Questions about juglone and effect on figs

MichaelTucson
1333920217

Hi. I'm trying to find facts about juglone, and its effect on fig trees. My dad has been growing fig trees in his yard near Buffalo NY since 1966. (He buries them for winter protection). He says they're Brown Turkey figs, but we've never done any careful identification so we're not certain of the variety.

Here's the story: sometime in the late 1970's a Black Walnut tree was planted about 60-80 feet from where the figs are growing. That tree was only about 4 feet tall at that time. Fig production continued to be good (maybe 100 figs/year on the biggest tree), but by sometime around 2002 the fig production started to tail off. In 2008, just a handful of figs. 2010 just one or two figs, and 2011 none at all. By now the Black Walnut is 25-30 feet tall. My dad is convinced it's the Black Walnut tree that is causing this (he may be right). Here's the thing though: the fig trees look very healthy still, based on leaf production, and stem/branch growth. The leaves are very healthy, full, lush, and green. No spots or yellowing. The branches and "trunks" (they're very shrublike because of the burying every year) are all growing well. They're just not producing any figs. Does this sound consistent with juglone being the problem? I guess there are many potential causes for lack of fig production, and (being a newbie here) I'm starting to research and learn about various techniques and how to grow figs.

A side note: the neighbor's tomatoes don't fruit either. They grow fine, but no fruit. His garden patch is between 140 - 160 feet from the walnut tree.

This business of juglone has me wondering a few things:

1. Does juglone cause a fig tree to become unhealthy in other ways besides lack of fig production?

2. If juglone is affecting the fig trees, would the leaves show any symptoms? (e.g. brown spots, yellowing...?)

3. Would juglone kill the fig tree?

4. Or just cause it to stop producing fruit?

5. In general, what symptoms would I see on a fig tree if juglone is the culprit?

6. How far away from a 30 foot high Black Walnut tree should I expect the juglone is spreading in a way that would affect our fig trees? (I've seen much conflicting information on this too... ranging from the width of the walnut canopy, to the height of the walnut tree, to 100 feet from the trunk, to... ?). What have you folks experienced on this yourself?

7. How long does juglone persist in the soil?

8. If I pot some of the fig trees, and rinse the roots / repot in soil gathered elsewhere, will a fig tree recover and start producing figs again?

9. Does my story sound consistent with juglone poisioning, or does it sound like something else is causing the lack of fig production?

I sure would appreciate any info you folks have. Whether from your own experiences with juglone poisoning, or if you know of other good factual sources of information (even if not from your own experience). I've looked on as many sites as I could find, and there's so much conflicting info out there, I'm not sure which to trust. So I figured I'd ask among the fig lovers here. :-)

- Mike

p.s. this figs4fun site seems a wonderful find. And great links to other info. I'm glad to have found this community! (And I plan to stick around... just ordered a couple of other varieties and am getting serious about tracking progress and refining our techniques).

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hblta
1333929064

Hi Michael,
I planted one fig tree within 30 feet of several, 50 to 80 foot tall, black walnut trees to see what effect, if any, the juglone would have. It appeared to have no impact. No wilting, no stunting of growth, no death, which are the effects of juglone on susceptible plants. I do not know about how black walnuts would impact fig fruiting since it was a first year cutting that I planted. I will know more this season.
Mulberry trees will grow and fruit right next to black walnuts. Figs are related to the Mulberry and may share the resistance to juglone.
I grew tomatoes in the same area as i planted the fig tree, they definitely showed signs of juglone poisoning. Stunted growth, skinny, spindly, but they did produce tomatoes, just very few. I highly doubt that your neighbours tomatoes are close enough to the tree to be affected. Too far for average wind and rain to carry it from the leaves, too far away for the walnut roots to reach there.
Juglone is most concentrated under the tree canopy, and becomes less so as you move away from the tree. Some plants can grow right under the canopy, some cannot. I have seen plants grow right up to the drip line, and then no farther, making a visible circle around a walnut tree, with different plants growing closer into the tree.

