Objective  A consensus in academia is that the construction of garden rockery should reflect the state of real mountain. Accordingly, planting design in rockery should also revolve around the purpose of "creating real environment and seeking artistic conception". However, most existing researches mainly focus on the summary of plant configuration in gardens, seldom involving the discussion on planting design within the scope of rockery, and fail to deeply explore the principles and methods for rockery planting. This research aims to explore the conventional method and technology for rockery planting design, and to provide planting design for "real mountain type" rockery.

Methods  Based on literature study, case analysis, interviews with artisans and field research, this research discusses the purpose, principle, method and technique of planting design in the construction of garden rockery under the concept of "realistic rockery construction".

Results  In the process of "realistic rockery construction", the purpose of plant planting design is to create a natural state that is intended to make rockery more real. The configuration of plants is to endow plants with specific connotation that may help, create the artistic conception of rockery, so as to stimulate the imagination of visitors with rockery as the media. In planting design, it should be clear that although some methods and techniques are based on painting, there are obvious differences between rockery planting and landscape painting from the perspective of viewing and visual effects, and there are also obvious differences between rockery planting and bonsai. The principles of planting design may be summarized as being "clear", "well-arranged", "suitable" and "auxiliary". 1) Being "clear" means that trees are shaped with no branches being blocked by leaves, so as not to affect visitors' appreciation; 2) being "well-arranged" means that trees should be planted in a scattered manner along the trend of rockery, which entails planting trees with different heights to create the sense of depth; 3) being "suitable" means that right tree species should be selected and planted in ecologically suitable places, with all the trees selected being characteristic in both posture and color; 4) being "auxiliary" means that planting design should clarify the positioning of plants, that is, plants should be subordinated to and highlight rockery, with the growth direction of plants being in line with the extension direction of rockery, so as to facilitate the construction of rockery. There are three general steps in planting design. First, designers should establish the planting style based on the style of rockery. The selected shape of trees should be fluffy and branches positioned high, so as to provide shade for visitors while covering up the flaws of rockery stones. Second, planting layout should be determined in line with the shape of rockery. The planting position of rockery plants should be special and different from that of flat planting, which is restricted by the soil volume and bearing capacity of rockery. Besides, it is not easy to move rockery plants after planting. So the layout should be completed before construction, and should consider the size of plants as they grow. Finally, planting area should be divided into three parts that are respectively positioned in the front, middle and back of rockery. After the division of planting area, detailed design should be carried out in such a way that it can highlight the viewing point of rockery and strengthen the sense of depth thereof, and different areas should be designed by different methods. Specifically, as for plants, the prospect of stones, it is better to select large trees that can provide visitors with comfortable and cool sightseeing environment. However, plants should not block the ornamental surface of rockery. The species and morphology of rockery plants should emphasize the height and thickness of rockery. As plants are mostly directly planted on rockery, where soil weight and volume are limited, designers should select clumpy small arbors or shrubs with dense branches. The size of plants selected should not be excessively large or small, so as not to negatively affect the momentum of rockery while enabling plants to well play the role of scenery barrier. Additionally, the plants should be properly pruned in the process of maintenance. Behind rockery, soil should be stacked to the same height as rockery, and large-sized plants should be selected and densely planted to form a forest background for rockery, provided that plants should not block the buildings nearby, and should be able to create the artistic conception of "mountain behind mountain". In addition, planting design should reflect the artistic conception of rockery through plants' color, smell and taste. Planting design techniques may be broadly summarized as follows: In the delicate space of rockery, the rockery body should have a clear texture well matches the surrounding plants, and the selection of tree species should pay attention to the size of trees and the matching thereof with stones. This research gives some examples of plants commonly used in rockery planting. Besides, pruning and maintenance of plants are also important. In the long run, suitable pruning can make plants rich in natural wildness, cover up flaws of rockery and set off artistic conception.

Conclusion  Centering around the theme of "realistic rockery construction", this research explores in detail the methods for planting design, which can help deepen the systematic understanding of the traditional techniques of rockery stacking, and provide guidance for gardening practice.