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Annie in Austin
Welcome! As "Annie in Austin" I blog about gardening in Austin, TX with occasional looks back at our former gardens in Illinois. My husband Philo & I also make videos - some use garden images as background for my original songs, some capture Austin events & sometimes we share videos of birds in our garden. Come talk about gardens, movies, music, genealogy and Austin at the Transplantable Rose and listen to my original songs on YouTube. For an overview read Three Gardens, Twenty Years. Unless noted, these words and photos are my copyrighted work.
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Tuesday, November 20, 2007

The Old Dogs Learn Something New

This post, "The Old Dogs Learn Something New", was written for my blogspot blog called The Transplantable Rose by Annie in Austin.

Philo and I were invited to a pig roast on Saturday afternoon. As I gathered ingredients for corn bread and some Meyer's Lemon/Cranberry relish that morning, Tom Spencer's garden radio show played in the background. Tom's answer to one caller sent me running down the hall to the office - Philo had to hear about this! A woman wondered whether she should put the shells from her pecans into the compost or use them as mulch - and she was told it might not be such a good idea... while pecans are not as allelopathic [not alleopathic*] as Genie's infamous Black Walnut, they do contain juglone, a substance that can prevent the healthy growth of certain other plants.

With that large canopy of pecan trees hanging over our garden and the ground covered with husks and shells discarded by the squirrels, how concerned should we be? Was this the reason our tomato plants grew well the first summer, but seemed progressively more spindly the last two seasons?

We'd heard for decades that some plants, including tomatoes, wouldn't grow under Black Walnut trees- friends in Illinois had that experience - but we hadn't realized Pecans also had some juglone. The two of us started searching and reading, finding references to
Black Walnuts, Pecans, Allelopathy and juglone in many articles, advice columns, forums, sites from universities and extension sites. As always, clip-and-paste ran rampant, with many sites using exactly the same wording and the authors disagreeing completely on the toxicity.

The conflicting articles stated that the leaves had juglone but the shells did not; that the juglone was concentrated in shells and bark; that it could persist for a long time or that a few weeks of composting eliminated it; that there was enough juglone in pecans to stop the growth of tomatoes or that the amount was so minimal it didn't count. Whether the soil was sandy or clay seemed to make a difference, as did the amount of moisture. Some sources recommended that adding lots of compost and improving drainage could remedy an area with high amounts of juglone. We read that juglone from black walnuts is used in traditional medicine to heal ringworm in humans and also read that allelopathy* swings both ways - the Department of Horticulture at Oklahoma State in Stillwater found that bermuda grass may inhibit the growth of pecan trees.

When I browsed a Project Gutenberg book called Growing Nuts in the North by Carl Weschke, one chapter told of the author's experiments in the early 1920's. It was pretty funny to hear him call the pesky squirrels "bushy-tailed rats" - that was definitely a bonding moment with someone from the past.

Our tentative conclusion after a couple of hours research was that for most areas of the garden, any juglone found in the pecan tree did not seem to have done any harm. On the other hand, it had probably been a mistake to incorporate such large amounts of pecan leaves into the tomato & pepper garden over the last 3 years and the waterlogged conditions of early summer may have intensified the effect.

Although our conclusions are tentative, we've noticed that several other plants in the nightshade family declined when in the root zone of the pecans - the Brugmansia got smaller instead of larger and only grew when moved to the far side of the garden. So to be on the safe side, we'll keep the pecan leaves, twigs and hulls out of the vegetable garden and not use them anywhere unless they've composted for a year. We'll add different compost to the tomato bed in spring, perhaps treating it with liquid compost now. A few weeks ago I transplanted that Solanum in the photo above to the triangle bed. It's one of the ornamental potato flowers but it wasn't growing or flowering. Now I realize this member of the nightshade family was also under the drip line of the pecan. Was that a factor in its failure to thrive?

This is more than you wanted to know about juglone, isn't it! If a pecan appears here again, I promise it will be in a pie! Let's move on to flower photos.

There were a few openings since the blooms were posted on the 15th - here's the peach iris unfolded. It sure looks odd backed by blue Plumbago, lemons, a 9-foot Brugmansia and the pink cuphea in bloom!

The Sasanqua camellia 'Shishi Gashira' opened a few flowers yesterday, but a fast moving gust of rain and wind shattered the flowers. More buds await their turn.

The next flower is difficult to photograph - a polaroid filter held over the lens helped a little.
That white line is the odd flower of a plant called Hoja santa, or Piper auritum, with large aromatic leaves that are used in Central Mexican cuisine. We once tried them parboiled and cut into squares, then filled with a chicken, pepper and rice mixture before folding into packets and baking.

