Black Walnut

I have never tapped a black walnut.

Same disclosure as the birch page, and for the same reason: this is the internet, everybody writes like they’ve done everything, and I’d rather you know what you’re reading. I run maple — sugar and red, buckets on spiles, a turkey fryer in the yard, fifty to two hundred taps in Michigan, and I sell the jars at a store and a farmers market. Black walnut I’ve read about and argued with myself about. I have not hung a spile in one. I have never tasted walnut syrup, mine or anybody’s.

So why does this page exist at all, if I can’t tell you what it tastes like?

Because black walnut is the best argument I’ve found for tapping something that isn’t maple. Not birch — birch is the one that adds calendar, and I still think it’s the more interesting tree. But birch asks you to buy a reverse-osmosis machine, learn a technique that’s the opposite of everything your hands know, and then explain to a stranger at a folding table why the black stuff tastes like balsamic. Walnut asks almost none of that.

Walnut runs on maple’s physics, in maple’s season, at a ratio in maple’s neighborhood, and it makes something a maple customer will put on a pancake without a speech. If you already sugar, you already own most of what walnut needs. That’s the hook, and it’s real.

Then you look closer, and the objections aren’t the ones you’d expect. They’re stranger and more interesting than “it’s hard.”

The pitch: it’s maple’s engine, in maple’s month

Here’s the part that makes a sugarmaker sit up.

Black walnut runs on freeze–thaw, the same mechanism as maple. Not root pressure. Not warm soil. The same freezing nights and thawing days I spend February praying for. I take the mechanism apart over on the science, because almost everybody gets it wrong — it’s stem pressure, gas and ice doing mechanics inside the wood, not roots pushing sap upward. Birch is the tree that works the way people think maple works. Walnut works the way maple actually does.

Which means the season is concurrent with maple, not after it. Cornell’s trial sites tapped mid-February. A SARE-funded project in Indiana ran late January through April 2024, deliberately in parallel with maple so they could compare the two side by side.

Everything I know how to do transfers. The spile goes in the same way. The sap comes out on the same nights. The pan does the same job. There’s no new chemistry to respect and no new machine to buy — see tapping for the practice, because it’s mostly the practice I already have.

And here’s the catch, immediately

⚠ Walnut sap sugar declines over the season. That’s the opposite of maple, and it’s confirmed independently by both SARE (“sugar content seems to diminish over the course of the season”) and Carriage House Farm, which is about as corroborated as this corner of the literature gets.

So walnut wants to be tapped early.

Read that again as a person with a job and a finite number of Februaries. Walnut doesn’t just share my season — it wants the best part of it. It wants my attention at the exact moment my maples are running and my fryer is going and I’m sleeping four hours. It’s not a second crop. It’s a competitor for the first one.

That’s the honest structural difference between these two pages. Birch adds weeks I don’t currently use. Walnut adds work to the weeks I’m already drowning in. Everything else about walnut is easier than birch, and this one thing is harder.

The ratio doesn’t resolve — and the ratio is the wrong number anyway

You’ll see “40:1, basically maple!” all over the place. Here’s what the sources actually say:

Source	Figure	Confidence
Carriage House Farm (producer)	40:1–50:1 early, drifting to ~60:1 late	Medium
Secondary research summary	57–86 gallons per gallon	Low/Medium
J&L Green Farm (producer marketing)	5 gal sap → one 8 oz jar (= 80:1)	Low
Cornell — measured yield per tap, not ratio	6–11 oz syrup/tap vs maple’s 32–64 oz/tap	High

40–50:1 versus 57–86:1. I’m not averaging those. That’s a factor of two, and averaging a factor-of-two disagreement into one confident number is how you get a page that sounds authoritative and is worthless. The sources genuinely disagree. Some of the spread is real biology — early sap versus late, and walnut’s declining-sugar curve guarantees a wide range within a single season on a single tree. Some of it is that half these numbers come from people with a bottle to sell. I can’t separate the two, so I’m handing you both.

But that argument is a distraction, and Cornell’s number is the one that ends it.

6 to 11 ounces of syrup per tap. Maple gives 32 to 64.

Sit with that. That’s the number that actually tells you what a season looks like, and it reframes the whole question.

Sugar content is not the problem. Sap volume is.

