In passing along the country roads, especially those which have suffered upheaval from the road machines, suddenly we are conscious of a perfume so sweet, so suggestive of honey and other delicate things, that we involuntarily stop to find its source. Close at hand we find this perfume laboratory in the blossoms of the sweet clover. It may be the species with white blossoms, or the one with yellow flowers, but the fragrance is the same. There stands the plant, lifting its beautiful blue-green foliage and its spikes of flowers for the enjoyment of the passer-by, while its roots are feeling their way down deep in the poor, hard soil, taking air and drainage with them and building, with the aid of their underground partners, nitrogen factories which will enrich the poverty-stricken earth, so that other plants may find nourishment in it.
Never was there such another beneficent weed as the sweet clover—beneficent alike to man, bee and soil. Usually we see it growing on soil so poor that it can only attain a height of from two to four feet; but if it once gets foothold on a generous soil, it rises majestically ten feet tall.
Like the true clover, its leaf has three leaflets, the middle one being longer and larger than the other two and separated from them by a naked midrib; the leaflets are long, oval in shape, with narrow, toothed edges, and they are dull, velvety green; the two stipules at the base of the leaf are little and pointed.
The blossoming of the sweet clover is a pretty story. The blossom stem, which comes from the axil of the leaf, is at first an inch or so long, packed closely with little, green buds having pointed tips. But as soon as the blossoming begins, the stem elongates, bringing the flowers farther apart—just as if the buds had been fastened to a rubber cord which had been stretched. The buds lower down open first; each day some of the flowers bloom, while those of the day before linger, and thus the blossom tide rises, little by little up the stalk. But the growing tip develops more and more buds, and thus the blossom story continues until long after the frosts have killed most other plants; finally the tip is white with blossoms, while the seeds developed from the first flowers on the plant have been perfected and scattered.
The blossom is very much like a diminutive sweet pea; the calyx is like a cup with five points to its rim, and is attached to the stalk by a short stem. The banner petal is larger than the wings and the keel. A lens shows the stamens united into two groups, with a thread-like pistil pushing out between; both stamens and pistil are covered by the keel, as in the pea blossom.
The flowers are beloved by bees and many other insects, which are attracted to them by their fragrance as well as by the white radiance of their blossoms. The ripened pod is well encased in the calyx at its base. The foliage of the sweet clover is fragrant, especially so when drying; it has been used for fodder. The sweet clovers came to us from Europe and are, in a measure, compensation for some of the other emigrant weeds which we wish had remained at home.
Leading thought—This beneficent plant grows in soil too poor for other plants to thrive in. It brings nitrogen and air into the soil, and thus makes it fertile so that other plants soon find in its vicinity nourishment for growth.
Method—Plants of the sweet clover with their roots may be brought to the schoolroom for study. The children should observe sweet clover in the field; its method of inflorescence, and the insects which visit it, should be noted.
1. What first makes you aware that you are near sweet clover? On what kinds of soil, and in what localities, does sweet clover abound?
2. Do you know how sweet clover growing in poor soils and waste places acts as a pioneer for other plants?
3. Dig up a sweet clover plant, and see how far its stems go into the soil.
4. How high does the plant grow? What is the color of its foliage?
5. Compare one of the leaves with the leaf of a red clover, and describe the likeness and the difference. Note especially the edges of the upper and the lower leaves, and also the stipules.
6. Describe the way the sweet clover blossoms. Do the lower or upper flowers open first? How does the flower stem look before it begins to blossom? What happens to it after the blossoming begins? How long will it continue to blossom?
7. Take a blossom and compare it with that of a sweet pea. Can you see the banner? The wings? The keel? Can you see if the stamens are united into two sets? Can you see the pistil? Note the shape of the calyx.
8. How many flowers are in blossom at a time? Does it make a mass of white to attract insects? In what other way does it attract insects? What insects do you find visiting it?
9. How do the ripened pods look?