How to Plant Summer Bulbs (Dahlias, Lilies, Gladiolus)
Summer bulbs -- dahlias, true lilies, gladiolus, cannas, and similar -- are planted in spring after frost danger has passed and bloom from midsummer through fall. Unlike spring bulbs, most summer bulbs originate in tropical or subtropical regions and cannot survive winters in zones 6 and colder.
Summer bulbs — dahlias, true lilies, gladiolus, cannas, and similar — are planted in spring after frost danger has passed and bloom from midsummer through fall. Unlike spring bulbs, most summer bulbs originate in tropical or subtropical regions and cannot survive winters in zones 6 and colder without being dug and stored.
The exception is Oriental and Asiatic lilies (Lilium spp.), which are fully hardy to zone 4 and can be left in the ground year-round.
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Dahlias (Dahlia spp.)
Planting time: After last frost, soil temperature minimum 60°F Planting depth: 4–6 inches (measuring to the tuber, not the eye) Spacing: 18–24 inches (dinner-plate types: 24–36 inches) Zones (overwintering): 8–10 in-ground; dig and store in zones 7 and colder
Per Penn State Extension, dahlias are planted with the tuber lying on its side with the growth eye (the small bud at the neck of the tuber) oriented upward or to the side — not straight down. If you cannot identify the eye, orient the neck (thin connector to the main tuber mass) upward.
Staking before planting: Per NC State Extension, place your stake in the planting hole before placing the tuber to avoid spearing the tuber when staking later. Dinner-plate dahlias need a stake of at least 5 feet; medium types need 3–4 feet.
Do not water until shoots appear (approximately 2–3 weeks after planting at optimal soil temperature). Per Penn State, watering before shoot emergence keeps the soil saturated and invites rot. Once shoots emerge, water regularly and deeply.
Pinching: Per Penn State, pinch out the growing tip when dahlia plants are 12–16 inches tall, leaving 3–4 sets of leaves below. This forces side branching and produces more but smaller blooms per plant. Skip pinching for fewer, larger exhibition-type flowers.
Storing Dahlia Tubers
Per Penn State, in zones 7 and colder, dahlia tubers must be dug before hard frost. Wait until the first light frost kills the foliage (this signals the tuber to harden), then cut the stem 2–4 inches above the tuber clump. Shake off loose soil. Allow to air-dry for 1–2 days, then pack in barely moist peat moss or sawdust in a ventilated box. Store at 40–50°F. Do not allow to freeze or to dry completely.
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