Summer-blooming bulbs can be purchased in the Spring from garden centers, catalogs, and on-line nurseries and planted as soon as you have them. If you live in an especially cold climate, the bulbs can be planted in containers and kept in a warm location until the leaves begin to emerge, then moved to a sunny location or given artificial light until the weather warms. Most summer-blooming bulbs prefer warm temperatures and humid conditions, and will be killed by frost or freezing.
When selecting your bulbs, corms, rhizomes, or tubers, make sure they are solid, heavy, and free from mold or rot. Select the larger bulbs, as these will have more food stored for the plant and will yield larger plants and flowers.
With the exception of winter hardy varieties, your summer-blooming bulbs will need to be stored in a warm place during the winter. Either dig the bulbs and store them in dry peat moss or wood chips in a warm (50 degrees F or so) dry location, or bring the entire pot indoors for winter storage. A few varieties are hardy to zone 4 (check your packaging when you buy your bulbs), but most are only hardy to zone 8 or 9.
Also called Lily-of-the-Nile, these come in purple, blue or white, miniature and regular sizes, and deciduous or evergreen cultivars. Will need to be divided every 5-6 years. Versatile, likes full sun but will do well with as little as three hours of sun a day. Miniature varieties have foliage 6 to 12 inches tall with 12 to 18 inch flower stalks topped with round clumps of 50 flowers or more. Regular size are typically 12 to 18 inch tall foliage with flower stalks at 2 to 5 feet, depending on the cultivar. Agapanthus needs only occasional water during the growing season.
Plant Agapanthus bulbs 5 inches deep and 12 inches apart. They look especially beautiful in large containers with 3 or more bulbs per container. The long slender leaves droop nicely over the container sides and new flower spikes will continually rise and bloom from the middle all summer long.
Also called Windflower, these are in the same family as Ranunculus. Anemone come in a wide variety of sizes and sun/shade needs, so check your package to choose ones for your needs. Flowers are typically red, pink, blue, purple or white. Be careful to not plant where pets or children might eat them, all parts are poisonous. Attractive leaves are typically finely divided, similar to parsley. Daisy-like or poppy-like flowers rise on 6 to 18 inches stems, depending on variety, and are typically 1 ½ to 2 ½ inches across.
Plant Anemone tubers 1 to 2 inches deep in light, well-drained potting soil. Keep soil moist but not overly wet. Will recover from dryness and wilting if watered well immediately.
Also called Monkey Root, blooms from late spring to summer. Flowers are red, blue, lavender or white. They prefer full sun but will do well with a small amount of shade. Leaves are typically 6 inches long and ribbed. Spikes of several fresia-like flowers grow 6 to 12 inches, depending on cultivar.
Plant Baboon Flower corms 4 inches deep in deep pots. Surround by small, cascading flowers like alyssum or hanging lobelia for a beautiful container. Water well during growth.
These are available in both hanging and upright cultivars. Flowers come in any combination except blue, and I know of one breeder who is working to develop a blue begonia so even those may be available soon. Tuberous begonia have numerous large blooms in singles, semi-doubles, doubles, and tight-centered shapes, and are available in solid colors and picotee with contrasting colored edges. They prefer filtered shade and high humidity, so mist them regularly or grow them in a green house or moist lath house for best bloom. Some are susceptible to powdery mildew, so watch for it and treat accordingly.
Plant tuber according to directions, usually very near the surface of the soil. Water regularly during the growing season. Reduce watering in the Fall when leaves begin to turn yellow and wilt. Dig and store dry for the winter when stems have fallen off, or allow entire pot to dry out and store in a cool dry place until spring.
The Common Calla (Zantedeschia aethiopica) grows too large for most containers, but many smaller and highly colorful varieties do wonderfully in container gardens. Some have spotted or even reddish leaves for added interest, and the flowers can be found in pinks, orange, yellow and red.
Plant rhyzome 2 inches deep in a 6 inch or larger pot. Especially beautiful if several are planted together in a large container. Water sparingly until the leaves emerge, then keep moist throughout the growing season. Reduce watering after bloom ceases and let dry out during the resting period. Feed weekly with a liquid fertilizer.
Regular Canna Lily are too tall for most containers, but dwarf cannas will do very well. These are a tropical and will require much water during the growing and bloom season, so plan accordingly. Leaves resemble banana plants and range from rich green to deep bronze in color, depending on cultivar. Flowers come in a wide range of colors and shapes and some are bi-colored. Note that even the dwarf varieties can reach 3 feet tall or more, so Cannas will require a large container.
