Plant crocosmia corms in spring after the danger of frost has passed, once the soil warms, about when you plant dahlias (UF/IFAS, NC State). Set them 3 to 5 inches deep and 6 to 8 inches apart (UF/IFAS) in full sun, with afternoon shade in hot climates (NC State). Crocosmia is hardy in about zones 6 to 9 or 10 (NC State, UF/IFAS); in colder areas, dig and store the corms each fall. Montbretia, the common hybrid, spreads and is invasive along the California coast (Cal-IPC).
Crocosmia is a summer-blooming perennial in the iris family, native to South Africa (NC State), with arching sprays of red, orange or yellow flowers that hummingbirds, bees and butterflies visit (NC State). It grows from corms, and some kinds also spread by rhizomes (NC State). Plants are usually 2 to 3 feet tall (NC State), and the RHS says cultivars range from 2 feet to over 6 feet. The popular 'Lucifer' has scarlet flowers on 4 to 5 foot stalks (UF/IFAS).
When to plant crocosmia by region
| Area | When to plant crocosmia corms |
|---|---|
| Zones 6 to 9 | Plant corms in spring after the danger of frost has passed, at the same time as dahlias (UF/IFAS, NC State). Corms can stay in the ground over winter (NC State) |
| Zone 5 and colder | Plant after your last frost once the soil warms, then dig, clean and store the corms in fall (NC State). A few cultivars such as 'Emberglow' are rated to zone 5 (UF/IFAS) |
| Mild-winter West (e.g., Sacramento) | UC Master Gardeners plant crocosmia in February and say it needs no winter protection |
| Coastal California and the Bay Area | Think twice about montbretia (C. × crocosmiiflora), which Cal-IPC lists as invasive there |
Our planting calendar shows your average last spring frost. Plant crocosmia after that date, alongside dahlias and gladiolus (UF/IFAS, GardenPal note).
How deep and far apart to plant crocosmia
| Crocosmia corms | |
|---|---|
| Depth | 3 to 5 in (UF/IFAS); NC State plants 5 in deep; the RHS plants at about three times the corm's depth |
| Spacing | 6 to 8 in apart (UF/IFAS); 4 to 8 in apart (RHS) |
| Which way up | Pointed end up, roots down (RHS) |
| Grouping | Plant about a dozen corms of one kind together for the best effect (UF/IFAS) |
| Light | Full sun; some afternoon shade in hot climates makes flowers last longer (NC State, UF/IFAS) |
| Soil | Moist, well-drained, slightly acidic soil of average fertility (UF/IFAS); avoid waterlogged or very dry spots (RHS) |
| Shelter | Protect from hot, dry wind (NC State); tall kinds may need support (RHS) |
Watering and feeding
- Keep the soil evenly moist. NC State says crocosmia does not like to dry out.
- Mulch. The RHS mulches with compost in autumn or spring to keep the soil from drying, which can reduce flowering.
- Go light on fertilizer in the ground. UF/IFAS grows them in soil of average fertility. In containers, the RHS uses a high-potassium liquid feed every two weeks in summer.
- After bloom: cut flower stems back to the leaves, and leave the foliage until it dies back naturally so it can feed the corms (NC State).
Crocosmia in containers
NC State calls crocosmia a good "thriller" for container plantings, as long as the pot drains well. The RHS suggests compact cultivars for large pots, which is also a good way to stop a spreading kind from taking over. Potted corms are less protected from cold than corms in the ground, so move pots to a sheltered spot or store the corms in cold areas (GardenPal note).
Overwintering and dividing
- Hardy zones: NC State lists zones 6a to 9b, and UF/IFAS zones 6 to 10. NC State says crocosmia is injured below 28°F. In cold sites, the RHS adds a thick mulch.
- Colder zones: dig the corms in fall, clean them, and store them cool and dry; NC State uses peat or vermiculite at 35 to 41°F. Replant in spring after frost (NC State).
- Dividing: lift and divide crowded clumps in early spring every 3 to 4 years (NC State), or every 3 to 5 years (RHS).
Pests and spreading
UF/IFAS says few pests or diseases trouble crocosmia, not even slugs. NC State notes spider mites, which a strong spray from the hose helps dislodge. The bigger issue is spread. The RHS says C. × crocosmiiflora (montbretia) tends to spread, though most cultivars form slowly expanding clumps. UF/IFAS adds that montbretia, C. masoniorum and some C. pottsii forms spread readily. Cal-IPC lists montbretia as an invasive plant along the California coast and in the San Francisco Bay region, where it forms dense patches that crowd out native plants. If you garden near wild land, choose a clump-forming cultivar or grow it in a pot (GardenPal suggestion).
Crocosmia around the vegetable garden
Crocosmia blooms from midsummer into fall, when many other flowers are tired (UF/IFAS), so it keeps hummingbirds and bees visiting a vegetable plot late in the season (GardenPal suggestion). UF/IFAS grows it behind short dahlias. Plant it at the back or north side of a bed so tall stems don't shade crops. For more summer bulbs planted after frost, see when to plant gladiolus, when to plant dahlias and when to plant cannas.
Frequently asked questions
When should I plant crocosmia bulbs?
In spring after the danger of frost has passed, about when you plant dahlias (UF/IFAS). Let the soil warm up first (NC State).
How deep do you plant crocosmia corms?
3 to 5 inches deep and 6 to 8 inches apart (UF/IFAS), pointed end up (RHS).
Does crocosmia come back every year?
Yes, in about zones 6 to 9 or 10 (NC State, UF/IFAS). In colder areas, dig the corms in fall and store them cool and dry.
Will crocosmia bloom the first year?
Often. The RHS says they usually flower the first year, though UF/IFAS warns some may wait until the following summer.
Is crocosmia invasive?
Montbretia (C. × crocosmiiflora) spreads readily, and Cal-IPC lists it as invasive along the California coast and in the San Francisco Bay region.
Does crocosmia attract hummingbirds?
Yes. NC State says hummingbirds, bees and butterflies are drawn to the flowers.
Enter your frost dates to see your last spring frost and time your crocosmia planting.
Open itSources
- Virginia Cooperative Extension, "Companion Planting in Gardening" (SPES-620P)
- University of Maryland Extension, "Vegetable Succession and Companion Planting"
- Oregon State University Extension, "Companion Planting"
- Penn State Extension, "Herbs Make Good Plant Partners and Companions"
- University of Minnesota Extension, "Planting the vegetable garden"
- USDA Plant Hardiness Zone Map
- NOAA NCEI U.S. Climate Normals (frost/freeze data)
- NC State Extension Gardener Plant Toolbox, "Crocosmia"
- UF/IFAS Extension Nassau County, "Fact sheet: Crocosmia"
- Royal Horticultural Society, "How to grow crocosmias"
- California Invasive Plant Council, "Crocosmia × crocosmiiflora profile"
- UC Master Gardeners of Sacramento County, "Sacramento bulb planting schedule"
Pairings are summarized in our own words from extension-service guidance. Research support for many companion effects is limited, so treat them as good habits, not guarantees.