Summer Bulb Primer: A Practical Guide

Depending on where you garden, summer blooming bulbs can be grown as annuals or perennials—or something in between.

Credit: iStock

Summer blooming bulbs

Summer blooming bulbs

18 of our favourite summer-blooming bulbs for a beautiful season of flowers

Summer bulbs are by nature tender and cannot survive severe winters without protection. Depending on where you garden, summer blooming bulbs can be grown as annuals or perennials—or something in between.

In warmer USDA zones, summer bulbs in the garden will readily come back as perennial performers. In cooler areas, they can be grown as annuals. Gardeners can also choose to store them in a protected area over-winter for growing the following summer. Where winter exposure is an issue, most bulbs grown in containers can be stored over-winter “as is” (right in their pots) in a protected area, with no more watering until it’s time for start-up next season. Or, if preferred, lift and store bulbs as described in the following notes. See www.bulb.com (Summer Flowering Bulbs) for select historical backgrounders and additional gardening notes.

BEGONIA

Pronunciation: Beh-GOn-euh Common name: Begonia or Tuberous Begonia Origin: South America Type of bulb: Tuber Light requirements: Light shade and bright filtered light are best. Too much sun can cause sunburn.

Planting:

Position tuber flat, with the curved/hollow side up, just barely below the soil surface (1/2 inches deep) in well-drained, moist, loamy soil. Plant into the garden once night temperatures remain above 54° F. The tubers can handle some frost thus can be planted out a good 2–3 weeks prior to the last frost in your area. To avoid drying, plant out of wind exposure. Optional: If early blooms are desired, pot up and start indoors up to six weeks ahead of last frost date. Unlike the unsprouted tubers, growing begonia plants are frost sensitive; do not plant out pre-potted plants until all threat of frost is past. In pots, begonias prefer tight quarters and moist conditions.

Watering:

Keep soil moist (once the plants begin growing, try to not let the tubers dry out), apply water at soil line, avoiding the leaves and flowers.

USDA Zones:

Hardy in zones 9–11, lift or protect elsewhere. Where tender: Begonias cannot tolerate frost. In fall, once flowering ceases and before the first frost, bring in begonias for the winter. Let stems fall away, then store. Store “as is” in pots or dug up. After drying a day or two, dug tubers can be stored in layers of vermiculite or sawdust at approximately 40–45° F.
Notes: Begonias typically begin flowering 12–15 weeks after planting. For best results (stronger stems, fewer but more spectacular flowers), pinch off all but 2 to four stems while the plants are young and developing. Begonias are more tempermental than other summer bulbs but well worth the extra effort.

ALOCASIA

Pronunciation: Al-o-KAY-zhi-a Common name: Elephant Ear Origin: Southeast Asia Type of bulb: Tuberous root, evergreen perennial tuberous herb, often sold as a potted vegetative cutting. Light requirements: Sun to partial sun to full shade

Planting:

Plant in rich moist soil once soil warms up, plant 4–6 inches deep, 20 inches apart. One to 12- to 16-inch pot.

Watering:

Frequent watering. This plant loves water: it’s not a problem if pots have no drainage hole; you can even place these, pot and all, right into ponds and water features (submerge pot and position it as you like). Keep evenly moist during spring and summer; allow the soil to dry out slightly during winter.

USDA Zones:

Hardy in zones 9–10, elsewhere lift or store over-winter.

Where Tender:

Treat as an annual or bring indoors over-winter. Best stored dry in the same pot it was grown it. Notes: See Colocasia and Xanthosoma

CALADIUM

Pronunciation: Ca-LAY-dee-yum Common name: Caladium Origin: South America Type of bulb: tuber Light requirements: Full sun (if kept watered) to partial shade to full shade

Planting:

Plant immediately—definitely pot up and start growth early indoors if an option. Do not plant out until soil is warm enough at planting depth. Caladiums must have warm soil (60° F) to get going. Plant in rich moist soil 2–3 inches deep, 6–12 inches apart. Do not plant bare bulb in cool soil. Likes heat—thrives in areas with hot summer season.

Watering:

Water regularly to keep soil moist.

