Outdoor Cultivation Of Tropical Hibiscus
Hibiscus plants grown outdoors have a few basic requirements, including adequate sunlight and warmth, ample moisture, sharp drainage and proper nutrients.
Sun and warmth
Ideally, you should plant hibiscus in the part of your garden that is warmest and receives sunlight throughout the day. In fact, the cooler the climatic condition, the more important it is to provide the plants with warmth and bright sunlight. If you are growing hibiscus in places near the tropics, these factors are not all that important. Many gardeners in such places have claimed that hibiscus planted under serrated shade of palm leaves have been found to grow as well as those grown in dazzling sunlight or sometimes even better.
Providing warmth to the hibiscus plants means that there would be no cold drafts. In fact, this is more of a challenge when the plants are grown in cooler climatic conditions where fine-netted trellises or walls can provide them adequate protection and where elevated beds having higher borders can protect the roots, particularly when they are mulched. At the same time, they also ensure proper soil drainage. Warmth also denotes the absence of extremely low temperatures. Hibiscus can only tolerate a brief and very low cold-snap during winter, for instance 37°F (3°C).
If it is really difficult to find an appropriate sunny location in your garden and you are unable to find a place where you can plant your hibiscus, it is advisable that you select a site that is in partial shade. When you plant the hibiscus in such locations, the plant will have thinner foliage and bear fewer flowers, but it will definitely grow there. It may not flourish in such sites, but will grow nevertheless.
Proper drainage is crucial for hibiscus plants to thrive. Grow your hibiscus on an elevated position even if there is a slight chance of the plant’s roots getting waterlogged when it rains for a prolonged period. Grow the plant on an elevated ground or atop the slopes and banks. Alternatively, you may also have raised beds. In case, neither of these is possible in your garden, you should dig up the area and develop a base using rocks and gravels prior to filling the place again.
Hibiscus grows best in porous soils. While sandy loam is perfect for growing hibiscus, they also grow well in volcanic soil that has a fast drainage. Although hibiscus grows well in coastal areas having just about pure sand, these soils create different other challenges, such as providing as well as retaining moisture and nutrients constantly. However, drainage is not a problem in such sites.
In addition, hibiscus roots require proper ventilation. Precisely speaking, the requirement for air-filled porosity for hibiscus is higher compared to other plants whose requirement is average. The term “air-filled porosity” is generally used by people in the nursery industry to mention the percentage or proportion, in terms of volume, of air spaces in the potting mix in a container, which has been watered to the maximum point and subsequently let to draw off. Therefore, a potting mix enclosing a large amount of coarse particles will generally have an elevated air-filled porosity. For instance, it has been found air-filled porosity of around 10% to 12% is most suitable for the robust growth of roses. On the other hand, the air-filled porosity of the growing medium for epiphytic plants that grow in tree forks in the wild is much higher – about 50% to 60%. Then again, majority of the cultivated bedding plants have a preference for a very low percentage of air-filled porosity in their growing medium. The soil or the potting mix that is most ideal for growing hibiscus ought to have about 25% to 30% air-filled porosity.
Hibiscus plants have a preference for high moisture. Nevertheless, they grow well in arid areas if their roots are watered adequately or they have a stable access to water. In addition, the foliage of the plants should also be watered regularly using a hose or misted often. The plants’ requirement for water is highest all through the growing season. In other words, hibiscus plants grown in open gardens or fields should be watered on a regular basis – their roots need to be soaked thoroughly. If the plants are grown in a soil that has a faster drainage, like in gardens on sandy beaches, they will require additional watering. Like all other plants in your garden, hibiscus’ requirement for water during the winter months is less, as they are not able to take up much water during this part of the year. If you are growing hibiscus in cooler climates where the winters are damp, the plants would not require watering.
You can test the moisture content of the soil by examining few inches of the soil’s surface. If you feel that the soil is actually dry, you should know that the plant requires watering. In fact, all knowledgeable gardeners know that providing the hibiscus plant with intermittent, but thorough soakings is much better compared to plenty of regular, light sprinklings that will possibly not even penetrate the soil.
