First ... kudos for thinking ahead on this potential problem. You say that the asphalt area is old, which MAY mean that its most volatile time is PAST. And IF that is true, it means that the wetland/woodland has thrived in spite of the years-long runoff. Will this parking area be repaved in the near future? Are there local/state enviro-regs that will prohibit use of toxic materials to repave? Beyond these questions, if a berm to chanel rain water away from the wetlands is possible, that seems like ONE among MANY things that might prove effective. Also, you comment that this area is a part of your gardening area. That suggests that a certain amount of the water run off is within your control, which may be another thread subject on how to maximize water retention in your garden soils. Well, there are certainly layers of problems and solutions in your question. That wetlands is fortunate to have alert "friends".

Good question wetsuiter. How is your back doing? Did you try the heat? Answer: They disrupt electrical grids and also cause/contribute to VERY unusual weather patterns. Especially record breaking solar flares. They can create sustained swings of below or above normal temps, blizzards, flooding rainfall vs. destructive drought, increased cyclonic storm intensity like tornados... starting to sound familiar:) We happened to benefit from it as an unusually mild winter and now super early Spring. However it also can swing back and strike us with an "prolonged" icy cold blizzard in April right down the East coast to DC. However, observing our "pattern" reveals that's more likely in Europe this year then us.

That is pretty amazing! Were no stranger to tornadoes here in the DC area, as we usually have a few. Ive actually SEEN two in real life here, and one way down in central VA. One of the ones I saw here passed about 2,000 feet from where I lived on the 14th floor. I watched the whole thing and saw the damage occuring. It was an EF0 when it passed us, and lifted and touched down a few times in Northern VA, Crossing interstate 395 twice and touching down next to the Pentagon, and passed the Washington Monument just above the ground. As it moved NE is turned into a monster EF4 and killed several people in College Park MD. THis was back in 2001 or 2002 I think. We have had a few EF4s here, but most are EF0 or 1s. We got hit be severe weather several times this summer, and my neighborhood got the worst storm of the summer. We took a direct hit. It was a microburst, with winds around 110MPH. IT was as was described here... a wall of rain and everything turned white like blowing snow. It ripped up around 1000 trees in our neighborhood, partially ripped off roofs, blew off several Chimneys, destroyed several large signs for businesses, blew out several large windows including that of our post office, ripped shingles and siding off of most houses including ours, bent METAL LIGHT POLES at a 90 degree angle, crushed about 150 cars, and killed 1 person. You name it it happened and people were finding property blown several blocks away. Many of my friends here took extensive damage. It literally looked like a BOMB had gone off here, and it sounded like a freight train when it went through. It only lasted about 5 minutes or so, and the gusts to 110 was only about 30 seconds, but man it was insane. This was easily a quarter century storm. I saw the PURPLE coming right for me on the radar, and we were under a severe warning for damaging winds of 80+. no one was expecting the 110+ MPH winds tho. I was outside trying my best to secure things, take down the umbrella, pile up the chairs, take the glass out of the coffee table, bring in the cushions.. etc. I heard the first gust coming and it sounded like a train coming. I could see debris and dust in the air about 30 seconds before hit hit. It was probably about 65 MPH. It was a dry gust before the rains. Then the rains started and each subsequent gust was stronger and stronger until the big one came. I would have gone in the basement but the only way in there is to go outside so I was stuck on the ground floor. I moved to the side of the house(front) that was not facing the winds and could see peices of siding and roof shingles and large tree branches flying through the air. The house shook like an earthquake and creaked. I was pretty damn scared because you couldnt see much. Fortunately the sudden wind direction change never came, and after 5 minutes of hell, it was over. No power, sirens going off all over, EVERY street blocked. Could not drive anywhere. It blew all fo my plants flat over, as well as all the furniture, and picked up a 200 pound shed and tossed it 30 feet like a toy. The yard was filled with 20+ foot branches but fortunately no entire trees came down right near me. Everywhere else was a different story. Every other house had a tree on it. The official wind gust recorded at National Airport 1 mile away was 74MPH, however they were not in the direct path of the microburst. The winds were estimated at about 105-115. I have been through a CAT 2 hurricane before, and this was IDENTICAL to what I experienced in that. Glad to hear you took no damage. Some how, none of our furniture nor plants got damaged. the only thing damaged was a couple of clay pots which were lifted and thrown. The plants (Bananas) in them were fine. The only other damage was some siding and shingles ripped off the roof, but that was it. We got VERY lucky because many right around us within 20 blocks got extensive damage. There are sections of our neighborhood now that look completely different. Where once the trees and yards were filled with 100 year old trees, there are very few left standing and it is very "open" looking now. Thanks for the story and sharing this with us. Its been a pretty violent summer for lots of people in lots of different places for sure.

One thing I know I would try would be Hart's Tongue fern but it looks like you are looking for understory (shrub/tree). Maple leaf and black haw viburnum are pretty adaptable. There is one anthracnose resistant Cornus florida, it is Apalachian Spring but I thought Dogwoods liked neutral to acidic? For herbaceous layer try columbine, ebony spleenwort, cliff brake, bulblet fern, walking fern (if you have any moist spots). Best to figure out what plant community type or ecosytem is supposed to be on a calcareous ridge in the piedmont(?) of New Jersey and start getting some ideas from there. Even if you aren't going native it will give you ideas. Eastern red cedars are pretty tough to grow anything beneath. Because they are evergreen (shading anything herbaceous) and also due to their efficient and opportunistic use of moisture they effect the soil and any groundcover beneath their canopy. They can actually further raise the soil surface ph of your limestone ridge and substantially decrease moisture. I think they have some kind of toxicity that impedes germination of some species too. Combine that with the known toxicity of black walnut on many plants and you've got a tough nut to crack (no pun intended). Black Walnut Toxicity Good luck.