Don't know about the lead but I think some similar discussions were had on this forum about that. You can probably transplant into your cleared area immediately after or in conjunction with mulching - that works for me anyway with flowers, shrubs and tree transplants. Your biggest concern is re-growth of that prior vegetation and weeds that germinate with the disturbance and increased sun more than the wood chips. Broadcasting seed would be less likely to succeed than transplanting with all of the mulch down but you would probably want a season or more of weed eradication before you open up bare soil and broadcast seed in that area anyway. Many folks on this forum advocate putting down a layer of newspaper or cardboard before mulching with the wood chips to help suppress the weeds - that systems works for me as well. Your area will be a little more difficult to cover with paper or cardboard in that it will be lumpy with the cutdown brambles etc. but it can probably be done with a little persistence. You will get more rips in the paper than on perfectly smooth soil but it's still better than nothing. Wood chips can take anywhere from a few months to a few years or more to decompose. Two years would not be an unusually long time for the wood chips to decompose where you and I do our gardening but there are lots of variables like climate, type of wood, size of the chips, etc.

I lived downstream from lead mines for several years as a child. I am only seventy years old and already -- what was the question?

Bob (and others), my reasoning for putting down one to two feet of woodchips was that it would act like a weed supressor and at the same time make beautiful dirt (to paraphrase one of my favourite gardening authors, Ann Lovejoy). But maybe that won't be enough to keep the brambles from pushing through? I can dump as much as 4 feet high of chips (if need be) before they'll start spilling over my stone wall to the neighbor's.

Any thoughts?

If, by 'brambles' you mean wild blackberry vines, you are fighting an implacable enemy. Experiments have been done where hay was dumped into bramble areas for 30 years, which enticed the cattle to eat both the hay and the bramble vines, and they never did kill them off. I've never seen anything on heavy-duty mulching, but I would keep a close eye for a few years and dig out anything you see sprouting.

I have an ongoing battle with them here. It should be interesting to discover whether the deep, dense mulch will shade them out enough to starve the food reserves in the roots, or find that the plants could work their way to the edges of the heavy mulch and pop up there.

Brambles: Mother Nature's reminder that she doesn't like bare areas of soil.

Nitrogen is requred for the chips to break down. If you were mixing the chips into the soil, the chips would take all the nitrogen for the process. One good source of nitrogen that you could either layer between several layers of chips, or spread on top and water in (or let rain do it for you, depending on where you live) is alfalfa meal. You can often get it from feed stores (40 or 50-lb bags) cheaper than gardening stores. If you can't find the meal, try to get the pelleted kind that doesn't have salt added, and use those instead. They will break down with moisture just like those pressed stove pellets.

It is probably safe to say that the more nitrogen you can provide to the chips, the faster they will break down.

Sue

Sue,

It's something I'd be willing to experiment with - heavy-duty mulching - since I have limited time available to me and I don't really see myself having the time and energy to take care of this future veggie plot till two-three years from now (I have young children).

Alfalfa pellets appeals to me. I already use them elsewhere in the garden and get them from a local feed store relatively cheeply. What kind of ratio should I use? Layering is not an option since I'm planning on having a tree service dump the chips and just spread them out at 2' depth.

Thanks all!

About lead in the dirt: previous research I did indicated that the problem with lead isn't the lead getting into the plants, but that the lead gets on your shoes and clothing from the soil and from there gets tracked into the house. So your rhubarb should in theory be okay to eat, as long as you wash it - but gardening in the lead-contaminated soil is potentially a bad idea. Consider either removing and replacing the soil, or building a raised bed on the site.

I somehow missed that you said 1-2 feet and not mere inches of woodchips. That will take a few years to break down. You definitely would need some sort of nitrogen material in bulk to make such a pile go quickly. If your brambles are blackberries they might be able to push up even through all of those chips. You could do a cut stem application of herbicide to reduce the chance of the blackberries coming back. Two feet of wood chips will suppress the germination of most weed seeds. Once the wood chips have decomposed they will make great soil.

