Hardy Hibiscus: Tropical Splendor in a Zone 5 Garden

Gorgeous Hibiscus, a dramatic perennial with large flowers, were first discovered in the swamps and marshes of the southern part of United States. They grew wild and were known as “rose mallow.” They have evolved, with help from gardeners worldwide, into hardy hibiscus which can be grown in many countries. Known as “flowers of celebration” in many countries, they may be best known as the tropical Hibiscus familiar in photos of Hawaiian hula girls. Now, Hibiscus can be successfully grown in zone-five gardens. The rose mallow genetics have produced some of the most beautiful flowering perennials known to gardens because of their eye-catching, saucer shaped flowers. You may almost feel as if you are in a tropical paradise the first time your Hibiscus blooms because the flowers can grow to be as large as nine inches across. They are the biggest and most exotic of any other cultivated perennial mallows.

hardy hibiscus
The exotic flowers of the Disco Belle hibiscus only look difficult to grow. This perennial, with its 9-inch flowers is hardy in the Northern hemisphere to a zone 5.

Hibiscus Stats:

Shape: Shrub-like with huge, flat to funnel-shaped flowers
Height: Sturdy, two and one-half to five feet tall
Width: Two to three feet across
Blooms: Late summer to frost
Colors: Shades of reds, pinks, and white
Site: Well-drained, moist soil
Light: Full sun
Hardiness: tolerates cold above zone five
Comments: Hibiscus only looks hard to grow but does well in some cooler, higher elevations.

Other well-known mallow family perennials are the attractive shrub, Rose of Sharon whose showy flowers bloom in fall. The indestructible Malva blooms non-stop all summer and of course, the old fashioned Hollyhocks that add height and beauty wherever they grow, are all family members. The rounded, flat, open-faced, five petaled, blooms in rich romantic shades of red, rose, pink, purple, and white are so distinctive they have made Hibiscus well-loved in American gardens.

red-hibiscus
This rose red hibiscus looks lovely with with splashes of contrasting yellow color (provided by annual marigolds) tucked in at its feet.

The size of the Hibiscus is large and dramatic enough to be considered a shrub. Each flower lasts only one or two days but they are so abundant, the shrub flowers for a long bloom period.  Hibiscus flowers are spectacular but the shrub-like size is also beneficial, especially if you have a large, barren spot to fill. Give your hibiscus shrub plenty of room to show off its flowers as well as its glossy, dark-green, oval shaped foliage. It grows on stiff, woody, hollow stems that generally do not need staking unless planted in a high wind area.

Cutting back the stems in early June can shorten, thicken and strengthen the bush but will cause delayed blooming. In a short growing season, you may want to skip this early-season trim.  A clump of three plants grouped as a focal point in an island bed or arranged at the back of the border will add flamboyant color and huge clumps of blooming foliage for six weeks or more.

Hardy Hibiscus should not be confused with tropical Hibiscus that grows only in hot humid climates. The state of Hawaii has named tropical yellow Hibiscus as their state flower, but its blooms are small while hardy Hibiscus flowers are larger and grander. Dinner plate-sized flowers are mind-boggling in the western Rockies because blooms this size are so rare. Creating a micro-climate so that this regal beauty can survive cold winters in higher elevations is worth the planning it requires:

For example, plant your shrub full sun on the south side of a home’s foundation. Provide freeze protection by using deep mulch placed around the base of the stems. This will help the plant retain moisture and protect it from freezing during dormancy. Hybridzers have introduced several new zone-four Hibiscus so perhaps this is something gardeners can look forward to.

This hibiscus hybrid is reported to be hardy to zone 4

This plant is so exotic that it looks difficult to grow but growing requirements are starndard. It only requires full sun and regular watering and fertilizing–much the same as most other perennials in your garden. Good soil will help the plant produce bigger and better blooms. Any yellowing of a few of the leaves is normal but if the entire bush turns yellow, it is a sign of stress signaling inconsistent water levels. Too much fertilizer can cause yellowing and so can excessive wind and rapid temperature changes. A strong blast from the hose will take care of spider mites if they invade.

fertilizing hibiscus
To keep Hibiscus at peak performance, fertilize during bloom time with a 20-10-20 feeding.

