(P. veris), oxlip (P. elatior), bird's eye (P. farinosa), yellow auricula (P. auricula), P. denticulata, and P. Cortusoides. Similarly, spring bulbs may be employed; plant them, for the most part, under a ground cover so that the soil will not show when they die down. Of the tulips, single ones of the early and cottage types may be used, if in a solid color, but most to be preferred are the species, such as the sweet yellow (Florentine) tulip of Southern Europe and the little lady tulip (Tulipa Clusiana). Crocuses are also best in type forms, and the small, single, yellow trumpet kinds are the finest daffodil material. Single white or blue hyacinths may be used, but better than the stiff spikes of bloom of new bulbs will be the looser clusters of bulbs that have begun to "run out" in the border. Other valuable bulbs are the snowdrop, Scilla
Sibirica, glory-of-the-snow (Chionodoxa Luciliæ), guinea-hen flower (Fritillaria Meleagris), grape hyacinth (Muscari botryoides), Triteleia uniflora, Allium Moly, and the wood and Spanish hyacinths (Scilla nutans and campanulata).
Taller plants that may be worked in, oftentimes best with only a single specimen or small clump, are autumn aconite (Aconitum autumnale), Yucca filamentosa, leopard's bane (doronicum), single peonies (either herbaceous or tree), German, Japanese, and Siberian iris, as well as the yellow flag (Iris pseudacorus), single columbines, Anemone Japonica, Hemerocallis flava, Sedum spectabile, Dielytra spectabile, Dielytra formosa, Jacob's ladder (Polemonium Richardsonii), fraxinella, Anthemis tinctoria, single Campanula persicifolia, Campanula rapunculoides, Campanula glomerata, globe flower
(trollius), snapdragon (antirrhinum), platycodon, lavender (where it is proven hardy), and musk mallow (Malva moschata).
Of the lilies, Lilium Philadelphicum, L. elegans, L. speciosum, and L. longiflorum are all desirable, and they thrive in partial shade, though in Japan L. elegans will be found standing out from the rocks in full sunshine. For peering over into the rock garden, rather than being placed in it, L. Canadense, L. tigrinum, and L. superbum are recommended.
The pick of the low shrubs are the charming Daphne cneorum, which flourishes better for being lifted above the ordinary garden level, and Azalea amœna. The latter, however, should be so placed that its trying solferino does not make a bad color clash. Rhododendrons and mountain laurel fringe a rock garden well,
and with one trailing juniper (Juniperus procumbens) will provide a great deal of the refreshing winter green.
Single roses, the species, fit in well where there is room for them. Good ones are R. setigera, R. rubiginosa, R. Wichuraiana, all rampant, and the low R. blanda. The roses would better be at or near the entrance or exit, or far enough above the rock work not to ramble over small plants.
The plants in this list cover all seasons and vary somewhat in their soil and moisture requirements. But the variation is nothing beyond the ordinary garden knowledge. Most will do better if their preferences are considered, but none is apt to perish with average care.