Hibiscus plants grown in gardens thrive best when they are cultivated in sites that are properly prepared and have a good quality friable (crumbly), loamy soil whose pH ranges between 6 and 7. In addition, the soil should essentially contain lots of organic materials and those should be replenished regularly. The plants grow really well when they are constantly provided with required nutriments, especially during the warm summer months, when their growth is active. You should especially include potassium in their feed because this essential mineral not only promotes profuse flowering, but also helps the plants to produce best flowers having very bright colors. Several gardeners have claimed that they have been hugely successful by using citrus fertilizers. There are many others who assert that they have successfully grown hibiscus using the commercial fertilizers meant for growing fruits and roses. You may also try these fertilizers provided you already have them in store. Majority of the nurseries growing hibiscus usually provide the plants with soluble form of chemical nutrients.
Hibiscus plants flourish well when they are supplied with compost. In fact, the entire organic substances, counting properly decomposed manure, are favourable for hibiscus, as they provide the necessary nutrients to the roots, support a good balance of organisms, in addition to adding consistency to the soils. Ensure that the compost you are using for growing hibiscus is well aged. Provided you have the time to prepare the planting site many months before the actual planting, you can also use freshly obtained manure, or else ensure that the manure has decomposed properly. You may also use dehydrated manure, for instance sheep pellets that are available commercially in packets, any time. Moreover, you may also dig out some decaying leaf mold or even stray and blend it thoroughly will the soil. Peat moss purchased from the market can also be used for the purpose, but ensure that you mix it carefully with the soil.
Similar to other plants, even hibiscus requires nitrogen as well as essential minerals like calcium, potassium, phosphorus, sulfur and magnesium, in addition to the trace elements. In fact, all superior quality soil that is replenished with organic substances on a regular basis should have all these minerals. For instance, chemical analysis of seaweed has shown that it contains all the nutrients required by the plants, while comfrey also possesses similar attributes. However, there may be a requirement for supplementary additives from time to time. At the same time, you may also use dolomite, which is useful in supplying the plants with magnesium. Dolomite can also help to change the pH of soil, which is extremely acidic. Similarly, borax provides the plants with the trace element boron, while potash provides the plants with potassium. In case the soil in your garden severely lacks these minerals and trace elements, you will notice that not only the hibiscus, but other plants too are not growing healthily. In such circumstances, it is advisable to check with a soil expert.
In addition to supplying the plants with nutrients in the usual way, you may also undertake maintenance feeding. When we talk of maintenance feeding, we denote digging the soil lightly further than the external limits of the shallow hibiscus roots, while ensuring that the roots are not disturbed in any way, or applying manure or fertilizers on the soil surface. Hibiscus takes up nutrients vigorously during its active growing season. Therefore, you may feed the plants quite often, for instance once in five to six weeks. However, if you are growing hibiscus in cooler climatic conditions, the feeding should be comparatively lighter.
People growing hibiscus in sub-tropical climatic conditions may often experience heavy showers of rain, which may wash out the nutrients from the soil. This is one reason why the plants should be fed heavily and also mulched properly during this period of the year. Following the feeding, you should essentially undertake hand watering, which is different from rain. Hand watering is all the more essential if you are using chemical fertilizers. The growth of hibiscus that is fed little quantities of nutrients, but quite often will be healthier compared to the plants that are fed too much, but at long intervals.
Mulching is a technique that helps to conserve soil moisture and, at the same time, lessen the requirement for watering the plants by means of restraining the evaporation rate. As the materials used for mulching usually have a coarse and loose texture, they also help in providing proper ventilation to the roots. Moreover, as the organic substances that comprise mulch decompose, they provide the plants with necessary nutrients and also slow down weed growth.
Hibiscus is considered to be more or less self-mulching, as the leaves and flowers of the plants drop nearly throughout the year. These leaves and flowers decay slowly forming natural mulch. This is one reason why gardeners always abstain from digging the soil at the base of the plants. Of course, you may dig a shallow trench or a moat further than the line where the leaves drop and utilize this for feeding compost as well as for placing mulch, which would eventually spread to the center. However, under no circumstances should you dig the soil at the base of the plants. Remember, the periphery covered by the leaf drip line is actually the area to which the hibiscus roots spread externally. In other words, the root area can be determined by the breadth of the furthest foliage. The mulch should always be applied inside this circle, but never place it very near the stem.
While ensuring that you stay away from the base of the hibiscus trunk, apply the mulch quite densely, about 6 inches to 8 inches (15 cm to 20 cm) thick. However, ideally the mulch should be applied less thickly, about 2 inches to 4 inches (5 cm to 10 cm) dense and keep topping it up on a regular basis. In fact, the weather can also suggest how heavily and how frequently you should mulch the plants. You need to apply more mulch when there is a drought.
