The Asiatic flowering shrubs mesmerize us with its enormous flowers in bright colors and long flowering periods. Apart from the frost-sensitive Rose Mallow, there are also winter-hardy varieties for the garden that are easy to care for.
The plant genus Hibiscus or Mallow (Hibiscus) includes several hundred species worldwide, all of which come from Asia, but are distributed throughout the tropical and subtropical regions of the world. They are a part of the large Mallow family (Malvaceae). They are annual as well as perennial, herbaceous plants, subshrubs, shrubs and trees. Chinese Rose Mallow (Hibiscus rosa-sinensis) are quite popular as indoor plants and container plants. Rose of Sharon or Swamp Rose mallow (Hibiscus syriacus) and the cultivated breed of the winter-hardy Swamp rose mallow (Hibiscus x moscheutos) are suitable for the gardens located on the central Europe latitudes.
Appearance and Growth
The Swamp Rose Mallow, also known as the garden Hibiscus or Rose of Sharon, is a funnel-shaped, upright shrub that is up to 9.84 feet high and 4.92 to 6.51 feet wide. It is a slow growing plant and does not sprout until late spring. Its shiny medium-green leaves are pointy-egg-shaped and have three lobes. Beginning from August you will see striking, wide-open bell-shaped blossoms open at the ends of the branches. This species grow as single blooms of purple color. There are also numerous varieties with white, pink and red or purple to blue colored single or partially double-flowered varieties. Often the flowers are seen with a striking dark red spot on the inside, which runs radially towards the edge. Tubular stamens, commonly seen in Mallow plants, from which the three-branched style of the flowers emerge, are also striking. Small fruit capsules develop from the pollinated flowers, which often remain on the plants throughout winter.
The Rose Mallow has eye-catching, brightly colored flowers that range in color from white to yellow, orange to red and pink. The neat indoor and container plants are available with double and single-flowered varieties and differently shaped leaves.
The cultivated forms of the Swamp Rose Mallow haven’t gained popularity in our country. They reach heights of between 47.24 and 78.74 inches with striking flowers from July to October that can reach up to 11.8 inches in diameter. The color spectrum ranges from white to pink and red to multi-colored flowers.
Location and Soil
The common Hibiscus requires a sunny, sheltered place, for example near the terrace or in inner courtyards. Be it in the garden or in the pot on the patio or as an indoor plant, the Hibiscus requires a well drained, fresh and slightly dry soil with high nutrient content. Flowering suffers if the soil does not contain enough nutrients. It thrives best in sandy-loamy soil that is slightly acidic to alkaline. If the drought persists, buds might fall off. However, the garden Hibiscus is not too fond of water. Although it prefers sufficiently moist soil in summer, it does not tolerate waterlogging.
The bloom also suffers if it rains continuously, especially in the case of double-flowered varieties. On the contrary, the Rose Mallow needs to be watered almost every day, especially during its flowering period. If you have planted your Hibiscus indoors in a pot, it will need a very bright place all year round. A sunny window sill is well suited, however, in midsummer you must ensure that the plant is not too exposed to the blazing midday sun. Normal room temperature is perfect, in winter it should be a few degrees less.
If possible, Hibiscus should only be planted in the garden in spring so that it is well rooted by the first winter. Dig a hole that is twice the size of the root ball. Before refilling, mix the excavated soil with some nutrient-rich compost. Be careful when compacting the soil so that no roots are damaged. A layer of mulch around the roots is advisable. Water the Hibiscus well and also make sure to water the young plants regularly if the drought persists, otherwise buds that have already sprouted may fall off.
The Rose Mallow needs some liquid fertilizer once a week during its growth phase. You can use conventional flower fertilizer for this. Fertilizing every two to three weeks is sufficient during the winter. If the pot is too small for your Hibiscus, it is best to transplant it in spring or summer. For older, larger specimens, it is often sufficient to just change the substrate. The Garden Hibiscus must not be fertilized in winter.
The Hibiscus must be pruned occasionally. In the case of the Rose of Sharon, all previous year's shoots can be shortened to around five leaf nodes in spring to get the plant into shape. If the sprouts are frozen, then the dead shoots thin out. If required, pruning into the old wood in late spring can be done for radical rejuvenation of the shrub. However, it takes a while for the slow-growing wood to grow back into a stately shrub. The Rose Mallow is thinned out at the same time and the shoots shortened a little.
Hibiscus can also grow high stems. However, it takes several years until this growth form is fully developed. All lateral branches are removed every spring and only the strongest main shoot is left untouched. Once it has reached the correct height, the tip is cut off to encourage budding. The topmost of the new side branches is now pulled as trunk extension. To do this, tie it to a rod to guide it straight up. The remaining three to four branches gradually form the crown. Shorten them at regular intervals so that they branch out nice and dense.