Austin garden photographer Valerie was the person who first introduced me to Hoja santa - she has more information on the plant.

A cold front with rain is expected tomorrow evening followed by a weekend of cold, wet weather with highs in the fifties and lows in the upper-thirties. [from 10 degrees down to 2 degrees for you who use Celsius].
But today I can still admire a gulf fritillary on the pink cuphea.

Today I can enjoy the red berries on the Yaupon holly as it arches across from the left side of the path to the gate, mingling with the sharp and pointed leaves of the holly tree growing next to the garage.

This post, "The Old Dogs Learn Something New", was written for a blogspot blog called The Transplantable Rose by Annie in Austin.

Happy Thanksgiving to all of you from Philo and Annie in our garden in Austin, Texas.

*Edited Nov 26 - my son pointed out that the words are allelopathic not alleopathic, and allelopathy not alleopathy. Thanks, kiddo - still learning .... Arf, arf.


  1. Nope, it's not more than I ever wanted to know about juglone at all. I have also experience marked decline in my ability to grow tomatoes and eggplants over the last ten years. I attributed it to increasing shade (by those same pecan trees). But it might be because I rake the leaves and compost them.

    What about juglone from the roots? The biggest problem my old vegetable garden experiences is that the roots of the pecan tree seem to suck all the life out of the soil. Could it be that in addition to sucking up water and nutrients that the roots are also putting out chemical inhibitors.

    Thanks for the info and the flower photos. Have a great Thanksgiving.

  2. Interesting info regarding the pecan tree. It is always good to hear new information even though we don't have pecans. You never know what you will be dealing with in the future.

    Love seeing those beautiful blooms. All blooms are lost in our garden.

    Happy Thanksgiving to you & Philo.

  3. Annie, the flower photos (and the butterfly photo) are beautiful! And amazing...I had no idea pecan trees had the hated juglone, but that makes total sense...thanks for the education!

  4. Count me as one who learned something new tonight. Not that I have pecan trees, but knowing they have juglone I'm sure will come in handy sometime. I wish our garden radio talk shows were as informative!

    Your flowers look wonderful, as always. Our temperatures are going to drop significantly in the next few days, and we are likely to see snow flurries for Thanksgiving.

    Happy Thanksgiving!
    Carol, May Dreams Gardens

  5. This is really, really interesting, Annie; I'm skittish of black walnuts because the bark, etc is toxic to horses (even in shavings), but it's a lovely tree. Pecans wouldn't grow here, sadly.
    I love seeing all your glorious flowers in late November--you'll sustain us through the next several months--but what I really LOVE is those lemons! I keep hearing about Meyer lemons but I've never seen one or tasted one. Thanks for giving us a much-needed November boost!

  6. Annie, your pink camellia is beautiful. I miss having butterflies in the garden, thanks for sharing yours.

    I also wanted to thank you for helping me. I believe you were spot on regarding the Pacasa storage problem I was having. I thought the picture resized automatically and had never properly resized them. No wonder they were taking up so much space. Now I have the tedious task of redoing them and reposting them to my blog. Oh well, it will give me something else to do over the winter.
    Happy Thanksgiving!

  7. There's no pecan tree in my garden, but I was interested in juglone all the same. And I was sighing over your sasanqua blossom. Even as petals strewn on the ground, it's beautiful.

  8. Or pecan tree was in a pasture so this problem never came up. I think you now have a good plan for keeping both the pecan and the other plants that didn't thrive this year.

    I really need to move south! The only thing still blooming here are the blanket flowers.

    Happy Thanksgiving

  9. Those lemons look so wonderful and refreshing! Love the butterfly shot, too.

  10. Awww...your hollies are holding hands! Very interesting about the pecans...I'd heard that sunflower seed hulls are poisonous to plants, and sure enough, all my plants near the bird feeder are growing much better since I stopped feeding sunflower seed in that area. Someimes I think it's good to safe, not sorry, even if scientific info doesn't definitively back you up. (Like when MD's used to say that your newborn can't be smiling at you, it's probably just gas-hooey!) Happy Thanksgiving!

  11. I didn't know about pecans and juglone either, but I was going to write what Lisa already wrote about sunflower seed hulls.

    Hoja santa looks like it would be worth growing even if it wasn't used in the kitchen - very tropical-looking.

    Happy Thanksgiving!

  12. I don't know much about nuts except for my own variety :o) But I can comment on your blooms. Jealous, jealous, jealous.

    There are no blooms here except for two waterlilies awaiting a very hard frost.

    Looks like you are in for a seasonal change.

    Happy Thanksgiving, Annie!

