Study finds protective willows best planted down to stone layer

In New Zealand willows are widely used to protect riverbanks from water erosion and are especially important during periods of high river flow, protecting land and property.

This study looked at how a normal tree willow root system develops on riverbanks, exploring the root system development from cuttings of Salix nigra L. willow (selected as a model tree willow) in layered riverbank sediments – silt over sand, over stones. 

The study found that while there was substantial root extension into all three substrates, the root development varied, reflecting the different properties of sediments. Overall, the study found that protective willows should be planted down to the stone layer. Planting in sand makes the tree vulnerable to destabilisation because roots do not branch much and bind particles together enough to resist erosion in high water flow periods. 

Journal Reference:

McIvor, I, Desrochers, V, 2019. Tree willow root growth in sediments varying in texture. Forests 10 (6) https://doi.org/10.3390/f10060517