Low-growing, annual and perennial hardy plants found wild in many countries and suitable for the rock garden and flower border. They belong to the family Rubiaceae. The word Asperula,from asper, rough, refers to the leaves.
Planting and Propagation. These plants thrive in a well-drained, woodsy soil and may be planted in early fall or spring. The best method of propagation is to lift and separate the plants in September and replant the rooted pieces. Seeds should be sown in pots of sifted sandy soil in March and placed in a shady frame.
For the Rock Garden. Among the perennial Woodruffs are several beautiful plants for the rock garden or moraine. The best of all is Asperula suberosa, from the summit of Mount Athos in Greece; it grows only 3 in. high, has gray leaves and bears pink flowers in May; it should be planted in very gritty soil. Others are A. Gussonei, from Sicily, a green, mosslike plant, 4 in. high, with blush-colored blooms; and A. hirta, 3-4 in., with white flowers which change to pink as they age—a Pyrenean plant which should be set in a rather damp part of the rock garden.
The common Sweet Woodruff of Europe and Asia (Asperula odorata) is useful for planting in shady corners or beneath trees; it spreads rapidly, soon covering a good deal of ground, and, when smothered with small white flowers in May, is very pretty, especially if associated with Forget-me-nots. It should not be put near choice plants, owing to its rapid growth. The leaves are scentless when fresh, but they give off a fragrance like that of new-mown hay when cut and dried; they are useful for placing among clothes, which they scent pleasantly. This plant is used to flavor May wine in Germany.
The hardy annual Woodruff, Asperula orientalis (azurea setosa), 9-10 in. high, bears pale-blue flowers in early summer. Seeds are sown where the plants are to bloom, the seedlings being thinned to 6 in. apart. In mild localities those from a sowing in September will bloom in May—June; seeds sown in April give plants that bloom in June—July.