You need not throw those bags away, the contents can be used as a mulch which is a ground cover, something you put on your soil to protect it from the ravages of the wind, rain, and sun. A mulch can be any vegetative waste, including compost, leaves, wood chips, or it could be stones but stones are not a very good mulch since they add nothing to the soil in the short term, although your soil is composed mostly of weathered stones. Compost is something man made, a mixture of vegetative waste products that have been digested by bacterial activity. Compost is a soil amendment, something you add to soil to improve its texture, that can be mixed into the soil (usually unnecessary) or put on the soil as part of the mulch. If your soil is good and healthy with an active Soil Food Web they will move any organic matter you put on your soil into the soil for you and will incorporate it into the soils structure far better than you ever could by "tilling" it in. Most likely you need both the compost and the mulch, except what you already have, to do what you want done.

Horseman, your question about the growth rate is similar to what I am wondering. My tree has not added any height at all since it was planted last year. Neither does the trunk seemed to have thicken enough for me to perceive, if at all. If the late winter freeze issues had not distracted me, I would have been posting questions about the slow growth rate. Yesterday, I read on a website describing the cultivar, that the 'Gold Rush' cultivar does grow slower than the species. My 'Gold Rush' has a clean trunk about 3 feet up before the trunk forks of into two thin, flexible and arching, but still slightly branched and well leafed out trunks which makes up the canopy of the tree. It looks to me that the only reason the trunk is not branching out lower on the trunk is due to the way the grower pruned and trained the tree prior to shipping it to me. I planted mine in mid May of last year, and yes in the heat and drought of the summer the leaves did tend to want to turn brown. Whenever I saw the slightest amount of browning in the leaves, I would water the tree well, and each time, the leaves responded quickly, by changing again to their nice bright healthy color. Currently the leaves of my 'Gold Rush' look golden, and I can see some of the healthy bright green of the cultivar's normal spring leaf color trying to emerge from the base of those golden colored leaves.

I've never heard of anyone describing epimediums as "invasive" or even very aggressively spreading - they tend to be colonizers, forming slowly expanding clumps over a period of time. In fact, I'd say many would consider their growth and spread not to be fast enough :-) The easiest way to control spread is to sever any rhizomes that stray too far away from the mother plant with a sharp spade and remove and replant elsewhere (or give to fellow gardeners). The edging could also work but would not be MY first choice from a purely aesthetic standpoint.

I would be very hesitant to think that RAISING the grade around my house would solve a drainage problem. Water flows underground too. But I would have no way of knowing unless I had a map that showed the overall grade of both your property and adjacent properties and what kind of soil you had, the dimensions of the lots, location of paved surfaces, etc. Your property does not exist in a vacuum as you have discovered, and anyone who designs anything on your property that does not consider how it relates to the whole area is not showing you signs that they are competent enough to handle your problem. Could they be, yes, but no guarantees. Best bet to find someone with a very long track record of handling drainage problems EFFECTIVELY. Everyone will tell you they can and have done it, you need to diligently check their portfolio and speak with references. I deal with water managers all the time and the good ones are few and far between. What you get is common solutions to common problems which do not always work when applied to every situation.