bottom of the wire in the dirt. Cover the staples with a strip of wood and paint the wood to match the porch.

In almost any light, it will be invisible.

The critical thing is to prevent wind-blown trash, which leads to vermin and fire hazards.