Anna B. Comstock

The Evening Primrose

Teacher's Story

To the one who has seen the evening primrose unfold, life is richer by a beautiful, mysterious experience. Although it may be no more wonderful than the unfolding of any other flower, yet the suddenness of it makes it seem more marvelous. For two or three days it may have been getting ready; the long tube which looks like the flower stem has been turning yellow; pushing up between two of the sepals, which clasp tips beyond it, there appears a row of petals. Then some warm evening, usually about sunset, but varying from four o'clock in the afternoon to nine or ten in the evening, the petals begin to unfurl; they are wrapped around each other in the bud as an umbrella is folded, and thus one edge of each petal becomes free first. The petal first in freeing its edge seems to be doing all the work, but we may be sure that all the others are pushing for freedom; little by little the sepals are pushed downward, until their tips, still clasped, are left beneath; and the petals now free, suddenly flare open before our delighted eyes, with a movement so rapid that it is difficult for us not to attribute to them consciousness of action. Three or four of these flowers may open on a plant the same evening; and they, with their fellows on the neighboring plants, form constellations of starry bloom that invite attention from the winged creatures of the twilight and the night. There is a difference in the time required for a primrose flower to unfold, probably depending upon its vigor; once I watched for half an hour to see it accomplished, and again I have seen it done in two or three minutes. The garden species seems to unfold more rapidly than the wild species, and is much more fragrant. The rapidity of the opening of the blossom depends upon the petals getting free from the sepals, which seem to try to repress them. The bud is long, conical, obscurely four-sided, and is completely covered by the four sepals, the tips of which are cylindrical and twisted together; this is an interesting habit, and one wonders if they hold the petals back until the latter are obliged to burst out with the force of repressed energy; after they let go of the petals, they drop below the flower angularly, and finally their tips open and each sepal turns back lengthwise along the seed-tube.

1. Evening primrose, showing buds, one ready to open, a flower just opened above at the left, an older flower at the right, a fading flower and seed-capsules below. 2. Seed-capsules. Cross section of seed-capsule with seeds above.

The four lemon-yellow petals are broad, with the outer margin notched. The eight stamens are stout, and set one at the middle of each petal and one between each two petals. The long, pale yellow anthers discharge their pollen in cobwebby strings. When the flower first opens, the stigma is egg-shaped and lies below the anthers; later, it opens into a cross and usually hangs off at one side of the anthers. If we try to trace the style back to the ovary, we find that it extends down into what seems to be the very base of the flower stem, where it joins the main stem. This base is enlarged and ribbed and is the seed-box, or ovary. The tube is rich in nectar, but only the long sucking-tubes of moths can reach it, although I have sometimes seen the ubiquitous bees attempting it. The butterflies may take the nectar in the daytime, for the blossoms of the wild species remain open, or partially open, for a day or two. But the night-flying moths which love nectar have the first chance, and it is on them the flower depends for carrying its pollen, threaded on filmy strings.

There are times when we may find the primrose blossoms with holes in the petals, which make them look very ragged. If we look at such plants carefully, we may find the culprit in the form of a green caterpillar very much resembling the green tube of the bud; and we may conclude, as Dr. Asa Fitch did, that this caterpillar is a rascal, because it crawls out on the bud-ends and nibbles into them, thus damaging several flowers. But this is only half the story. Later this caterpillar descends to the ground, digs down into it and there changes to a pupa; it remains there until the next summer, then, from this winter cell, emerges an exquisitely beautiful moth called the Alaria florida;  its wings expand about an inch, and all except the outer edges of the front wings are rose-pink, slightly mottled with lemon-yellow, which latter color decorates the outer margins for about one-quarter of their length; the body and hind-wings are whitish and silky, the face and antennæ are pinkish. Coiled up beneath the head is a long sucking-tube which may be unfolded at will. This moth is the special pollen-carrier of the evening primrose; it flies about during the evening, and thrusts its long, tubular mouth into the flower to suck the nectar, meanwhile gathering strings of pollen upon the front part of its body. During the day, it hides within the partially closed flower, thus carrying the pollen to the ripened stigmas, its colors meanwhile protecting it almost completely from observation. The fading petals of the primrose turn pinkish, and the pink color of the moth renders it invisible when in the old flowers, while the lemon-yellow tips of its wings protruding from a flower still fresh and yellow, forms an equally perfect protection from observation.

Winter rosette of evening primrose.  Photo by Verne Morton.

The evening primrose is an ornamental plant in both summer and winter. It is straight, and is ordinarily three or four feet tall, although it sometimes reaches twice that height. It is branched somewhat, the lower portion being covered with leaves and the upper portion bearing the flowers. The leaves are pointed and lanceolate, with few whitish veins. The leaf edges are somewhat ruffled and obscurely toothed, especially in the lower leaves. The leaves stand up in a peculiar way, having a short, pink petiole, which is swollen and joins the stalk like a bracket. The upper leaves are narrower; the leafy bracts at the base of the flower grow from the merest slender leaflet at the base of the bud, to a leaf as long as the seed-pod, when the flower blooms.

The seed-capsules are four-sided, long and dark green. In winter they are crowded in purplish-brown masses on the dry stalks, each one a graceful vase with four flaring tips. At the center of each there projects a needlelike point; and within the flaring, pale, satin-lined divisions of these urns, we may see the brown seeds which are tossed by the winter winds far and near. The young plants develop into vigorous rosettes during the late summer and autumn, and thus discreetly pass the winter under the snow coverlet.

Method—The form of the evening primrose may be studied from plants brought to the schoolroom; but its special interest lies in the way its petals expand in the evening, so the study should be continued by the pupils individually in the field. This is one of the plants which is an especially fit subject for the summer note-book; but since it blossoms very late and the plants are available even in October, it is also a convenient plant to study during the school year. The garden species is well adapted for this lesson.

2. Are the leaves near the base the same shape as those at the top of the plant? What is their shape? Are the edges toothed? What is there peculiar about the veins? How do the leaves join the stem? How do the leaves look which are at the base of the flower stem? Those at the base of the buds?

3. Where on the plant do the flowers grow? Which flowers blossom first, those above or below? Take a bud nearly ready to open; what is there peculiar in the appearance of the bud stem? What is the general shape of the bud? Describe the sepals. Look at their tips carefully, and see how they hold together. Cut a bud across and see how the petals are folded within it.

4. Take an open flower; where are the sepals now? Describe the open petals, their shape and color.

5. How many stamens are there? How are they placed? What is the shape of the anthers? How does the pollen look?

6. What is the shape and the position of the stigma in the freshly opened flower? Later? Open the flower-tube and find how far down the style extends. Where is the ovary? How does the ovary look on the outside? Taste the opened tube; can you detect the nectar? What sort of a tongue must an insect have to reach this nectar? How do the fading flowers look and act?

7. Describe the seed-pod. Cut it across, and see how many compartments there are within it. How are the seeds arranged in it? How do the pods open and how are the seeds scattered?

8. Watch the flower of the evening primrose open, and describe the process carefully. At what hour did it open? What was the movement of the petals? Can you see how they unfold in relation one to another? How do they get free from the sepals? How many minutes is required for the whole process of the opening of the flower? How many flowers on a plant expand during the same evening? Look at the open blossoms in the dark; can you see them? How do they look? What insects do you find visiting these flowers?

9. How long does the primrose blossom remain open? How do the young plants of the evening primrose pass the winter?

Supplementary reading—Blossom Hosts and Insect Guests, Gibson.