Keys to Nature
Key to Ceanothus, Physocarpus, and Ribes in the Chicago Region

© Paul Rothrock, Ribes cynosbati - Keys to Nature Project

Key to Ceanothus, Physocarpus, and Ribes in the Chicago Region
William S. Alverson
This key is an extension of one branch of Paul Rothrock's "Shrubs of the Chicago Region" key (at, which was itself created as a test to see how content from Paul's printed color guide "Shrubs of the Chicago Region" (available at could be repurposed into the format of an illustrated web-key. One branch of Paul's web-key ends in a group of species, including Ceanothus, Physocarpus, and Ribes. The key you are about to enter demonstrates how an author can create a key that is complimentary to an existing web-key but independent of the previous author. In this case, the key simply teases apart the eight species in these three genera in a slightly different manner than Paul's web-key. It was written using characters from Paul's key, Swink and Wilhelm, and Rosendahl's Trees and Shrubs of the Upper Midwest, as well as an hour looking over specimens in the herbarium at The Field Museum. Jennie Kluse moved the text into HTML format as the first test of the project's web forms, created by Ryan Peters. She also searched through the images available to us, cropping and reorienting them so as to best illustrate the characters discussed in the text.


Key Structure:
1. Stipules or stipule scars present (look at the bases of the new leaves!) - 2.
1. Without stipules or stipule scars - 4.

2. Leaves 3-lobed; teeth without sharp, dark tips - Physocarpus opulifolius
2. Leaves unlobed; teeth tipped with sharp, brown or black tips - 3.

3. Leaves oval-shaped, to over 2 cm wide, and densely hairy; found throughout the region - Ceanothus americanus
3. Leaves narrow, less than 2 cm wide, smooth above but slightly hairy below; in sand prairies along Lake Michigan - Ceanothus herbaceus

4. Leaves with tiny, disc-shaped yellow glands underneath (stems without spines, flowers yellow, ripe fruits black) - Ribes americanum
4. Leaves without yellow glands underneath - 5.

5. Flowers in racemes, i.e., borne on a long, hanging stalk of 5 to many flowers; stems without spines and without thorns at nodes - Ribes triste
5. Flowers axillary, in clusters of 1 - 4 arising from stem at base of leaves; stems sometimes with spines and nodes usually with thorns) - 6.

6. Calyx lobes shorter than the tube (the bottom part of the calyx where the lobes are fused together); berries usually prickly - Ribes cynosbati
6. Calyx lobes as long or longer than the tube; berries usually smooth - 7.

7. Stamens much longer than petals ("long exerted");
flowers long and narrow, whitish - Ribes missouriense
7. Stamens more or less equal to the petals in length ("included"); flowers greenish or purplish - Ribes hirtellum


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This page was last modified on: Mon, 13 Oct 2008 17:10:00 -0500.