Cornell measured walnut sap at 2–3.5% sugar in spring — one reading hit 6.2%. That’s maple-class or better. My maples run around 2%. So per gallon of sap, walnut is genuinely competitive; the “ratio like maple’s” claim isn’t a lie.

And yet the tap gives you a fifth to a third of what a maple tap gives. A walnut simply doesn’t move as much sap. Great sugar, not much liquid.

So the ratio claim is true and misleading in the same breath. Per gallon of sap, walnut is nearly maple. Per tap — which is the only unit I actually budget in, because taps are what I hang and hours are what I spend — walnut is roughly three to six times worse.

Nobody budgets in gallons of sap. You budget in taps, buckets, and trips through the woods in the dark. Anyone quoting you only the ratio is telling you half the story, and it’s the flattering half.

Run my numbers. At 200 maple taps I’m working with something on the order of 50–100 gallons of finished syrup as a rough ceiling. Two hundred walnut taps — if I had two hundred tappable walnuts, which I’ll get to — would be somewhere near 10–17 gallons. Same walking. Same buckets. Same February.

Where it does grow, and the Michigan problem

Black walnut is unambiguously a Michigan tree. Juglans nigra’s native range runs from Massachusetts to northwestern Florida and west to southern South Dakota and Texas, which takes in Michigan comfortably. It’s well established across the southern Lower Peninsula. There are walnuts in fencerows all over this end of the state.

But look at how it grows, because for a sugarmaker that’s the whole thing.

Maple grows in stands. Walnut grows scattered. Fencerows, old farmsteads, the edges of open fields, the corner of a pasture where somebody’s grandfather left one. That’s the shape of it around here. And a scattered tree is a bucket tree — a tubing run to four trees spread across a quarter mile isn’t a system, it’s a chore with extra steps.

Now stack that on 6–11 oz per tap. Scattered trees, a fifth the yield, walked one at a time in the same weeks my maples are running. Realistically this is a specialty crop, not a volume business. I could see a shelf of small walnut jars next to the maple. I cannot see a walnut operation.

⚠ Michigan-specific guidance: it does not exist

I could not find an MSU Extension source — or any Michigan source — on tapping black walnut.

Not a bulletin, not a fact sheet, not a news piece. MSU has plenty on maple; I lean on it constantly. The nearest Michigan-institutional thing I found was Birmingham, Michigan’s municipal maple-tapping page, and it’s maple-only.

That’s the same gap I hit on birch, and it’s worth naming twice, because it means the same thing both times: on tapping anything but maple, my state’s extension service has published nothing I can find. Every practical number on this page is borrowed from New York (Cornell), Indiana (SARE), West Virginia, or Ohio.

I’ll also flag a sourcing problem honestly, because it’s exactly the kind of thing that gets laundered into fact. There’s a line circulating that black walnut is among “common trees in Michigan that can be tapped for syrup,” with the sensible caveat that tappable walnuts are far fewer than tappable maples. It’s plausible and it matches what I see out the truck window. But I could not trace it to a specific MSU Extension publication — it surfaced through search aggregation, which is not a source. So: I believe it, and I can’t cite it.

Of the borrowed guidance, Indiana is the closest climate analog, so the SARE season — late January through April — is the best proxy I can offer a Michigan reader. Better than a date, though, is the mechanism: it’s freeze–thaw, same as your maples, so your walnuts run when your maples run. You don’t need Indiana for that. You need a thermometer and the season you already know.

The practice: what’s actually different from maple

Not much — which is the appeal. But the differences are specific and a couple are strange.

Drill between the bark ridges, not through them. Walnut’s bark is deeply furrowed, and that’s a real obstacle in a way maple’s never is. Cornell adds that the thick bark may need scraping down to the inner bark with a hatchet before you drill. That is not a sentence from my maple season. Corroborated by SARE and Carriage House Farm.

Spouts: standard 5/16” (some run 7/16”); 3/16” lines show up in the vacuum research. Tree size 12” diameter and up — the same threshold instinct I use on maple.

⚠ “Don’t use stainless steel taps.” Nobody says why.

This one I want to flag precisely, because it’s the clearest example on this page of how tapping advice propagates.