USDA Zones:

Hardy in zones 10–11, elsewhere lift for winter protection

Where Tender:

Treat as an annual or lift after the first frost, let dry and store over-winter indoors. Layer in peat of vermiculite, keep in a warm place close to room temperature.

CANNA

Pronunciation: CAN-ah Common name: Canna, less commonly Indian Shot Origin: South and Central America Type of bulb: Rhizome Light requirements: Full sun to part shade

Planting:

Plant rhizome flat, about 2–3 inches deep. Plant 12–18 inches apart. Plant in the garden when soil temperature reaches 60° F. For a head start, pot up and grow indoors for four weeks prior to the usual last threat of frost in your area. Cannas are excellent container plants.

Watering:

Water regularly, will not tolerate dry conditions. This plant loves water: it’s not a problem if pots have no drainage hole; you can even place these, pot and all, right into ponds and water features (submerge pot and position it as you like).

USDA Zones:

Hardy in zones 7–10, elsewhere lift or protect over-winter . Where tender: After first fall frost has blackened the foliage, or the foliage begins to wither, cut stems back to 4 to 6 inches. Store cannas grown in containers right in their container, as is, with no further watering. Or lift the bulbs: gently dig up rhizome and allow to dry off. Do not wash. Store in slightly moistened sand, vermiculite or peat moss in a cool (40° to 50°F) location. Do not allow to dry out.

COLOCASIA ESCULENTA

Pronunciation: kol-o-KAY-see-ah ES-cu-len-tah Also known as: Elephant Ear, Taro (Dasheen) Origin: Indo-Malayan regions, then spread to Southeast and Eastern Asia, Pacific Islands, Egypt, Africa, Caribbean and America. Type of bulb: Tuberous root, evergreen perennial tuberous herb Light requirements: Just about anywhere: full sun, partial sun, shade, deep shade.

Planting:

Colocasia is a bulb (and is not sold as a potted vegetative cutting). Plant 4” to 6” deep, about 20 inches apart, one to a 12–18-inch pot.

Watering:

Frequent watering. This plant loves water: it’s not a problem if pots have no drainage hole; you can even place these, pot and all, right into ponds and water features (submerge pot and position it as you like).

USDA Zones

Hardy in zones 8–11, elsewhere lift or protect over-winter

Where Tender:

Bring indoors over-winter. Best stored dry in the same pot it was grown in.
Notes: Colocasia, Alocasia and Xanthosoma are related members of the Araceae family, all are edible airoids (featuring edible leaves and roots). Colocasia esculenta and Xanthosoma are the most important of the edible genera of Araceae. Colocasia esculenta, a.k.a. taro, is the root from which the Polynesian food poi (taro paste) is made. When Captain Cook arrived in Hawaii in 1778, taro was a primary diet staple for the population of 300,000.

CROCOSMIA

Pronunciation: Kro-KOZ-mee-a Also known as: Montbretia Origin: South Africa Type of bulb: Corm, bulbous herb Light requirements: Prefers full sun, can handle bright partial shade

Planting:

Plant 4 inches deep, 6 inches apart

Watering:

Though Crocosmia is drought-tolerant, water regularly during periods of growth and blooming.

USDA Zones:

Hardy in zones 6–10, except for ‘Lucifer’ which is often hardy to zone 5 if heavily mulched.

Where Tender:

Before first fall frost, dig and store on a tray in dry peat moss at 40–48°F.
Notes: Pest-resistant. May not bloom until second season. For best flowering, leave corms undisturbed until they become over-crowded (after three or more years), then lift and store over-winter and replant in spring. [pagebreak]

DAHLIA

Pronunciation: DAL-eyuh Common name: Dahlia Origin: Mexico Type of bulb: Tuber Light requirements: Best in full sun, can handle a little shade in warmest areas.

Planting:

Place crown just below or at soil surface level. Set tubers horizontally beneath 4 inches of deeply prepared soil, making sure ‘eyes’ are facing upward. Dahlias can be planted out when soil reaches 50° F. For a head start, pot up early (4–6 weeks prior to last threat of frost) to begin growth indoors. Space 12–24 inches apart, depending on variety, if planted in the garden. Stake taller varieties.

Watering:

Water regularly, keeping soil moist but not soggy.