Breaking Dormancy – Hibiscus Requires a Little Extra Patience

An interesting trait of Hibiscus is that it is probably the last perennial to break dormancy (start to grow above ground again) in the spring. When cutting Hibiscus back in the fall, do not cut it to the ground but leave a ten-inch stem. By spring this stem will look very unattractive–almost like a brown colored pencil–but leave these stems to mark where your hibiscus is planted. Toward the end of May, about the time a gardener decides the plant is dead and needs to be replaced, bright green leaves will start to unfold. After breaking dormancy, the shrub can develop quickly.

hibiscus breaking dormancy
Hibuscus stems breaking dormancy. Leave the brown pencil-like sticks of hibiscus as a marker when it is cut down in fall. Don’t get impatient. Towards the end of May the green growth will erupt.

There are short hibiscus like the ‘Luna’, group and there are huge shrub-like hibiscus, the’ Belle’ group that can be used as a hedge. Other taller Hibiscus such as the patented, red ‘Fireball’ #13631, ’stripped Kopper King’, #10793, and dark pink ‘Sweet Caroline’ #7608, make fantastic four-foot focal points at the back of the garden. They will also take center stage in an island bed. As a focal point at the back of the border or in the center of an island bed, the heavy blooms require little staking. The sturdy stems are erect and substantial.

luna hibiscus
‘Luna’ hibiscus

Hibiscus, ‘Luna’ is a dwarf plant that is small enough to fit into a container or planter. ‘Luna’ may be a smaller plant but still has seven-inch, huge blooms. Potted Hibiscus necessitates considering these an annual for they will not survive living in a pot over winter.

 

 

disco belle hibiscus
‘Disco Belle’ hibiscus has large pink petals with a wine center.

Starting a Hibiscus from Seed

The wide open, colorful blooms and prevalent centers of Hibiscus like this Disco Bell are an invitation to pollinators, hummingbirds and gardeners who harvest the protruding seed and grow their own ‘Disco Belle.’ This is the one hibiscus that seeds well.

Hibiscus is easy to start from seed, or by cuttings and divisions. Seeds can be purchased or collected from parent plants. The high protruding seed centers are easy to harvest and they germinate better if they are fresh. Hibiscus sown in germination trays in winter or early spring will produce flowering plants by fall. Even a single stem will flower. Hard seed will need to be soaked overnight. Moisture improves germination. Any seeds still floating by the following morning will need the shell nicked or sanded before planting. Plant the tiny seeds with a dampened chopstick, pushing the seed about a half inch into the ground. Sprinkle or sift soil over the potting mix to fill any indentations rather than pressing the soil down as this may push the seed deeper. A loose plastic covering will help the seeds stay moist. Place the tray in sunshine to help the seeds germinate and mist water regularly. Varieties that are grown from seed are the dwarf Belle series, such as ‘Disco Bell’ that blooms in solid colors and ‘Dixie Bell’ with flowers in a mixture of rose, pink and white. ‘Southern Belle,’ also a seed propagated variety, blooms in a mixture of the other Belle’s colors. The Belle’s woody bases are strong-stemmed with serrated green leaves and are noted for having the largest of the Hibiscus flowers.

lord baltimore hibiscus
Lord Baltimore hibiscus

‘Lord Baltimore’ and his partner, ‘Lady Baltimore’are famous hybrids that grow on very manageable four-foot stems. The pink Lady Baltimore is elegantly refined and Lord Baltimore is a deep powerful red. Hybrid Hibiscus can only be propagated by cuttings or division.

Starting a Hibiscus from a Stem Cutting

Stem cuttings can be taken on fresh soft wood shoots after they break dormancy in late spring or early summer. Cuttings are a preferred method of propagating Hibiscus because the results will be an exact duplicate of the parent plant. Make the cutting about five inches long. Remove the leaves except the top set. Trim the cutting just below the leaf bump node. Dip the cutting in a powered rooting hormone and stick it into a wet soil that drains well, preferably with half of the soil being Perlite (a growing medium available at any gardening center and many hardware stores). Place a plastic covering over the cuttings and move them to a partially shaded spot. Keep the cutting damp until the starts are rooted. This takes close to eight weeks but the plants are so worth it!

Starting Hibiscus from a Division

Divisions are made in spring. Carefully divide the woody clumps and replant the divisions at least three feet apart. The hardiness of Hibiscus can be questionable in the high elevations of the Rocky Mountains when a bitter winter drops temperatures below normal. Unfortunately, if your hibiscus freezes, it becomes an “annual, and you’ll have to say adieu to the spectacular flowers.

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