Both SARE and Carriage House Farm say: do not use stainless steel taps on black walnut. Use poly taps. Two independent sources, same instruction.

Neither one explains why. Not a sentence. Not a mechanism.

I have a drawer of stainless spouts. They are the good ones. And the guidance says leave them in the drawer, for a reason that appears nowhere in anything I could find. I can invent explanations — some tannin or juglone reaction with the metal, some staining, some off-flavor — and I’m not going to, because inventing a mechanism to justify a rule you can’t source is exactly how bad advice becomes permanent.

So here’s the honest shape of it: this is a repeated instruction, not an explained one. Two sources that have actually tapped walnut both say poly. That’s worth something — I’d follow it, if only because poly taps are cheap and being wrong costs me nothing. But understand what you’re following. You’re following custom, not chemistry.

🔴 Pectin — and the irony worth the whole page

Here’s the practical gotcha, and for anyone running an existing maple operation it’s the most important line in this section.

Black walnut sap contains significant pectin. Boiled sap takes on a jelly-like consistency, and it clogs filters and reverse-osmosis membranes. That’s from mapleresearch.org, and the peer-reviewed compositional paper independently notes a “pectin-like” substance preventing reverse osmosis filtration — two separate sources arriving at the same problem from different directions.

Now put the two pages side by side:

Birch cannot be made without an RO. Walnut may destroy one.

I find that genuinely funny in a bleak way. The two species a maple producer might branch into make exactly opposite demands on the single most expensive thing you’d buy. If you go out and buy the RO that birch requires — the capital that stops me every time I think about it — walnut’s sap is the sap that gums up the membrane you just financed.

For me it’s academic; my whole operation is buckets and a propane burner and I have no membrane to protect. If you own an RO, this is the line to think hardest about.

Flavor: the thing birch isn’t

I have not tasted this. I want that clear before I quote anybody, because a tasting note is the easiest thing in the world to fake and this page would be worse for it.

What I can tell you is that the research and the marketing agree, which almost never happens and is itself a kind of evidence. When an extension service and a guy with bottles to move describe a product the same way, the description is probably doing real work.

• Cornell: “surprisingly similar to maple syrup (with a bit of a nuttier flavor)”; “buttery and nutty”; darker batches show a “strong coffee” color.
• mapleresearch.org: “very similar to maple syrup with the addition of notes of nuttiness and bitterness for a slightly more complex flavor.”
• Tonoloway Farm (producer): “complex butterscotch & nutty.”
• 1913 Kickapoo Orchard: “rich and nutty… caramel-hinted.”

Butterscotch. That’s the word that keeps me reading about this tree. Maple has a hundred notes and butterscotch isn’t quite one of them — mine goes vanilla and caramel and, late in the season, something almost like coffee. A butterscotch edge is a thing maple doesn’t do, and it’s the only flavor argument in this whole section that isn’t “it’s like maple but harder.”

The strongest single data point is peer-reviewed and it’s the one that matters: a consumer preference study (Matta et al.) compared maple against black walnut syrup and found no significant difference in consumer preference.

That is the entire pitch in one finding, and it’s the exact opposite of birch. Cornell warns that birch customers are “unfamiliar with the product and skeptical of its taste.” Walnut needs no such warning. Walnut is a table syrup a maple customer will accept. Birch isn’t.

Which lands directly on my folding table. With birch I’d have thirty seconds to explain balsamic to somebody who came for pancake syrup. With walnut I’d have thirty seconds to say “it’s like maple, with butterscotch” — and hand them a spoon. That’s not a marketing project. That’s a Saturday.

Composition (the same peer-reviewed paper): finished at 67.4 ± 1.9 °Brix — same density target as maple, so my hydrometer works. Very dark (L* 17.6–18.09). Total phenolics 1669 ± 653 µg/mL, significantly higher than maple, and DPPH antioxidant activity 66.1 ± 9.7%, also significantly higher than maple. Hold onto that phenolic number. It comes back in a minute, and it does more work than you’d think.

⚠ Don’t confuse the products

Most “black walnut syrup” you’ll find in a shop is not this. It’s maple or cane syrup flavored with black walnuts — Nora Mill’s, for instance, is straightforwardly “pancake or waffle syrup with chunks of black walnuts.” Completely different product. J&L Green Farm explicitly markets “no corn syrup or other sweeteners” precisely because the adulteration is common enough to need saying.

