Add organic matter, like leaves, compost, yard trimmings from your mower bag (as long as there aren't weed/grass seeds in it,) smallish trimmings from other plants, finely shredded mulch, anything to prevent the moisture from evaporating so fast, and to add tilth and humus to the soil as it decomposes.

Once you have the soil amended with some organic matter, check the pH and adjust if needed. State cooperative extension services often offer this service free of charge - it's a quick and simple test, and important as a plant's ability to take up nutrients is compromised if the pH is outside its preferred range.

There are several plants that will grow in dry shade; just a sampling is listed below. You will have to check to be sure these are winter hardy in your zone 5 (I'm in USDA zone 7, so have milder winters).

Epimedium (one of my favorites; some varieties are clumping, others are creeping), tiarella (another favorite), heuchera, heucherella, some ferns (wood fern - dryopteris, Christmas fern), solomon's seal (spreads by underground runners; the variegated variety will brighten a shady area), liriope (evergreen, does tend to creep), native wild ginger all can create a nice groundcover. For late winter/early spring color, plant a few snowdrops (galanthus). Crested iris should do well, also. All are perennials.

A few shrubs: kerria, cotoneaster, aucuba (gold dust plant - doesn't look it, but it's evergreen ... here), sweet box (I love this evergreen low-growing shrub that spreads politely and has very fragrant but inconspicuous flowers in late winter/early spring).

For the shade under the large tree, remember that any plants you place there will be competing not only for light and water, but for nutrients as well, so look for plants that will do well in poor (or "lean") soils. Oaks usually cast a dappled shade and prefer a slightly acidic soil; you should be able to find several perennials, shrubs, bulbs and understory trees that will happily coexist, as they would naturally in the forest, with that oak.

Dealing with shade can be a challenge, but please try to avoid turning to plants that are invasive in your area. In my region, English ivy, vinca, bishop's weed (aegopodium), Japanese barberry, Japanese honeysuckle (native honeysuckle, lonicera sempervirens, is OK), are some common ones. And chameleon plant (houttuynnia) - don't go there - in my innocence I bought some for my bog years ago, believing the line that it would not survive outside the moist boggy soil or our winters. Hah. I'm still trying to get rid of it. We are fortunate to have several resources in our region, among them the New Jersey Invasive Species Strike Team (www.njisst.org). If you don't have a local resource, some national sites you might check out are
The U.S. National Arboretum's site: http://www.usna.usda.gov/Gardens/invasives.html
USDA National Agricultural Library's site:
http://www.invasivespeciesinfo.gov/plants/main.shtml
or do a search for "invasive plants" and you'll probably get lots - just evaluate the sites carefully.

This post was edited by agardenstateof_mind on Tue, Jul 16, 13 at 19:43

I agree with purpleinopp. I had a garden bed like you describe. I put 3-4" of fine bark mulch on it and I haven't had to water it yet this year. Last rain was over 2 weeks ago. I even wasted money putting in a drip system. If possible I highly suggest mulching the top.

SCG

Plants that are thriving in my dry shade are Liriope, perennial vinca, lemon balm, and blue spruce sedum.An odd mix, right? I'm in zone 7A/B Oklahoma.