Fertilizing Time, Suitable Fertilizers, and Transplanting Methods for Rhododendron simsii of the Ericaceae Family

Rhododendron simsii, also known as rhododendron or mountain pomegranate, is an evergreen or semi-evergreen shrub. Because of its bright red corolla, it is a famous flowering plant with high ornamental value and is cultivated in parks around the world. So, when should Rhododendron simsii of the “Ericaceae family” generally be fertilized? What fertilizer is best? How should it be transplanted?

I. When should Rhododendron simsii of the “Ericaceae family” generally be fertilized? What fertilizer is best?

In late winter and early spring each year, it is best to apply some organic fertilizer to the rhododendron garden as a base fertilizer. After rhododendrons bloom from April to May, because the plants consume a large amount of nutrients during the flowering period, as the leaf buds sprout and new shoots elongate, a topdressing can be applied about every 15 days. After the dog days begin, most branch tips have stopped growing. This is the high-temperature season, and physiological activity weakens, so topdressing can be stopped. After autumn, the climate gradually becomes cooler, and there are often continuous autumn rains. The temperature and humidity are suitable for rhododendron growth, so the last topdressing can be applied at this time. After winter begins, fertilization is generally not advisable.

Rational fertilization is the key to growing rhododendrons well. They like fertilizer but cannot tolerate concentrated fertilizer. During the peak growth seasons of spring and autumn, apply a thin cake fertilizer liquid water once every 10 days. It can be made by fermenting rice-washing water, fruit peels, vegetable leaves, and so on. In autumn, some phosphorus and potassium fertilizer can also be added. It can be made by fermenting fish and chicken innards, water from washing meat, rice-washing water, and some fruit peels. In addition to the above homemade household fertilizers, some household fertilizers can also be purchased for combined use, but remember to apply “thin” fertilizer appropriately. Before winter begins, apply 1 application of dry fertilizer (a small amount). When repotting, do not apply fertilizer at the bottom of the pot. In addition, whether watering or fertilizing, do not use tap water directly. It should be acidified (by adding ferrous sulfate or edible vinegar) and used after the pH value reaches about 6.

II. How should Rhododendron simsii be transplanted?

Rhododendron simsii is generally dug up and transplanted in late autumn and early winter or in early spring. Generally, to make Rhododendron simsii bonsai, old Rhododendron simsii stumps that have grown for many years, have peculiar and antique roots and trunks, and meet the basic conditions suitable for bonsai making can be selected. They can be dug up and transplanted in late autumn and early winter or in early spring. When transplanting, carry as much original soil as possible. According to the modeling needs of the Rhododendron simsii bonsai, the branches, trunk, and root system should be properly pruned. Cut off branches, trunk, and roots that affect the shape, retain more lateral fibrous roots, and balance the ratio of roots to trunk. It is best to first plant it in loose acidic sandy loam with good drainage for a 1-3 year trunk-cultivation stage. During this period, plastic film can be used in winter to keep it warm and moist. In summer, shade it to protect it from sunlight, and frequently spray water on the trunk, leaves, and surroundings to increase plant and air humidity and keep the soil moist. However, the soil must absolutely not be too wet or waterlogged. Avoid root rot caused by soil water accumulation and ensure the plant survives.

During the trunk-cultivation stage of Rhododendron simsii bonsai, it should be determined according to its growth condition. For weak trees, in addition to strengthening fertilizer and water management, they should also be allowed to grow freely as much as possible to strengthen tree vigor, and flower buds should be removed early to prevent flowering, reduce nutrient consumption, promote vegetative growth, make them grow vigorously, restore tree vigor as soon as possible, and accelerate shaping. For Rhododendron simsii with relatively strong growth vigor, pinching, pruning, wire wrapping, shaping, and potting can be carried out in time according to the actual needs of the Rhododendron simsii bonsai. This can shorten the trunk-cultivation time and promote early shaping.

Rhododendron simsii bonsai, like other bonsai plants, can be made into many forms such as multi-trunk style, forest style, slanting-trunk style, and cascade style. The branches and trunk of Rhododendron simsii are relatively hard and brittle, especially during the dormant period, and are easy to break, which is not conducive to adjusting branch and trunk angles or bending branches for modeling, let alone twisting them arbitrarily for modeling like other miscellaneous woods. Modeling time is mostly chosen during the spring, summer, and autumn growing seasons. At this time, because sap flows, the branches and trunk are soft and relatively less likely to break. The modeling methods are mainly pruning and pinching, supplemented by wire wrapping, combining pruning, pinching, and wiring.