  13. I am intrigued with the Hoja santa. The flower is so different. What do the leaves taste like when baked?

    Your discussion of juglone was great - I laughed at your comment about bushy-tailed rats. They do have that look after stealing tulip bulbs, don't they?

    I love your Sasanqua Camellia.

    I wish I could teach my old dog something new!!

  14. That's interesting. I thought I had learned that plants from the nightshade family were able to tolerate juglone. Maybe I learned the opposite...
    Hope you had a wonderful Thanksgiving.

  15. I'm curious to see how your tomatoes will do next year now that you have all this interesting info Annie. They'll probably do much better!

    My Camellia is in bloom too and it looks like we'll be having the same temperatures this weekend. Suddenly Austin doesn't seem all that far away from the Netherlands.;-)

    Never seen or eaten a Hoja santa before, those flowers are pretty special and I love those big leaves.

  16. Hello MSS, some of the sources say the roots have more juglone than any other part, and for Black Walnuts they advise raised beds with some kind of barrier material under them. But the juglone only affects a small number of plants.
    This year even the grass under the pecan looks like heck, even though last year under the trees was where the grass survived best. My guess is that manufacturing our big nut harvest took a lot of water and a lot of extra nitrogen.

    Hi Lisa at Greenbow, if a squirrel plants a Black Walnut for you, you'll be forwarned ;-]

    Genie - I was totally bonding with you and our mutual need for some tomatoes!

    Carol, we have wonderful radio garden gurus here - and they're all actual gardeners, not just talkers.

    Our warm spell is gone - 38 degrees this morning!

    The black walnut danger to horses came up on several sites, Jodi- pretty creepy.

    We tasted Meyer's lemons for the first time last year- as a hybrid they have a different taste. I first heard of them at the Zanthan Gardens blog.

    It's getting colder, but we usually see an occasional butterfly here even in winter, Robin.
    I'm glad my guess helped you figure where all your photo quota went - it may be tedious, but you'll get to look at your lovely photos again!

    Pam/Digging, you're probably rejoicing that you moved into a comparatively empty garden!

    You could try one for less than $10 - this is a dwarf sasanqua, supposedly good in containers where one can control the soil composition. Or you could just come visit this one ;-]

    They're growing all over backyards in Austin, Apple, and off to the SE there are commercial nut farms. As a native tree planted by squirrels they pop up everywhere!

    It must be harder for you to be cold since you once lived in a more southern state - it's probably easier moving north to south.

    Welcome Connie - the lemons really are wonderful - not as tart as regular lemons.

    That's just what I thought, Lisa! The Asian holly had been clipped to keep it a big ball-shaped shrub, but a few years of experimental pruning turned it into a small tree. No berries, though - it's a male holly.

    I've seen the sunflower thing happen, too, and figure my remedies for potential juglone are not drastic or expensive so it's worth a try.

    Didn't some recent infant behavior research find out the babies really were smiling? Of course my four ALL smiled...even though they also had gas!

    Entangled, why didn't I ever consider that walnuts and pecans were related? I knew about the black walnuts and the sunflowers. it was a real duh moment.

    Hoja santa spreads like the dickens in a damp spot - on garden tours you frequently see huge stands of it around ponds or other water features. En masse it gives an unbelievably tropical effect!

    We're also new to harvestable nuts, Mary, but have come to count on at least a few flowers all winter. The impatiens were hit by cold already, but we haven't frozen yet!

    Kate, the smell is sort of like anise, and a sort of anise or tarragon flavor was infused into the filling.

    That author may have been writing about 1924, but his remark felt contemporary to me!

    Hello Anna maria - maybe some of them can? It's a big family! The sites specifially mentioned tomato, eggplant, potato, peppers and one site listed the Brugmansia.

    Philo is very curious, too Yolanda! Since the leaves are still on the trees, we can start the experiment now!

    A few years ago some restaurants using the Hoja santa were featured in the NYTimes dining section - we're only used ours a couple of times, but it was delicious. Just brushing against the leaves releases the fragrance.

    I hope you all had a wonderful Thanksgiving - thank you for all the comments!


  17. Annie: I didn't know that either! I can't grow pecans but I sure love to eat them! No pecan pie this Thanksgiving. I wish I had a piece right now!

  18. Gosh, I always learn something when I come over to visit you. I have a friend who has a walnut grove, and it always seemed pecular to me that nothing seemed to grow underneath the trees, but there were bazillions of slugs. The ground under the trees was carpeted with them.

    Gorgeous photos on your blog, as usual. I hope you had a wonderful Thanksgiving.

  19. Well, I didn't know this about pecans! That is my favorite nut, by the way. I love love love them, but they're so expensive here!

    We don't have any black walnut trees in our yard, but we do have a shagbark hickory. Wonder if that might affect anything?

