Everything you need to know about Summer flowering bulbs

In any gardener’s inventory of beauty, the group of plants known collectively as “summer-flowering bulbs” may be the most unknown and under-utilised of them all.

A collection of standout summer bulbs; By Cort Sinnes In any gardener’s inventory of beauty, the group of plants known collectively as “summer-flowering bulbs” may be the most unknown and under-utilised of them all.

Every gardener has at least a passing awareness of spring-flowering bulbs–the tulips, daffodils, hyacinths, and crocuses of the world–but ask even an accomplished gardener to list more than three summer-flowering bulbs and you’ll probably hear a lot of stammering and stuttering. Too bad. Comprised mainly of exotic species from foreign lands, summer-flowering bulbs can lend impressive amounts of colour and beauty to the summer and late-summer landscape for very little effort or expense. And, if you choose them right, many have the added benefit of becoming permanent residents in your garden–not only returning every summer, but actually multiplying in the process.

In the following section, we’ll introduce you to some of the summer bulbs we consider “must-haves.” Be aware, however, there are many other worthy members of this clan–just ask your local nursery or garden centre what their list of “must-haves” would be for your area, and we can just about guarantee that you won’t be disappointed.


This cross between Amaryllis belladonna and Crinum moorei would benefit from a catchy common name. (Its Latin name, x Amarcrinum spp., certainly doesn’t help.) This beauty blooms from August to the first fall frost with clusters of 10 to 16 soft-pink, trumpet-shaped blooms atop each sturdy 24- to 30- inch stem. Excellent as a cut flower, it is both deer- and rodent-proof, and fragrant!

Dark green, strap-like foliage is evergreen in Zones 8 through 10. Plant in full sun to partial shade in a rich, very well-drained soil. It’s not particularly fussy about water or fertilizer, and is very disease-resistant. In zones colder than Zone 7, plant this beauty in containers; allow soil to dry completely late in the fall, and store in a cool, dark, dry location for the winter, pot and all.


Native to South America, caladiums (Caladium bicolour) are valued for their splashy, colourful foliage in shades of green, pink, red, and white, and their willingness to grow in shaded locations. Most caladium varieties are 12 to 15 inches tall. These lovely plants are now being bred with thicker leaves so they can withstand sun. Caladiums like consistently moist soil (like a squeezed-out sponge). Drip or “ooze” irrigation works well for this.

Plant caladiums in a rich loam soil, in a shaded to full sun location. The one thing caladiums cannot abide is cold soil; don’t plant the tubers until the soil has warmed to 60 degrees F. Many gardeners get a head start on the season by planting their caladium tubers in pots in a warm indoor location. Caladiums like monthly applications of a liquid fertiliser during the growing season. Plant tubers 1 inch deep, about 8 inches apart.

In Zones 10 and 11, caladiums can be left in the ground all year; in colder climates, dig caladium tubers in the fall and store them in a cool, dry place for the winter.

Look for some of the following caladium standouts: ‘Florida Cardinal’, with burgundy leaves outlined in green, is a member of the “Florida” series, known for tolerating direct, hot sun; ‘Jubilee’, one of the tallest, has extra-large leaves with ivory centres, large red spots, and a dark grey-green border. ‘White Christmas’, with its snow-white centre and wide pine-green midribs, is a standout, particularly in the evening when it fairly glows.


Long known by some as the funeral lily, callas (Zantedeschia spp.) have a strikingly elegant flower. The plants can grow up to 3 feet tall and about a foot across with flowers in shades of pink, red, orange, yellow, or white that can be several inches tall. All callas have attractive leaves that are dark green and arrow-shaped, but some have the benefit of being brightly spotted in white.

Give callas a spot that gets sun all day and has rich, moist soil. Don’t let the soil dry out or your plants may suffer. Because of their relatively small size, they are wonderful either in the garden or in containers.

Look for Zantedeschia albomaculata, with white flowers; Z. rehmannii, with pink flowers; or the striking Z. ‘Black Forest’ with dark, maroon coloured blossoms.


If you think you don’t like cannas (Canna spp.), you might think again. Yes, they are big, bold, and a little garish, but hybridizing efforts have tamed cannas considerably, making some of them into model garden citizens.

Today’s cannas range in height from demure 2-foot-tall varieties to others which reach an amazing 8 feet. With their lush, banana-like foliage (many of the newer varieties have beautiful variegated foliage), and exotic-looking blossoms, cannas naturally draw attention to themselves.

Cannas are native to the tropics, so they like warm weather, rich soil, ample moisture (they’ll even grow in pots submerged in ponds and pools), and a full-sun to light-shade location.

If you garden in an area where the soil does not freeze, canna rhizomes may be left in the ground all year (they’ll probably even spread). In colder regions, dig the rhizomes and store over winter in a cool, dry place.