If it is juglone, washing the roots and potting the trees in juglone free soil would solve the problem. Given that your father's fig trees are otherwise healthy vigorous plants I would suspect something else.
Only thing I can think of is perhaps, in an attempt to counter the effects of the evil walnut tree, he is over-fertilizing which would produce healthy vigourous plants but little to no fruit.

Grant
Ontario Canada, Z5b

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satellitehead
1333933361

I planted two plum trees within 5' of where a Black walnut tree was located and seem to be having no issues (although a lot of fruit drop this year for some reason).

I have several Blueberry bushes, herbs and other things equidistant from the trunk on the same chunk of dirt, and they are producing fruit abundantly.

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hoosierbanana
1333940072

My bro planted a BB bush under a BW tree at the rents house, it died back steadily over 2 years before I dug it out to save it. Almost all of the root ball that I dug was BW roots, they leach juglone and kill other roots, then invade their space. It does not sound like the walnut is to blame if your tree is growing well, although it may have lost only some of its roots at this point. I have never found evidence that walnuts are toxic to figs, but they may well be. Dig around if you want to know for sure, BW roots are thick and rubbery.

Tomatoes not fruiting sounds like a pollination problem, or some other cultural thing. They would not be affected so far away from the tree anyway. Their growth would be stunted if they were, and they will still (try to) fruit...

p.s. A BW killed my parent's mountain laurel hedge as well. They were planted at around the same time the BW volunteered and it killed them a dozen years later over about a four year period. They died in a row as the roots spread, the tree was about 15-30 ft. away and about 25 ft tall.

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MichaelTucson
1333949620

Hi, and many thanks for the comments from each of you.

It really does sound as though juglone is not really our problem... the fig trees are healthy and leafy (just don't make fruit any more), and it sounds as though juglone poisoning (when it happens) is much more toxic to the whole plant. I do believe that juglone is a problem for figs though (from other research I've found in other sources)... I just didn't know whether the mechanism was such that it attacks the fig tree systemically or just in some chemical disruption that inhibits fruit. So I sure appreciate hearing all your comments about how juglone works. I'm reasonably convinced that although juglone exposure is a problem for fig trees, it isn't the problem that's causing our lack of figs (not close enough, and different symptoms).

Thanks Noss for the idea about shade... yes these trees are considerably more shaded now than they were 40 years ago. The black walnut tree is part of that, but in truth there are lots of other trees that have grown up around the figs also, so the amount of sunlight has steadily declined over the years. That sounds a whole lot more plausible than juglone anyway, since we've seen the fruit production decline rather gradually. Somehow the timing just seems wrong for it to be juglone (along with the info from all of you).

I'm going to try moving a couple of the trees (or some parts of them anyway) to a sunnier spot. I won't be able to move any of the entire trees, but they're rather bushy with multiple "trunks", and it won't be hard to propagate with a shovel and still have plenty of roots.

As I've been reading more tips on this site and related places, I'm thinking I may also try some of the techniques mentioned in this forum... e.g. "pinching" (which we've never done at all), and potentially if we get some fruit, oiling the eye with vegetable oil. I saw those ideas on UC Davis and a couple of sites. In the past we never had to do much at all once we exhumed (or "unburied") the trees in the spring... we just left them alone and they produced up to around 100 figs per tree! (Seemed pretty neat that they didn't require much care other than basic watering in a dry spell). But overall, the issue of sunlight versus shade sounds the most plausible.

So, thank you! I'm real happy to have found this figs4fun community. Thought I'd also mention that I've also purchased a couple of other varieties now... I bought a couple of Hardy Chicago (and Bensonhurst Purple... are they the same variety?), also some cuttings of Sal's. I'd like to find some Abruzzi to try also (maybe UC Davis has them?)... if any of you folks know of a good source for Abruzzi I'm interested to hear. I'm kind of excited to be getting back into figs... it's a fun thing for me to do with my dad... he's getting up there in years now but still pretty interested in figs. And I seem to have caught the interest again :-).

Mike

p.s. No, I'm not in Tucson. My dad is in the Buffalo NY area, and I'm a couple hundred miles east of there near Binghamton NY. It's zone 5 in both places, 5a for me. Tucson is a middle name... being a second son and all. (And dad has a sense of humor :-)

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