Many people often ask what materials they should use for mulching. In fact, mulching is simple and you may use any organic substance, preferably leaf mold, pine needles, hay, straw (pea and barley straw are wonderful for this purpose), nut husks, corn husks, shredded or chopped prunings (ensure that they are not infested or infected), peat products, rinsed seaweed, tree-fern fiber, shredded newspaper (don’t use the glossy or colored type), dried out pine cones, used up mushroom compost, barks (you should avoid fresh pine bark, as it oozes lots of resin, however, you may blend small amounts of it with other different materials), derivatives from sugarcane industry, coconut fiber and any other similar substance.
You should avoid using fresh lawn clippings, unless you use it in very small amounts blended with other substances. Discarded doormats made from coir, jute or open-weave sisal can prove to be very helpful as well as stable mulch, as they are organic materials, decompose very slowly and make wonderful aerating covers.
Selection and sitting
These days, gardeners have a wide range of choice as far as the shape, size, flowers and habitats of hibiscus are concerned. This is mainly due to the availability of numerous tropical hybrids, which did not exist before. While pruning the plants will help you to maintain the desired size and shape of hibiscus bushes, it is prudent to opt for the right variety when you start gardening. Currently, professional hibiscus growers as well as the officials of the hibiscus society identify three sizes – low (below 3 feet, or 1 meter), medium (3 feet to 6 feet, or 1 meter to 2 meters) and tall (6 feet to 10 feet, or 2 meters to 3 meters). Apart from these there are other sizes which may include the occasional extremely lofty or extremely low (almost prostrating) plants. Here it is important to note the term “low” instead of “miniature”. Different from the rhododendrons, camellias and other different shrubs, where the term “miniature” portrays the overall bush size, in the case of hibiscus, this description or term denotes the size of the flowers and not the size of the shrub.
In addition, the plants can be divided into three categories depending on their form – bushy, erect or open. You also need to consider the leaves of hibiscus. The entire tropical hibiscus plants are evergreen and the variation of their leaves range from nearly spherical leaf to extremely narrow leaf and there are many other leaf forms in between. The margins of the leaves can also vary greatly ranging from smooth to somewhat jagged to extremely depressed or indented. As far as the classification of hibiscus flowers is concerned, this is entirely a subject that needs to be handled by specialists. The variety of hibiscus flowers is really immense, especially owing to the great number of crossbreeds developed in modern times. Therefore, listing the hybrid hibiscus as well as the requirement for dependable standards to judge shows have necessitated some rules for maintaining consistency. Four bloom sizes have been recognized by contemporary hibiscus societies – miniature (flowers below 4 inches, or 10 cm), medium (flowers sizes from 4 inches to 6 inches, or 10 cm to 15 cm), large (blooms that are between 6 inches and 8 inches or 15 cm to 20 cm) and extra large (flowers sizes of 8 inches or 20 cm and more).
Apart from the flower sizes mentioned above and in addition to the three classifications of single, double plus semi-double blooms, there are several other forms as well as textures. Some of the forms in which hibiscus blooms appear include windmill (very slender petals parted by spaces in between), cartwheel and cartwheel overlap (while the base has a twisted formation, the petals have resemblance to wheels), crested (may be found in single as well as double forms having a petaloidal growth – a small growth akin to petals, on the tip of the style), fringed petals (the external edges of the petals are fringed and split), recurved (the external edges of the petals are curved towards the back), and cup-and-saucer (flowers having a central clump of petaloids in the middle and they are clearly detached from the external petals). The textures of hibiscus petals also vary greatly – veined (veins of contrasting colors noticeable as threads), ruffled, fluted (petals with soft ribs or waves) and frilled or picot edges.
From the view point of the grower, the prime consideration is the space as well as the site of the wished-for plant. This is apart from the issue of selecting the right varieties that would appear most attractive in their gardens. While buying the plants from the nursery, it is important to take the eventual size of every hibiscus variety. In fact, you are in the best position to judge the finest plants for the most excellent sites in your own garden. Therefore, while you are purchasing the plants you need to ensure that you are choosing the plants that display vitality, sturdy stems, excellent and healthy foliage as well as potential of copious fresh growths.