Some cultivars to look for include ‘Black Knight’, a 4-foot-tall canna with almost black leaves and deep scarlet flowers; ‘Pretoria’ (sometimes sold as ‘Bengal Tiger’) has large, intricately variegated leaves and orange flowers, but only grows to a height of 2 1/2 feet; ‘Rose Futurity’ makes a splash with its burgundy foliage and huge coral flowers; it reaches 3 feet in height.


This is a wonderful, easy-to-grow corm originally from South Africa. Crocosmia (Crocosmia spp.), which is also known as montbretia or sword lily, has attractive, sword-like foliage, a little like a gladiolus. Its flowers are borne on thin, stiff, 24- to 36-inch arching stems (perfect for flower arranging), with up to 50 tubular blooms on each stem, in shades of yellow and orange. Amazingly pest- and disease-resistant, crocosmia blooms in late summer when few other flowers are in bloom. Corms can be left in the ground, all year in Zones 6 through 10, with the exception of the variety ‘Lucifer’, which is hardy to Zone 5.

In colder climates, lift crocosmia corms in the fall and store through the winter in a warm, dry place. Where they can be left in the ground, expect crocosmia to multiply over the years; in fact, crocosmia is so long-lived that it occasionally can be found in gardens surrounding old houses even after the house has crumbled away.

Plant crocosmia in full sun, preferably in a very well-drained sandy loam soil, about 2 inches deep and 3 inches apart. This plant looks best arranged in natural drifts instead of straight lines. Crocosmia does best if the soil is kept evenly moist throughout the growing season.

Named varieties to look for include: ‘Constance’, with bright orange flowers and buttercup yellow centres; ‘Lucifer’, the hardiest of all crocosmia, with deep, orange-red flowers borne on dark bronze stems; and ‘Polo’, with its brilliant reddish-orange flowers.


Dahlias are a little like cannas in that some gardeners think they don’t like them. However, dahlias (Dahlia spp.) have changed. Sure, you can still buy dahlia varieties which produce monstrously huge flowers, but now there are hybrids in almost every color (except true blue), height (from under 2 feet to over 6 feet), and flower form (from small, tight pompons to spiky “cactus – flowered” varieties, to the old-fashioned, huge “dinner plate” dahlias). Types with smaller blossoms make excellent, long-lasting cut flowers.

Dahlias are immensely satisfying to grow: They are practically pest- and disease-free, they bloom and bloom and bloom–right up to the first killing frost in fall–and require little care.

Plant dahlias in a full-sun to partially shaded location, in a good loam soil with excellent drainage. If you garden in a mild climate (USDA Zones 8 through 10), you can leave tubers in the soil year round. Some gardeners in Zone 7 have succeeded in overwintering them by adding an extra-thick layer of mulch over the top of the bed. In cold winter regions, dig the tubers in the fall and store in a cool, dry location.

For the record, you may want to use a felt-tip marking pen and write the name of the variety right on the dahlia tuber after digging but before storing. This saves a lot of confusion come spring.

To plant dahlias, dig a hole about 1 foot deep and about as wide for each tuber. Space large dahlias 4 to 5 feet apart and put smaller ones 1 to 2 feet apart. Throw a handful of low-nitrogen fertiliser (such as 2-10-20) in the bottom of each hole and mix into the soil.

To aid in drainage and to make the tubers easier to dig up in the fall, add a layer of sand or well-rotted compost over the top of the fertiliser. Lay the dahlia tuber on its side in the hole to check for depth. Make sure the “eyes” (like the eyes on a potato) are pointing up. The top of the tuber should be about 6 inches below the soil surface.

When planting tall dahlias, pound a 5-foot stake into the soil about 2 inches from the tuber. This will prevent you from accidentally driving a stake through the tuber after it has been covered with soil. Cover the tuber with soil and water thoroughly.

Some varieties to look for include: ‘Bishop of Llandoff’, a 3-foot-tall dahlia, with striking dark mahogany foliage and anemone-type, garnet- red flowers; ‘Happy Caroline’, a 2-foot-tall variety, with cheery pink pompon blossoms excellent as cut flowers; and ‘Park Princess’, with pink, semi-cactus type blooms on 3-foot-tall plants.


Definitely qualifying as “exotic,” any of the plants known as gingers is bound to earn you extra credit as an extraordinary gardener. As a group, they have large, lance-shaped leaves and truly other – worldly, long-lasting, pinecone-like flowers. Talk about a focal point!

Plant gingers in a rich garden loam, in full sun or partial shade. Keep soil evenly moist (like a squeezed-out sponge), and fertilize monthly during the growing season with a liquid fertilizer. In all but Zones 10 and 11, rhizomes must be lifted and stored in a cool, dry place for the winter.

