By Natalie Carmolli, Proven Winners® ColorChoice®
Photographs courtesy of Proven Winners ColorChoice
The National Garden Bureau has declared 2021 the Year of the Hardy Hibiscus! While “hibiscus” is both the common name and the botanical genus for a few species of this bountiful bloomer, and more than one is cold hardy, only one is technically called hardy hibiscus. So how can you tell the difference?
Let's start by outlining how the plants in the genus Hibiscus are the same.
Hibiscus Berry Awesome
All are noted for splashy, colorful, trumpet-shaped blooms. They are also all androgynophores, meaning the pistil and stamen are fused, forming that single, showy, reproductive stalk in the flower's center. They all thrive in full sun and are heat tolerant. And they are all called hibiscus. But that's pretty much where the similarities end.
To help better understand naming, allow me to unpack some history. In the late-1700s, Swedish botanist Carl Linnaeus formalized a little thing called binomial nomenclature – the two-name system for living organisms that is still used today. This was important because before that, plants only had common names, so the same plant could have many different names. How could a roving botanist keep them all straight? Now, all plants have two (binomial) names to identify them, the genus and the species.
H. White Chiffon
Hibiscus is a genus of flowering plants in the Malvaceae (Greek for mallow), also known as the mallow family. That's why you might hear them referred to commonly as rose mallow, or swamp mallow.
Although the genus Hibiscus has more than 200 species, we'll focus on the most common. The species is the second part of each name, following the genus, Hibiscus.
Hibiscus rosa-sinensis: Common name tropical hibiscus or Chinese hibiscus.
Hibiscus syriacus: Common name shrub hibiscus (also known as rose of Sharon or althea).
Hibiscus moscheutos and Hibiscus laevis: Common name hardy hibiscus, swamp, or rose mallow.
H. Azurri Blue Satin
With the exception of patio plants, you won't see a Hibiscus rosa-sinensis in an outdoor landscape unless you live in warm, subtropical, and tropical regions of the world (USDA Hardiness Zones 10-11). Native to tropical Asia, this shrub blooms in colors from white to yellow to pink and red. Although the 4-8" flowers only last a day, they bloom continuously all summer. You'll find them planted in the ground where they can reach heights of 15', but will stay under 3' in containers. It's a broadleaf evergreen with green, glossy foliage and can be trained as a standard in containers. Notable cultivars include H. rosa-sinensis 'Beau Vie', 'Bonne Nouvelle’, and 'Madam Dupont'.
H. Bonne Nouvelle
Fun fact: The state flower of Hawaii is the yellow hibiscus. There are seven species of Hibiscus that are native to Hawaii, but the most commonly grown is Hibiscus rosa-sinensis.
Hibiscus syriacus gets its species name from the Latin word for Syria. Remember Carl Linnaeus? Well, he made a mistake on this one. You can't blame him though, he didn't have the internet to check his work, and honestly, he really was making it up as he went along. Linnaeus misidentified this species as being from Syria, when in actuality it is native to China and India. But the name stuck. Shrub hibiscus is most often called rose of Sharon or althea. Due to the fact that it is very cold hardy, this shrub is often referred to as a hardy hibiscus, even though technically, that name is reserved for perennial hibiscus.
H. Lil’ Kim
Blooming late summer to early fall, flowers can measure up to 3" and will last 1-2 days before falling to the ground. Hardy in zones 5-9, these shrubs reach 12' tall and typically grow in an upright, vase-shaped habit. Smaller cultivars include the Lil' Kim® series, which mature at just 3-4' tall. Rose of Sharon blooms from summer to fall and has a broad range of flower colors, ranging from white to pink to purple to true blue. Sometimes known for self-seeding, non-invasive cultivars with little-to-no seed set have gained popularity, such as the Chiffon® series and Satin® series of H. syriacus from Proven Winners® ColorChoice®.
Fun fact: Hibiscus syriacus is also known as the Korean rose, and it is the national flower of South Korea. You can see the flower's five petals, which all have meaning, in the center of its national emblem, the Taegeuk, which represents peace and harmony.
H. Holy Grail
Finally there's hardy hibiscus: Hibiscus moscheutos and Hibiscus laevis. They are native to North America and boast huge, 7-9" flowers in the red-to-white color spectrum. They earn the name hardy, as they will withstand temperatures down to -30°F/-34°C (USDA Hardiness Zone 4). They bloom a bit later than other garden plants, but once they take off, they are capable of adding an inch of growth a day. Like tropical hibiscus, the blooms only last one day, but they are prolific rebloomers. A herbaceous perennial, it will die down to the ground each year, unlike H. syriacus which has a woody structure that remains intact through the winter. These perennials typically grow to about 3-7', but the Proven Winners® Summerific® collection of hardy hibiscus is a more garden-friendly size, maxing out at about 4-5'. Popular cultivars include Summerific® 'Holy Grail' and 'Berry Awesome.'
And there you have it! It may indeed be the year of the hardy hibiscus, but hibiscus is such a beautiful and varied genus, maybe we should just consider it the year of the hibiscus to include all of the species? I think Linnaeus would approve.
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