"We studied the 85 types to see where and how to plant them," he said. "We brought plants with natural beauty from the mountains to nursery gardens and then to streets in the city."
For example, in 2015, experts chose a type of sedge from the southwestern district of Fangshan and started to grow it on a larger scale elsewhere in the city.
In recent years the sedge has been grown on a total area of between 10 million and 20 million square meters, Zhang said.
"It turns yellow in autumn and because it is locally grown, the cost of planting it is much lower than putting down grass. By using our research and different techniques, we can produce shrubs on land in the city that are yellow, green and even blue, instead of being merely green," he said.
Jinghuang Chinese ash trees are commonly seen in Beijing. Their leaves turn golden in the autumn sunshine, while the leaves of another type of Chinese ash remain green, even in late November.
"We are making all the necessary improvements and adjustments to enable these trees to be prettier and stay green longer," Zhang added.
The bureau has also worked to diversify the type of plants in a particular area. In the past, there used to be some 10 plants in one place, displaying green leaves. Now, a more comprehensive and scientifically designed system and structure is being used to grow plants in a single location.
Wang Lu, who lives near Lianhuachi Forest Park in Fengtai district, said that since the venue was upgraded, more young people are visiting it during weekends.
The number of plants grown in the park has risen to about 80.
Zhang said: "Growing trees is not enough. We plant grasses and flowers under the trees, and also ask visitors not to clear away weeds, in order to include them in our ecosystems.
"Gardens and parks should not only be green and colorful, they should also work."