Is there a cover crop that would grow under 2" of pine bark nugget mulch? Then how would I kill it?

My 1/2 acre yard in a Superfund remediation zone has been excavated to 1', and backfilled with roughly 1" of clay, 5" of sand, 5" of topsoil, and 1" of composted cow manure. The contamination was from airborne dust from a factory down the street and was confined to the top 6" of soil as determined by 30 years of testing, so replacing the top foot is adequate to ameliorate the contamination.

I will be planting a permaculture food forest with over 70 fruit and nut trees, guild plants, vegetable and herb beds, etc. Any day now they will install 2" of pine bark mulch over top. I am concerned about the soil because:

1. it's all new and needs to be built up
2. the precious, expensive cow manure compost layer on top will have spent at least a week baking in the hot Florida sun by the time they put the pine bark nuggets on it.

I like the idea of quickly throwing a cover crop over the entire thing, but is there such a thing in the world as a cover crop that would grow under 2" of pine bark nuggets? Which one?
And if it did, how would I kill it now that it's under 2" of pine bark nuggets? We have 2-3 months before installing the fruit trees and everything at the end of September/October.

Thanks very much for your suggestions.

Picture 1 is one side of my yard all backfilled and ready for the next step. The dark area is a thin layer of cow manure compost. The lighter part toward the front is the city right of way and shows the topsoil they put underneath my compost.

Picture 2 is an example of the pine bark nugget mulch.

I can't think of anything that will grow under 2" of mulch in the Plant Kingdom. Now from the Fungal Kingdom, anything and everything would love to grow under 2" of mulch.

What I would suggest doing is:

#1) as soon as the pine bark mulch goes down, inoculate it with fungi. There are tips on how to do this in my thread on mycoremediation.

#2) Just put the plants in as you get them. Fall is a great time to plant in our climate -- the sun is not beating down as much, and the temperatures are not as stressful on new seedlings.

#3) Throw seeds on top of the pine mulch in the Masanobu Fukuoka style and see what comes up. Rather than have dedicated herb beds, throw the seed on top of the mulch and let Nature do the rest. I do this with catnip, dill, cilantro, parsley, maybe some flowers too, like zinnia and marigold. I don't mind these coming up wherever they want and it's not like they are aggressive or invasive.

You might want to consider perennial peanut in some your area. I don't have any experience with it, and it will take a good bit more global warming before the climate zones move this far north, but it sounds like an interesting thing to try.

I'd suggest something large seeded, so the seedling has enough reserve to push through 2" of mulch. I think some kind of large legume (large seed that is), like peas or beans would be able to handle that.

Not sure what the best way to kill it would be though. Maybe just mowing after they flower.

Alex

Another thing to consider is that if it is all mulched with 2 inches of stuff, you probably don't really need a cover crop right now. As long as the soil is not bare, baking, and blowing and washing away, your should be good an 2" of mulch should do the trick. Sorry I didn't really answer your question, but if I were you, I just wouldn't worry about it.

Maybe try seed balls? Just shove them into the mulch and they have everything to germinate. You can add whatever seed when you make them.

First a couple of questions, How large is that area?, will it support 70 fruit and nut trees with out their being over crowded? Fruit and nut trees usually need at least 20 feet (in every direction) between them to have enough room to breathe and not have fungal infections or mildew take over their leaves.

If you want to grow a cover crop prior to it being buried in the mulch, any clover, or buckwheat would work. Once they throw down the mulch it will decline and nurture the soil below, or it will survive and grow through. Either way your new soil will win.