QuestionQUESTION: My lawn does well in the early Spring, but as Summer approaches, it starts getting very thin and yellow. I'm convinced this is due to bedrock under my property that is closer to the surface in these problem areas. Is there a hearty grass that doesn't require a very thick layer of topsoil, or will I need to bring a truck full of soil and start from there?
Separate question for the future: I am also thinking about putting in a sprinkler system (from well water) putting the pipes above ground then backfilling with enough soil to cover it all up. Do you think this would work?
Thank you!
ANSWER: I hate bedrock questions and this one has been haunting me all day. It just seems like one of those setups where we hope against hope. But let me ask you a few questions. And I'll bring up a few things for your comment. Maybe you can get somewhere with this bedrock-under-soil problem.
1. DO YOU HAVE A DRAINAGE PROBLEM? That's a key problem. Does water pool up in those areas in a hard ran? When snow melts, does it take longer to drain from those same spots? How's the Grass look there? This could be a deal breaker. I need an honest answer.
2. Where do YOU think the bedrock begins? If you put a stake down there at several of the problem spots, at what point does it stop? Inches? Feet?
3. Was this property razed of trees before you built on it? Were there trees growing on your current yard? Where? How does the grass look where trees used to be? DO YOU KNOW?
4. You are 'convinced' -- an educated guess based on your life experience, your competence, your level of education and practical common sense?
5. Do you have neighbors? What is their situation as far as grass, bedrock, etc?
6. What kind of seed/sod did you put down there that is thinning? Any prep for that before it went down? Did the builder do that for you? Are you the builder?
FYI: Sprinkler systems are a great modern convenience. But you may not need one. It's a selling point for a house that people love to hear about and it does come in handy, depending on how much rain you get, how dry it gets, the grass you have, etc. The problem is that most people set the sprinklers on to water the Grass every single night. They over-water, and a lot of problems follow. A LOT of problems. Hold off on the auto sprinkler until we can solve the bedrock/topsoil situation. rsvp
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QUESTION: Thank you for responding. I'll hit your numbered questions one at a time:
#1 - definitely no drainage problem at all, no puddles, standing water, etc.
#2 - there are a few places where you can see the surface of some rock (it doesn't come above the ground level ... I can mow over it with no problem). As far as where do I think it begins, I think it's all over the yard, but at varying depths. Sometimes I can shovel an area just fine, but others (especially in the areas where the grass is dying, I hit rock within a few inches, if not immediately.
#3. We did not build this house, but there were trees and scrubby plants on the lot before it was built. There were some trees that were left (three black walnuts that I know of ... the previous owners had them cut down ... stumps are still present).
#4. I would say "an educated guess based on my life experience" ... in that I know Western Maryland sits on a lot of bedrock close to the surface ... AND ... "practical common sense".
#5. We are in a cul-de-sac and the backyards of the houses that are on either side of us are on higher ground (not sure if that is due to backfilling on their part. I know one next door neighbor's back yard was backfilled quite extensively ... the other next door yard has a sprinkler system. This is a hilly neighborhood. Ironically, we are the only house in our cul-de-sac of 4 homes that has a basement ... the previous owners were lucky in that there was enough of a dip in the center of the lot to have a basement.
#6. The original lawn was seeded (from what I'm told) and top soil was spread down (the previous owner was kind enough to give us photos from when the house was being framed and built). However, the previous owner told us they had the same problem and she thinks there wasn't enough topsoil laid down originally, but wasn't sure. The house was built 16 years ago.
* As far as having a sprinkler system, I don't think I'd run it every night ... probably every other night.
Thank you!
ANSWER: Allelopathic Juglone, Lignin, and Bedrock: 3 big problems, my friend.
First, the Juglone. Fescue and maybe Bluegrass are on the short list of plants that live long, healthy lives inside the dripline of the Black Walnut tree. Most plant life ceases there; the roots of Black Walnuts -- Juglans nigra to botanists -- and their relatives, Pecans, Butternuts and Hickories, ooze with Juglones, toxins that shut down respiration in groundcovers and most other things you would normally grow without too much trouble under a Tree.
The jury is still out as to how grass will grow in Juglone-tainted soil. Some plants wilt, some yellow, some grow in odd patterns. Some plants are not affected at all.
University of Minnesota Extension Service points out on its Black Walnuts page, 'The extent of the damage depends on how resistant a particular species is to juglone, and the amount of physical contact the plant has with the black walnut roots. Root contact, or close physical proximity to the roots (within 1/4 in - 1/2 in), seems to be necessary before the actual harm is done. Minor amounts of juglone are supposedly generated in several other ways: by leaf decay on the soil surface, from nut husks, and even from rain water dripping through the leaf canopy. The quantity generated by these other means, however, is small. In addition, juglone is not very water soluble, so it will not move far in the soil.' (http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h407blkwal-tox.html)
U of Minn also maintains that Clover and Bluegrass are 'resistant' to juglone. The Walnut Council promises that 'other plants are allelopathic to Walnut trees. These are Fescue Grass and Goldenrod.' (http://www.walnutcouncil.org/botanical_description.htm)
For the benefit of the rest of the world reading this, 'allelopathic' is 'The inhibition of growth in one species of plants by chemicals produced by another species.' (American Heritage Dictionary)
But the Black Walnut Tree is gone, you say!
