There's a fish in my home town called a dogfish, which as far as I can tell is a purely local name and means different things in different areas. This also is true of flower names, I've been told.

You got me started. The dogfish can be either and eelpout/burbot (a freshwater cod) or a bowfin. What they have in common is ugliness. They're considered trash fish by sport fishermen but are good to eat.

The bowfin may not be good to eat.

Well, this page asks the same question. Could it be that tacamahac (Populus) and hackmatack (Larix) got confused (the words, not the trees)? The tree books we have here go no further than to say that those were Indian words; no hint of tribe or original meaning.

Where I live now, there are neither dogfish nor hackmatacks, as the Great Intelligent Designer didn't bother to put them here, so they must exist only in the imaginations of East Coast liberals.
Nonetheless, this passage cited by LH illustrates beautifully what James Payne Smith calls the "disadvantages of common names": the same plant may have more than one common name, but, conversely, "the same common name may be used for a wide variety of unrelated plants", which seems to be the case here. Hortus Third lists two distinct specific epithets for "hackmatack": Populus balsamifera, a member of the Salix (willow) family; and Larix laricina, of the Pinaeceae (pine family). The former is a decidous tree, the latter a conifer; both are distributed widely throughout northeast North America, and have many commercial uses. (Common names for P. balsamifera include balsam poplar, hackmatack, and tacamahac; common names for L. laricina include American larch, tamarack, hackmatack, and black larch.)
To muddy the waters further, M. Grieve shows "hackmatack" as a synonym for yet another tree, the "yellow cedar", listed under Thuja occidentalis (Linn.), of the (now-outdated) Natural Order Coniferae. (Other common names for Grieve's "yellow cedar" include the tree of life, arborvitae, American arborvitae, Cedrus Lycea, Western arborvitae, false white cedar, thuia du Canada, and lebensbaum.) Clearly, it is no mean feat to know all the common names of a plant!
Having spent considerable time in New England, I was always aware of those conifers commonly referred to as "larches", and I always thought a hackmatack tree was some sort of larch, hackmatack being a corruption of a Wampanoag or Massachusett word. There is, in fact, a Hackmatack Road on Cape Cod, which is, interestingly, located near an old development called "The Larches".
Anyway, the point is that the same common word can, and often does, refer to completely different plants, so it doesn't surprise me that dictionaries would indicate very different specific epithets for the "same" tree.
(Incidentally, I always thought a "dogfish" was a nasty little shark, about 3' long, which favors rocky coastlines. So much for common names!!)

The Dictionary of American Regional English, which is very, very good on common plant and animal names, has, "1. Any of several conifers...a....=tamarack 1; also the wood of such a tree. chiefly Nth, esp NEng....b. A juniper (here Juniperus communis)...c.=lodgepole pine...d. A white cedar (here: Thuja occidentalis). 2. A spirea...3.=sassafras...4=balsam poplar." Many alternative spellings are offered, as well.

I forgot to mention the salt-water dogfish, which is a kind of shark and is an important food fish,IIRC.

Cedars are also called cypresses, though there is also a cypress which is not a cedar, IIRC.

Maybe we're dealing for two Native Americans which both meant "tree".

Thanks, Dotty and Grant! I think we've clarified the confusion about as much as it can be clarified, which is not very much. We should all be using Linnean terminology, I guess. "Among alnus and young Larix laricina" doesn't have quite the same ring to it, though.

When I read this entry, I knew I'd heard the word before - and, yes, there's a summer repertory playhouse in Berwick, Maine called the Hackmatack Playhouse. When I looked further, I found that up there (which would be closer to E.B. White's summer home, right?) it means "balsam poplar" and that the word may be Abenaki in origin. The Abenaki origin seems plausible to me, from the sound of it, and from living in N. New England where we have plenty of Abenaki names. But I also found this, at nativetech.org: "The Latin name for Tamarack is Larix laricina. Other common names are Eastern Larch, American Larch, Red Larch, Black Larch, takmahak and Hackmatack, which is an Abenaki word for ëwood used for snowshoesí (Erichsen-Brown 1979)." Personlly, I'd buy the tamarack definition: the words are fairly similar, and the further north you go into NH and Maine, the more you hear "larch" called "tamarack".

Absolutely right, Sir Hat! But it's true that Linnaen terminology, however accurate it may be, is not, well, appropriate for all contexts, esp. speech, poetry, memoirs, etc. (although J.P. Smith does point out that many scientific names have "elegant Latin or Greek roots".) I myself may not know precisely what someone means by "jack-go-to-bed-at-noon", "Indian hippo", or "devil's cherries", but someone knows what those names refer to, and they sure sound euphonious besides!

As a native of rural northern Maine who is now living in Honolulu, I have been encountering more than my share of these confusions lately -- I'm finding that it is more common to find the same term used for a different plant in different regions/climates than to find the same term used differently in a single area.

That said, I can testify as a native speaker of northern Maine-ese that in Piscataquis County in the 1970s, "hackmatack" clearly referred both to the tamarack (notable, according to my sixth-grade science teacher, for being the only deciduous needleleaf tree) and for a kind of poplar-ish tree that was also popularly known as "popple," technically the quaking aspen. The former usage was more common than the latter.

The two that are getting to me lately are "ironwood," which here in Hawai'i means a variety of Casuarina sp. native to Australia (I think). Back in Maine, the term ironwood clearly referred to the common hop hornbeam. I find with a little googling that it also refers to a kind of tamarisk tree in the American southwest, Olneya tesota, and to the Indian rose chestnut, Mesua sp. The other one is "plantain," which here in Polynesia refers to all the varieties of starchy bananas (Musa sp.) used in Caribbean (and other) cooking, but which in my childhood referred to a low-lying weed with a vertical seedy stem, Plantago sp.

Weird.

So would that Australian Casuarina be a "tea-tree" (ti-tree) or "she-oak" :-) ?

Toby: it's the one called "she-oak" though that term is not in colloquial usage in Hawaii.

I forgot to mention the salt-water dogfish, which is a kind of shark and is an important food fish,IIRC.

Indeed. Sold in British fish-and-chips shops as "rock salmon". Never tried it myself. Apparently they're suffering from overfishing.

My dogfish is a salt water shark that has skin that can be used as sandpaper, and bears its young live.

My father grew up in Nova Scotia in the early 20th century. His ancestors were shipbuilders first in Connecticut and then Nova Scotia. Dad said the hackmatack was a native name for the tamarack (American, or black, larch (Larix laricina)), the roots of which were commonly used to make ships' knees (a piece used to fasten keel to hull, I believe, which had to be very strong). See http://www.mainepreservation.com/dayswork/dayswork6.shtml or the Columbia Electronic Dictionary quoted at http://www.factmonster.com/ce6/sci/A0828878.html

Fathers and sons forever!