There really is no grass ( turf) that does well under oaks. Oak trees don't much like grass under them either. From the link St Augustine For Florida Lawns "'Palmetto' 'Palmetto' was a selection found by a Florida sod grower in 1988 and was released in the mid 1990s by Sod Solutions. It is of intermediate growth, with shorter leaf blades and internodes than many other cultivars, but is slightly larger than the dwarf St. Augustinegrass cultivars such as 'Seville' and 'Delmar'. It has a nice growth habit and does well in full sun or partial shade, but not in dense shade. It is sometimes referred to as drought-tolerant, but research has not shown that it has any greater degree of drought tolerance than other St. Augustinegrasses. It often has problems with disease, particularly in Florida's humid environment. It tends to have a lighter green color than many other cultivars." The link below has good info too. Here is a link that might be useful: Growing Turfgrass in the Shade

I have six large white oaks in my yard and I live in the Willamette Valley in Oregon (lucky in every way). Oaks are allelopathic but certain plants in Oregon are adapted to grow near and under the trees. Ferns, hostas, heucheras all grow under Oak trees naturally in Oregon. The trees are very sensitive to water especially along the base and mushrooms will grow on the base of the trunk as well as the root lines if irrigated/watered heavily. It is important to keep plants a distance away so that water doesn't creep onto the tree base. The roots spread equally about 3 feet down with some deeper rooting at the center - one fell in the oak grove behind my house last winter...very unusual. It is important not to disturb these roots when planting around the tree as injured roots make the tree more susceptible to disease. I have planted Astilbe, coral bells, azalias, rhododendron, Hydrangeas, heliotypes, forsythia and hellebores, coleus and begonias in addition to plants mentioned previously, under the canopy of the oaks, but I have so many I have a larger area to plant in without disturbing the trees. I am trying Japanese Anemone, but it is poisonous so it requires more care to assure animals (dogs, cats) don't get into it. These plants do well in dappled shade under the oaks rather than total shade. I try to supplement my soil with mulch every year. I carefully cultivate by hand the 7 foot by 45 foot garden under my trees with a special rake to break up the soil, add in commercial mulch and organic soil by hand and use a drip watering system with small water lines going to the base of each plant to prevent over watering. The first year is the worst, it gets better as the soil gets more an more conditioned, especially because my soil is a bit "clay" like. Hope this was helpful.

I wouldn't cut down a tree to grow flowers; you just need to find out what kind of flowering plants do well in your environment. You can check with garden clubs or with the county agricultural extension office in your county to see what plants thrive in your area. The ones I can think of that grow in acid soil in shady conditions are azaleas & camillias. If you post an ad on craigslist or freecycle, "free pine needles, rake your own", I bet you'll get a lot of fresponses from eager gardeners!

I agree that (some) ferns are as tough as old boots. Also, they don't necessarily require damp conditions. I have planted a number of ferns - basically whatever K-Mart was selling as Baby Ferns - along the narrow passageway between fence and house. Although they are protected from our heavy frosts, they still have to contend with the winter cold of the Canberra region. Some turned up their toes in the first winter, the survivors went on to endure our drought. Over the past 3 years, the only water they have received is the odd shower of rain. The oak tree, at 100 years, should be providing high shade - that is, shade from direct sun but still allowing for a lot of light underneath. There are oodles of plants which would enjoy the environment, including shrubs. I would definitely recommend the old acanthus (oyster plant or bear's britches). After dying back after flowering in summer, it shoots up again in autumn. The large dark green leaves are quite impervious to cold and would provide a luxurious green under the bare oak. If it were my garden, I would plant lots - they grow from root cuttings. The leaves themselves look fantastic edged with a rim of frost. Lots of photos on the net of the flowers, but finally found this one of the plant. Here is a link that might be useful: http://www.hgtv.com/hgtv/gl_plants_perennials/article/0,1785,HGTV_3610_1956068,00.html