Growing Tip:

Pinch shoot tips twice to encourage fullness, first after two or three sets of leaves have developed, and again after a few weeks. Cut flowers regularly or deadhead to boost further flower production. The more you cut, the more they bloom.

USDA Zones:

Hardy in zones 8–10, and sometimes 7 with heavy mulch.

Where Tender:

Store in pots or lift bulbs. Be careful not to break or cut root clumps when lifting in the fall. Do not wash. Dry for a day. Store away from drafts at 40–50° F in a paper bag or box filled with peat moss or dry sand.

EUCOMIS

Pronunciation: YOU-ko-mis Common name: Pineapple lily Origin: South Africa Type of bulb: Bulb Light requirements: Full sun (am) or partial shade

Planting:

Plant in rich well-drained soil, wait till season begins to warm up. In a pot, plant just below soil surface, three bulbs to a 12-inch pot. In the ground, space 6–10 inches apart, 3–5 inches deep.

Watering:

Water during growing season, needs plenty of sun and water. Mid- to late-summer: less sun and water required.

USDA Zones:

Hardy in zones 7–10.

Where Tender:

Grow in containers, for winter bring pots in, cease watering and leave bulbs undisturbed.

GLADIOLUS CALLIANTHUS

Pronunciation: glad-ee-OH-lus cal-E-ann-thus Common name: Acidanthera, Peacock Orchid, Abysinnean gladiolus Origin: Ethiopia, Abyssinia Type of bulb: Corm Light requirements: Full sun

Planting:

Plant after threat of frost is past in rich, well-drained soil. Position five inches deep and four to five inches apart. Plant additional bulbs every two weeks or so to extend the bloom season.

Watering:

Keep soil moist but do not over-water.

USDA Zones:

Hardy in zones 7–10, lift or protect elsewhere. Where tender: At summer’s end: lift and store in a protected area at a cool room temperature (60–68° F); or if in pots simply stop watering and bring the pots indoors to store “as is.” Or simply toss out and start anew.

GLADIOLUS NANUS

Pronunciation: Gladi-O-lus NAN-us Also known as: Small flowering gladioli Origin: Nanus Hybrids were developed in the Channel Islands Type of bulb: Corm Light requirements: Full sun

Planting:

As this is a small flowering variety, plant 2–3 inches deep. (Planting depth increases for medium and large flowering gladioli.)

Watering:

Water regularly and amply. Avoid light, frequent watering.

Of Interest:

Nanus glads are smaller overall than garden glads. They also mature earlier, flowering about 50 days from planting—a great choice if you live in an area with a short growing season. Each corm produces 2–3 flower spikes, each 9–14 inches in length. Each flower spike produces up to seven loosely arranged, 1.5–2 inches in diameter, flower buds, with three to five buds open at a time.

USDA Zones:

Hardy in zones 6–10, with heavy mulch sometimes zone 5.

Where Tender:

Harvest corms after foliage dies (before first hard frost). Store dry in mesh bags at 40–48°F.

INCARVILLEA

Pronunciation: in-car-VILL-eh-ah Common name: Hardy Gloxinia, Chinese Trumpet Flower Origin: Turkestan, Tibet, India, China Type of bulb: Fleshy root Light requirements: Full sun to partial shade

Planting:

Plant in rich well-drained soil, amended by humus and sand. Position 12 inches apart with crown one inch below soil surface. Excellent in containers, one fills an 8-inch pot. Protect from winter wet.

Watering:

Keep moist not soggy.

USDA Zones:

Zones 5–9

Where Tender:

Leave in pots over-winter, cease watering, leave undisturbed.

LEUCOCORYNE

Pronunciation: loo-Koh-KOR-ry-nee Common name: Glory of the Sun Origin: Chile Type of bulb: Bulb Light requirements: Full sun

Planting:

Prefer well-drained, even sandy soil. Best in containers—outdoors, plant 15 to 18 bulbs in a 12-inch pot. Space bulbs 2 inches apart, 3 inches below soil surface. This is one to start-up inside (early) to get a jump on the season; place outside after threat of frost is past.

Watering:

Water in season, let dry out and go dormant after foliage dies back.

USDA Zones:

Hardy in zones 8–10.

