Question
I have a 40-year-old pecan tree in my yard, and this year, for the first time, the grass under it died almost completely. (This is about a third of my front yard.) The grass is a mix of Bermuda and St. Augustine. I'm in North Texas (Dallas area). I was first told that drought killed the grass, even though I watered daily, and also sowed Bermuda seed. Then I was told that shade killed it. Now someone has told me that the pecan drips oils on the grass that makes it difficult for the grass to grow. This certainly wasn't our worst drought years; if any of these are correct reasons -- drought, shade, oil -- why would this be the first year for this to occur? And, of course, the big question -- what should I do? Should I put out St. Augustine or Bermuda? Plugs, sod, seed? None of my neighbors have the same grass problem, and none have pecan trees. Thank you!

Answer
Yet another follow up to your question about problems with Grass under your Pecan Tree, triggered by my sudden realization that Pecans are relatives of the Black Walnut Tree.  Your friend who surmised that something in the Pecan Oil dripping down to Grass and causing damage was right on target.

Black Walnuts of course are famous for the Juglone thy exude which destroys many plants that venture near.

And although they are a different species, Pecans are members of the Juglandaceae Family.  Which is where we get the word 'Juglone'.  I stand corrected!

Most literature on this subject maintains that Pecans and its weaker relatives produce a minute amount of Juglone compared to the quantity made by a Black Walnut.  Some even say the effect is so minor it would escape notice completely.  Perhaps this was the case with your Pecan.  Perhaps there was damage that escaped notice.

Bermuda and St Augustine are NOT on the short list of Grasses that can take brushes with Juglone.  Kentucky Bluegrass IS.  Why is the effect most noticeable now?  Perhaps one of your Grasses dominates now and is less able to endure a repeated Juglone punch in the nose.  Or maybe this past year your Pecan just upped the production of Juglone, maybe because it was big enough to do that now.

This is of course all guesswork as to why Juglone damage to the Grass would be exhibited now and not in the past, and I apologize for not remembering this little detail.  In my mind, though, there is no doubt the Pecan Juglone is only to happy to lay down the law on the Grass you want to grow.  Here is a link to Juglone-comfortable groundcovers, which in my book are probably your best option for now, provided of course you do not have one down there already:

       http://greenwoodnursery.com/page.cfm/27196

Hope your Pecan is thriving still.  Enjoy your Summer!
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My first Pecan Tree question - this is a historic occasion.

Must admit, I have not grown Pecans yet.  But I would love to.  I would be out there eating breakfast under them every day with my coffee - right next to the Orange trees (which I HAVE grown).  While milking the cow.  And feeding the chicken.

OK OK.  It's been a long weekend.  Let's get serious.

The Pecan (Carya illinoensis) is a high-maintenance tree that shows symptoms when exposed to drought or deficiency.  You did not mention any problem with your Pecan tree, which is nothing short of miraculous given that you are having such trouble with your (comparatively simple) grasses.

But I have to make sure of that.  I don't want to just assume that your Pecan was growing Pecans all over the place while the grass languished.  Is that true?

And if your Pecan is doing well, is that because you are treating it - i.e., are you SPRAYING it for anything?  What, exactly, is going onto those leaves?

Are you doing this work yourself, or is someone doing it for you?

Point of information: When a region experiences a drought, Pecan Trees can yield damaged Pecans, by the bucketfull.  The Pecans will drop if the drought takes place early in the year.

Generally speaking, most trees and grass grow best when a layer of mulch or a tough groundcover (here that would be Pachysandra or Hostas) fills in up to the drip line - the edge of the tree canopy.  Grass rarely thrives (I can't think of anyone who has ever been the exception to this rule) under trees.  There's always something missing - light, air, water, nutrition.

I think you are right to question whether drought would be the problem, assuming the Pecan tree was growing without any complaints.  Consider, however, that water was scarce, and that the Pecan, which is now 40 years old, boasts a massive root system with massive demands for water and nutrients.  If you were grass, would you be able to win this uphill battle forever?  What would it take for you to kick the bucket here?

Any well established, mature tree would be less vulnerable to stresses.  Grass is not so tough.  Not even Bermuda and St Augustine.  If you are trying to grow your grass in shade, St. Augustine is the ne plus ultra turfgrass.  Bermuda can take a LOT more drought than St. Augustine grass - Bermuda is king of the water shortage.

Now, Pecan is a VERY hungry species.  Pecans being highly nutritious, and very oily, they need tons of water and incredibly high amounts of Nitrogen, among other things.  That Nitrogen would be needed by your grass for basic survival.  Both grasses (am I right here?) are doing badly or outright keeling over, so it is not a water shortage (or you would have some Bermuda Grass surviving) and it is not the shade (or you would have St Augustine left).  But they are both in trouble.  To me, that's a sign of deficiency of nutrients.  Are you fertilizing properly?

Finally, if you are trying to take good care of your lawn and believe that generous helpings of things made by multinational corporations - such as the Scotts Companies, which dominate this business many times over - are one way to show your love for your lawn, note that many of those fertilizers and weedkillers are toxic to certain lawn grasses.  2,4-D, for instance, is a strictly cool-grass chemical for those people crazy enough to use them.  The Intelligent Gardener does not apply these ever.  If you are guilty of this mortal sin, you can rest assured that THIS is what is killing your grass.

I know of no evidence that indicates that Pecan oil is toxic to grass.  And if it was, there would have to be a lot of uniform Pecan oil pouring out of those nuts to kill all that grass.  It might be possible, and it might be someone else's problem, but I do not think that is your problem.

RSVP.

When replying, please include your favorite recipe for Pecan Pie.  Thank you.

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Still wondering how you made out with your Pecan/grass problem.  I still believe the mature Pecan is way too hungry and thirsty for the poor grass -- your Pecan-shaded grass will always lose that Battle of the Nitrogen.  That's my theory, anyway.

If I'm right, extra doses of slow-release Nitrogen would green the grass up to its former beautiful self.

But be careful.  You don't want to kill anything.  That's why an Organic or slow-release fertilizer (Milorganite would do the trick) is your best choice.

If you're made of money, you can spend it on a high-N Organic top dressing like aged manure, blood meal, etc.  Something with a number only for N and a 0 for the P and K (N-P-K).

I'd warn against Fish Emulsion.  Your house will smell like a dead fish all summer long.  Your neighbors will hate you and you'll have to find another place to move.  In small doses it's great, but on that level you do not want that problem.

Just checking.