  20. Annie, hope that you had a wonderful Thanksgiving! You may laugh, but I thought about you when it came time to eat the pecan pie. :)

    By the way, did you add those lines of italicized text at the top and bottom of your post to thwart content-theives who steal via feeds?

  21. Like everyone else, I found this post interesting Annie, even though I'll probably never live in a zone where pecans grow. Juglone is completely new to me. So I learned something new today too.
    I sure hope you have better luck with your tomatoes next year. It's rather exciting to think that you may have hit on a solution to the problem of the spindly plants, isn't it?
    Sounds a bit like a detective story.
    Your butterfly photo is gorgeous, and so is the color of that beautiful camellia. Love your Holly too.
    I hope you and Philo had a wonderful Thanksgiving!

  22. I found your article quite interesting and full of good information. Kind of like you.

    I love the shot of the butterfly and cuphea. I have many different kinds in my yard. It is one of my farvorite plants.


  23. I did not know that sunflower seed hulls were toxic to plants. Hmmm. And I will have to check on toxicity of juglone to animals... I didn't know that horses were sensitive to it and I just filled up the chicken pen with leaves that are mostly Black walnut. While I am envious of your colorful blooms sitting here in gray and dreary Pennsylvania, I am most covetous of your Meyer Lemon. How wonderful that must be to be able to grow citrus fruits, esp. since lemons are so expensive here.

  24. Layanee, I always buy lots of pecans for Christmas cookie baking, and quite a few don't make it into the dough, because I love them, too.

    Hello Josie - this is my first experience with tree nuts - how cool to have a friend with a walnut grove. I guess Juglone doesn't bother slugs!

    Kylee, it's closely related and has a small amount of juglone. You probably have enough space to avoid your one hickory so it should have little impact; our pecans dominate the back of our quarter-acre lot so they impact everything.

    Wow, Blackswamp Kim - that's pretty cool - you've come to mind when I see certain plants in the nursery!

    I don't think the text will thwart anyone, but the Transplantable Rose is being reblogged. The idea was that if someone liked one of the reblogged posts they could get here to read more. It's just peeing on a forest fire.

    Kerri, if Philo could get some good tomatoes he'd be thrilled - we hope it will happen!

    We did have a fun Thanksgiving, and hope you did, too.

    Hello Chigiy, what a nice thing to say! The cupheas don't always live over, but I like them a lot and will replant to get them.

    Hello Meresy - maybe it's just horses? Juglone does not appear to slow down either White-winged doves or squirrels.

    We had light frost on Monday so the Meyer's Lemon went in the garage. Soon I'll move it to the breakfast room for winter. Some Austin people with southern brick walls and a sheltered area can grow Satsuma oranges.

    We just get a few lemons from this little tree, but the blossoms smell great and it's a fun plant to grow.

    Thank you all,


  25. I had a call on the MG hotline last spring about this. The caller was convinced that her pecan tree's roots were harming some of her other plants. I never found anything to confirm it in any of the "official" sources we were allowed to use though!

  26. That 'Shishi Gashira' is nice! Quite an accomplishment too. My one Meyer's lemon is still green - hopefully it will start turning yellow soon. Have you ever tried satsumas? I have one in the ground (this will be it's first winter there) and I have about six satsumas, just starting to turn orange. I got familiar with them when I lived in the Florida panhandle region for a few years.

    I loved your observations - the first scientific conference that I ever went to, when I was working on my MS degree on sunflower, was an allelopathy conference in Illinois. Your talk of juglone took me back to those days! It seems like several (scientific) lifetimes ago now.

  27. I can testify to the ringworm cure. The kids and I got ringworm from my neighbor's rabbit. The same neighbor found some black walnuts (they need to be green, as that is the part you use) and we all tried it. It cleared up the ringworm in a matter of days. Lotrimin didn't help at all. But, beware the juice from the green pulp does stain.

  28. Thanks for the information on juglone. I was just talking about that very subject with someone yesterday, and I did not know what the name of the chemical was.

    As usual, a great post filled with lovely flowers.

  29. Hello Rurality- even though I realize that as a representative of an organization you must use official sources, it would be sooo impossible for me to follow those rules!

    Oh my, Pam, I love Meyer's lemons but wouldn't a satsuma be wonderful! I might try to grow one someday, but in the meantime will rejoice that clementines are available.

    Just the idea of Sunflower leading you to an MS degree makes me smile.

    Hi Dee - thanks for the confirmation on the ringworm cure. We found out about the staining - our hands were streaked with brown for weeks after we handled the hulls.

    There's something pretty cool, HealingMagicHands, about being gardeners - a milieu where subjects like this one can come up.

    Thank you for the comments,



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