Unlike many other flowering plants, which are also grown commercially, hibiscus is essentially a houseplant. Hibiscus shrubs and trees are valued for their attractive flowers. Therefore, it is essential to nurture the plants carefully. In fact, pruning the shrubs and trees is very vital. Irrespective of whether the plants are being grown outdoors or in pots and brought indoors during the winter months in northern climatic conditions, they all need to be pruned. It is important to remember that hibiscus plants flourish when they are pruned and they produce flowers only when there is new growth. In order to avoid unsightly stubs, it is advisable that you make the cuts just above the lateral branch or the buds.
If the climatic conditions in your region are warm, you can prune the hibiscus trees heavily at the start of spring. Pruning the plant during the period between February and March helps to promote new growth as well as flowering. At the same time, it helps the hibiscus plants to remain in "shape" and not have an unkept look. However, be careful not to undertake heavy pruning either during winter or in fall.
On the contrary, if you are growing hibiscus in cooler climatic conditions, it is essential that you bring them indoors before the cold winters. This is to ensure the survival of the plants. In fact, you need to relocate the plants in a warmer place indoors even before the night temperatures drop lower than 40°F. Prior to bringing the hibiscus indoors, you need to prune them heavily. You may cut back the branches of the plant to about 4 inches to 5 inches from the main stem. When you prune the plants you not only make them capable of adjusting to the new weather conditions, but also get rid of pests that made them their home during the summer. When they are pruned properly, the performance of the plants will also be better. They will bear more blooms next summer.
In fact, it may be necessary to prune hibiscus at any time of the year. This is important for them to flourish and also bloom. You may undertake a light pruning of the plants in case they have contacted any disease or there is some dead wood on the hibiscus. Light pruning may also be essential if there is any rubbing branch or there is a weak or wilting growth. In fact, you may also undertake maintenance pruning to retain the showy shape of the plant and facilitate its blooming.
Ideally, you should prune hibiscus while the plant is active during the growing season. However, never prune the plants too vigorously as this may not only delay blooming, but also reduce the flowers. This is primarily because hibiscus always blooms from its new growth. Hence, just cut back the longest branches by three-fourth length at the appropriate time with a view to minimize any disturbance to the plant, which may affect its appearance as well as blooming. Wait for about a month and then again prune three-fourth of the longest branches. Undertaking such light pruning from time to time will either lessen or completely do away with the requirement for pruning the plants heavily.
If you do not care for the hibiscus plants and allow them to grow unrestricted, they will become messy and shapeless soon. At the same time, they will bear smaller and less number of flowers, which will also be duller. Majority of the hibiscus varieties are evergreen. In addition, there are a group of hibiscus species that are classified as herbaceous (herb-like), including small sized annually or biennially growing sub-shrubs that are found in the wild. On the other hand, H. mutabilis and H. syriacus are the only two cultivated species that are deciduous in nature. These two species are woody shrubs and they need to be pruned heavily in order to allow them to perform well. Akin to the tropical hibiscus that bears flowers on new growths, these two species bloom on their latest wood growth. Unlike the tropical hibiscus, which needs to be pruned in spring, you should prune H. mutabilis and H. syriacus only during the winter months, when their branches have shed all their leaves. No other hibiscus species or cultivars should be pruned during winter.
As for the tropical hibiscus, you should always prune them just at the beginning of spring or the beginning of their growing season. At times, you may also require pruning the plants during the middle of the growing season when the plant's growth is vigorous. This is more important for plants growing in warm climatic conditions. Most professional hibiscus growers prune their plants as soon as they notice new buds emerging at the end of the cooler weather. It is advisable that you cut back the plant even before these buds open up into leaves. Pruning the plants at this time will help you to gain control over their growth. On the other hand, allowing the plants to have new foliage will make you lose some control over them. When you trim the new growths, you may deprive the plants of their energy, instead of discarding their waste products. The plants might have used this energy for better and more leaves and blooms, which you actually desire.
