Wednesday, August 23, 2017

Hardy Hibiscus



Hibiscus moscheutos takes its own sweet time emerging from the ground in the spring, but when its enormous, satiny blooms finally open in late summer, it puts on quite the show. In the production of these impressive blooms, I have no doubt that summer is complicit. There is no way summer is going to fade demurely into fall. She is determined to go out with a flourish.

Hibiscus moscheutos has a bevy common names; Rose Mallows, Swamp Mallow, Dinner-plate Hibiscus and Hardy Hibiscus. Though they look quite tropical, the species forms of Hibiscus moscheutos are a cold-hardy woodland plant native to U.S. and Canada. Here in Ontario, Hibiscus moscheutos are considered to be a native plant at risk, but a few colonies with pale pink flowers can still be found growing in the shoreline marshes of the Carolinian and Great Lakes- St. Lawrence forest regions.

Like other herbaceous perennials, Hibiscus moscheutos has foliage and woody stems that die back to the ground in winter. They are tall, vase-shaped plants that reach an average of two to six feet in height and approximately three feet in width. Though these plants will perform best in areas with long, hot summers, but they are hardy to zones 4 or 5.

The blooms of Hibiscus moscheutos consist of five flat overlapping petals and can reach up to 10-12 inches across. As well as bi-colored flowers, they come in solid shades of lavender, rose, peach, red and white.

Each individual flower opens for just one or two days and fades as soon as it is pollinated. While the flowers are short-lived, a single plant can be covered in flower buds insuring a succession of blooms from mid-summer right up until the first frosts of fall.

A look at the foliage above and below.


Many of the cultivars have matt, medium-green foliage, but there are a few varieties have bronze or eggplant colored foliage. As Hibiscus moscheutos bloom late in the gardening season, cultivars that have this dark attractive foliage come with a definite bonus.

Hibiscus moscheutos do have one drawback– like Rose of Sharon (Hibiscus syriacus) they can self-sow and become a bit weedy. And the seedlings may not be the same color as the parent. Deadheading spent flowers is one way to limit this problem.


How to Plant


Nurseries tend to showcase hardy Hibiscus in late summer when they are in full flower, but planting them that late in the season doesn't really give Hibiscus moscheutos enough time to get properly established before winter. It is much better to take a few notes now and hold off making your purchase until next spring.

Hibiscus moscheutos do best in moist, rich organic soil. They will however tolerate average garden soil provided that the soil is not allowed to dry out completely. Plant them in full sun in an area that has good air circulation, but is protected from the wind.

When you do your planting, it's a good idea to add some organic material, such as compost, to your soil. A top dressing of bark mulch will help preserve soil moisture and keep your new plant happy. Even so, deep and consistent watering is especially important during that first season.

Ongoing Care


Hibiscus moscheutos are slow to emerge in the spring, and depending on your garden's zone, may not appear until sometime in June.
A layer of compost applied each spring will help encourage that fresh new growth.

Spent flowers can look a bit bedraggled, so deadhead them to keep your hibiscus looking tidy.

Every fall cut back the stems to three or four inches above the ground. In northern garden zones, it's a good idea to protect the crown of the plant with some bark or straw mulch.


Pests and Problems


• Japanese Beetles can be an annoying problem, and if left unchecked, can cause extensive damage to the foliage and flowers. The easiest solution is to knock any Japanese Beetles you find into a large jar or bucket filled with soapy water.

• Sawflies, whiteflies and aphids can also be occasional pests.

• Leaf scorch can occur if the soil is allowed to dry out completely. 

• Hibiscus moscheutos also has some susceptibility to leaf blight, rust and canker.

A few of the Cultivars Available



White Hibiscus x 'Blue River II' has large white flowers and green foliage. Full sun. Height: 120-150 cm (47-59 inches), Spread: 75-90 cm (29-35 inches). USDA zones: 4-9.


Hibiscus 'Plum Crazy' has rose-purple flowers with a dark purple eye. The foliage also has a hint of purple. Full sun. Height: 90-105 cm (35-41 inches), Spread: 75-90 cm (29-35 inches). USDA zones: 4-9.


