Eucalyptus cinerea. (Myrtaceae) Florist gum, Penny Gum, Silver dollar tree. A fast-growing tree with ash-grey foliage, which makes it suitable for contrast planting. Popular with flower arrangers. An excellent windbreak tree for large dry gardens, but it needs pruning to encourage the development of branches. Sowing: Seed should be sown in spring or during summer, in a well-drained seedling mix, and need only be covered lightly with the sowing mix, clean coarse sand or milled bark. The trays should be kept moist in a warm but shaded position.