In addition, it is also possible that when you trim the new foliage, you may also lose lots of flower buds. However, don't consider to be a loss, as you will be getting lots more flowers when you prune the plants timely. This is because each trimmed stem of branch will give rise to several stems and branches, which, in turn, will produce numerous additional blooms.
When you undertake pruning of the plants, your objective is to enhance the shape as well as the vigour, especially the main branches which may be spreading or erect subject to the hybrid, of the hibiscus. At the same time, pruning helps in opening up the center of the plant, thereby allowing lots of sunlight and air ventilation. This, in turn, promotes plenty of new blooms. In fact, pruning does not only mean cutting back the branches and side shoots to reduce the size of the plant. When you undertake pruning you also remove dead wood, if any; get rid of the weak and diseased branches and those damaged by bugs. You also remove any gangly, odd-angled branches that may appear aesthetically disturbing, in addition to any or all misshapen. Pruning your hibiscus also means giving them the desired shape - either the standard or espaliered form. Provided your hibiscus is properly nourished as well as healthy and you prune them prudently, you will be happy to see them repaying you with copious beautiful blooms.
When you trim the hardwood of the previous year to lessen the plant's size by getting rid of the useless stems with a view to bring the hibiscus to shape and enhance its vigour, the plant will possibly develop into a lush bush and be two-thirds of its size prior to the pruning. In fact, if your hibiscus is healthy, it will be able to endure a harsh pruning - bringing it down to half its original size. On the other hand, just prune about a quarter or one-eighth of the plant if it is young. In fact, professional hibiscus growers often prefer slight pinching out the initial new growths of young shrubs or, at times, even larger trees instead of pruning the larger branches. These growers claim that such actions gives rise to a better shaped and densely textured plant. They usually reserve the hard pruning - cutting back the plant by one-third, for the mature plants.
Prior to undertaking pruning, ensure that your lopping shears and secateurs are not only sharp, but also meticulously clean so that the cuttings too are sharp as well as clean. It is advisable that as in the case of all hardwood, your cuttings should be made at a somewhat slant - at about a 45° angle, and the uppermost part of the slant is a little above a bud, also referred to as an "eye" of the plant. This will help the water to overflow instead of collecting on the cut. On the contrary, an uneven cut is likely to promote infection by bacteria.
If you wish to get rid of the unnecessary stems growing from the main stem at angles just cut them a little away from the place where they are joined with the trunk. The same method can be applied for the branches that grow very close to the ground and may be sweeping the ground close to the trunk's base. However, a number of gardeners prefer the bushes to have a dense growth right from the ground to the top. On the other hand, several gardeners are of the view that the lower branches should be removed for the sake of the plant's hygiene. They further argue that when there is some space at the base of the ground, it makes maintenance and mulching somewhat easier.
In fact, gardeners also have different views regarding using pruning tar. Some favour its use saying that when you seal the fresh cuts with pruning tar right after trimming it helps to put off infection and, at the same time supports the plant's health. On the other hand, several arborists have given up this practice now with forest trees. Instead, they prefer to allow the trees to heal their wounds themselves. According to them, when you cut the branches/ stems at a place further away from the tree trunk promotes self-healing leaving the wound on the trunk to become smooth again, while the severed stub rots away naturally.
You need to have a bold approach while dealing with hibiscus that has developed from neglected shrubs to large trees. Before pruning such trees, it is essential to feed as well as water them properly throughout their active growth season with a view to advance their health. Subsequently, allow the plants to rest during the entire winter. Prepare yourself with a strong, properly sharpened saw when they are back to growth next spring. Cut down the tree up to the height of a table while preserving about six or so strong branches extending outwards. Ensure that you do away with all the branches that angle inwardly creating a mess at the center. Clear the base of the tree from the ground. Don't feed the plant after such heavy pruning. Now that the shrub/ tree has been reduced to half its original size and lost a large part of its foliage the tree will not be able to take up either water or food. Therefore, providing the plants with nutrients at this stage, particularly any concentrated fertilizer, may possibly damage the remaining bush. So it is advisable that you allow the plant sufficient time to recuperate slowly. In fact, the pruned plant may take as long as an entire season to recover.The foliage as well as the blooming of the plant will be revitalized again.