Hardy hibiscus (Hibiscus moscheutos), also called rose mallow, is a shrub-like perennial with saucer-shaped flowers 6 to 12 inches across. NC State Extension gives its height as 18 inches to 8 feet depending on variety, and says it tolerates wet sites, creek edges and poorly drained areas.
Hardy Hibiscus (Rose Mallow) at a glance
| Type | Flower |
|---|---|
| Season | Perennial |
| Sun | Full sun to partial shade |
| Plant spacing | 60 in |
| Row spacing | 60 in |
| Per square foot | 1 |
| Seed depth | At surface |
| Days to maturity | Late to emerge in spring; blooms summer to frost |
| How to start | Plant hardy hibiscus in full sun to partial shade in moist, rich soil, be patient because it is very late to emerge in spring, and knock Japanese beetles into soapy water |
| Water | 1 in per week |
These are the same numbers our plant spacing, square foot and harvest date calculators use. See every crop in the plant database.
When to plant hardy hibiscus
Illinois Extension says it is “very late to emerge in the spring.” NC State’s Lee County Extension says stems start emerging in April and flowers arrive around June in North Carolina, and that bloom lasts to frost with new flowers for 4 to 6 weeks on each plant. NC State lists seed or division for propagation. Illinois lists hardiness as USDA zones 4 to 9; NC State’s newsletter says zones 5 to 9. Check your growing zone.
How to plant hardy hibiscus
- Sun and soil: full sun to partial shade. Choose moist soil high in organic matter; the plant tolerates wetlands and poorly drained areas but also tolerates drier soil, though it may be smaller and less lush.
- Give it room. NC State Extension reports a mature size of 5 to 7 feet tall and 7 to 10 feet wide in North Carolina, though cultivars vary widely; check the label. See the plant spacing calculator.
- Winter: Illinois says it may need winter mulch in colder areas.
Caring for hardy hibiscus
Keep soil consistently moist for the largest flowers. See the garden watering calculator. Illinois describes it as a heavy feeder; fertilize in spring. It is long-lived and needs no division for many years.
Japanese beetles are the major pest (NC State): knock them into a bucket of soapy water. The native hibiscus sawfly can skeletonize leaves for a couple of weeks; deer may nibble when hungry. See the pest identifier.
Companion plants
| Grow nearby | A specimen, a water-garden edge or a perennial border |
|---|---|
| Keep apart | Dry, hot spots that stunt the plant, and cutting back before April in cold areas, because it emerges very late |
Sources do not list specific companion plants. Check other pairings with the companion plant finder.
Common problems
| Problem | What you see | What to do |
|---|---|---|
| Nothing growing in spring | No sprouts by late spring | Normal: hardy hibiscus is very late to emerge (Illinois). Stems begin in April in North Carolina; mark the spot so you do not dig it up. |
| Beetle-chewed leaves | Lace-like holes in leaves and flowers | Japanese beetles are the major pest. Knock them into a bucket of soapy water. |
| Skeletonized leaves | Widespread skeletonizing for a couple of weeks | Native hibiscus sawfly larvae, which look like caterpillars (NC State). The damage lasts only a couple of weeks. |
Not sure what you are looking at? The plant problem identifier ranks likely causes from the symptoms you see.
When and how to harvest
Hardy hibiscus is grown for its flowers, which are mostly open in the morning. Propagate by division or seed.
Plan your hardy hibiscus
- Plant spacing calculator: how many plants fit your bed
- Planting calendar: sowing and transplant dates for your frost dates
- Frost dates by ZIP code: your last spring and first fall frost
- Harvest date calculator: when your crop will be ready
Frequently asked questions
How far apart should I plant hardy hibiscus plants?
Space hardy hibiscus plants 60 inches apart in rows 60 inches apart. In a square foot garden, plant 1 per square foot.
How deep do I plant hardy hibiscus plant?
Plant at the same depth as the nursery pot in moist, organic-rich soil.
How long do hardy hibiscus plants take to grow?
Stems emerge around April and flowers from June to frost in North Carolina; Illinois notes it is very late to emerge.
How much water do hardy hibiscus plants need?
About 1 inch of water a week, from rain and watering combined. Keep soil consistently moist; it tolerates drought and wet sites but flowers best with even moisture.
Why hasn’t my hardy hibiscus come up?
It is very late to emerge in spring (Illinois Extension); stems start around April in North Carolina.
How big are the flowers?
6 to 12 inches across (NC State), up to 12 inches with even moisture.
What eats hibiscus leaves?
Japanese beetles are the major pest, and the native hibiscus sawfly can skeletonize leaves for a couple of weeks.