If you go looking to taste the real thing before you commit taps, read the label like a hostile witness. The tapped-sap producers I could identify: Tonoloway Farm (MD/PA, walnut-sap-only, hand-bottled; online sales were paused when I checked), Simple Gourmet Syrups, J&L Green Farm (VA), 1913 Kickapoo Orchard (WI, 8 oz), and Miller Dohrmann Farm.

🔴 Juglone: the part where I have to tell you nobody knows

This is the section I expected to be easy, and it turned out to be the most interesting thing on the page.

Everybody knows the juglone story. It’s why nothing grows under a black walnut — the tomato that dies, the ring of bare ground, the tree that poisons its neighbors. It’s real, it’s well documented, and it’s the first thing anyone says when you mention tapping one.

What’s established (and it’s solid):

• Juglone occurs in all parts of black walnut, concentrated especially in buds, nut hulls, and roots. It’s an allelopathic compound — a herbicide and insecticide the tree makes against its competition.
• Juglone is poorly water soluble. Remember that one. It’s the crux.
• Inside living tissue it exists as prejuglone — nontoxic, colorless. Oxidation on injury converts it to juglone.
• Walnuts are eaten routinely and are not considered hazardous. In a controlled study of crops grown in juglone-containing soils, juglone showed up only in the roots — not in leaves, not in fruits.
• Skin contact causes irritation and staining. That’s the real, everyday juglone effect for anyone who’s handled hulls, and it’s well documented.

So: does juglone end up in the syrup?

Nobody has measured it.

I want to be precise, because this is the claim I checked hardest. I found no study that measures juglone in black walnut sap or in black walnut syrup. Not one.

And the silence is loud, because it’s in exactly the places that should have spoken:

1. The peer-reviewed compositional analysis of black walnut syrup never mentions juglone anywhere — despite profiling 54 phenolic acids and 22 flavonoids. Juglone is itself a phenolic naphthoquinone. That is precisely the study that would have caught it. It says nothing.
2. The SARE tapping-practices project doesn’t mention juglone.
3. On Cornell’s walnut article, a commenter raised juglone toxicity directly — and no researcher answered.

That third one stuck with me more than it should have. Somebody asked the exact question, in the exact right place, of the exact right people. Nothing came back.

Where that leaves us — and I’m not going to pretend it’s tidier than it is

The reassuring argument is good. Juglone barely dissolves in water; sap is overwhelmingly water; therefore little juglone should partition into it — and syrup is only concentrated sap. It’s chemically plausible, and it’s consistent with every indirect line I have: no detection in a thorough 54-compound phenolic profile, an established commercial product, people eating the stuff, a consumer study in which participants simply ate it and compared it to maple.

But that’s inference. It is not a measurement.

And the counter-reassurance is weaker than it sounds. The “no reported ill effects, it’s not really toxic to humans” line you’ll read everywhere traces to foragers and hobby blogs, not to a primary source or an extension food-safety review. Absence of reported harm from a cottage product with very few consumers is thin evidence. It isn’t nothing. It isn’t a safety assessment either.

So here’s my actual position:

Juglone is real, it’s in the tree, and it’s why nothing grows underneath one. Whether it makes it into the syrup is a question nobody has actually measured. The chemistry says probably not. A peer-reviewed analysis that catalogued 54 phenolic acids and 22 flavonoids in black walnut syrup never mentions it. People have been eating this syrup commercially without incident. But “no one has found a problem” is not the same as “someone checked.” If you see a site state flatly that juglone is absent from the syrup — or that it’s dangerous — neither of them is citing a measurement, because there isn’t one.

I’ll admit this surprised me. I went in expecting to find a study putting the question to bed one way or the other, because it’s such an obvious question and walnut syrup isn’t that obscure. There isn’t one. The confident sites on both sides are confident about nothing.

I’m not telling you it’s dangerous. I’m not telling you it’s fine. I’m telling you it’s unmeasured, which is a different thing from both, and you’re entitled to know which one you’re standing on.

Separately and more mundanely: black walnut also contains tannins, and excessive tannin intake can cause stomach upset. That’s from a consumer-health source, about black walnut preparations generally — not a finding about syrup, and I won’t dress it up as one.

