Above the inferior ovary is a ± well-developed floral tube, either cylindrical or flaring, with prominent calyx lobes. The petals are inserted on the tube and are rather small, never exceeding the calyx lobes, which are the more conspicuous part of the perianth. All species bloom in May or early June.

Ribes has achieved some notoriety as the alternate host for the white pine blister rust, Cronartium ribicola, a serious fungal disease of an important timber tree, Pinus strobus, the state tree of Michigan. The rust was introduced into North America from Europe about 1900 and spread rapidly. In the 1930’s and early 1940’s, aggressive campaigns were waged against both wild and cultivated species of Ribes, attempting to eradicate them within a certain distance of white pine. The rust fungus does not spread from one pine to another, but certain spores must grow on Ribes to complete the life cycle; other spores are then blown from Ribes to pine needles, where new infections occur.

Ribes alpinum L. (mountain or alpine currant), a European species, may persist from cultivation as an ornamental. It is functionally dioecious (though flowers have rudimentary organs of the opposite sex), with small greenish flowers (the fruit red) in strongly ascending racemes, rather small leaves, the ovaries and leaves essentially glabrous and glandless. It has been collected as “long persistent” in northwestern Baraga Co. The garden gooseberry, Ribes uva-crispa L., a native of Europe, sometimes escapes from cultivation in North America, and it or its hybrids might be expected in Michigan. The stem has well-developed nodal prickles. The fruit is usually pubescent and the calyx lobes are longer than the tube; the peduncles are very short.

1. Flowers solitary or in corymb-like clusters of 2–3 (–4); pedicels not jointed at the summit; stems usually with bristles or prickles at least at the nodes (sometimes completely unarmed, especially in R. hirtellum).

2. Flowering peduncles (from base to lowest bract) mostly 7–18 (–20) mm long; bracts fringed with gland-tipped hairs.

3. Stamens not exserted, shorter than the calyx lobes, ca. 1.5–2.5 mm long; calyx lobes distinctly shorter than the tube; ovary and fruit usually prickly with stiff bristles, occasionally glabrous.

R. cynosbati

3. Stamens long exserted beyond the calyx lobes, ca. 7–11 mm long; calyx lobes equaling or longer than the tube; ovary and fruit usually glabrous.

R. missouriense

2. Flowering peduncles ca. 2–3 (–5) mm long; bracts glandless (in common species) or ± glandular.

4. Leaves without glands, the blade cuneate to subcordate; bracts also glandless (or sparsely glandular-margined); stamens at maturity distinctly exceeding the petals; fruit smooth.

R. hirtellum

4. Leaves with sessile or stalked glands (at least on veins beneath, sometimes on both surfaces), the blades truncate to subcordate at base; bracts glandular-margined; stamens about equaling the petals (ends of anthers at most barely exceeding them); fruit smooth to glandular-bristly.

R. oxyacanthoides

1. Flowers in racemes of usually 5 or more; pedicels jointed at the summit (i.e., fruit articulated at base); stems without bristles or prickles (except in the very prickly R. lacustre).

5. Stems ± densely prickly; ovary and fruit with gland-tipped hairs or bristles (berries black, in drooping racemes).

R. lacustre

5. Stems without bristles or prickles of any kind; ovary and fruit smooth (except in R. glandulosum, with red berries in ascending racemes).

6. Floral tube 9–15 mm long; calyx lobes ca. half as long as tube or shorter; leaf blades less (usually much less) than 3.5 cm long, even when full-grown, 3 (–5)-lobed, each lobe with at most 2–3 (–7) teeth.

R. odoratum

6. Floral tube less than 4.5 mm long; calyx lobes about equaling the tube or longer; leaf blades often more than 3.5 cm long, at least in summer, and with many teeth.

7. Leaves with resinous dots, at least on underside of blade; ripe fruit black.

8. Bracts of inflorescence longer than the pedicels; calyx glabrous or with a few scattered hairs; ovary without resinous dots; flowers yellow (or cream) to greenish, in pendent (or rarely only spreading) racemes.

R. americanum

8. Bracts of inflorescence much shorter than the pedicels; calyx ± pubescent; ovary usually with a few resinous dots; flowers white or whitish (greenish white to purplish in R. nigrum), in pendent to erect racemes.

9. Flowers and fruit in erect or ascending racemes; calyx lobes ca. 3 times as long as the tube; native, in northern Michigan.

R. hudsonianum

9. Flowers and fruit in spreading to pendent racemes; calyx lobes about equaling the tube or slightly longer; escaped from cultivation near roads and gardens.

R. nigrum

7. Leaves without resinous dots (sometimes short-stalked glands on veins beneath); ripe fruit red.

10. Ovary and fruit with gland-tipped hairs or bristles; bruised foliage and fruit with skunk-like odor; flowering and fruiting racemes ascending.

R. glandulosum

10. Ovary and fruit smooth; plant without skunk-like odor; flowering and fruiting racemes spreading to pendent.

11. Pedicels essentially glabrous and eglandular; anthers ± dumbbell-shaped, the lobes well separated by the connective; terminal lobe of leaf ± ovate (sides rounded in outline).

R. rubrum

11. Pedicels (or most of them) with a few very short-stalked glands and usually also ± loosely pubescent; anthers ± cordate, the lobes contiguous; terminal lobe of leaf usually broadly deltoid (sides straightish).

R. triste