Look for the following varieties: Curcuma alismatifolia, with long, dark-green leaves and bright pink flowers resembling a small, double tulip. C. roscoena, also known as the ‘Jewel of Burma’, has large orange flowers, looking for all the world like a large, open pinecone, and C. zedoaria, where each leaf has a 1-inch red stripe down the centre and maroon, purple, and green flowers on stems to 3 feet tall.

Gloriosa lilies

Native to tropical Africa and Asia, this is one of the only summer-flowering bulbs that qualifies as a vine. Gloriosa lily (Gloriosa spp.) stems, which can be 18 to 72 inches long, cling to arbors or trellises with the aid of tendrils at their leaf tips. The exotic-looking flowers have reflexed orange and yellow petals (meaning they turn back), revealing very long pistils and stamens. These beauties remind some gardeners of brilliant butterflies.

Plant gloriosa lilies where their roots can be shaded, but where their foliage and flowers can reach for the sun. They prefer a rich, well-drained loam. Keep soil evenly moist (like a squeezed-out sponge), and fertilize monthly with a liquid fertilizer during the growing season. Each tuber should be planted about 4 inches deep and 10 inches apart.

Look for the following varieties: Gloriosa ‘Lutea’, with glowing yellow-orange flowers, and G. ‘Rothschildiana’ with yellow-edged, brilliant red flowers.


By far the most common of all summer bulbs, the lily (Lilium spp.) has earned its place in the garden. These plants range from colourful Asiatic types to giant trumpet lilies and the elegant Orientals. They grow anywhere from 2 to 6 feet tall, and the hardiest species grow in Zones 3 to 9.

Lilies like a spot that gets full sun and has moist, but well-drained soil. Too much moisture will cause the bulbs to rot. Smaller lilies work well in containers; plant the taller types in the garden. If you use lilies as a cut flower, try to leave as much foliage on the plant as you can. Like other bulbs, the lily needs its leaves to produce energy for next year’s blooms.

A few of our favourites include: ‘Le Reve’, an Oriental with reddish-purple flowers with maroon spots; L. regale, the intensely fragrant regal lily which grows to 6 feet; L. ‘Connecticut King’, a bright yellow Asiatic; and L. martagon, the turkscap lily, with reflexed pinkish flowers.


Known also as shamrock or wood sorrel, many people confuse these non-invasive natives of South Africa and South America with the invasive, weed-like clovers (with more than 500 species of Oxalis, some are, indeed, noxious weeds). Selected oxalis varieties make wonderful garden plants, with well-behaved mounds of plants with three or four leaves, and flowers in shades of pink, lavender, rose, yellow, and white.

Plant oxalis about 1 inch deep, 2 to 6 inches apart, in almost any type of garden soil as long as it is well-drained. A good choice for partially shaded locations, oxalis will also perform admirably in full sun, even in hot, humid climates. Oxalis will need some water during the growing season, but little or no fertiliser. As a group, these plants are remarkably pest- and disease-free.

A few favourites: The hardy Oxalis adenophylla, (Zones 6 to 10); O. tetraphylla is known as the “lucky clover” and is grown more for its foliage than its rose-red flowers. O. tetraphylla ‘Alba’ has a distinctive white triangle on the leaves.


Summer-blooming tuberoses (Polianthes tuberosa) are known for their waxy, single or double white flowers–most of all for their legendary fragrance, which some describe as a combination of orange blossom and hyacinth. Truly, their perfume is heady, and one or two cut flowers will scent an entire room. Foliage reaches about 1 foot in height; clusters of flowers are borne above the foliage on 18- to 36-inch tall stiff stems, great for flower arranging.

Tuberoses are native to Mexico and consequently they like a long, warm growing season–at least four months long. Do not plant the tubers until the soil is thoroughly warm and air temperatures are above 60 degrees F during the night. In all but the mildest climates, most gardeners get a jump on the warm weather by starting them indoors about six weeks before outdoor conditions are sufficiently warm.

In mild climates, plant tuberoses in full sun; in areas with hot summers, a semi-shaded spot is preferred. For best results, plant 1 to 2 inches deep, 6 inches apart, in a rich, well-drained, loamy soil. Keep soil on the moist side (about as damp as a wrung-out sponge), but not overly moist. In all but Zones 8 through 10 (where tuberoses can be left in the ground), lift the tubers and store in a warm, dry location through the winter. Some gardeners in Zone 7 have had luck overwintering tuberoses in the garden by adding an extra-thick layer of winter mulch.

Varieties of tuberose to look for include ‘Single Mexican’, which, as the name suggests, bears single waxy flowers–as many as 20 or more per stem, and the well-known ‘The Pearl’, with its double, long-lasting, rose-like, creamy-white flowers. Both varieties bear the signature tuberose perfume.

Leave a comment

Your email address will not be published. Required fields are marked *