Planting and transplanting
It is vital to plant hibiscus outdoors only during spring – just when their growing season begins. If you are growing hibiscus in places having mild climatic conditions, you may possibly plant them during the end of winter and throughout the fall. Nevertheless, you should adopt additional care if you are doubtful about the weather conditions. In fact, planting hibiscus outdoors too early in spring may be detrimental for the plants, especially in cooler places. Similarly, planting hibiscus out later in fall may also harm the plants, especially when winter is approaching fast. You can plant a small, young plant directly into the ground without trimming it. On the other hand, prior to planting, a comparatively larger hibiscus plant may require trimming the stems that are loaded with buds.
Be cautious while planting hibiscus outdoors so that you do not harm the roots. Deal with the roots very gently. The best way to handle the plants is to turn the growing bag or container upside down. Next, hold the base of hibiscus in your palm along with the roots and the soil clinging to them. Observe the spread of the plant’s roots – you will find them spreading sideways rather than downwards at the center. In order to have room for this propensity, the planting hole needs to be broad, but shallow. At the same time, make sure that the planting hole is properly dug and prepared somewhat deep below. Gently position the plant in the middle of the planting hole.
Plant the hibiscus in such a manner that the joint of the plant’s roots and stem are parallel to the surface of the soil, in the same manner as you plant hibiscus in pots. In other words, the collar or bole area of the plant should be just above the soil surface. If you are planting grafted hibiscus it is extremely important to keep the graft area of the plant about the soil surface and avoid applying mulch to that area. Hence, it is advisable that you should never plant grafted hibiscus too deep into the ground. Bear in mind that shallow roots always grow close to the solid surface. Cover the planted area with growing mix and press lightly. Then water the plant properly.
In case you are transplanting a hibiscus, which was established in a location for a long period, to a new site, it is essential to first prune the plant by reducing its size by roughly two-thirds or maybe even more. Prior to transplanting, the plant should also be very thoroughly watered for a couple of days. Before you transplant the hibiscus, make sure that the new location has been prepared properly. Having done these, dig around the base of the plant from the external periphery of the leaf drip-line. While doing so, ensure that you do not harm the roots in any way. In case the roots extend further than the area you are digging, cut the extended part cleanly. Start digging from the sides of the plant in stages and subsequently place the fork below the shrub and raise the plant very carefully.
A mature and well established hibiscus will also have a well established root system. Therefore, it will require more than one person to dig up, remove and relocate the plant. Placing an old rung or sack will prove to be helpful in carrying the plant to its new location. Therefore, it is advisable that you keep one ready before digging up the plant. Carefully lower the plant into the prepared planting hole. Once again, ensure that the joint of the plant’s roots and stem/ trunk are kept at the level of the soil surface. Once you have placed the shrub properly, cover the place with the growing mix and water the plant well. Here is a word of caution: remember, you should never provide a hibiscus with nutrients/ fertilizers soon after transplanting it. This is all the more true if you are using chemical fertilizers instead of organic substances. It is important to give sufficient time to settle in its new home.
As the hibiscus roots are shallow, they are not anchored deeply into the soil. Therefore, the question is whether or not you need to stake the plants. It is suggested that you stake the plants to be on the safe side. Even if you are in doubt, you should still stake the plants. In fact, the anchorage of the plants is not the sole concern. In case, a hibiscus is uprooted by a strong wind, its roots may be injured and if the damage is significant, it may result in root rotting. Hardwood stakes are ideal for hibiscus. Put the stakes before planting and tie them with the plant using soft materials. Be careful not to ever use hard strings or wire or any other material that may injure the plants.
However, you may not require staking the plant provided you have a suitable place for growing hibiscus, such as a site against any wall, a niche of a lower-level pocket, a place adequately sheltered by a projection and encircled by thick foliage or any other exceptional location. Alternatively, you may also use trellising or build a bank using boulders subject to the requirement at the site. It is best if the climatic conditions in your place are calm all the times, which is a rare situation, as in such circumstances the hibiscus will not require any buttressing. As low-growing hibiscus plants are less susceptible to such damages, it would be prudent to select plants that will not grow to a significant height. Doing so will serve as a preventive measure, especially in places that are too windy.
History of hibiscus
Growing hibiscus in containers
Propagation of hibiscus
Pruning and maintenance of hibiscus
Pests of hibiscus
Diseases of hibiscus