Here's what the Toronto Master Gardener Fact Sheet has to say about that: 'Toxicity may persist for several years after a tree is removed due to the juglone released from rotting roots.' (http://www.torontobotanicalgarden.ca/mastergardener/Juglone.shtml)
University of Wisconsin Extension authorities concur: 'Even if a Walnut Tree is removed, Juglones will not be immediately eliminated, because it is next to impossible to remove all root pieces from the soil and remaining pieces may continue to exude toxins as they decay' (http://www.uwex.edu/ces/wihort/gardenfacts/XHT1017.pdf). Where there's smoke there's fire; where there's stump there's roots; where there's roots, there's juglone.
Something tells me you have been worrying about this for a while.
It gets worse.
You have Tree Stumps. You have Tree Roots. Trees are wood, and wood is Lignin.
It takes YEARS for Lignin to decompose. Underground, it takes MORE YEARS.
The Joint Genome Institute points out that White-Rot Fungi -- so named because they turn tough Brown Lignin into soft White Cellulose -- 'are the only microbes capable of efficient depolymerization and mineralization of Lignin' (http://genome.jgi-psf.org/whiterot1/whiterot1.home.html). Get to know and LOVE your White-Rot Fungi. They and they alone are in charge of making your Tree stumps vanish.
Some quick notes on Fungi: They are ALL aerobic. They ALL need moisture to work. Wood decays fastest at higher temperatures; below 50 degrees F, decay slows considerably as the Fungi metabolism drops, and at lower temps, Fungi go dormant and all work comes to a halt. Since Black Walnut is a dense, rot-resistant wood, you can expect these Tree stumps to be around for a very, very long time, under the best of circumstances.
Cornell University scientists at the School of Engineering have studied ways to speed up the way Fungi break down the Lignin in wood. The school published their findings, 'The Effect of Lignin on Biodegradability', and posted them online (http://compost.css.cornell.edu/calc/lignin.html): 'Adding small quantities of Nitrogen to woody materials can increase Lignin degradation rates.'
Other authorities point out the Sugar is the perfect White-Rot Fungus food; 'feeding' those areas will help to accelerate the breakdown of the Black Walnut Wood.
Still, this is daunting. There has got to be a better way to get rid of those stumps. Marty, don't even THINK about putting a foot or two of topsoil over those areas. Submerging them in soil will slow down decomposition (your great grandchildren may still be dealing with this problem) by severely limiting the Oxygen available to those aerobic Fungi. Any Grass you plant, even Grass that laughs at Juglone, will struggle and eventually fail the way all Grass fails when planted over old Trees that are no longer there. Look through my previous q's and a's -- there are lots of people with this problem, and it can last for DECADES. You need some heavy equipment that will physically, totally remove those dead stumps and their roots. Good luck with that.
Finally, the Bedrock. In contrast, these seems simple. Topsoil, amended as generously as you can with things that make soil rich and famous.
Tonight I just know I'll be dreaming of Juglone. I wonder why they removed those Walnuts. Are you in touch with them? Ask.
Thank you sir for your clear and candid reply. Your comments on this would be of interest. Consider turning this into a Reality TV show. I'm sure there's going to be some producer who would love to follow Marty of Bedrock on BravoTV.
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QUESTION: Thanks so much for your thorough explanation and answer (though I think I have a headache that may last quite a while now!). The previous owner had the walnut trees removed because they simply were sick of collecting the walnuts and disposing of them. There is still one left just on the other side of our property line, on the other side of our fence in a wooded area. The few walnuts we get from that tree are a real pain to collect ... I can only imagine what they went through with three right in the middle of the back yard.
Well, I think I will see what can be done to remove the stumps and, potentially the roots ... then take it from there.
I will read, and re-read your response in the coming days to let it all soak in.
Again, thanks for the educated, well documented response!
Take care,
Marty Robinson
AnswerNot to belabor this, but it just occurred to me one option that you must have thought of by now. It makes life much easier. And that would be the use of a groundcover instead of the more impossible dream of Grass.
Groundcovers will be socked with the same swimming-upstream real estate, but they may find it easier to navigate than Grass.
A good landscape architect (you probably know several) can give you other options - hardscapes, structures like fountains and sculptures and even raised flower beds. A pool or fishpond. Even a large local boulder. There are all kinds of creative possibilities.
I should have said that earlier. But those answers seemed endless at times. In the final cut, it slipped my mind.
Good luck with your landscaping. This should be interesting to see how you handle it. Thanks for writing.
