Tom Volk's Fungus of the Month for May 2005

Urnula craterium, the black tulip fungus

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Urnula craterium with tulips

The black tulip fungus is a harbinger of spring in the northeastern and midwestern United States and into Canada. It's much more common than you think and can be found about the same time as morels-- but you have to look really closely! Although Urnula can be rather abundant in the forest, it is usually very difficult to see because of its black color and leaf-like shape. Usually if you find one, there are others nearby. Often they are even found fruiting in clusters of several fruiting bodies. It's likely that this fungus causes a wood decay. Urnula seems to fruit from the sides of fallen logs, but really comes out at the interface of the log and the soil, an area where it's most moist. It can also be found growing from buried wood and wood that barely breaks the surface of the soil-- again this is a habitat that is wetter than the surrounding area. It often grown in the vicinity of trees such as oak, aspen, and cottonwood, eventually growing on their wood. I usually find Urnula in rather deep, shaded woods. Members of the Ascomycota generally produce a soft rot, which means that they digest the glucans in the wood. If you remember, the Basidiomycota decay the lignin and/or cellulose of the wood. It would seem to be more efficient and to decay the more abundant lignin and cellulose, but the Ascomycota seem to be doing just fine, thank you. See this page for more information on wood decay by fungi.

Black flowers are often given as a joke or a "dig" on the occasion of someone's 40th or 50th birthday. Sometimes a bouquet of black flowers is sent as a not-so-veiled threat. But are there really black flowers?

Urnula from the side

Is there really such a thing as a black tulip flower? The International Bulb Society provides some interesting information about black tulips in their Flower Bulb FAQs.

Q. Where can I buy the rare black tulip?

A. Actually, black tulips are not rare -- black tulips do not exist! What do exist are some very, very deep purple tulips, some of which appear almost black. The search for the fabled black tulip has been an epic quest for centuries.

In 1850 Alexander Dumas, famed French author of "The Count of Monte Cristo," "The Three Musketeers," and "The Man in the Iron Mask," captured the popular fancy with "The Black Tulip" (now with Oxford University Press), a romantic tale in which a fictional black tulip figures in a love story laced with murder, torture, greed, dastardly intrigue, and sudden surprises.

Today, the lure of a black tulip still attracts. Dutch hybridizers have achieved some very, very deep purples. 'Queen of Night,' for example, is officially listed as "deep velvety maroon" and is very, very dark in color. But achieving a true black tulip, say the experts, is not possible (yet still worth the try!). For a near-black experience also try: T. 'Burgundy' (deep purple-violet), T. 'Black Parrot' (violet-black) or T. 'Black Diamond' (deep mahogany).

Thus a truly black flower is the holy grail of flower breeders, but no true black flowers exist. Even the so-called black rose is actually a very deep red. So although the black tulip fungus isn't truly black (it looks like it has a touch of brown, except when you dry it and it becomes a deeper black), maybe avid gardeners everywhere would like to have a black organism like Urnula in their flower beds-- However, I would say about 25% of emails I get are from gardeners who want to get rid of "some awful fungus" such as stinkhorns or slime molds in their gardens. I think this is kind of silly-- why not have something different and exciting to show off to your friends and the garden club?

Urnula beginning to dry out on the outsideUrnula is one of the spring cup fungi, along with Sarcoscypha coccinea, the scarlet cup, and Scutellinia scutellata, the eyelash cup fungus. -- and who could forget morels? These members of the phylum Ascomycota, cup fungi sometimes called the "Discomycetes," are characterized by their ascospores, which are sexual spores borne internally in sacs called asci. These asci are borne in layers on the outside of the fruiting body, on the inner surface of the cup. There are usually eight ascospores per ascus, the products of a meiotic division (producing 4 nuclei) followed by one mitosis (producing 8 nuclei). The nuclei are then incorporated into spores by the de novo production of spore walls around the nuclei, a process that is known as free-cell formation. If you're lucky, you can blow gently into the cups and watch the ascospores "puff" out. Very cool.

Of course, the most often asked question about any fungus has to be,

"Is it edible?"

    I think the answer for Urnula is mostly unknown, although we do have some limited data. Here's an email I got last May:

Q. I am from California, and I am in Wisconsin visiting my brother and his friend. I think I found Craterellus fallax in the woods here. Do you find the black trumpet in this area? I cooked it up and it didn't taste the same, maybe it was old. Thanks for your time.

I wrote back:

A. I'm almost certain you did not eat black chanterelles. We have them here, but I have never seen them before the end of August. I am pretty sure you ate the black tulip, Urnula craterium. We don't really know much about the edibility of this fungus, but you seem to have survived it fine. You should always be careful about eating mushrooms when traveling to another area, since the fungi are usually very different.

Urnula beginning to dry out on the outside

Although it's a pretty cool fungus, it's unlikely that you would search for this fungus on purpose, but here's an opportunity for you to do so. We're doing some experiments with Urnula in our lab, so here's your chance to help with science. We need as much Urnula craterium as possible. If you'd like to help, please gently air dry the fruiting bodies (indirect light is good--not in the sun!) and send them in a paper bag in a box or envelope (not plastic!!) to:

********************************************  (0)  ************
Tom Volk                                     (000)
Professor of Biology                        (00000)
3024 Cowley Hall                            (00000)
University of Wisconsin-La Crosse           (00000)
La Crosse, Wisconsin  54601  USA             (000)
                                              | |
********************************************  | |  *************

We will be eternally grateful, and cite your name in any publication or presentation on this fungus. Thanks!!!

I hope you enjoyed learning about Urnula craterium. It' s not really black, and it's not really a tulip, but it is a fun fungus to find in the woods. It means that spring is here, and we can get out of the house and look at nature in the spring. You can't beat that!

If you have anything to add, or if you have corrections, comments, or recommendations for future FotM's (or maybe you'd like to be co-author of a FotM?), please write to me at

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