Marianne,

Concerning lead contamination:

There was a discussion a few years ago about lead in someones backyard. There I learned of the word "Phytoremediation" (phyto = plant and remediation = correct evil). Basically it involves using plants to remove toxic material from the soil. By adding compost to the soil and planting plants such as sunflower or mustard greens (Indian greens), the plants remove the toxic material into their roots, stem, and leaf where the toxic material can be then removed. The link below leads to the EPA site that describes the technology. As it relates to eating any food grown in soil that may be contaminated, I must ask this question: Would you feed your children food that may have been grown in soil contaminated with lead? Would you take the chance on eating food that may be contaminated with lead? I didnÂt think so; throw the plants away would be the best and safest way to deal with this dilemma until the lead question is resolved is my suggestion.

I understand the lead can be removed in one season (not exactly sure), but could you grow in containers or in another area for the time being? IMO, better safe than sorry...

Blutranes

Here is a link that might be useful: EPA Land Remediation

If you can wait until later in the spring (May? June?) to have the woodchips delivered, it will actually be a mixture of wood chips & chopped green leavers. This mix heat up quickly & you may not need to add extra nitrogen.

How long it would take for wood chips to be digested depends on how healthy the soil they were plunked down on was. The more active your Soil Food Web, the healthier your soil is, the quicker those wood chips will be digested. The thickness of the layer of chips is also a determining factor and it will take much longer for a 2 foot layer of chips to get digested than a 2 inch layer.
Lead in soil would be a problem with root crops because there is a chance the paint chips could adhere to the root of the vegetable. It should not be a problem with anything growing above the soil such as Rhubarb unless the soil is left exposed to the ravages of the sun, wind, and rain so contaminated soil can be splashed onto the food.

Bluetranes, thank you for the EPA site about phytoremediation. Very useful, indeed. You are right, what's the point in risking lead exposure. But just to be clear, the site where I plan to dump all the woodchips is not a site that I expect to be contaminated by lead. It is far from the house and not in the vicinity of any buildings. What I was going to do was to dig up the rhubarb plants from their current location and move them to a safe environment and I was just wondering if they would be safe to harvest after having been in the new location for a couple of years, that's all.

mommyandme, great idea about waiting till later in the season to have the chips delivered so they are a mix of chips and green leaves. Why didn't I think of that?? Another source of nitrogen might be used coffee grounds. I thought I might sprinkle UCGs on the wood chips every so often to help things along.

Thanks all for your great suggestions.
Marianne

If you want to get rid of the lead in the soil, and you're having wood chips delivered anyways, considering dumping some wood chips where you suspect the lead is and growing some mushrooms there. Some types of mushrooms are proven to pull contaminants out of the soil. Once they appear, just dispose of the mushrooms safely and your soil is fine. Plus the wood chips, as said before, decompose into nice soil. This method is called mycoremediation. Here's a link to a website where you can find the mushroom spore for sale plus info on what type to get.

Here is a link that might be useful: Fungi Perfecti

>Some types of mushrooms are proven to pull contaminants out of the soil. Once they appear, just dispose of the mushrooms safely and your soil is fine.

"...and your soil is fine." Sounds like the perfect solution.

Still, I'd like to see the real-world data that proves it before trusting my health to such a simplistic solution.

Wayne

Wayne said:

"Still, I'd like to see the real-world data that proves it before trusting my health to such a simplistic solution."

While I canÂt speak of mushrooms, as it relates to Phytoremediation the following was taken from the website of "Edenspace Systems":

"In 1998, lead impacted soil from DaimlerChyslerÂs Detroit Forge site was treated using phytoremediation. Approximately 4,300 cubic yards of soil with lead concentrations ranging from 75 to 3,450 mg/kg were excavated to a depth of four feet and placed in a 24-inch deep ex situ treatment cell on an impermeable concrete base.
The cell was tilled and planted with successive crops of sunflower and Indian mustard to remove lead from the soil through plant uptake. Each crop was harvested and the biomass removed. At the conclusion of the growing season, the soil was again sampled and analyzed for total lead concentration.
The results of the sampling showed that the single season phytoremediation treatment had achieved the regulatory goal of 900 mg/kg. The soil from the cell was removed and replaced in its original location. Total cost of the phytoremediation treatment was less than $50 per cubic yard."

