Propagating Hibiscus vegetative cuttings in Rootcubes® Growing Medium ensures successful and uniform rooting
Brenton Williams, Greenhouse Research Technician, Smithers-Oasis Company, Kent, OH USA
Vijay Rapaka, Ph.D., Manager, Corporate Grower Research & Technical Support, Smithers-Oasis Company, Kent, OH USA
The ornamental Hibiscus plants are extremely popular for their large and showy colorful flowers. Hibiscus belong to Malvaceae family and the two groups of hibiscus plants that we grow in our garden are hardy or perennial hibiscus and tropical hibiscus. Hardy hibiscus (Hibiscus moscheutos) is an herbaceous perennial, and the stems and leaves are very soft, dull green, and tender. Hardy hibiscus are generally propagated using soft terminal cutting and they root very fast with good success rate. Tropical hibiscus (Hibiscus rosa-sinensis) are a very popular choice for container plants and tropical gardens. They have extremely colorful blossoms with woody stems and thick, glossy, dark green leaves. Tropical hibiscus are also generally propagated using shoot-tip cuttings and they are considered as very finicky to propagate. They need very precise misting and do not root very well if the propagation media stays too wet.
Propagating hibiscus in OASIS® Rootcubes® Growing Medium ensures successful and uniform rooting because of the following reasons:
- The Rootcubes® Medium is engineered propagation medium formulated with optimal air/water ratio and is consistent from cell to cell which promotes faster and uniform rooting.
- The unique cell structure allows the cuttings to uptake water easily, and as a result, the cuttings rehydrate and establish quickly in the propagation area. This will help to reduce the requirement for frequent misting and as a result the media doesn’t stay too wet and the cuttings root faster.
- The foam media is a thermoset material and is considered to be sterile because of the high temperature involved during the manufacturing process.
Following is the general procedure for propagation of hibiscus cuttings in Rootcubes® Wedge Medium:
- Start with clean shoot-tip cuttings harvested from a healthy stock plants.
- Cuttings can be inserted into the propagation medium for immediate rooting. The cuttings do not store very well. If they need to be stored, place them at 10° C for no longer than 24 hours.
- Prepare the propagation area by placing the foam medium on the bench.
- Thoroughly water the medium using complete nutrient solution. Complete saturation of the foam can be achieved by sub irrigation or overheard water. Note: With overhead watering consider using a hose and a nozzle. It takes several passes to completely saturate the foam medium. If you are using foam medium for the first time, break open and inspect the center of the foam plugs to ensure the foam is completely saturated or not.
Note: Overhead misting is not sufficient enough to saturate the foam medium.
- Insert the cuttings ~25% of the height of the foam and space them ~5 cm apart.
- Use rooting hormone (IBA) as a dip or an overhead spray as it will significantly improve the uniformity and speed of rooting. Conduct trials with various concentrations to identify the optimal concentration for your particular cultivar and growing conditions.
- Misting: The frequency of misting depends on greenhouse conditions such as light intensity temperature, humidity, and also the air movement. Generally, mist for 6 seconds every 8 minutes. Reduce the misting frequency as the cuttings establish in the propagation environment. Never let the cuttings wilt and foam media to dry out excessively during the course of propagation.
- Fertilizer and watering: After 10 days into propagation consider watering with a hose and a breaker every 2 to 3 days with complete nutrient solution with 150 ppm N.
- Humidity and Air circulation: Maintain high humidity (90 – 100%) levels and reduce air circulation to avoid wilting of the cuttings.
Following is the general procedure for propagation of hibiscus cuttings in Rootcubes® Wedge® Medium:
- Light levels: The recommended light levels for propagation are 200 to 250 μmol•m-2•s-1 or a daily light integral (DLI) of 4 to 5 μmol•m-2•s-1. Once the cuttings are 2 weeks old, a light level of 300 μmol•m-2•s-1 can be provided.
- Temperature: Optimal rooting occurs when root zone temperatures are maintained (usually with bottom heating) between 78° and 83° F (26° to 28° C). The recommended day time air temperatures are between 76° and 82° F (24° to 28° C) and night time air temperature are between 70° to 74° F (21° to 23° C).
- Rooting: Generally, it takes about 4 to 5 weeks for rooting hibiscus cutting. After that, they are ready for transplant.
Transplanting Rootcubes® Wedge® or Horticubes® Medium
- Rootcubes® Wedge® Medium can be transplanted into a pot or a container to be grown inside a greenhouse or in an outdoor location as long as the growing media can be maintained moist with a drip or some other sort of irrigation system until the plants are established. Following are the general procedures:
- Fully saturate the Rootcubes® Medium before transplant.
- Always transplant into a moist media and burry the surface of the foam. Note: Make sure to transplant into a well aerated growing medium.
- Note: Do not let the foam dry out excessively before or during transplant process.
- Note: Transplanting into dry media can jeopardize the survival of the plant because foam can dry out excessively.
- Thoroughly water the medium immediately after transplant. After that, water just as required.
- Note: Once transplanted water quickly moves out of the foam into surrounding matrix. As a result roots grow rapidly into the surrounding media. Even if you happen to see the foam surface dry after transplant, it is totally fine as long as the media surrounding the foam plug is wet.
- Note: Overwatering can delay the transplant performance because the root will not quickly grow out of foam.