Possibly powdery mildew. Does it look like the pictures in this link? Here is a link that might be useful: Powdery Mildew

The only way to know if this is a soil nutrient deficiency, or soil pH related, is with a good, reliable soil test. Contact your local office of the University of Idaho Cooperative Extension Service about having this done. You can also dig in with these simple soil test, 1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top. 2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up. 3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart. 4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell. 5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy. to see what else is going on with your soil and what to do to work on and make your soil into a good, healthy soil that will grow strong and healthy plants. What you have might also possibly be a plant disease, although most often that appears as blotchy leaves that then turn yellow, or maybe, possibly due to some herbicde although most often plants sprayed will wilt, not become rigid. Here is a link that might be useful: UI CES

I second catbird on the epimedium. Just started growing them this summer. They take DRY shade, I'm told, and so far, the one I bought is faring well. If nothing else, you can always grow mint! LOL. Also, I have variegated gold and green ivy. It's not as invasive as the common ivy. Also, liriope, which comes in the regular green, green & gold, and green & white. The regular green is much more invasive than the varigated ones. None of these plants mind the tree roots. I have dry shade and tons of trees all around the perimeter of my yard. If you want, you can also grow moneywort, chameleon plant (invasive nature), and most ferns don't mind tree roots either. That is where they mostly grow naturally is under the canopy of trees. A truly pretty one is the Japanese Painted fern. Hope this helps and good luck. Susan

This is my soil exactly. We live in a sugar maple woods, smattered with black cherry, beech and walnut, with soil that is sand and powdered clay so any water the soil gets, either gets stolen by the maples or drained quickly away to the gravel bed below. Still we have an abundance of things that grow here... Jack-in-the-pulpit by the thousands Blue Cohosh by the thousands Dog tooth violets by the hundreds Wild violets Christmas Fern loves it in our dry ground as well Crested Shield Fern Hart's Tongue Fern Male Fern doing very well Nannyberry bush Witch Hazel bush Serviceberry bush and despite the totally WRONG conditions we have a Highbush Cranberry (normally likes acidic and wet) that is thriving in our basic and dry conditions. We have a TON of other stuff but it all tends to need watering a couple times a week. In these dry conditions it seems that trial and error needs to be accepted as one of your methods as well as a lot of research into sun/soil conditions and plants that thrive in them. It also seems to be easier to grow things from seed in these conditions so that the plant/shrub/tree is adapted to the poor soil right from the start. We have a Redbud that we bought that has struggled along but it has thrown 2 very healthy seedlings about 20 feet away from it that are thriving after sprouting from seed. Find out what works for people in these conditions and then put a "WANTED" list for seeds over at the seed exchange forums. Have fun... Barb southern Ontario, CANADA zone 6a