The site offers many other case studies including an US Army munitions test firing range. And too, since it is well known that compost is used to cleanup toxic oil spills and other materials, it appears the addition of certain plants enhance the operation. I am sure other examples can be found using a search engineÂ

Blutranes

Here is a link that might be useful: Edenspace Systems Corp.

Agronomist Neal Kinsey tells farmers that to break down crop residue into humus, it requires roughly one pound of actual nitrogen per one hundred pounds of residue.

I found a site that says a cubic yard of damp softwood chips weighs about 400 lbs.

I just googled a site that lists the typical percentages of several natural soil fertilizers [http://www.doityourself.com/stry/naturalfuels] , and it says alfalfa pellets contain 3% actual nitrogen (the meal is 2.5%). If my math is correct, a 50-lb bag of alfalfa pellets would contain 1.5 lbs of actual nitrogen, which would be good for about 150 lbs of chips. I think. That would be about 3 bags of pellets per cubic yard of wood chips. Hmmm, quite a lot.

Blood meal has 12% actual nitrogen, so it would only take a quarter as much, but costs $48/50# around here, which would come out about equal. And it can attract dogs, raccoon, etc.

There may be other things with higher nitrogen levels, but I wouldn't want to get into waste materials like sewage sludge and manufacturing waste that could be contaminated.

Sue

Here is a link that might be useful: Compost calculator

Blutranes, that's very interesting, the stuff about bioremediation of contaminated soil (aka, brownfields). In this day and age of biofuels, it seems like a no-brainer to grow sunflower, corn and other fuel feedstock crops on contaminated soil; it would serve two or three purposes - remediation of the soil, use of otherwise unusable soil, and crops for biofuels. Two ecological wins and a production win.

I think it should be public policy to pursue this sort of goal. Heck, our taxes go to G**damned corn farmers so that they can grow corn for fuel, why not extend this sort of thing to brownfield farmers?

Idaho Gardener,

Agreed, why not encourage positive endeavors? Not to mention charcoal (bio-char) to rejuvenate the soil and clean up our atmosphere, rock dust to re-mineralize our food supply, sea finds to produce abundant nutritious crops; why not indeed? Simplistic yet infinitely profound, and not too mention cheap. That may lie at the heart of the matter; there is no money (profit) in doing the right thing. Yet, I feel there is change coming that may indeed alter our behavior away from self-centeredness and more towards investing in life. For now all we can do is continue in our positive efforts and offer encouragement to those who seek out our combined wisdomÂ

Blutranes

There is some good advice here about lead, but it jumps out at me that you (we) have absolutely no DATA regarding lead levels in your soil other than that you have an old house. The idea that you should move plants, wait two years, do phytoremediation, etc. is all ahead of the game. First you need to know what you have!

With old houses the lead is often around the base of the house where the paint flakes off, and at the downspouts if they are or ever were lead or painted with LBP.

How about getting an inexpensive soil test for lead? Call your health dept. or county extension agent. Lead is cheap to have analyzed, you could probably get several samples for $50 or so. I'd take a composite around the base of the house, one where your rhubarb is growing, and one in your garden space.

Someone reported above a project that reduced lead from so and so to such and such, but gave no numbers for what's safe. Background is often in the low (single digits) mg/kg to up around 100 generally speaking. Don't know about your state. EPA considers 400 safe for residential use, including gardening. My state (MO, one of the most lead polluted in the country) uses 260. Just to give you an idea.

People mean well, but don't run off half cocked. Armed with data, you can make a better decision.