🔴 The other thing nobody measured: what tapping does to the timber

This one gets less attention than juglone and I think it deserves more, because unlike juglone it has a dollar figure attached.

Black walnut is a high-value timber species. Veneer-grade walnut is one of the most valuable hardwoods that grows in this country. That fencerow tree isn’t just a tree — it may be the single most valuable object on that piece of ground.

Now: what does tapping do to it?

The SARE project checked “the degree of closing of the taphole” after three weeks of bucket tapping. That’s the right question. But I found no published results on walnut taphole closure, compartmentalization, or long-term health effects of tapping.

Think about what that means. Staining or defect around a taphole is a legitimate economic question for a species sold by the board foot with the grain inspected — and the literature does not appear to answer it.

On maple I don’t worry about this, and I want to be clear about why, because the contrast is the point. Maple taphole closure and compartmentalization are well studied; the trees are tapped for generations; and honestly, nobody’s cutting my sugarbush for veneer anyway. The tree’s value is the sap. A black walnut’s value may be the log.

So: if you have veneer-grade walnut, the honest answer is that nobody has published what tapping does to its timber value. Not “it’s fine.” Not “it ruins it.” Nobody has said. I won’t imply otherwise, and if a site tells you confidently either way, ask them where they read it.

That’s a real consideration in a way it never is with maple — you might be trading a handful of ounces of syrup a year against an asset you can only sell once, on evidence that doesn’t exist.

The market, and the strange convergence

Pricing (one source, but a good one — mapleresearch.org): West Virginia bulk walnut syrup at $150–$250/gallon last season, with retail topping $500/gallon.

Here’s the convergence I keep turning over. Walnut retails around $500 a gallon. So does birch. Same shelf price — for completely opposite reasons.

Birch is expensive because of a 104:1 ratio and mandatory RO capital. Walnut is expensive because of 6–11 ounces per tap and no economies of scale whatsoever. Two totally different bottlenecks, one price. The market doesn’t care why your gallon was hard. It just charges for hard.

And the industries are nothing alike. Birch has Alaska and it has Kahiltna Birchworks — a dominant producer moving 135,000 gallons of sap a year. I found no large-scale commercial walnut operation at all. Cornell’s trials describe small personal and farm-scale projects. Walnut syrup is a cottage industry. Birch syrup is a small but real industry with a dominant player.

Which, for someone selling at a store and a farmers market, is not obviously the bad news it sounds like. I’m not trying to found an industry. I’m trying to fill a shelf.

Where I actually land

Walnut is the easier product and the harder logistics, and that’s the cleanest way I can put it.

It needs no new flavor pitch — a peer-reviewed study found consumers don’t prefer maple over it, which is a sentence birch will never get to say. It needs no new chemistry, no new finishing technique, no new machine. It hits 67 brix like maple. My hydrometer works, my pan works, my hands work.

What stops me is the calendar and the arithmetic. It competes for my February, and it wants the early part, which is the part I have least of. It yields a fifth to a third per tap. The trees are scattered through fencerows instead of standing in a bush. And two things I’d want to know before I put steel — sorry, poly — into a valuable tree are simply unmeasured: what juglone does in the syrup, and what the taphole does to the log.

That’s not a no. Ten gallons of butterscotch-edged syrup, in small jars, next to the maple, at $500 a gallon of shelf value — that’s a genuinely good idea and I know it. It’s a “not this February,” which is a different thing, and it’s honest.

If I ever run it, this page changes. It gets tasting notes I earned, a photo of my own dark jar, and probably a paragraph about a filter I ruined. Until then it’s research, told by somebody who taps a different tree thirty feet away.

The thing I’d want you to keep either way: three trees in the same Michigan woods, and each one is a different argument. Maple gives you sucrose that forgives you and a customer who already knows. Birch gives you weeks you don’t currently have and a flavor you’d have to sell from scratch. Walnut gives you the flavor for free and asks for the one thing I can’t spare — February. Nobody gets all three.

For the mechanism both maple and walnut run on, see the science. For the practice — spiles, drilling, buckets — see tapping. For the species that goes the other way on every single count, see birch. For the tree I actually run, see maple.