Summer bulbs are the ultimate for instant gratification – just plant in spring, then stand back and watch as lush, exotic flowers and sumptuous tropical foliage fill the space. The tropical style is a result of their origins in hot climates such as Africa and Brazil.
Red flowering tuberous begonia,
one of the most poplar summer bulbs
They are not hardy in northern climates and must be grown as annuals, then dug up in the fall to overwinter in a frost-free location. (Or if you are a lazy gardener you can let them die off in the fall when frost comes, just like regular annuals.)
Like flowering annuals summer bulbs need rich soil, excellent drainage and regular watering. But if you provide for their winter comfort, you can keep these bulbs coming back year after year.
Here’s a selection of summer bulbs to give garden beds and containers a blast of color and the feeling of a sultry jungle all summer long.
Abyssinian Gladiolus or Acidanthera (Gladiolus callianthus)
Abyssinian Gladiolus or Acidanthera
Grow these African summer bulbs just like gladiolus – plant 4 inches deep in fertile loam in a sunny location after soil warms in the spring.
The leaves are sword-shaped and the mid- to late-summer flowers are white and star shaped growing 3-4 inches wide with a purple splotch in the center. They are sweet-scented and make good cut flowers.
Planting them in containers will give you earlier flowering. Dig up bulbs before frost and store in a cool, dry place over winter.
Calla Lily (Zantedeschia sp.)
Yellow-flowering calla lily
Calla lilies provide masses of color all summer long. The color selection is large – red, white, purple, lavender, pink, rose and yellow.
Plants vary from 18-36 inches tall depending on cultivar, with lavish solid green or spotted foliage and uniquely beautiful flowers resembling cup-shaped upright trumpets. They can be used in beds or containers in full sun or part shade.
Barely cover the tubers with soil in the spring and water heavily during the growing season. Fertilization every other week will keep the plants blooming all summer. Dig tubers or store containers with tubers in a frost free location for the winter.
Canna (Canna sp.)
Orange-flowering canna lily
Cannas lend a true touch of the tropics to any garden. The plants grow strongly upright with large banana-like leaves that may be green, bronze, burgundy, or striped with white or brilliant yellow.
Flower stalks shoot from the top of the plant in a dizzying array of colors – orange, red, yellow, cream, pink or coral.
These summer bulbs may grow into tall giants – 36-60 inches, or be dwarf – 24-48 inches tall. Giant cannas make superb screens and eye-catching beds or borders, while dwarfs are ideal for containers.
In the spring, overwintered rhizomes should be rinsed and divided into sections containing one or more “eyes" or buds. When danger of frost has passed, plant sections in deeply prepared fertile soil in full sun. Water and fertilize regularly and carefully dead-head flowers (new flower stalks form to the side and just below the first flower stalk). Don’t cut spent flowers all the way back to the foliage or they won’t reflower.
After the first light frost, cut stems to the ground and dig the clumps of roots. Leave soil clinging to roots to protect from drying or store covered in peat moss. Ideal storage temperature is 40-50 degrees F.
Tuberous Begonia (Begonia sp.)
These lovely summer bulbs are the ideal plants for shady locations and they flower abundantly all summer. The flowers, resembling old-fashioned roses or camellias, are 2-4 inches wide.
The single, semi-double, or double flowers come in pastel pink, yellow, white, deep rich red or rose, and vibrant yellow or orange. The leaves are thick and waxy – a perfect foil for the incredible flowers. “Non-Stop" varieties have great strength and vigor and are quite wind resistant.
All this beauty grows from a brown tuber that should be potted up in March. Place tuber on top of rich potting soil with the concave side up and keep warm until new shoots are visible. Then keep the temperature between 60-70 F until weather is settled enough for planting outside. Plants grow from 8-15 inches tall. Tubers can also be planted into ground beds (2 inches deep and 12 inches apart) when there is no longer a chance of frost, but they won’t bloom as soon.
Tuberous begonias can be planted in shady ground beds, but don’t fare well in bad weather – they are easily beaten and broken by hard rains and fall prey to disease in very hot, humid weather. Flower boxes, hanging baskets and other containers that are at least partially protected from the elements are the ideal method for displaying these gorgeous plants.
Regular watering and fertilization will keep the plants blooming all summer. In the fall, cut off the plant tops, shake the soil from the tubers and store in potting soil or sphagnum moss at about 45 degrees F for the winter.
Burgundy Shamrock (Oxalis triangularis)
Oxalis with hosta, Japanese forest grass
These are uncommon but delightful summer bulbs for shade in northern climates. Deep maroon/burgundy shamrock-like leaves grow from small tubers into mounded plants 7-10 in. tall and 10-15 in. wide. Dainty pink flowers are produced generously for most summer.
It is handsome alone in a hanging basket or combined with other annuals in containers or planted in beds with contrasting plants such as Japanese forest grass (Hakonechola macra ‘Aureola’) or other bright green annuals or perennials. The leaves have the fascinating habit of being open by day and folding up at night.
Plants grow quickly from tubers placed in potting soil in spring. Water sparingly until plants are established, then water regularly but fertilize lightly for the remainder of the season. Store tubers in their pot or in paper bags in a frost-free location for the winter.
Pineapple Lily (Eucomis bicolor)
Pineapple lily in flower
How about an interesting exclamation point in the garden? The plant resembles a pineapple with its long strap-shaped leaves and 1-2 foot tall upright flower stalk that looks like a chartreuse pineapple fruit. Each tiny floret is edged in purple and there is a tuft of bracts at the top of the flower.
These summer bulbs should be planted in sunny beds or containers in the spring, covered with soil up to the neck. They are carefree, requiring little more than regular watering and biweekly fertilization during the summer.
When frost threatens, the tops should be cut down and the bulbs stored in a frost-free location for the winter.