Hibiscus 'Kopper King' has white flowers with a red eye. The foliage is a deep copper color. Mulch in late fall in zones 4 and 5 for better winter hardiness. Full sun. Height: 90-105 cm (35-41 inches), Spread: 75-90 cm (29-35 inches). USDA zones: 4-9.

Hibiscus 'Kopper King' 


Hibiscus 'Sweet Caroline' has bright pink flowers with darker pink veining and a dark red eye. Full sun. Height: 90-120 cm (36-48 inches), Spread: 75-90 cm (29-35 inches). USDA zones: 5-9.


Dwarf Hibiscus 'Luna Red' is a compact variety that has bright green foliage and large red flowers. Plant it in rich, moist garden soil. Mulch in late fall in zones 4 and 5 for better winter hardiness. Full sun.  Height: 60-90 cm (23-35 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 5-9.

Dwarf Hibiscus 'Luna Rose' is similar to 'Luna Red, but has pink flowers.

Dwarf Hibiscus 'Luna White' is yet another compact variety that has white flowers with a large red eye.

Hibiscus 'Kopper King' at the Toronto Botanical Gardens.

Hibiscus 'Kopper King' at the Lucy Maud Montgomery Garden in Norval, Ontario.

There is no denying that these are magnificent flowers make a dramatic end to the summer season.

Up next is a post on the redesign of the Lucy Maud Montgomery Garden in Norval, ON. 
(Lucy Maud was the author of the Anne of Green Gables series of books.)

11 comments:

  1. These are beautiful, Jennifer.
    My white hibiscus bloomed today, and the enormous red one that I have will probably bloom in about 2-3 weeks (it is a very late summer bloomer). Their increase in size of the plants from year to year, never ceases to amaze me. I do wish that they would last a bit longer though.
    Have a wonderful week!!

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    1. It is too bad that they don't bloom a bit longer. Late summer/early fall always seems to be such a short period of time, doesn't it?

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  2. I have several Rose of Sharons. Are they the same thing? If not, what do you recommend for them in the fall? Should I cut them back as low as you said above? Also, I have one that is a pink and white variegated flower which is so beautiful but the plant has grown straight up like a rocket so that you can barely see the blooms. I really don't like the shape. Is there anything I can do to make it bush out? Thank you. I love the ones you have pictured.

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    1. Hibiscus moscheutos are a perennial plant. A Rose of Sharon (Hibiscus syriacus) are a deciduous shrub (not the same thing at all). There is no need to cut it to just above the ground in the fall.
      A Rose of Sharon generally has a fairly upright vase-like shape. It flowers on new growth. If you want to prune it, you can do so in the late fall or first thing in the early spring before the leaf buds open. Begin by removing any dead or damaged branches. You also might want to thin out a few of the inner branches that hide the flowers. Then stand back and take a look to determine what else to prune to address the overall shape. Top upright growth can be cut back to encourage side branches. Hopefully this will give you a shape that you like better.
      It's a bit dry, but here's a Youtube video on pruning a Rose of Sharon: https://www.youtube.com/watch?v=yl_QE_UBCpI
      Hope that helps Karen!

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  3. I have only one hibiscus, a 'Cajun Blue,' that is not hardy so I pampered it indoors all winter. While the foliage is healthy it failed to bloom this summer. I am so disappointed especially when I see your beauties, Jennifer. Maybe I should look for a more hardy cultivar. P. x

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    1. 'Cajun Blue' is very pretty, so I can see why you pamper it Pam. (For other readers Hibiscus rosa-sinensis 'Cajun Blue' is a tropical hibiscus that is usually sold as a houseplant).
      I am no expert on growing tropical hibiscus, but it seem to me that all that green growth is a good sign of the plants overall health. I have a feeling your hibiscus will begin to flower as temperatures cool a bit and summer wanes.

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    2. Thanks, Jennifer. I hope you are right.

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  4. So beautiful! Yet another plant I need to add to my gardens.

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  5. oh that Blue River II is stunning! Now that we've moved I no longer have a hibiscus in the yard and no room for one. The one we had in our last yard was right by the driveway entrance and would garner many comments in the summer.

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