Actually, it is not the freezing of the soil that injures bulbs (this occurs in open ground), but it is the pressure and counter pressure exerted by frost on the sides of containers, which are firm and do not give. As a result, bulbs are bruised and thrust out of the soil, their roots torn. Where there is no hard freeze, but sufficient cold weather, hardy bulbs can be grown successfully in containers of small size.
Achimenes. Warmth-loving trailing plants with neat leaves and tubular flowers in blue, lavender, red and white. Related to gloxinias and African violets, they are nice in hanging baskets and window boxes or in pots on tables, shelves, or wall brackets. Start the small tubers indoors and give plants a sheltered spot with protection from strong sun and wind. Achimenes, an old standby in the South, is worthy of more frequent planting.
Agapanthus or Blue Lily of the Nile. Fleshy-rooted evergreen plant, with strap leaves, often grown in tubs and urns on terraces and steps during the summer, when the tall blue spikes unfold. Culture is easy, but plants require a well-lighted, frostproof room or greenhouse in winter. This is an old-time favorite, often seen in gardens of Europe.
Calla Lily. Showy, hardy outdoors in warmer regions, but a tender pot plant in the North. Most familiar is the white one with large, shiny, heart-shaped leaves. Start bulbs indoors in February or March in rich soil and, when weather settles, transfer to large pots and take outdoors. Calla lilies do well in full sun or part shade, are heavy feeders and need much water. There is also a dainty yellow with white-spotted leaves. Rest bulbs after foliage ripens and grow again.
Dahlias. Colorful and free-flowering, they provide bounteous cut blooms. Tall, large-flowering kinds can be grown only in large planters and boxes, but the dwarfs, even freer flowering, are excellent in small containers.
Attaining one to two feet tall, they grow easily from tubers in average soil in sun or part shade. They may also be raised from seed sown indoors in February. If tubers are stored in peat or sand in a cool, frostproof place, they can be grown for years. Check bulbs during winter, and if shriveling, sprinkle lightly.
Gladiolus. Summer-flowering with spearlike leaves and many hued spikes. Corms can be planted in containers outdoors after danger of frost is passed. Set them six inches apart and four to six inches deep. If several containers are planted every two to three weeks, there will be a succession of bloom. Stake stems before flowers open. After the leaves turn brown, or there is a frost, lift corms, cut off foliage and dust with DDT to control thrips. Store corms in a dry place at 45 to 55 degrees F.