2' of wood mulch will ACTUALLY kill the horribly invasive native roses around here if you cut the offensive beast to the ground first.

The roses laugh at 6" though.....

The sad part is that these are the only roses I can grow :(

I did the same thing with mulch and found that it took about two years for, say, 8" of wood chips to break down with no added nitrogen. A couple of the truckloads of chips had leaves/pine needles mixed in, but they just don't last long enough to really change the overall timeframe. To my horror, however, I learned that broken down wood chips make beautiful soil - that every weed in creation wants to grow in! Well, well, that's tomorrow's problem, eh?

For the brambles, I decided to actually weed them up by hand in most places. It didn't really take that long and it was almost 100% effective. The remaining volunteers died promptly under RoundUp. In the area that was too large to weed by hand, I hired a guy with a Gravely and he mowed it a few times. I finished it off with spot treatments of RoundUp.

Yup. The older wood chip piles do act as a nice growing medium. I've had jewel weed and several other plants sprout in my older wood chip piles.

Yes, that's the whole point!! And the weeds are so darn easy to pull out that I don't mind.

Also, I do plan to have my soil tested for lead before moving my rhubarb.

Thanks all for your very helpful insight. This is one of the greatest fora on GW - right up there with Wintersowing ;-)

Marianne

Bump for embedded links.

what about putting spent brewery grains underneath your layer of chips? i'd imagine it might even work against the invasive plants, as well as aiding in the decomposition of the chips...
speaking of mycoremediation, i had my first experience with Oak chips, used as mulch, this winter. the fungi seem to thrive on oak more than any other wood i've encountered. we mulched the paths with something like 5-8" of them, and after a few weeks and a tiny bit of rain, the mycelium had filled the spaces between the chips, all the way up to the surface. you'd see white spots, where mold was growing on the path. total awesomeness.
also, we've been getting rain for the past week or so, and the usual heavy run-off has been totally absent. the chips (and whatever's living among them) are just soaking it all up. it's like walking on a sponge.
i've wondered about planting in mulches for a while now. i've been meaning to ask someone.. would it be be good, say in a thick mulch, 1-2', to dig a hole through the entire mulch, and then partially or completely fill the hole with soil to plant in? that would eliminate shadows from a steep mulch wall, as well as danger of weeds growing through a thin, tapered mulch edge. you know what i mean?

Lloyd, nice bump.

I did some more web searching about lead and arsenic in soil and discovered that current research is identifying fungus as the agent in the phytoremediation of contaminated soils. That would indicate that wood chips are a good medium for amending soils that are to be planted with sunflower and mustard greens. The fungi create a symbiotic relationship with the roots and transport the metals to the plant. And, of course, humic acid, available at your local home improvement store. It's cheap, it can't burn the lawn and it provides food for fungi. Dump it on.

The local utility trimmed trees in our area about three years ago. I asked for the chips they were in a big pile 2-3 feet thick after the calves played on the pile. Now that stuff is crumbly and the color of peat moss. The bermuda grass is creeping in on the edges, but no weeds growing in it. I am using it as a mulch and on paths; it is beautiful stuff.

Planting in deeply mulched beds can be done, you just need to provide plenty of nitrogen fertilizer (but without giving too much) to the plants since the mulch can sometimes rob the soil while the wood chips break down. This is kinda how people plant in hay or straw bales but they usually don't use more than a small amount of soil right at the seed or seedling.

I can suggest a free way to add nitrogen to the wood chips but some people might think it is yucky. Urine is a really strong compost activator. But it will take a lot so the whole family will need to start peeing in bottles. Funnels make it possible for the women to do this too. As to smell, yep, urine that has been stored in a bottle for a time will have a very stong odor. To keep the chip pile area from stinking too bad, you might simply make a little furrow in the chips, pour the contents of the bottle and cover over with the chips. Do this progressively each week or month or whatever across the top of the 2' deep mulch bed and you will greatly speed up the break down. Of course the faster the break down, the quicker the weeds will thank you for the nice soil.