Plant tubers 4 to 5 inches deep in rich, loose potting soil, 6 to 10 inches apart. Remove flowers after they fade, and cut flower stalk to soil level after all flower clusters have bloomed. Feed weekly or bi-monthly.
Dahlia come in tall and dwarf varieties – the tall can reach 5 feet in height or more and can be as bushy as a small hedge, the dwarf varieties are 12 inches tall and mounding. Both do well in containers, though the tall varieties will need large, deep pots and should be staked. Dahlias prefer sun to part shade. In especially hot areas give them light shade in the afternoon. The flowers have a wide range of shapes and are available in nearly every color except blue. Some are bi-colored or even tri-colored.
Plant full-sized dahlia bulbs 8 to 12 inches deep and the dwarf varieties 3 inches deep. Water regularly after the shoots emerge for the entire growing season. Most dahlia will not need fertilizer, but if you do feed them use a low-nitrogen type. Deadhead regularly throughout the bloom season. After first frost and tops turn yellow, cut stems to 4 inches for full-size and 1 inch for dwarfs and dig bulbs. Let bulb clumps dry in the sun for several days. Cover with sawdust, peatmoss, or vermiculite, and store in a cool, dry place for the winter. In mild climates bulbs can be left in the ground year round; simply remove dead foliage and stems after the plants die back.
Tall Glads will do well in containers and look especially elegant surrounded by mounding plants (such as dwarf dahlias) or low annuals. Mini-glads are great for smaller containers, and most are hardy to zone 4 so they will need little extra care in most areas. Colors, shapes and sizes cover a wide range, and bloom times can be anywhere from spring to fall, depending on time of planting and the cultivar. Remove spent flowers as they wither and cut back flower spikes after all blooms have faded. Do not allow to go to seed as this will take energy away from the corm needed for next-year's growth.
Plant corms 4 to 6 inches deep and 6 inches apart for large corms, 3 or 4 inches apart for smaller ones. Water regularly throughout the growing season, then cut back water in the fall. Dig corms when foliage starts to yellow and allow to dry out for 3-4 weeks. Remove old stalks and corms and store for the winter at 40-50 degrees in single layers or ventilated flats to avoid rot. In mild climates some varieties can be left in their containers to naturalize. Dig every 2 to 3 years to separate and remove old corms as plants become crowded.
These lily hybrids typically bloom in July and August and are the most fragrant of all the lilies. They bloom with multiple 6 to 9 inch flowers on 2 to 4 foot stems, though dwarf or miniature varieties also exist. Most are white to pink to deep rose in color and have spots or bands of darker and lighter color at the centers and edges of the petals. Oriental lilies prefer a rich well-drained soil and do not like their roots to become too hot, so keep your container shaded in hot weather or plant mounding and cascading plants around your lilies to shade the container and roots in the heat of summer. Note that the plant tops require full sun.
Plant the bulbs 2 to 5 inches deep, depending on size of bulb, spreading the roots. It is better to plant too shallow than too deep. Firm the soil around the bulb to remove air pockets. Water well and mulch to keep soil slightly moist – never allow the soil to dry out completely. Note that lily bulbs never go completely dormant, so do not dig them in the fall. Instead, move the containers to an area protected from freezing and keep the soil slightly moist all winter. When all danger of frost has past, move the containers back outside. Bulbs can be repotted in late fall or early spring if desired or when they become too crowded.
The most commonly grown varieties of Ranunculus are Persian or Turban Ranunculus (R. asiaticus) These have bright green fern-like leaves and a ball shaped flower of many tightly-packed petals. Large tubers can produce 50 to 75 blooms of yellow, pink, orange, red or white over a season on 1 to 1 ½ foot tall stems. Dwarf varieties are 8 to 10 inches tall. Plant in your containers with Icelandic poppies, snapdragons, pansies, or nemesias (or all of the above!) for a beautiful summer-long show of color. They require full sun and regular watering during the growing season.
Plant tubers, prongs facing down and 2 inches deep. Water thoroughly. Do not water again (unless the weather is especially hot and dry) until foliage starts to appear. Note: birds love the young shoots of ranunculus, so start indoors or protect with netting until leaves are well established. Let plants dry out after all blooming stops, then remove tubers from the soil, cut off the tops, and store in a cool, dry place over the winter.