Where Tender:

Lift and store dry. Notes: Fragrant and deer-resistant. [pagebreak]

ORNITHOGALUM

Pronunciation: or-ni-tho-GAL-um Common name: Star of Bethlehem, Chincherinchees Origin: South Africa Type of bulb: Bulb Light requirements: Full sun to partial shade

Planting:

Plant in well-drained soil once weather has warmed up. Position 6–7 inches apart, and 3–5 inches below soil surface. Excellent container plants, start them up indoors to get a jump on the season.

USDA Zones:

Hardy in zones 9–10

Where Tender:

Lift and store dry.

OXALIS

Pronunciation: ox-AL-is Common names: Wood sorrel, clover, shamrock, good luck plant Origin: Central and South America Type of bulb: Depending on variety: bulb, tuber, rhizome or root stock Light requirements: Full sun to shade, can handle heat and humidity

Planting:

Plant 1–2 inches deep, 2–4 inches apart (closer in pots)

Watering:

Water regularly

USDA Zones:

Hardy in zones 8–10

Where Tender:

Can be brought indoors as a houseplant. Or store in pots.

SPARAXIS

Pronunciation: spah-RAX-sis Also known as: Sparaxis tricolor, as each flower always features three colors Common names: Harlequin flowers or wand flowers Origin: South Africa Type of bulb: Corm Light requirements: Full sun

Planting:

In the garden, plant corms in rich, well-drained soil, 3 inches deep and 3 inches apart. In pots, plant closer together (15 bulbs are perfect for a 12-inch pot).

Watering:

Water routinely through bloom season, then let dry out.

USDA Zones:

Hardy in zones 7–10

Where Tender:

Grow in containers and store “as is” in their pot—sparaxis like to be left undisturbed. If lifted, store at 60–68°F. Notes: This flower is particularly heat tolerant. It excels in containers and as a cut flower.

TIGRIDIA

Pronunciation: ty-GRID-ee-ah Common name: Mexican Shell Flower, Tiger Flower, Origin: Mexico Type of bulb: Corm Light requirements: Full sun

Planting:

Plant 3–4 inches deep and 4–5 inches apart.

Watering:

Water well over the growing season.

USDA Zones:

Hardy in zones 9 and above. In zones 7 and 8, mulch well. In colder zones, treat as tender.

Where Tender:

In colder areas, lift bulbs to story dry, or treat as inexpensive annuals.

XANTHOSOMA

Pronunciation: Zan-tho-ZOH-mah Common name: Elephant Ear or Taro, but more accurately Malanga Origin: Tropical South and Central America, Caribbean Type of bulb: Tuberous root (corm or rhizome), evergreen perennial tuberous herb, often sold as a potted vegetative cutting Light requirements: Light shade to shade

Planting:

Plant in rich moist soil once soil warms up, plant 4–6 inches deep, 20 inches apart. One to a 12–16-inch pot.

Watering:

Takes abundant water and frequent watering. This plant simply loves water: it’s not a problem if pots have no drainage hole; you can even place these, pot and all, right into ponds and water features (submerge pot and position it as you like).

USDA zones:

Variously, per type: hardy in zones 7b to 10. Elsewhere grow as annuals or store indoors over-winter. Best stored dry in the same pot it was grown in.

Where Tender:

Treat as an annual or bring indoors over-winter. Best stored dry in pot.
Notes: Similar to Colocasia and Alocasia.

ZANTEDESCHIA

Pronunciation: zan-teh-DES-kee-ah Common name: Calla lily Type of bulb: Rhizome Origin: South Africa Light requirements: Full sun to partial shade

Planting:

In the garden, plant 4–5 inches deep and 12 inches apart in well-drained soil. In a pot, plant 3 inches deep. Three rhizomes are perfect for a 12 inch pot.

Watering:

Provide regular, plentiful water. Callas must not dry out during their active growing period.

USDA Zones:

Hardy in zones 7–10

Where Tender:

Callas can be started up early indoors, then planted out after threat of frost is past. At seasons end, callas grown in pots, can be brought indoors to continue growing over-winter as houseplants. Take them outdoors again in spring once frosts are past and night temperatures remain over 40° F.