Overwintering or Winter Protection
Most Hibiscus species are not winter-hardy and need to be placed in their winter quarters very early in fall to ensure safe wintering. Rose Mallow also belongs to this species. If it remains outside in the pot at temperatures below 53 degrees Fahrenheit, it will be too cold. Check your plants for pests before bringing it indoors and remove any dead parts of the plant. A bright location is also essential in winter, otherwise the Hibiscus will lose its leaves. A few falling leaves is normal. Moderately heated rooms (60.8 to 64.4 degrees Fahrenheit) or a placing in the cool winter garden are ideal - this also applies to plants that are kept indoors all year round. If the surroundings are too dry or warm, the risk of spider mite infestation increases. It needs only moderate watering, enough for the root ball to not dry out completely. There is no fertilization at all during the winter hibernation. From spring onwards, you can slowly increase the watering and add liquid fertilizer every two weeks. From May on, the Hibiscus can be placed outside again.
Many species of the Rose of Sharon, on the other hand, are hardy and can be planted in the garden. Young Hibiscus plants, in particular, need winter protection such as a thick layer of mulch made of leaves and brushwood around the roots. Alternatively, even well grown ground covers keep the heat in the soil. If one of these hardy specimens is kept in a pot, bring the planter close to a protected house wall in fall and place it on an insulating base made of wood or styrofoam.
Where to plant
Hibiscus spreads tropical flair and creates a vacation mood - inside and outside. A particularly beautiful sight is created by planting different varieties of Hibiscus together. Suitable companions in the garden are Bed Roses in fall, Lavender (Lavandula), Hollyhock and Bush Mallow (Lavatera). In addition, Hibiscus is also a bee pasture and attracts numerous bumblebees, bees and other useful insects. If you plant the Rose of Sharon with an evergreen ground cover, these protect the soil from drying out in summer and from frost in winter.
Important Species and Varieties
Among the various Hibiscus varieties, those with simple flowers are hardier varieties and tend to flower more. The Rose of Sharon Hibiscus syriacus ‘Helena’, for example, has beautiful simple white flowers with a red point in the middle that tapers off in a star shape. Depending on how much space you have, we recommend fast growing Rose of Sharon varieties such as”Lady Stanley” or slow growing varieties such as ‘Red Heart’. The blue flowering rose of Sharon variety ‘Blue Bird’ (Hibiscus syriacus ‘Blue Bird’) is a hardy variety and is therefore also suitable for colder regions. A rarity among the Rose Mallow is the Hibiscus rosa-sinensis “Cooperi” variety. Its red flowers are relatively small, but their unconventional white-green leaves make the Hibiscus an exceptional eye-catcher on the windowsill. A note of caution: ‘Cooperi’ requires relatively high humidity.
The Rose of Sharon varieties are usually propagated through grafting. Sometimes, however, the Hibiscus also sows itself in the garden, whereby the flower color and shape of the seedlings can later differ from the mother plant. Propagation by stem cuttingsby cuttings from woody, annual shoots in fall is also possible, but the failure rates are high: As a rule, only one out of ten cuttings grows. A covered, evenly moist propagation bed with very humus-rich, slightly loamy soil is important. It should be covered with fleece until winter sets in.
For Rose Mallows, non-woody cuttings are suitable for propagation. These root at a soil temperature of at least 71.6 degrees Fahrenheit, better still in commercially available planting soil.
Diseases and Pests
Unfortunately, all Hibiscus species and varieties are often plagued by Aphids that feed on the young shoots and flower buds. Especially in indoor culture, but also in winter quarters, spider mites often become a plague. Pay attention to cool temperatures and air that is not too dry.
Frequently Asked Questions
Where does the Hibiscus grow?
Hibiscus is originally from Asia, but can be found in all tropical and subtropical regions of the world. It prefers growing on the banks of streams and rivers, but also in forests that are particularly humid there.
When can you plant Hibiscus?
The best time to plant Hibiscus is in spring. This gives the young shrub enough time to grow until winter.
What kind of soil is suitable for Hibiscus in the garden?
In the garden, Hibiscus prefers a permeable clay soil that is rich in nutrients and humus and which is not overly dry.
What kind of soil is suitable for Hibiscus in a pot?
Normal potting soil is suitable for a Hibiscus in a pot. To avoid the shrub from getting wet at the base, mix sand into the soil.
When can you replant Hibiscus?
Be it in the pot or in the garden: Hibiscus should be replanted in spring or summer. So that it has enough time to get used to its new home. However, Rose of Sharon (Hibiscus syriacus) does not tolerate replanting once it is fully grown.
When can you prune the Hibiscus?
To prevent the shrub from aging, the annual shoots of the Hibiscus are pruned in spring. If the crown is very dense, it can also be thinned out.
What kind of fertilizer is suitable for the Hibiscus?
Hibiscus prefers compost or organic fertilizer.
Why does my hibiscus not bloom?
A Hibiscus may not bloom for a number of reasons, but most of the time it is because the soil is too dry. Lack of nutrients or aphids can also be responsible for it. You should also prune your Hibiscus regularly to keep it blooming.
What goes well with Hibiscus?
Hibiscus goes well with Annual Mallow, Bed Roses or Hollyhocks.
What kind of Hibiscus is suitable to make tea?
Not all Hibiscus varieties are suitable for tea making. The popular Hibiscus tea is made from dried flowers of the Roselle (Hibiscus sabdariffa).