What is the white stuff brushed on trees?
When strolling through urban sidewalks or orchards, it's common to see the lower part of tree trunks painted with a striking white color. This special coating not only forms a unique landscape symbol but also carries important plant care functions. We will delve into the material characteristics and ecological value of this maintenance technique.
The scientific formula for tree trunk whitewashing
Liming-based mixed materials
Traditional whitewash is mainly made from quicklime, mixed with lime sulfur, table salt, and clay in a ratio of 10:2:2:2. Quicklime, when mixed with water, generates calcium hydroxide, forming an alkaline protective layer; lime sulfur enhances the fungicidal effect; salt improves adhesion, preventing the coating from cracking; and clay adjusts the consistency of the paint to ensure even coverage.
Construction cycle and techniques
The best time to apply the coating is after the leaves fall in late autumn (November) and before the sprouts appear in early spring (February-March). Use a brush to apply the paint from top to bottom, maintaining a coverage height of 1.2 meters on the main trunk and the main branch crotch. New trees need to be painted twice at intervals of 10 days, while old trees require annual touch-ups.
Three core protective functions
Biological control barrier
The alkaline coating effectively kills overwintering insect eggs and destroys the structure of fungal spores. Experimental data shows that standard whitewashing can reduce the孵化 rate of aphids by 70% and suppress the incidence of ulcer diseases by 65%. The white reflective characteristic breaks the insects' tendency to lay eggs in the dark, forming a physical isolation zone.
Temperature regulation mechanism
In winter, the temperature difference between day and night can reach over 15°C. The white coating reflects 30% of solar radiation, reducing the trunk's daytime heat absorption. The bubble structure within the coating forms a thermal insulation layer, preventing rapid night-time temperature loss. This dual action reduces the skin temperature fluctuation by 40%, avoiding frost crack damage.
Safety warning function
Under the illumination of car headlights at night, the reflectivity of the whitewashed layer reaches 200 candela/square meter, extending the visibility of street trees by 3-5 meters. This characteristic effectively prevents traffic accidents and facilitates the night-time inspection work of gardeners.
With the advancement of ecological city construction, tree trunk whitewashing has evolved from traditional agricultural techniques to a systematic maintenance project. This seemingly simple maintenance method is actually a multidimensional protection system integrating material science, plant physiology, and environmental engineering, continuously safeguarding the green lifeline in the process of urbanization.