Quick-Reference: Zone-Based Overwintering Guide
Zone 9-10+: Leave everything in the ground. Mulch lightly after frost. Let plants rest and re-emerge in spring.
Zone 8: Cannas and callas can stay with heavy mulch. Dahlias and glads: consider digging, especially in colder parts of the zone.
Zone 7: Mulching is a gamble. Reliable: dig dahlias and glads. Cannas may survive with very heavy mulch in milder Zone 7.
Zone 6 and colder: Dig everything. Cure properly. Store in cool, dry, dark, frost-free conditions. Replant after soil warms to 60°F in spring.
Bloom Timing and Vase Life at a Glance
Dahlias — Bloom: midsummer to first hard frost | Vase life: 5–8 days | Zone to leave in ground: 9+
Gladiolus — Bloom: ~70–90 days after planting | Vase life: 7–10 days | Zone to leave in ground: 8+ (with mulch)
Cannas — Bloom: midsummer to frost | Vase life: 4–7 days | Zone to leave in ground: 8+ (with mulch)
Calla Lilies — Bloom: summer | Vase life: 10–14 days | Zone to leave in ground: 8–9+ depending on type
Tuberous Begonias — Bloom: summer all season | Vase life: 3–5 days | Zone to leave in ground: 9+
References
University of Minnesota Extension — Dahlias: From Garden to Vase. extension.umn.edu
University of Missouri Extension — Growing Dahlias (G6600). extension.missouri.edu
NC State Extension Gardener Toolbox — Dahlia pinnata. plants.ces.ncsu.edu
Colorado State University Extension — Dahlias, Fact Sheet 7.418. extension.colostate.edu
Iowa State University Extension — Gladiolus for the Home Garden (PM 874). extension.iastate.edu
University of Florida IFAS Extension — Gladiolus Production. edis.ifas.ufl.edu
University of Illinois Extension — Canna Lily in the Garden. web.extension.illinois.edu
Michigan State University Extension — Digging and Storing Tender Bulbs. canr.msu.edu
University of Vermont Extension — Storing Tender Bulbs Over Winter. uvm.edu
USDA Plant Hardiness Zone Map (2023). planthardiness.ars.usda.gov
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