Illustration
Red Heart
Hibiscus syriacus 'Red Heart'
Red Heart blooms from July through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Red Heart
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 5–9. Expect it to reach about 8 ft tall and 6 ft wide at maturity, in roughly 4 years (a house reading).
Pets
- Not yet checked for pets.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
No toxicity note is on file for Red Heart. That is not a clearance: check its safety for people and pets before planting.
What was checked
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Red Heart
Plant Red Heart in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 7, the middle of its hardy zones 5 to 9, spring means March to May and fall means September or October. Once settled, it blooms from July to September.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 7, the middle of this plant's hardy range, start with zone 7 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Red Heart get?
8 fttall5 ft 7 inan adult6 ftwideSee Red Heart in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Red Heart
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Red Heart about 6 ft apart, center to center, so each plant has room to reach its full width.
Add Red Heart to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Red Heart's height, spread, hardiness zones, sun, water, bloom months and color and trait tags were checked against 9 published sources on October 23, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- conservationgardenpark.jvwcd.govConservation Garden Park (Jordan Valley Water Conservancy District)height, spread, hardiness zones, sun, water and bloom months and color
- colesvillenursery.comColesville Nurseryheight, spread, hardiness zones, sun and bloom months and color
- himanursery.comHima Nurseryheight, spread, sun, water and bloom months and color
- Chicago Botanic Gardenheight, hardiness zones and bloom months and color
- RHSRoyal Horticultural Societysun, water and bloom months and color
- Missouri Botanical Gardensun, water and trait tags
- NC State Extensionbloom months and color and trait tags
- University of Illinois Extensionbloom months and color
- deneweths.comDeneweth's Garden Centersun
How the checking works, and what each standard covers, is on the verified plants page.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.